Device for additively manufacturing a tread of a tyre comprising at least one extruder and method for regulating the pressure in the extruder

Abstract

The invention relates to a method for additively manufacturing all or part of a tread of a tyre configured to smooth any reliefs (R) present on a circumferential bearing surface (5) of the tyre by depositing an extruded material forming the tread, wherein a pressure-regulating member (24) inside the extruder is controlled in real time, via a pressure-regulating loop, in accordance with a pressure measured by the pressure sensor and a constant pressure setpoint value. The method is configured to smooth a plurality of reliefs (R) present on a circumferential bearing surface (5) of the tyre.

Description

[0001] DESCRIPTION

[0002] TITLE: Device for additive manufacturing of a tire tread comprising at least one extruder and method for regulating pressure in the extruder

[0003] The present invention relates to the field of manufacturing a tire tread.

[0004] Conventional wheels are familiar, consisting of a rim onto which a tire is mounted, comprising a tread and two sidewalls. This type of wheel includes an inner tube inflated to the recommended nominal inflation pressure.

[0005] We also know of another type of tubeless wheel known as "tubeless" in Anglo-Saxon terms, comprising a layer of waterproof butyl rubber to replace the inner tube.

[0006] We are still familiar with integral wheels, known as "airless" wheels, which consist of a radial load-bearing structure, generally made of fiberglass-reinforced plastic, around which a solid tire is fixed, comprising a tread and two sidewalls. The solid tire is not subjected to internal pressure.

[0007] Such an integral wheel offers the advantage of being flexible in the event of impacts, puncture-proof, and durable thanks to its constituent materials. Furthermore, once worn, the tread can be removed and recycled. Thus, such an integral wheel also helps to meet environmental requirements.

[0008] It is known to retread worn treads on conventional tires with inner tubes. Tires used on heavy-duty vehicles are particularly susceptible to any renewal process that extends their lifespan. This process involves removing the worn tread and replacing it with a new one by wrapping and securing it onto the tire casing.

[0009] Other techniques are known for renewing tire treads. For example, document W0-A1-2013086577 describes an apparatus and a method for retreading a worn tire tread. The tread is made of a thermoplastic elastomer. The apparatus includes a heating device to heat the worn surface of the tread and a three-dimensional printer, known as a 3D printer, to apply one or more layers of thermoplastic elastomer to the heated surface. The 3D printer comprises a series of print heads arranged in a row.

[0010] However, this process is specifically designed for retreading conventional tire treads with inner tubes. Furthermore, the heating steps for the surface area are energy-intensive and expensive, requiring specialized heating equipment.

[0011] Furthermore, such a process only allows material to be deposited on flat surfaces and not on curved surfaces, and in a continuous and non-fractional manner.

[0012] Document FR-B 1-3 067 281 proposes a simpler, less energy-intensive process that can be implemented anywhere. This document describes a system for manufacturing the tread of a tubeless, integral tire. The device includes a construction robot with one or more additive material deposition nozzles. The nozzles are arranged side-by-side and move laterally to cover the entire tread area to be built.

[0013] However, this process is particularly slow because the tire is positioned at a specific azimuth before the nozzle deposits material, and the operation is repeated until the entire tread is manufactured. This solution only allows for the deposition of a few tens of grams per hour, for example, 50 g / h per print head. Furthermore, the slow tread manufacturing process can lead to oozing problems.

[0014] To reduce tread manufacturing time, large extruders with 5 mm to 10 mm material deposition nozzles could be used. However, in this case, although the material deposition rate is higher, on the order of 900 g / h per extruder used, the precision is much lower.

[0015] The proposed solutions are therefore not satisfactory since they require a choice between the speed of manufacturing the tread or the quality of the tread pattern.

[0016] Furthermore, in order to obtain optimal strength of the manufactured object, the fusion between the molten filaments deposited in a horizontal plane and between the layers must be as complete as possible.

[0017] In all known solutions, imperfections in the support generating a variation in altitude can lead to unsatisfactory filling, i.e. the presence of cavities in the printed sculpture.

[0018] Control of the filling process is therefore a determining factor in the strength of the manufactured object.

[0019] Indeed, above 100% infill, excess material can flow down the sides of the printed object or accumulate on the surface of solid areas, disrupting the printing of the upper layers. This excess then propagates from layer to layer, with a cumulative and detrimental effect.

[0020] To address this problem of insufficient filling, a known solution is to control the molten material deposition rate relative to the surface. This solution is particularly complex because it requires reading the substrate's topography and adjusting the extruder's height relative to the substrate to achieve a consistent layer height. Furthermore, in this case, surface irregularities are retained, and a positive displacement pump may be necessary to regulate the molten material flow rate. Therefore, there is a need to improve manufacturing processes, particularly for tire tread resurfacing.

[0021] The objective of the invention is to manufacture, in particular to recharge, quickly a tire tread while maintaining the quality of the tread pattern, with a filling rate close to 100%, between 99.5% and 100%, including terminals.

[0022] The present invention relates to an additive manufacturing device for all or part of a tire tread configured to deposit a layer of extruded material comprising a thermoplastic elastomer material having a viscosity between 34 Pa.s and 11000 Pa.s, forming the tread on a circumferential carrier surface of said tire having a plurality of reliefs with progressive variation along the circumferential surface of the carrier surface.

[0023] Reliefs are defined by an amplitude less than 60% of the nominal height of the layer, that is to say an altitude value, in absolute value, according to the radial dimension between the circumferential carrier surface and a hollow or a bump less than 60% of the nominal height of the layer.

[0024] The nominal layer height corresponds to the radial dimension of the deposited extruded material layer. For example, the nominal layer height is 0.7 mm.

[0025] The relief length is equal to 6mm for a layer printing speed less than or equal to 300 mm / s.

[0026] The length is understood in the circumferential direction of the bearing surface.

[0027] The said device is configured to smooth, correct, or erase the said plurality of reliefs and includes:

[0028] - a pneumatic rotation drive element capable of driving said pneumatic around a horizontal axis of rotation;

[0029] - a fixed base attached to the ground;

[0030] - a mobile support in translation relative to the base;

[0031] - at least one printing module attached to the mobile support and comprising:

[0032] - a mobile extruder along an extension axis, for example radial, relative to the pneumatic and configured to produce a rod of molten material;

[0033] - a material dispensing nozzle fed with a molten material stream by the extruder, comprising at least one dispensing orifice and a molten material receiving chamber from the associated extruder in fluidic communication with said dispensing orifice; and

[0034] - a device for moving the extruder along the extension axis.

[0035] The system includes:

[0036] - a pressure regulating device inside the extruder comprising a pressure sensor configured to measure pressure values ​​in a chamber upstream of the molten material receiving chamber; and

[0037] - an electronic control unit comprising a pressure regulation loop configured to control in real time the pressure regulation device inside the extruder as a function of the pressure measured by the pressure sensor and a constant pressure setpoint value, the pressure regulation loop having a bandwidth from 0Hz to at least 100Hz.

[0038] By "real time" we mean a response time of less than 1ms for a molten material deposition speed between 0.01m / s and 0.3m / s.

[0039] Pressure regulation in the extruder chamber allows for the application pressure of the molten material to be as suitable as possible for the relief of the carrier surface, and thus to smooth out reliefs with a height less than the height of a layer.

[0040] Such pressure regulation thus makes it possible to obtain a good level of filling, between 99.5% and 100%, and good cohesion between the layers.

[0041] Such a manufacturing device allows for the rapid production, particularly the resurfacing, of a tire tread while maintaining the quality of the tread pattern. The material bead, for example, has a thickness of 0.7 mm and a width of 2 mm when deposited on the carrier surface. Indeed, before deposition, the material bead has a cross-section identical to that of the material dispensing nozzle. The material bead then has a circular cross-section when the material dispensing nozzle has a circular cross-section.

[0042] The bandwidth of the pressure sensor is preferably greater than 200 Hz.

[0043] The extruder is configured to deposit molten material with a flow rate of 1000g / h.

[0044] Additive manufacturing refers to a manufacturing process by adding extruded material, called fused deposition modeling, abbreviated as EDM in English.

[0045] By "pneumatic" we mean all types of toroidal elastic bandages subjected to internal pressure or not.

[0046] The "tread" of a tire refers to a quantity of rubber material bounded by lateral surfaces and two main surfaces, one of which is called the tread, intended to come into contact with the road surface when the tire is in motion. The tread comprises a plurality of cuts or grooves extending onto at least one of the lateral surfaces.

[0047] The "sidewall" of a tire refers to the portion of the tire's lateral surface located between the tire tread and the wheel's support structure. In the case of a conventional wheel tire, the sidewall begins at the edges of the tread grooves and extends to a tire bead.

[0048] The additive manufacturing device is configured to deposit an extruded material forming the tread onto a circumferential carrier surface or peripheral outer contour of the tire and includes a drive element for rotating the tire around a horizontal axis of rotation. "Width" refers to the direction parallel to the tire's axis of rotation.

[0049] By "thickness" or "height" we mean the direction along the radial direction to the axis of rotation of the tire.

[0050] Additive manufacturing on a support, for example the carrier surface of the tire, or more generally the tire, set in continuous rotation makes it possible to manufacture or completely reconstitute the tread over its entire circumference.

[0051] The tire here has only one degree of freedom, namely around its axis of rotation. In other words, the tire is not free to move in translation along any of the X, Y, or Z axes.

[0052] The device is also compact and autonomous and can apply treads to new or retreaded tires as well as to "air-less" wheels in a short period of between 10 and 20 minutes and without a vulcanization step.

[0053] Such a device is preferably, but not exclusively, intended to equip automotive centers, car dealerships, fleet management centers, or to be installed in small utility vehicles in order to be able to recharge tire treads anywhere, for example in a parking area, a motorway rest area, etc.

[0054] Advantageously, the pressure regulation loop of the electronic control unit is configured to control in real time the pressure regulation organ inside the extruder according to the pressure measured by the pressure sensor and the constant pressure setpoint value so as to compensate for the measured pressure variations due to the reliefs of the circumferential surface bearing said tire and to regulate the flow rate of depositing the extruded material according to said reliefs.

[0055] Advantageously, the electronic control unit's control loop includes a module for retrieving pressure values ​​measured by the pressure sensor, a module for comparing the pressure value measured by the pressure sensor with a constant pressure setpoint value, and a module for controlling the movement of the pressure regulating element based on the comparison between the measured pressure value and the constant pressure setpoint value.

[0056] When the measured pressure is greater than the said pressure setpoint value, the control module is configured to command the pressure regulating device so as to lower the pressure in the extruder in real time, and consequently the deposition rate of the extruded material, and when the measured pressure is less than the said pressure setpoint value, the control module is configured to command the pressure regulating device so as to increase the pressure in the extruder in real time, and consequently the deposition rate of the extruded material.

[0057] The pressure setpoint response time is fast, allowing for real-time adjustment of the extruded material quantity. The material extrusion rate is regulated by controlling the pressure within the extruder chamber.

[0058] The control module for the movement of the pressure regulating device has a bandwidth greater than or equal to 1000Hz.

[0059] According to one embodiment, the pressure regulating element comprises a worm screw that rotates about the extension axis in a conduit supplying the molten material rod to a chamber upstream of the molten material receiving chamber of the printing nozzle.

[0060] In this case, when the measured pressure is greater than the said pressure setpoint value, the control module is configured to command the deceleration of the rotational speed of the screw of the pressure regulating element and when the measured pressure is less than the said pressure setpoint value, the control module is configured to command the acceleration of the rotational speed of the screw of the pressure regulating element.

[0061] Indeed, increasing the rotational speed of the worm screw causes an increase in pressure inside the chamber. Conversely, decelerating the worm screw causes a decrease in pressure inside the chamber.

[0062] For example, the pressure setpoint value is between 50 bars and 300 bars, preferably between 60 bars and 120 bars.

[0063] The worm gear includes a motor with a bandwidth greater than or equal to 200 Hz.

[0064] The combination of the pressure sensor bandwidth greater than 200 Hz, the screw drive bandwidth greater than 200 Hz and the speed control bandwidth greater than or equal to 1000 Hz makes it possible to obtain a pressure control loop with a bandwidth ranging from 0 Hz to at least 100 Hz.

[0065] According to one embodiment, the printing module includes a nozzle closure device comprising a movable closure means between a closure position and a plurality of nozzle orifice opening positions, and an actuator for controlling the movement of the closure means between the closure and opening positions.

[0066] For example, the obturating means is in the form of a needle actuated by the actuator to move the obturating means in translation along the extension axis.

[0067] The needle valve allows for clean stops in the flow of molten material, without burrs, and clean restarts of said flow.

[0068] The needle stroke is preferentially dependent on the material flow rate and variable with the objective of matching the opening of the distribution orifice to the rheology of the thermoplastic material "TPE" in order to allow the pressure regulator to manage the transient phases.

[0069] This variable stroke advantageously limits the sudden pressure drop at needle opening, which would otherwise result in over-extrusion followed by under-extrusion with each sealing cycle. This is highly detrimental to the infill rate and lateral cohesion between the rods. For example, this stroke can vary between 0.5 mm and 0.8 mm depending on the viscosity of the printed material and the desired flow rate. Such a device allows for continuous or fragmented material deposition on curved surfaces with precise control over the volume and its distribution across the tread. In other words, this device allows for depositing the right amount of material in the right place.

[0070] Variable stroke sealing needles ensure the cross-section of the rods laid during transient phases, i.e. the opening and closing of the distribution orifice, depending on the printing pressure, the viscosity of the deposited material and the thickness of the layers.

[0071] For example, the actuator includes a piezoelectric device (not shown) to close or open the distribution orifice of the corresponding nozzle.

[0072] Alternatively, any other means of closure could be provided for each of the nozzles, such as a valve.

[0073] According to one embodiment, the device comprises a plurality of printing modules fixed on the mobile support and arranged circumferentially around the tire, and offset along the longitudinal axis by a longitudinal pitch from each other, each printing module extending along an extension axis, for example a radial axis perpendicular to the axis of rotation of the tire or an axis inclined with respect to the radial axis.

[0074] Having individual modules, each containing an extruder and a sealing needle, allows for precise control of the material deposition rate at variable speeds. Complex shapes can also be created.

[0075] Preferably, the printing modules are distributed circumferentially and not regularly on the mobile support, i.e., the circumferential gap between two adjacent printing modules is different.

[0076] Alternatively, the printing modules could be evenly distributed circumferentially around the mobile support. For example, the mobile support could be shaped like an arch extending over an angular range of up to 360°.

[0077] The arch shape allows for a "gravity-fed" type feeding at the inlet of the extrusion screw.

[0078] The support is mobile in translation relative to the base along the longitudinal axis, for example, on parallel longitudinal guide rails.

[0079] In the case where there are several printing modules, the means of sealing all the printing modules can be controlled independently of each other.

[0080] In cases where multiple printing modules are used, the pressure regulator associated with each extruder allows for independent pressure control. The variable distance between extruders along the extension axis enables variations in cross-section, facilitating complex and more resilient stacking strategies. Each nozzle has its own shut-off mechanism configured to interrupt the flow of molten material through its corresponding nozzle dispensing orifice.

[0081] Each of the nozzles can be interrupted independently and reactively, so as to generate any sculpture on the wheel in a short time, preferably less than 15 minutes.

[0082] Such a loading time corresponds to a material deposit rate of between 5kg / h and 15kg / h, preferably equal to 10kg / h.

[0083] The shutter frequency is between 0.05Hz and 20Hz, for example equal to 0.1 Hz for a continuous underlayer and 10Hz on average for a sculpture featuring many blocks of gum.

[0084] Thus, each of the material depositing nozzles is configured to deposit molten material onto the tire, in particular its circumferential carrier surface, which can be driven in rotation continuously or discontinuously around an axis of rotation in a single direction of rotation.

[0085] "Continuous rotation" refers to rotation in a single direction, without interruption and at a constant speed. "Discontinuous rotation" refers to rotation in a single direction at a variable speed during material deposition.

[0086] By "opening position" of said distribution orifice, we mean a fully open position of the distribution orifice, but also intermediate positions in which the distribution orifice is partially open.

[0087] The extruders can be fed centrally or individually with another material, allowing the characteristics of the plastic to be varied depending on its position in the tread. This makes it possible to produce multi-material treads.

[0088] The printing modules are mobile independently of each other along a radial axis specific to each printing module and simultaneously with the other modules along the longitudinal axis parallel to the axis of rotation of the tire.

[0089] The tread is manufactured by depositing extruded material layer by layer onto the carrier surface of the tire.

[0090] The extruded material either inter-diffused or heat-welded by inter-diffusion onto the previously deposited layer of material and solidified when the temperature dropped.

[0091] Each of the nozzles is configured to deposit the molten material onto the bearing surface of the mobile tire rotating around a horizontal axis of rotation.

[0092] The extruders are mounted on the support and can move longitudinally with a variable distance between each extruder along the radial axis, allowing for helical laying or cross-section variation during circumferential and helical laying.

[0093] According to one embodiment, the displacement member comprises a base fixed to the support, a worm screw rotated by an electric motor and a fixing lug integral with the extruder and comprising a tapped hole cooperating with the thread of the worm screw.

[0094] Thus, the rotation of the worm screw causes the extruder to move along its associated extension axis. For example, the dispensing orifice of each material depositing nozzle has a dimension between 0.6 mm and 1.6 mm, preferably between 0.6 mm and 0.8 mm to create a 1 mm wide material deposit, and preferably between 1 mm and 1.6 mm to create a 2 mm wide material deposit.

[0095] For example, the distribution orifice of each nozzle has a rectangular or circular cross-section. A rectangular cross-section improves the level of detail in the sculpture and the quality of the breaks.

[0096] Material dispensing nozzles can be identical to each other or different, in their dimensions, such as the diameter of the dispensing orifice, the length of the conduit located after the needle seat or their external dimension.

[0097] For example, the rotating drive element is in the form of a rotating drum or cylinder cooperating with the wheel hub and configured to rotate the tire via the wheel hub.

[0098] For example, a tire can be configured to be mounted on a so-called "conventional" wheel, which includes a rim and a mounting hub. The tire, or pneumatic tire, is mounted on the rim. The tire comprises a circumferential tread surface, a tread itself, and two sidewalls surrounding the tread surface on either side. The rim is preferably the final rim intended for mounting on a motor vehicle. The mounting hub forms the interface between the wheel and the vehicle. The tire is subjected to internal pressure, either directly or indirectly, via an inner tube inflated to a recommended or lower nominal inflation pressure.

[0099] The wheel can be a wheel with or without an inner tube, called "tubeless" in Anglo-Saxon terms.

[0100] Alternatively, the tire can be configured to be mounted on an "integral" type wheel comprising a radial support structure around which the tire or solid tire is fixed. This structure includes a support radially external to the support structure. The support extends around the entire circumference of the support structure and includes an external peripheral contour forming a circumferential bearing surface for the tread. The tread is structurally integrated into the support via a tread bearing surface. The solid tire is not subjected to internal pressure. The radial support structure includes a mounting hub for attaching the wheel to a vehicle.

[0101] According to a first application example, in the case where there are several printing modules, each printing module is configured to deposit extruded material forming the tread on the tire, in particular its circumferential carrier surface, following a circumferential line of material Lj.

[0102] Material deposition along a "circumferential line of material" Lj means material deposition along a circular path of the tire, with j ranging from 1 to x, x being the total number of material lines.

[0103] By "layer of material" Ch, we mean the set of circumferential lines of material Lj side by side across the entire width of the tread to be manufactured, with h ranging from 1 to y, y being the total number of layers of material to form the total thickness of the desired tread.

[0104] A layer of material C corresponds to a thickness of molten material deposit.

[0105] According to this first example, the lines Lj have a constant width and the layers Ch have a constant thickness.

[0106] In a second application example, each printing module is configured to deposit extruded material forming the tread onto the tire, specifically its circumferential carrier surface, along a circumferential line of material L. This is achieved by varying the pressure inside the printing nozzle chamber to obtain variable line widths Lj. Thus, the lines Lj have a variable width, while the layers Ch have a constant thickness. In a third application example, where there are multiple printing modules, each module is configured to deposit extruded material forming the tread onto the tire, specifically its circumferential carrier surface, along a circumferential line of material L. This is achieved by varying the radial distance between the extruder and the carrier surface to obtain variable layer thicknesses Ch.Thus, the Lj lines have a constant width and the Ch layers have a variable thickness.

[0107] Preferably, the start of each line Lj is offset along the transverse axis, in order to avoid stress concentrations.

[0108] According to one example, the material is deposited in circumferential lines Lj parallel to the direction of movement of the tire.

[0109] In another example, the material is deposited in lines Lj inclined relative to the direction of travel of the tire. In other words, the material is deposited in a helix by movement of the support along the longitudinal axis combined with the movement of the extruders along the radial axis and the rotation of the tire around its axis of rotation.

[0110] In another example, the material is deposited in inclined and intersecting lines Lj relative to the direction of travel of the tire. In other words, the material is deposited in a crossed helix by moving the support along the longitudinal axis, from right to left and then from left to right, combined with moving the extruders along the radial axis and rotating the tire around its axis of rotation.

[0111] For example, during a complete tire rotation, the material deposition nozzles of each print module are activated simultaneously to deposit material along a circumferential line on the lower material line. Then, the support is moved longitudinally along the tire's axis of rotation after each complete tire rotation, so that the material deposition nozzles deposit material along the adjacent material line, and so on until the desired tread pattern is achieved. Thus, a portion of the layer, dependent on the number of extruders in use, is produced with each complete tire rotation. If the number of lines to be printed exceeds the number of print modules, the support is offset along the tire's axis of rotation by the width of the entire set of print modules to continue depositing material on subsequent circumferential lines.In this case, an entire layer is created during several complete rotations of the tire.

[0112] In another aspect, the invention relates to an additive manufacturing process implemented by the additive manufacturing device as described above and comprising a method for regulating the pressure in the extruder of the printing module, in which the pressure regulating element inside the extruder is controlled in real time, via a pressure control loop, according to the pressure measured by the pressure sensor and a constant pressure setpoint value. The pressure control loop has a bandwidth ranging from 0 Hz to at least 100 Hz.

[0113] The process is configured to smooth or eliminate reliefs present on a circumferential surface bearing said tire, said reliefs being progressively varied along the circumferential surface of the bearing surface.

[0114] Reliefs are defined by an amplitude less than 60% of the nominal layer height, that is to say an altitude value, in absolute value, according to the radial dimension between the circumferential carrier surface and a hollow or a bump less than 60% of the nominal layer height.

[0115] The nominal layer height corresponds to the radial dimension of the deposited extruded material layer. For example, the nominal layer height is equal to 0.7 mm.

[0116] The relief length is equal to 6mm for a layer printing speed less than or equal to 300 mm / s.

[0117] The length is understood in the circumferential direction of the bearing surface.

[0118] By "real time," we mean a response time of less than 1ms for a molten material deposition speed between 0.01m / s and 0.3m / s. Pressure regulation in the extruder chamber allows for the application pressure of the molten material to be best suited to the surface relief, thus smoothing out reliefs with a height less than the thickness of a layer.

[0119] Such pressure regulation thus makes it possible to obtain a good level of filling, between 99.5% and 100%, and good cohesion between the layers.

[0120] The pressure setpoint value is a theoretical value, determined in order to provide synchronous and appropriate dynamic variations for the pattern to be printed.

[0121] Advantageously, according to the method:

[0122] - we retrieve pressure values ​​measured by the pressure sensor;

[0123] - the pressure value measured by the pressure sensor is compared with a pressure setpoint value; and

[0124] - The movement of the pressure regulating element is controlled according to the comparison between the measured pressure value and the constant pressure setpoint value. When the measured pressure is greater than said pressure setpoint value, the pressure regulating element is controlled so as to lower the pressure in the extruder in real time, and consequently the deposition rate of an extruded material comprising a thermoplastic elastomer material having a viscosity between 34 Pa.s and 11000 Pa.s. When the measured pressure is less than said pressure setpoint value, the pressure regulating element is controlled so as to increase the pressure in the extruder in real time, and consequently the deposition rate of the extruded material.

[0125] For example, when the measured pressure is greater than said pressure setpoint value, the rotational speed of a screw of the pressure regulating member rotating about the extension axis in a duct supplying the molten material rod to a chamber upstream of the molten material receiving chamber of the printing nozzle is decelerated, and when the measured pressure is less than said pressure setpoint value, the rotational speed of said screw of the pressure regulating member is accelerated.

[0126] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0127] [Fig 1] represents very schematically an additive manufacturing device for a tread according to the invention configured to manufacture a tread on a tire of a wheel according to a first embodiment;

[0128] [Fig 2] illustrates another example of a wheel on which the additive manufacturing device of Figure 1 can be used;

[0129] [Fig 3] illustrates a detail of a material deposition module of the additive manufacturing device in Figure 1;

[0130] [Fig 4] is a cross-sectional view of the material deposition module in Figure 3 showing an example of a temporary shut-off system for the dispensing orifice of a material deposition nozzle;

[0131] [Fig 5A], [Fig 5B], [Fig 5C] are examples of reliefs printed by the additive manufacturing device in Figure 1; and

[0132] [Fig 6A], [Fig 6B], and [Fig 6C] are examples of printing line inclination by the additive manufacturing device in Figure 1;

[0133] [Fig 7] illustrates the steps of a pressure regulation process in the extruder implemented by an electronic control unit of the manufacturing device in Figure 1; and

[0134] [Fig 8A], [Fig 8B] and [Fig 8C] schematically represent the steps of depositing the extruded material onto the carrier surface of the tire of the additive manufacturing device in Figures 1 to 4.

[0135] In the following description, we consider an orthonormal basis X, Y, Z, defined with respect to the additive manufacturing device 10, in which we find:

[0136] - a longitudinal axis X, horizontal and extending from back to front on figure 1;

[0137] - a horizontal transverse axis Y, perpendicular to the longitudinal axis X and extending from left to right in Figure 1; and

[0138] - a vertical axis Z, orthogonal to the longitudinal axis X and transverse axis Y and extending from bottom to top in figure 1.

[0139] As illustrated in Figure 1, a wheel assembly 1 comprises a rim 2 including a mounting hub 3 and a tire 4 or pneumatic tire mounted on the rim 2. The tire 4 comprises a tread carrier surface 5, a tread 6 and two sidewalls 7 surrounding the tread carrier surface 5 on either side, only one of which is visible in Figure 1.

[0140] Rim 2 is preferably the final rim intended to be mounted on a motor vehicle.

[0141] The mounting hub 3 forms the mounting interface between the wheel 1 and the vehicle.

[0142] The fixing hub 3 here defines a hollow fixing cylinder in which a wheel axle (not referenced) can be housed.

[0143] Tire 4 is here subjected to internal pressure via an inner tube (not shown) inflated to a recommended or lower nominal inflation pressure.

[0144] Alternatively, the assembled unit 1 could be a tubeless wheel, also known as a "tubeless" wheel, comprising an insert (not shown) made of several layers of expanded plastic to replace the inner tube.

[0145] The assembled unit 1 could also be a so-called "airless" tire. The tread 6 comprises two lateral surfaces (not referenced), an inner surface (not visible) integral with the tread carrier surface 5 and a tread surface 6a opposite the inner surface and intended to come into contact with a road surface S when the wheel 1 rolls.

[0146] The tread 6 comprises a plurality of cutouts or carvings extending over at least one of its lateral surfaces.

[0147] Rim 2 here forms a radial load-bearing structure for tire 4.

[0148] As illustrated in Figure 1, an additive manufacturing device 10 for a tread 6 is configured to deposit an extruded material forming the tread 6 onto a circumferential carrier surface 5 of the tire 4 of the wheel 1.

[0149] In general, the additive manufacturing device 10 for a tread 6 is configured to deposit an extruded material forming the tread 6 onto a tire 4. Indeed, it would be possible to plan for the manufacturing of the tread 6 on a tire 4 not mounted on a wheel.

[0150] It is also possible to plan for the application of a new tread 6 over a worn tread. In this case, the bearing surface corresponds to the worn tread.

[0151] The additive manufacturing device 10 includes a fixed base 12 fixed to the ground S and a printing module 20 mounted in translation relative to said fixed base 12.

[0152] In no way limiting, the fixed base 12 includes a base 14 fixed to the ground S and a mobile support 16 for fixing the material depositing module 20.

[0153] The printing module 20 is positioned here above the wheel 1, and in particular above the tread of the tire 4.

[0154] The printing module 20 extends along an extension axis Ai, here radial with respect to the pneumatic 4. Alternatively, it could be provided that the printing module 20 extends along an extension axis inclined with respect to the radial axis with respect to the pneumatic 4. Figures 3 and 4 illustrate an example of a printing module 20 that can be used.

[0155] As illustrated in detail in Figures 3 and 4, the printing module 20 includes:

[0156] - an extruder 21 regulated to a set pressure S between 50 bar and 300 bar, preferably between 60 bar and 120 bar, movable along the extension axis Ai, here radial to the pneumatic 4 and configured to produce a rod of molten material, for example from granules of material, preferably made of plastic, for example thermoplastic elastomer, acronym TPE. The granules of material are therefore hot extruded;

[0157] - a material dispensing nozzle 22 fed with a molten material stream by the extruder 21. The material dispensing nozzle 22, or nozzle, comprises a chamber 22a for receiving the molten material from the associated extruder 21 and a distribution orifice 22b communicating with the chamber 22a. The distribution orifice 22b has a dimension between 0.6 mm and 1.6 mm, preferably between 0.6 mm and 0.8 mm for a 1 mm wide material deposit, and preferably between 1 mm and 1.6 mm for a 2 mm wide material deposit. The distribution orifice 22a of each nozzle has a rectangular or circular cross-section. A rectangular cross-section improves the level of detail in the sculpture and the quality of the discontinuities;

[0158] - a displacement member 23 of the extruder 21 along the extension axis Ai. The displacement member 23 here comprises a base 23a fixed to the movable support 16, a worm screw 23b rotated by an electric motor 23c and a fixing lug 23d integral with the extruder 21 and comprising a thread cooperating with the thread of the worm screw 23b. Thus, the rotation of the worm screw causes the displacement of the extruder 21 along the associated extension axis Ai;

[0159] - a pressure regulating device 24 inside the extruder 21.

[0160] The pressure regulating organ 24 includes a worm screw 24a movable about the radial axis Ai in a conduit 24b supplying the molten material rod to a chamber 24c upstream of the chamber 22a receiving the molten material from the printing nozzle 22 and a pressure sensor 24d configured to measure pressure values ​​Pmes in the chamber 24c.

[0161] The additive manufacturing device 10 includes an electronic control unit 30 configured to control the pressure regulating organ 24 inside the extruder 21.

[0162] The electronic control unit 30 includes a control loop 3 1 comprising a module 32 for recovering the pressure values ​​measured Pmes by the pressure sensor 24d.

[0163] The molten material preferably comprises a thermoplastic elastomer material having a viscosity between 34 Pa.s and 11000 Pa.s.

[0164] The control loop 31 of the electronic control unit 30 further includes a module 34 for comparing the pressure value measured Pmes by the pressure sensor 24d with a threshold value S corresponding to a constant pressure setpoint.

[0165] The control loop 31 of the electronic control unit 30 includes a control module 36 for the movement of the pressure regulating element 24, here the worm gear 24a, based on the comparison between the measured pressure value Pmes and the threshold value S.

[0166] When the measured pressure Pmes is higher than the setpoint pressure S, this means that the surface has a material bulge, such as a bump. In this case, the control module 36 commands the deceleration of the rotational speed of the screw 24a of the pressure regulating element 24 in order to lower the pressure in the extruder in real time, and consequently the deposition rate of the extruded material.

[0167] When the measured pressure Pmes is lower than the setpoint pressure S, this means that the surface exhibits material reduction, such as a depression. In this case, the control module 36 controls the acceleration and deceleration of the rotational speed of the screw 24a of the pressure regulating element 24 in order to increase the pressure in the extruder in real time, and consequently the deposition rate of the extruded material.

[0168] Indeed, the acceleration of the rotational speed of the worm screw 24a causes an increase in pressure inside said chamber 24c. Conversely, the deceleration of the worm screw 24a causes a decrease in pressure inside said chamber 24c.

[0169] The pressure setpoint response time is fast, allowing for real-time adjustment of the extruded material quantity. The extruded material deposition rate is regulated by pressure control within chamber 24c of extruder 21.

[0170] Each extruder is configured to deposit molten material with a flow rate of 1000g / h.

[0171] The pressure regulation in chamber 24c of extruder 21 allows obtaining an application pressure of the molten material that is as suitable as possible for the relief of the carrier surface.

[0172] Such pressure regulation thus makes it possible to obtain a good level of filling, between 99.5% and 100%, and good cohesion between the layers.

[0173] Without limitation, the printing module 20 includes a nozzle 22 material dispensing device 25. The nozzle 25 includes a movable shutting means 25a between a shutting position and an opening position of the dispensing orifice 22b, and an actuator 25b for controlling the movement of the shutting means 25a between the shutting and opening positions. The shutting means 25a can be controlled independently of each other.

[0174] Thus, each nozzle 22 includes its own shut-off means 25 configured to interrupt the flow of molten material through the distribution orifice 22b of the corresponding nozzle.

[0175] Each of the nozzles 22 can be interrupted independently and reactively, so as to generate any design on the wheel 1 in a short time, preferably less than 15 minutes. Such a loading time corresponds to a material deposition rate of between 5 kg / h and 15 kg / h, preferably equal to 10 kg / h.

[0176] The shutter frequency is between 0.05Hz and 20Hz, for example equal to 0.1 Hz for a continuous underlayer and 10Hz on average for a sculpture featuring many blocks of gum.

[0177] In the example illustrated in Figure 4, the obturating means 25a is in the form of a needle actuated by the actuator 25b to move the obturating means in translation along the radial axis Ai.

[0178] The actuator 25b includes, for example, a piezoelectric device (not shown) for closing or opening the distribution orifice 22b of the corresponding nozzle 22.

[0179] The 25a needle valve allows for clean stops of the molten material flow, without burrs, and clean restarts of said flow.

[0180] The needle stroke is primarily dependent on the material flow rate and is variable in order to match the dispensing orifice opening to the rheology of the TPE, allowing the pressure regulator to manage transient phases. This variable stroke advantageously limits the sudden pressure drop at needle opening, which would otherwise result in over-extrusion followed by under-extrusion with each capping cycle (very detrimental to the fill rate and lateral cohesion between the rods). For example, this stroke can vary between 0.5 mm and 0.8 mm depending on the viscosity of the printed material and the desired flow rate.

[0181] Alternatively, any other means of closure could be provided for each of the nozzles, such as a valve.

[0182] It could also be envisaged that the printing module 20 would be without a sealing device. In this case, the extrusion of extruded material is continuous.

[0183] The terms "downstream" and "upstream" are defined by considering the direction of flow of matter.

[0184] Alternatively, a plurality of printing modules 20 could be provided, fixed to the mobile support 16 and arranged circumferentially around the tire 4, with a circumferential distance that may be different or the same between two adjacent printing modules. The printing modules 20 could be offset along the longitudinal axis X by a distance or longitudinal spacing from each other.

[0185] In this case, the 21 extruders of the printing modules can be fed centrally or individually with a different material, making it possible to vary the characteristics of the plastic material depending on its position in the tread. This allows for the creation of multi-material treads.

[0186] The material bead, for example, has a thickness of 0.7 mm and a width of 2 mm when deposited on the carrier surface. Indeed, before deposition, the material bead has a cross-section identical to that of the material dispensing nozzle. The material bead then has a circular cross-section when the material dispensing nozzle has a circular cross-section.

[0187] By "width" we mean the direction in the direction parallel to the axis of rotation XX of the tire 4.

[0188] By "thickness" or "height" we mean the direction along the radial direction to the axis of rotation XX of the tire 4.

[0189] In the case where there are several printing modules 20, said modules are mobile independently of each other along a radial axis Ai specific to each printing module and simultaneously with the other modules along the longitudinal axis X parallel to the axis of rotation XX of the tire 4.

[0190] In the case where there are several printing modules 20, thanks to the pressure regulation organ 24 associated with each extruder 21, the independent pressure regulation from one extruder to another and the variable distance along the extension axis Ai between the extruders allows for variations in cross-sections enabling complex and more resilient stacking strategies.

[0191] The tread 6 is manufactured by depositing extruded material layer by layer onto the carrier surface 5 of the tire 4. The extruded material melts onto the previously deposited layer and solidifies as the temperature drops. Each of the nozzles 22 is configured to deposit the molten material onto the carrier surface 5 of the tire 4, which rotates about a horizontal axis of rotation XX.

[0192] Additive manufacturing on a support, here the carrier surface 5 of the tire 4, or more generally the tire 4, set in continuous rotation, makes it possible to manufacture or completely reconstitute the tread 6 over its entire circumference.

[0193] For this purpose, the additive manufacturing device 10 includes a drive element 15 for rotating the tire 4 around the axis of rotation X-X'.

[0194] As illustrated in Figure 2, the rotational drive element 15 is in the form of a rotating drum or cylinder cooperating with the wheel hub 3 and configured to rotate the tire 4 via the wheel hub 3.

[0195] These variants are interesting in cases where it is necessary to manufacture tread 2 without removing wheel 1 from the vehicle.

[0196] The tire 4 here has only one degree of freedom, namely around its axis of rotation XX. In other words, the tire 4 is not free to move in translation along any of the axes X, Y or Z.

[0197] The additive manufacturing device 10 for a tread can also be used to manufacture or reload a tread 6' on a carrier surface 5' of a tire 4' of an integral wheel 1' as illustrated in Figure 2.

[0198] The integral wheel 1' here comprises a radial load-bearing structure 2' around which is fixed a tire 4' or solid tire comprising a support 7' radially external to the load-bearing structure 2'. The support 7' extends over the entire circumference of the load-bearing structure 2' and carries the tread 6'. The tread 6' is here structurally integrated into the support 7' by means of a tread-bearing surface 5' forming a peripheral external contour of the radial load-bearing structure 2'.

[0199] The solid tire 4' is not subjected to internal pressure. As illustrated in Figure 2, the radial support structure 2' includes a mounting hub 3' for attaching the wheel 1' to a vehicle.

[0200] The 3' fixing hub here defined as a hollow fixing cylinder in which a wheel axle (not shown) can be housed.

[0201] The radial load-bearing structure 2' is, for example, made of glass fiber reinforced plastic material.

[0202] The supporting structure 2' here includes a plurality of poles or stays 8' connecting the hub 3' to the support 7'.

[0203] As illustrated in Figure 2, the supporting structure 2' comprises five 8' rods. Alternatively, a number of 8' rods between three and nine could be used.

[0204] Openings or windows 9' are defined between two adj acent bars 8'. The openings 9' are here regularly distributed circumferentially.

[0205] The 9' openings here have ovoid profiles. Alternatively, other profile shapes could be used for the 9' openings.

[0206] The load-bearing structure 2' and the support 7' here comprise a network or three-dimensional structure of beams or trusses.

[0207] Alternatively, the radial support structure 2' could be provided for to include a plurality of radially arranged slats to support the tire 4' and in particular the support 7'.

[0208] A first example of material deposition is illustrated with reference to figure 5A.

[0209] In this example, each printing module 20 is configured to deposit extruded material forming the tread 6 onto the tire 4, including its circumferential carrier surface 5, along a circumferential line of material Lj.

[0210] By material deposition along a "circumferential line of material" Lj, we mean the deposition of material along a circular trajectory of the tire 4, with j ranging from 1 to x, x being the total number of lines of material.

[0211] By "layer of material" Ch, we mean the set of circumferential lines of material Lj side by side over the entire width of the tread 6 to be manufactured, with h ranging from 1 to y, y being the total number of layers of material to form the total thickness of the desired tread 6.

[0212] A layer of material C corresponds to a thickness of molten material deposit.

[0213] The Lj lines have a constant width and the Ch layers have a constant thickness.

[0214] A second example of material deposition is illustrated with reference to Figure 5B.

[0215] In this example, each printing module 20 is configured to deposit extruded material forming the tread 6 onto the tire 4, including its circumferential carrier surface 5, along a circumferential line of material L, by varying the pressure inside the chamber 22a of the printing nozzle 22 in order to obtain variable line widths Lj.

[0216] The Lj lines have a variable width and the Ch layers have a constant thickness.

[0217] A third example of material deposition is illustrated with reference to Figure 5C.

[0218] In this example, each printing module 20 is configured to deposit extruded material forming the tread 6 onto the tire 4, specifically its circumferential carrier surface 5, along a circumferential line of material L, by varying the radial distance Ai between the extruder 21 and the carrier surface 5 in order to obtain variable layer thicknesses Ch.

[0219] The Lj lines have a constant width and the Ch layers have a variable thickness.

[0220] Figures 6A, 6B, and 6C are examples of print line inclination using the additive manufacturing device shown in Figure 1. In all the illustrated examples, the starting point of each line Lj is offset along the transverse Y axis to avoid stress concentrations.

[0221] In the example illustrated in Figure 6A, the material is deposited in circumferential lines Lj parallel to the direction of travel D of the tire 4. In the example illustrated in Figure 6B, the material is deposited in lines Lj inclined with respect to the direction of travel D of the tire 4. In other words, the material is deposited in a helix by displacement of the support 16 along the longitudinal axis X combined with the displacement of the extruders 21 along the radial axis Ai and the rotation of the carrier surface 5.

[0222] In the example illustrated in Figure 6C, the material is deposited in inclined and crossed lines Lj with respect to the direction of travel D of the tire 4. In other words, the material is deposited in a crossed helix by displacement of the support 16 along the longitudinal axis X, from right to left and then from left to right, combined with the displacement of the extruders 21 along the extension axis Ai and the rotation of the carrier surface 5.

[0223] During a complete rotation of the tire, the material depositing nozzles 22 of each printing module 20 are actuated simultaneously to deposit material along a circumferential line of material on the lower material line, then the movable support 16 is moved in longitudinal translation along the rotation axis XX of the tire 4 after each complete rotation of the tire, so that the material depositing nozzles deposit material along the adjacent material line and so on until the desired tread is obtained.

[0224] Thus, a portion of the layer dependent on the number of extruders used is produced with each complete rotation of the tire.

[0225] In the case where the number of lines to be printed is greater than the number of printing modules 20, the mobile support 16 is offset along the axis of rotation XX of the tire 4 by the width of the set of printing modules 20, i in order to continue the deposition of the material on the following circumferential lines.

[0226] In this case, an entire layer is created during several complete rotations of the tire.

[0227] Figure 7 is a flowchart illustrating the steps of a pressure regulation process 100 within the extruder 21 of the additive manufacturing device. The pressure regulation process 100 is part of an additive manufacturing process implemented by the additive manufacturing device 10, which will not be described further.

[0228] The pressure regulation process 100 operates via the pressure regulation loop 31 of the control unit 30 described with reference to Figures 3 and 4.

[0229] The pressure regulation process 100 includes a step 102 of retrieving the pressure values ​​measured Pmes by the pressure sensor 24d.

[0230] The pressure regulation process 100 further includes a step 104 of comparing the measured pressure value Pmes by the pressure sensor 24d with a threshold value S corresponding to a constant pressure setpoint.

[0231] The pressure regulation process 100 includes a step 106 of controlling the displacement of the pressure regulating element 24, here the worm gear 24a, according to the comparison between the measured pressure value Pmes and the threshold value S.

[0232] When the measured pressure Pmes is higher than the setpoint pressure S, this means that the surface has a material bulge, such as a bump. In this case, in step 106a, the rotational speed of the screw 24a of the pressure regulating device 24 is decelerated in order to lower the pressure in the extruder in real time, and consequently the rate at which the extruded material is deposited.

[0233] When the measured pressure Pmes is lower than the setpoint pressure S, this means that the surface exhibits material reduction, such as a depression. In this case, at step 106b, the rotational speed of the screw 24a of the pressure regulating device 24 is accelerated in order to increase the pressure in the extruder in real time, and consequently the deposition rate of the extruded material.

[0234] The additive manufacturing device is compact and autonomous and can print treads on new or retreaded tires as well as on "air-less" wheels in a short time of between 10 and 20 minutes and without a vulcanization step, while allowing the deposition of an extruded material on a carrier surface of any curve with a high infill rate of between 99.5% and 100%.

[0235] The reliefs R present on the circumferential carrier surface 5 and which the pressure regulation loop 31 as described above seeks to erase or smooth, are defined, with reference to figures 8A to 8C, by an amplitude A less than 60% of the nominal layer height H nom, that is to say an altitude value, in absolute value, according to the radial dimension between the circumferential carrier surface and a trough or a bump less than 60% of the nominal layer height.

[0236] The nominal layer height H nom corresponds to the radial dimension of the deposited extruded material layer. For example, the nominal layer height is equal to 0.7 mm.

[0237] The length L of the relief is equal to 6mm for a layer printing speed less than or equal to 300 mm / s.

[0238] The length L is understood in the circumferential direction of the bearing surface.

[0239] The said reliefs R are progressively varied along the circumferential bearing surface 5 of the tire.

[0240] The pressure regulation unit allows such reliefs to be corrected or smoothed out in real time using the extruded material as defined.

[0241] The pressure regulation loop 31 has a bandwidth ranging from 0Hz to at least 100Hz

[0242] The bandwidth of the 24d pressure sensor is preferably greater than 200 Hz.

[0243] The control module 36 for the movement of the pressure regulating organ has a bandwidth greater than or equal to 1000Hz.

[0244] The 23b auger includes a motor with a bandwidth greater than or equal to 200 Hz. The combination of the pressure sensor bandwidth greater than 200 Hz, the auger motor bandwidth greater than 200 Hz and the speed control bandwidth greater than or equal to 1000 Hz makes it possible to obtain a pressure control loop with a bandwidth ranging from 0 Hz to at least 100 Hz.

[0245] As illustrated in Figure 8A, the nozzle 22 of the extruder 21 deposits a layer Ch of extruded material onto the circumferential carrier surface 5 of the tire 1, upstream of a relief R.

[0246] The pressure measured Pmes by the pressure sensor 24d is measured continuously and is continuously compared with a threshold value S corresponding to a constant pressure setpoint.

[0247] When the extruder nozzle 22 begins depositing extruded material into the relief R, here a hollow, the measured pressure Pmes drops and becomes lower than the setpoint pressure S. In this case, the control module 36 commands the acceleration of the rotational speed of the worm gear 24a of the pressure regulating element 24 in order to increase the pressure in the extruder in real time, and consequently the deposition rate of the extruded material. The relief R is thus filled as can be seen in Figure 8C.

[0248] Similarly, if the relief R were an elevation of material such as a bump, the measured pressure Pmes would be greater than the setpoint pressure S. In this case, the control module 36 controls the deceleration of the rotation speed of the worm screw 24a of the pressure regulating member 24 so as to lower in real time the pressure in the extruder, and consequently the flow rate of the deposited extruded material.

[0249] Pressure regulation in the extruder chamber allows for the application pressure of the molten material to be as suitable as possible for the relief of the carrier surface, and thus to correct or smooth out reliefs with a height less than the height of a layer.

[0250] Such pressure regulation thus makes it possible to obtain a good level of filling, between 99.5% and 100%, and good cohesion between the layers.

Claims

1. CLAIMS 1. Device (10) for additive manufacturing all or part of a tread (6, 6') of a tire (4, 4') configured to deposit a layer (Ch) of extruded material comprising a thermoplastic elastomer material having a viscosity between 34 Pa.s and 10000 Pa.s, forming the tread (6) on a circumferential carrier surface (5, 5') of said tire (4, 4') having a plurality of reliefs (R) with progressive variation along the circumferential carrier surface (5, 5'), the reliefs (R) being defined by an amplitude (A) less than 60% of the nominal height (Hnom) of the layer (Ch), and a length (L) equal to 6 mm for a layer printing speed less than or equal to 300 mm / s, said device (10) being configured to smooth said plurality of reliefs and comprising: - a rotating drive element (15) of the tire (4, 4') capable of driving said tire (4, 4') around a horizontal axis of rotation (XX); - a fixed base (12) fixed to the ground (S); - a support (16) that is mobile in translation relative to said base (12); - at least one printing module (20) fixed to the mobile support (16) and comprising: - an extruder (21) movable relative to the pneumatic (4, 4') along an extension axis (Ai) and configured to produce a rod of molten material; - a material deposit nozzle (22) supplied with molten material by the extruder (21) comprising at least one distribution orifice (22b) and a molten material receiving chamber (22a) from the associated extruder (21) in fluidic communication with said distribution orifice (22b); - a displacement element (23) for the extruder (21) along the extension axis (Ai), characterized in that it comprises: - a pressure regulating device (24) inside the extruder (21) comprising a pressure sensor (24d) configured to measure pressure values ​​(Pmes) in a chamber (24c) upstream of the molten material receiving chamber (22a); and - an electronic control unit (30) comprising a pressure regulation loop (31) configured to control in real time the pressure regulation device (24) inside the extruder (21) as a function of the pressure measured (Pmes) by the pressure sensor (24d) and a constant pressure setpoint value (S), the pressure regulation loop having a bandwidth from 0Hz to at least 100Hz.

2. Device (10) according to claim 1, wherein the pressure regulation loop (31) of the electronic control unit (30) is configured to control in real time the pressure regulation member (24) inside the extruder (21) as a function of the pressure measured (Pmes) by the pressure sensor (24d) and the constant pressure setpoint value (S) so as to compensate for the measured pressure variations due to the reliefs of the circumferential surface bearing said pneumatic and to regulate the flow rate of deposit of the extruded material as a function of said reliefs.

3. Device (10) according to claim 1 or 2, wherein the pressure control loop (31) of the electronic control unit (30) comprises a module (32) for retrieving the pressure values ​​measured (Pmes) by the pressure sensor (24d), a module (34) for comparing the pressure value measured (Pmes) by the pressure sensor (24d) with a constant pressure setpoint value (S), and a module (36) for controlling the movement of the pressure control element (24) based on the comparison between the measured pressure value (Pmes) and the constant pressure setpoint value (S). When the measured pressure (Pmes) is greater than said pressure setpoint value (S), the control module (36) is configured to control the pressure control element (24) so ​​as to lower the pressure in the extruder (21) in real time, and when the measured pressure (Pmes) is less than said pressure setpoint value (S),the control module (36), is configured to control the pressure regulating device (24) so ​​as to increase the pressure in the extruder (21) in real time.

4. Device (10) according to any one of the preceding claims, wherein the pressure regulating member (24) comprises a worm screw (24a) rotatable about the extension axis (Ai) in a conduit (24b) supplying the molten material rod to a chamber (24c) upstream of the molten material receiving chamber (22a) from the printing nozzle (22).

5. Device (10) according to claims 3 and 4, wherein when the measured pressure (Pmes) is greater than said pressure setpoint value (S), the control module (36) is configured to control the deceleration of the rotational speed of the screw (24a) of the pressure regulating member (24) and when the measured pressure (Pmes) is less than said pressure setpoint value (S), the control module (36) is configured to control the acceleration of the rotational speed of the screw (24a) of the pressure regulating member (24).

6. Device (10) according to any one of claims 3 to 5, wherein the pressure setpoint value (S) is between 50 bars and 300 bars, preferably between 60 bars and 120 bars.

7. Device (10) according to any one of the preceding claims, wherein the printing module (20) comprises a sealing device (25) for the material depositing nozzle (22) comprising a sealing means (25a) movable between a sealing position and a plurality of opening positions of the distribution orifice (22b) of the nozzle (22), and an actuator for controlling the movement of the sealing means (25a) between the sealing and opening positions.

8. Device (10) according to claim 7, wherein the sealing means (25a) is in the form of a needle actuated by the actuator (25b) to move the sealing means (25b) in translation along the extension axis (Ai).

9. Device (10) according to any one of the preceding claims, comprising a plurality of printing modules (20) fixed on the mobile support (16) and arranged circumferentially around the tire (4, 4'), and offset along the longitudinal axis (X) by a longitudinal step from each other, each printing module (2) extending along an extension axis (Ai).

10. Device (10) according to any one of the preceding claims, wherein the displacement member (23) comprises a base (23a) fixed to the support (16), a worm screw (23b) rotated by an electric motor (23c) and a fixing lug (23d) integral with the extruder (21) and comprising a tapping cooperating with the thread of the worm screw (23b).

1. An additive manufacturing method implemented by the additive manufacturing device (10) according to any one of the preceding claims, comprising a method (100) for regulating the pressure in the extruder (21) of the printing module (20), wherein the pressure regulating element (24) inside the extruder (21) is controlled in real time, via a pressure control loop (31), as a function of the pressure measured (Pmes) by the pressure sensor (24d) and a constant pressure setpoint (S), the method (100) being configured to smooth a plurality of reliefs (R) present on a circumferential carrier surface (5, 5') of the tire, said reliefs (R) being progressively varied along the circumferential carrier surface (5, 5') and defined by an amplitude (A) less than 60% of the nominal height (Hnom) of the layer (Ch),and length (L) is equal to 6mm for a layer printing speed less than or equal to 300 mm / s, the pressure regulation loop having a bandwidth ranging from 0Hz to at least 100Hz.

12. A method according to claim 11, wherein: - We retrieve measured pressure values ​​(Pmes) from the pressure sensor (24d); - the measured pressure value (Pmes) from the pressure sensor (24d) is compared with a pressure setpoint value (S); and - the displacement of the pressure regulating element (24) is controlled according to the comparison between the measured pressure value (Pmes) and the constant pressure setpoint value (S), when the When the measured pressure (Pmes) is greater than the said pressure setpoint value (S), the pressure regulating element (24) is controlled so as to lower in real time the pressure in the extruder (21), and consequently the deposition rate of an extruded material comprising a thermoplastic elastomer material having a viscosity between 34Pa.s and 11000Pa.s, and when the measured pressure (Pmes) is less than the said pressure setpoint value (S), the pressure regulating element (24) is controlled so as to increase in real time the pressure in the extruder (21) and consequently the deposition rate of the extruded material.

13. Method according to claim 12, wherein when the measured pressure (Pmes) is greater than said pressure setpoint value (S), the rotational speed of a worm (24a) of the pressure regulating member (24) is decelerated. The worm is rotating about the extension axis (Ai) in a conduit (24b) supplying the molten material rod to a chamber (24c) upstream of the molten material receiving chamber (22a) of the printing nozzle (22), and when the measured pressure (Pmes) is less than said pressure setpoint value (S), the rotational speed of said worm (24a) of the pressure regulating member (24) is accelerated.

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