Additive manufacturing device for a tire tread comprising at least one extruder and method for regulating pressure in the extruder

Abstract

An additive manufacturing process for all or part of a tire tread configured to smooth any raised areas (R) present on a circumferential bearing surface (5) of said tire by depositing an extruded material forming the tread, wherein a pressure regulating device (24) inside the extruder is controlled in real time, via a pressure control loop, according to a pressure measured by the pressure sensor and a constant pressure setpoint. The process is configured to smooth a plurality of raised areas (R) present on a circumferential bearing surface (5) of the tire. Figure for the abstract: Fig 8A

Description

Title of the invention: Device for additive manufacturing of a tire tread comprising at least one extruder and method for regulating the pressure in the extruder

[0001] The present invention relates to the field of manufacturing a tire tread.

[0002] Conventional wheels are known, comprising a rim on which a tire is mounted, including a tread and two sidewalls. This type of wheel includes an inner tube inflated to the recommended nominal inflation pressure.

[0003] Another type of tubeless wheel known as "tubeless" in Anglo-Saxon terms is also known, comprising a layer of waterproof butyl rubber to replace the inner tube.

[0004] Integral wheels, known as "airless" wheels, are also known, comprising a radial load-bearing structure, generally made of glass-fiber-reinforced plastic, around which a solid tire is fixed, comprising a tread and two sidewalls. The solid tire is not subjected to internal pressure.

[0005] Such an integral wheel has the advantage of being flexible in the event of impacts, puncture-proof, and durable due to the materials from which it is made. Furthermore, once worn, it is known that the tread can be removed and recycled. Thus, such an integral wheel also helps to meet environmental requirements.

[0006] It is known to retread worn treads on conventional tires with inner tubes. Tires used on heavy-duty motor vehicles are particularly affected by any renewal process that extends their service life. Thus, it is known to remove the worn tread and replace it with a new one by wrapping and securing it onto the casing of the tire that no longer has a tread.

[0007] Other techniques are known for renewing tire treads. For example, document WO-A1-2013086577 describes an apparatus and a method for retreading a worn tire tread. The tread is composed of a thermoplastic elastomer. The apparatus includes a heating device for heating the worn surface of the tread and a three-dimensional printer, known as a 3D printer, for applying a or several layers of thermoplastic elastomer on the heated surface. The 3D printer includes a series of print heads arranged in a row.

[0008] However, such a process is specifically designed for retreading conventional wheel tire treads that include an inner tube. Furthermore, the heating steps for the receiving surface are energy-intensive and costly, and require suitable heating equipment.

[0009] Moreover, 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.

[0010] Document FR-B1-3 067 281 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 wheel tire. The device includes a construction robot with one or more nozzles for depositing material by addition. The nozzles are arranged side by side and are laterally movable so as to cover the entire tread to be constructed.

[0011] However, such a process is particularly slow since the tire is positioned at a given azimuth before the nozzle deposits material, and the operation is repeated until the entire tread is manufactured. Such a solution only allows for the deposition of a few tens of grams per hour, for example, 50 g / h per print head.

[0012] Furthermore, the slow manufacturing of the tread can generate seepage problems.

[0013] In order to reduce the manufacturing time of the tread, large extruders with material deposition nozzles of 5 mm to 10 mm could be used. However, in this case, although the material deposition rate is higher, on the order of 900 g / h / extruder used, the precision is much lower.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] Control of the filling process is therefore a determining factor in the strength of the manufactured object.

[0018] Indeed, above 100% infill, excess material can flow onto the lateral faces of the manufactured 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 unfavorable effect.

[0019] To address this filling failure problem, a known solution is to control the molten material deposition rate relative to the surface. Such a solution is particularly complex because it requires reading the substrate's topography and moving the extruder vertically relative to the substrate to obtain a uniform layer height. Furthermore, in this case, the substrate's surface irregularities are preserved, and it may be necessary to use a positive displacement pump to regulate the molten material flow rate.

[0020] Thus, there is a need to improve the manufacturing processes, particularly the recharging, of a tire tread.

[0021] The objective of the invention is to manufacture, in particular to recharge, quickly a tread of a tire 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 equal to 0.7 mm.

[0025] The length of the relief 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] Said device is configured to smooth, correct or erase said plurality of reliefs and comprises: - a pneumatic rotation drive element capable of driving said pneumatic around a horizontal axis of rotation; - a fixed base attached to the ground; - a mobile support in translation relative to the base; - at least one printing module attached to the mobile support and comprising: - a mobile extruder along an extension axis, for example radial, relative to the pneumatic and configured to produce a rod of molten material; - 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 - a device for moving the extruder along the extension axis.

[0028] The device comprises: - 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 - 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.

[0029] By “real time”, we mean a response time of less than 1ms for a molten material deposition speed between 0.0lm / s and 0.3m / s.

[0030] Pressure regulation in the extruder chamber makes it possible to obtain an application pressure of the molten material that is 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.

[0031] 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.

[0032] Such a manufacturing device makes it possible to manufacture, in particular to refill, a tire tread quickly while maintaining the quality of the tread pattern.

[0033] The material rod has, for example, a thickness of 0.7 mm and a width of 2 mm when deposited on the carrier surface. Indeed, before deposition, the material rod has a cross-section identical to that of the material dispensing nozzle. The material rod then has a circular cross-section when the material dispensing nozzle has a circular cross-section.

[0034] The bandwidth of the pressure sensor is preferably greater than 200 Hz.

[0035] The extruder is configured to deposit molten material with a flow rate of 1000g / h.

[0036] By "additive manufacturing", we mean a manufacturing process by adding extraded material, called "fused deposition modeling", acronym FDM in Anglo-Saxon terms.

[0037] By "pneumatic" we mean all types of elastic bandages of toroidal shape subjected to internal pressure or not.

[0038] The term "tread" of a tire means a quantity of rubber material delimited by lateral surfaces and by two principal surfaces, one of which is called the tread, intended to come into contact with a 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.

[0039] The term "sidewall" of a tire refers to a portion of the tire's lateral surface located between the tire tread and a wheel support structure. In the case of a conventional wheel tire, the sidewall begins at the ends of the tread grooves and extends to a tire bead.

[0040] The additive manufacturing device is configured to deposit an extruded material forming the tread on a circumferential carrier surface or peripheral external contour of said tire and comprising a drive element for rotating the tire capable of driving said tire around a horizontal axis of rotation.

[0041] By "width" is meant the direction in the direction parallel to the axis of rotation of the tire.

[0042] By "thickness" or "height" is meant the direction along the radial direction to the axis of rotation of the tire.

[0043] 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.

[0044] The tire here comprises 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.

[0045] The device is also compact and autonomous and can deposit treads on new or retreaded tires as well as on "air-less" wheels in a short period of time between 10min and 20min and without a vulcanization step.

[0046] Such a device is preferably, but not exclusively, intended for use in automotive centers, car dealerships, fleet management centers, or for installation in small utility vehicles in order to be able to recharge treads anywhere, for example in a parking area, a motorway rest area, etc...

[0047] Advantageously, the control loop of the electronic control unit includes a module for retrieving the 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.

[0048] When the measured pressure is greater than said pressure setpoint value, the control module is configured to control the pressure regulating element so as to lower in real time the pressure in the extruder, and consequently the deposition rate of the extruded material, and when the measured pressure is less than said pressure setpoint value, the control module is configured to control the pressure regulating element so as to increase in real time the pressure in the extruder, and consequently the deposition rate of the extruded material.

[0049] The pressure setpoint response time is fast and allows for real-time adjustment of the extruded material quantity. The extruded material deposition rate is regulated by regulating the pressure inside the extruder chamber.

[0050] The control module for the displacement of the pressure regulating element has a bandwidth greater than or equal to 1000Hz.

[0051] According to one embodiment, the pressure regulating member comprises a worm screw movable in rotation about the extension axis in a feed conduit of the molten material rod to a chamber upstream of the molten material receiving chamber of the printing nozzle.

[0052] In this case, when the measured pressure is greater than said pressure setpoint value, the control module is configured to control the deceleration of the rotation speed of the screw of the pressure regulating member and when the measured pressure is less than said pressure setpoint value, the control module is configured to control the acceleration of the rotation speed of the screw of the pressure regulating member.

[0053] Indeed, accelerating the rotational speed of the worm screw causes an increase in pressure inside said chamber. Conversely, decelerating the worm screw causes a decrease in pressure inside said chamber.

[0054] For example, the pressure setpoint value is between 50 bars and 300 bars, preferably between 60 bars and 120 bars.

[0055] The worm screw includes a motorization having a bandwidth greater than or equal to 200 Hz.

[0056] The combination of the bandwidth of the pressure sensor greater than 200 Hz, the bandwidth of the screw motorization greater than 200 Hz and the bandwidth of the speed regulation control greater than or equal to 1000 Hz makes it possible to obtain a pressure regulation loop having a bandwidth ranging from 0 Hz to at least 100 Hz.

[0057] According to one embodiment, the printing module includes a material deposition nozzle closing device comprising a movable closing means between a closing position and a plurality of opening positions of the nozzle distribution orifice, and an actuator for controlling the movement of the closing means between the closing and opening positions.

[0058] 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.

[0059] The needle valve allows for clean stops in the flow of molten material, without burrs, and clean restarts of said flow.

[0060] The stroke of the needle is preferentially dependent on the flow rate of material 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.

[0061] This variable stroke advantageously limits the sudden pressure drop at needle opening, which results in over-extrusion followed by under-extrusion with each sealing cycle, a situation that is 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.

[0062] Such a device makes it possible to deposit material onto curved surfaces continuously or in fragments with precise control over the volume and its distribution on the tread. In other words, such a device makes it possible to deposit the right amount of material in the right place.

[0063] The variable stroke sealing needles make it possible to guarantee the 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.

[0064] For example, the actuator includes a piezoelectric device (not shown) for closing or opening the distribution orifice of the corresponding nozzle.

[0065] Alternatively, any other means of closure associated with each of the nozzles could be provided, such as for example a valve.

[0066] 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.

[0067] Having individual modules, each comprising an extruder and a sealing needle, allows for control of the material deposition rate at variable speeds. Complex shapes can also be created.

[0068] Preferably, the printing modules are distributed circumferentially not regularly on the mobile support, i.e. the circumferential gap between two adjacent printing modules is different.

[0069] Alternatively, the printing modules could be regularly distributed circumferentially on the mobile support.

[0070] For example, the mobile support has the shape of an arch extending over an angular range of up to 360°.

[0071] The shape of an arch allows a "gravity" type feeding at the inlet of the extrusion screw.

[0072] The support is mobile in translation relative to the base along the longitudinal axis, for example, on parallel longitudinal guide rails.

[0073] In the case where there are several printing modules, the means for closing all the printing modules can be controlled independently of each other.

[0074] In the case of multiple printing modules, thanks to the pressure regulating element associated with each extruder, independent pressure regulation from one extruder to another and the variable distance along the extension axis between the extruders allows for cross-sectional variations, enabling complex and more resilient stacking strategies. Thus, each nozzle includes its own shut-off mechanism configured to interrupt the flow of molten material through the distribution orifice of the corresponding nozzle.

[0075] 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.

[0076] Such a loading time corresponds to a material deposit rate of between 5kg / h and 15kg / h, preferably equal to 10kg / h.

[0077] The shutter frequency is between 0.05Hz and 20Hz, for example equal to 0.1Hz for a continuous undercoat and 10Hz on average for a sculpture featuring many blocks of gum.

[0078] 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.

[0079] By “continuous rotation” is meant a rotation in a single direction of rotation, without interruption and at a constant speed.

[0080] By "discontinuous rotation" is meant a rotation in a single direction of rotation at variable speed during the deposition of material.

[0081] 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.

[0082] The extruders can be fed centrally or individually with another material, which makes it possible to vary the characteristics of the plastic material depending on its position in the tread. Multi-material treads can thus be obtained.

[0083] 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.

[0084] The tread is manufactured by depositing the extruded material layer by layer onto the carrier surface of the tire.

[0085] The extruded material inter-diffused or heat-welded by inter-diffusion onto the previously deposited layer of material and solidified during the temperature drop.

[0086] Each of the nozzles is configured to deposit the molten material onto the carrier surface of the mobile tire rotating around a horizontal axis of rotation.

[0087] The extruders are mounted on the support and can move longitudinally with a variable distance along the radial axis between each extruder, which allows for helical laying or variation of the cross-section during circumferential and helical laying.

[0088] 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 tapping cooperating with the thread of the worm screw.

[0089] Thus, the rotation of the worm screw causes the extruder to move along the associated extension axis.

[0090] 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 make a deposit of material 1mm wide and preferably between 1mm and 1.6mm to make a deposit of material 2mm wide.

[0091] For example, the distribution orifice of each of the nozzles has a rectangular or circular cross-section. A rectangular cross-section improves the level of detail in the carving and the quality of the breaks.

[0092] The material depositing nozzles may be identical to each other or different, in their dimensions, such as the diameter of the distribution orifice, the length of the conduit located after the needle seat or their external dimension.

[0093] For example, the rotating drive element is in the form of a rotating drum or cylinder cooperating with the wheel hub and configured to drive the tire in rotation via the wheel hub.

[0094] For example, the tire can be configured to be mounted on a so-called "conventional" wheel comprising a rim with a mounting hub. The tire, or pneumatic tire, is mounted on the rim. The tire comprises a circumferential tread-bearing surface, a tread, and two sidewalls surrounding the tread-bearing surface on either side. The rim is preferably the final rim intended for mounting on a motor vehicle. The mounting hub forms the attachment 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.

[0095] The wheel can be a wheel with or without an inner tube, called "tubeless" in Anglo-Saxon terms.

[0096] 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. The support structure includes a support radially external to the support structure. The support extends over the entire circumference of the support structure and includes an external peripheral contour forming a circumferential tread-bearing surface. The tread is structurally integrated into the support structure by means of 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.

[0097] 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, along a circumferential line of material Lj.

[0098] By material deposition along a "circumferential line of material" Lj, we mean the deposition of material along a circular trajectory of the tire, with j ranging from 1 to x, x being the total number of lines of material.

[0099] 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 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.

[0100] A layer of material C corresponds to a thickness of molten material deposit.

[0101] According to this first example, the lines Lj have a constant width and the layers Ch have a constant thickness.

[0102] According to 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, by varying the pressure inside the printing nozzle chamber to obtain variable line widths Lj. Thus, the lines Lj have a variable width and the layers Ch have a constant thickness.

[0103] According to a third application example, in the case where there are several printing modules, 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, by varying the radial distance between the extruder and the carrier surface in order to obtain variable layer thicknesses Ch. Thus, the lines Lj have a constant width and the layers Ch have a variable thickness.

[0104] Preferably, the start of each line Lj is offset along the transverse axis, in order to avoid stress concentrations. According to one example, the material is deposited in circumferential lines Lj parallel to the direction of movement of the tire.

[0105] According to 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 displacement of the support along the longitudinal axis combined with the displacement of the extruders along the radial axis and the rotation of the tire around its axis of rotation.

[0106] According to 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 displacement of the support along the longitudinal axis, from right to left and then from left to right, combined with the displacement of the extruders along the radial axis and the rotation of the tire around its axis of rotation.

[0107] For example, during a complete rotation of the tire, the material deposition nozzles of each printing module are actuated simultaneously to deposit material along a circumferential line of material on the lower material line. Then, the support is moved longitudinally along the axis of rotation of the tire after each complete rotation of the tire, so that the material deposition nozzles deposit material along the adjacent material line, and so on until the desired tread pattern is obtained. Thus, a portion of the layer, dependent on the number of extruders used, is produced with each complete rotation of the tire.

[0108] If the number of lines to be printed exceeds the number of printing modules, the substrate is offset along the tire's axis of rotation by the width of the entire set of printing modules in order to continue depositing the material on the subsequent circumferential lines. In this case, an entire layer is produced during several complete rotations of the tire.

[0109] According to 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, wherein 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 having a bandwidth ranging from 0 Hz to at least 100 Hz.

[0110] The method 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.

[0111] Reliefs are defined by an amplitude less than 60% of the nominal height of 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 layer height.

[0112] 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.

[0113] The length of the relief is equal to 6mm for a layer printing speed less than or equal to 300 mm / s.

[0114] The length is understood in the circumferential direction of the bearing surface.

[0115] By "real time" is meant a response time of less than 1ms for a speed molten material deposition rate between 0.0 lm / s and 0.3 m / s.

[0116] Pressure regulation in the extruder chamber makes it possible to obtain an application pressure of the molten material that is 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.

[0117] 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.

[0118] The pressure setpoint value is a theoretical value, determined in order to provide synchronous and appropriate dynamic variations to the pattern to be printed.

[0119] Advantageously, according to the process: - we retrieve pressure values ​​measured by the pressure sensor; - the pressure value measured by the pressure sensor is compared with a pressure setpoint value; and - 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.

[0120] For example, when the measured pressure is greater than said pressure setpoint value, the rotational speed of a worm gear of the pressure regulating member rotating about the extension axis in a feed conduit of 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 worm gear of the pressure regulating member is accelerated.

[0121] 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:

[0122] [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;

[0123] [Fig.2] illustrates another example of a wheel on which the additive manufacturing device of [Fig.1] can be used;

[0124] [Fig.3] illustrates a detail of a material deposition module of the additive manufacturing device of the [Fig.l];

[0125] [Fig.4] is a cross-sectional view of the material deposition module of [Fig.3] showing an example of a temporary sealing system for the dispensing orifice of a material deposition nozzle;

[0126] [Fig.5A], [Fig.5B], [Fig.5C] are examples of reliefs printed by the additive manufacturing device of [Fig. 1]; and

[0127] [Fig.6A], [Fig.6B], and [Fig.6C] are examples of the inclination of the printing lines by the additive manufacturing device of [Fig.1];

[0128] [Fig.7] illustrates the steps of a pressure regulation process in the extruder implemented by an electronic control unit of the manufacturing device [Fig. 1]; and

[0129] [Fig.8A], [Fig.8B] and [Fig.8C] schematically represent the steps of depositing the extruded material onto the carrier surface of the tire in the additive manufacturing device in Figures 1 to 4.

[0130] 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:

[0131] - a longitudinal axis X, horizontal and extending from back to front on the [Fig.l];

[0132] - a horizontal transverse axis Y, perpendicular to the longitudinal axis X and extending from left to right across [Fig. 1]; and

[0133] - a vertical axis Z, orthogonal to the longitudinal axis X and transverse axis Y and extending from bottom to top on the [Fig.l].

[0134] As illustrated in [Fig.1], a mounted assembly 1 or wheel comprises a rim 2 including a fixing 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 [Fig.1].

[0135] Rim 2 is preferably the final rim intended to be mounted on a motor vehicle.

[0136] The fixing hub 3 forms the fixing interface between the wheel 1 and the vehicle.

[0137] The fixing hub 3 herein defined as a hollow fixing cylinder in which a wheel axle (not referenced) can be housed.

[0138] The tire 4 is here subjected to internal pressure via an inner tube (not shown) inflated to a recommended or lower nominal inflation pressure.

[0139] 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.

[0140] The assembled unit 1 could also be a so-called "airless" tire.

[0141] The tread 6 comprises two lateral surfaces (not referenced), an internal surface (not visible) integral with the tread carrier surface 5 and a tread surface 6a opposite the internal surface and intended to come into contact with a roadway S when the wheel 1 rolls.

[0142] The tread 6 comprises a plurality of cutouts or carvings extending over at least one of its lateral surfaces.

[0143] The rim 2 here forms a radial load-bearing structure for the tire 4.

[0144] As illustrated in [Fig.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.

[0145] In general, the additive manufacturing device 10 for a tread 6 is configured to deposit an extruded material forming the tread 6 on a tire 4. Indeed, it would be possible to manufacture the tread 6 on a tire 4 not mounted on a wheel.

[0146] It would also be possible to provide for the resurfacing of a new tread 6 over a worn tread. In this case, the bearing surface corresponds to the worn tread.

[0147] 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.

[0148] Without limitation, 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.

[0149] The printing module 20 is here positioned above the wheel 1, and in particular above the tread of the tire 4.

[0150] The printing module 20 extends along an extension axis Ai, here radial with respect to the tire 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 tire 4.

[0151] Figures 3 and 4 illustrate an example of a 20-print module that can be used.

[0152] As illustrated in detail in Figures 3 and 4, the printing module 20 comprises:

[0153] - an extruder 21 regulated at a setpoint pressure S between 50 bar and 300 bars, preferably between 60 bars and 120 bars, movable along the extension axis Ai, here radial to pneumatic 4 and configured to produce a molten material rod, for example from material granules, preferably made of plastic, for example thermoplastic elastomer, acronym TPE. The material granules are therefore hot extruded;

[0154] - a material dispensing nozzle 22 fed with a rod of molten material by The extruder 21. The material deposition 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 interruptions;

[0155] - 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 tapped hole cooperating with the thread of the worm screw 23b. Thus, the rotation of the worm screw causes the movement of the extruder 21 along the associated extension axis Ai;

[0156] - a pressure regulating organ 24 inside the extruder 21.

[0157] The pressure regulating member 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.

[0158] The additive manufacturing device 10 includes an electronic control unit 30 configured to control the pressure regulating organ 24 inside the extruder 21.

[0159] The electronic control unit 30 includes a control loop 31 comprising a module 32 for recovering the pressure values ​​measured Pmes by the pressure sensor 24d.

[0160] The molten material preferably comprises a thermoplastic elastomer material having a viscosity between 34 Pa.s and 11000 Pa.s.

[0161] 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.

[0162] The control loop 31 of the electronic control unit 30 includes a control module 36 for the movement of the pressure regulating member 24, here the worm gear 24a, according to the comparison between the measured pressure value Pmes and the threshold value S.

[0163] When the measured pressure Pmes is greater than the setpoint pressure S, this means that the surface has a material elevation, 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 member 24 so as to lower the pressure in the extruder in real time, and consequently the deposition rate of the extruded material.

[0164] When the measured pressure Pmes is lower than the setpoint pressure S, this means that the surface exhibits a reduction in material, 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 so as to increase in real time the pressure in the extruder, and consequently the deposition rate of the extruded material.

[0165] 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.

[0166] The pressure setpoint response time is fast and allows for real-time adjustment of the extruded material quantity. The extruded material deposition rate is regulated by means of pressure regulation inside chamber 24c of extruder 21.

[0167] Each extruder is configured to deposit molten material with a flow rate of 1000g / h.

[0168] The pressure regulation in the chamber 24c of the extruder 21 makes it possible to obtain an application pressure of the molten material that is as suitable as possible for the relief of the carrier surface.

[0169] 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.

[0170] Without limitation, the printing module 20 includes a sealing device 25 for the material depositing nozzle 22. The sealing device 25 includes a sealing means 25a movable between a sealing position and an opening position of the distribution orifice 22b, and an actuator 25b to control the movement of the sealing means 25a between the closed and open positions. The sealing means 25a can be controlled independently of each other.

[0171] Thus, each nozzle 22 includes its own sealing means 25 configured to interrupt the flow of molten material through the distribution orifice 22b of the corresponding nozzle.

[0172] Each of the nozzles 22 can be interrupted independently and reactively, so as to generate any sculpture on the wheel 1 in a short time, preferably less than 15 minutes.

[0173] Such a loading time corresponds to a material deposit rate of between 5kg / h and 15kg / h, preferably equal to 10kg / h.

[0174] The shutter frequency is between 0.05Hz and 20Hz, for example equal to 0.1Hz for a continuous undercoat and 10Hz on average for a sculpture featuring many blocks of gum.

[0175] In the example illustrated in [Fig.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.

[0176] The actuator 25b includes, for example, a piezoelectric device (not represented) to close or open the distribution orifice 22b of the corresponding nozzle 22.

[0177] The needle obturator 25a allows for clean stops of the flow of molten material, without burrs, and clean restarts of said flow.

[0178] The needle stroke is preferentially dependent on the material flow rate and is variable in order to match the opening of the dispensing orifice to the rheology of the TPE, thus allowing the pressure regulator to manage the transient phases. This variable stroke advantageously limits the sudden pressure drop at needle opening, which results in over-extrusion followed by under-extrusion with each sealing 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.

[0179] Alternatively, any other means of closure associated with each of the nozzles could be provided, such as for example a valve.

[0180] It could also be envisaged that the printing module 20 is without a shutter device. In this case, the extrusion of extruded material is continuous.

[0181] The terms "downstream" and "upstream" are defined by considering the direction of flow of matter.

[0182] Alternatively, a plurality of printing modules 20 could be provided, fixed to the movable support 16 and arranged circumferentially around the tire 4, with a different or identical circumferential spacing between two adjacent printing modules. The printing modules 20 could be offset along the longitudinal axis X by a distance or longitudinal spacing from one another.

[0183] In this case, the extruders 21 of the printing modules can be fed centrally or individually with another material, which makes it possible to vary the characteristics of the plastic material depending on its position in the tread. Multi-material treads can thus be obtained.

[0184] The material bead has, for example, 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.

[0185] By "width" is meant the direction in the direction parallel to the axis of rotation XX of the tire 4.

[0186] By "thickness" or "height" is meant the direction along the radial direction to the axis of rotation XX of the tire 4.

[0187] 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.

[0188] 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.

[0189] The tread 6 is manufactured by depositing the extruded material layer by layer onto the carrier surface 5 of the tire 4. The extruded material melts on the layer of material previously deposited and solidifies when the temperature drops.

[0190] Each of the nozzles 22 is configured to deposit the molten material onto the carrier surface 5 of the tire 4 which is mobile and rotates around a horizontal axis of rotation XX.

[0191] 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.

[0192] 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'.

[0193] As illustrated in [Fig.2], the rotational drive member 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.

[0194] These variants are interesting in the case where it is necessary to manufacture the tread 2 without removing the wheel 1 from the vehicle.

[0195] The tire 4 here comprises only one degree of freedom, namely around its axis of rotation XX. In other words, the tire 4 is not mobile in translation along any of the axes X, Y or Z.

[0196] 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 [Fig.2].

[0197] The integral wheel 1' here comprises a radial support structure 2' around which is fixed a tire 4' or solid tire comprising a support 7' radially external to the support structure 2'. The support 7' extends over the entire circumference of the support structure 2' and carries the tread 6'. The tread 6' is here structurally integrated into the support 7' by means of a tread carrier surface 5' forming a peripheral external contour of the radial support structure 2'.

[0198] The solid 4' bandage is not subjected to internal pressure.

[0199] As illustrated in [Fig.2], the radial support structure 2' includes a fixing hub 3' for fixing the wheel 1' to a vehicle.

[0200] The fixing hub 3' 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 comprises a plurality of poles or stays 8' connecting the hub 3' to the support 7'.

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

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

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

[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 to comprise 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 [Fig.5A].

[0209] In this example, each printing module 20 is configured to deposit extruded material forming the tread 6 onto the tire 4, in particular 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 lines Lj have a constant width and the layers Ch have a constant thickness.

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

[0215] In this example, each printing module 20 is configured to deposit extruded material forming the tread 6 onto the tire 4, in particular 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 lines Lj have a variable width and the layers Ch have a constant thickness.

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

[0218] In this example, each printing module 20 is configured to deposit extruded material forming the tread 6 onto the tire 4, in particular 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 lines Lj have a constant width and the layers Ch have a variable thickness.

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

[0221] In the example illustrated in [Fig. A], the material is deposited in circumferential lines Lj parallel to the direction of travel D of the tire 4.

[0222] In the example illustrated in [Fig. B], 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 in 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.

[0223] In the example illustrated in [Fig.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.

[0224] 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 axis of rotation 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.

[0225] Thus, a portion of the layer dependent on the number of extruders used is produced at each complete revolution of the tire.

[0226] 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.

[0227] In this case, an entire layer is made during several complete revolutions of the tire.

[0228] The [Fig.7] is a flowchart illustrating the steps of a process 100 of regulating the pressure inside the extruder 21 of the additive manufacturing device.

[0229] The pressure regulation process 100 is included in an additive manufacturing process implemented by the additive manufacturing device 10 and will not be further described.

[0230] The pressure regulation method 100 operates via the pressure regulation loop 31 of the control unit 30 described with reference to Figures 3 and 4.

[0231] The pressure regulation method 100 includes a step 102 of retrieving the pressure values ​​measured Pmes by the pressure sensor 24d.

[0232] The pressure regulation method 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.

[0233] The pressure regulation method 100 includes a step 106 of controlling the displacement of the pressure regulating element 24, here the worm screw 24a, in function of the comparison between the measured pressure value Pmes and the threshold value S.

[0234] When the measured pressure Pmes is greater 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 so as to lower the pressure in the extruder in real time, and consequently the rate of deposition of the extruded material.

[0235] When the measured pressure Pmes is lower than the setpoint pressure S, this means that the surface exhibits a reduction in material, such as a depression. In this case, in step 106b, the rotational speed of the screw 24a of the pressure regulating device 24 is accelerated so as to increase the pressure in the extruder in real time, and consequently the deposition rate of the extruded material.

[0236] 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 10min and 20min and without a vulcanization step, while allowing the deposition of an extruded material on a carrier surface of any curvature with a high infill rate of between 99.5% and 100%.

[0237] 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 hollow or a bump less than 60% of the nominal layer height.

[0238] 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.

[0239] The length L of the relief is equal to 6mm for a layer printing speed less than or equal to 300 mm / s.

[0240] The length L is understood in the circumferential direction of the bearing surface.

[0241] Said reliefs R are progressively varied along the circumferential carrier surface 5 of the tire.

[0242] The pressure regulating device allows such reliefs to be corrected or erased in real time using the extruded material as defined.

[0243] The pressure control loop 31 has a bandwidth ranging from 0Hz to at least 100Hz

[0244] The bandwidth of the pressure sensor 24d is preferably greater than 200 Hz.

[0245] The control module 36 for the displacement of the pressure regulating element has a bandwidth greater than or equal to 1000Hz.

[0246] The worm screw 23b includes a motorization having a bandwidth greater than or equal to 200 Hz.

[0247] The combination of the bandwidth of the pressure sensor greater than 200 Hz, the bandwidth of the screw drive greater than 200 Hz and the bandwidth of the speed control greater than or equal to 1000 Hz makes it possible to obtain a pressure control loop having a bandwidth ranging from 0 Hz to at least 100 Hz.

[0248] As illustrated in [Fig.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.

[0249] The pressure measured Pmes by the pressure sensor 24d is measured continuously and is compared continuously with a threshold value S corresponding to a constant pressure setpoint.

[0250] When the extruder nozzle 22 begins to deposit 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 controls the acceleration of the rotational speed of the worm gear 24a of the pressure regulating member 24 so as to increase in real time the pressure in the extruder, and consequently the deposition rate of the extruded material. The relief R is thus filled as can be seen in [Fig. 8C].

[0251] Similarly, if the relief R was 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 deposit of the extruded material.

[0252] Pressure regulation in the extruder chamber makes it possible to obtain a molten material application pressure that is 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.

[0253] 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. Demands 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 (H_nom) 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 mobile support (16) 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); - an extruder (21) displacement element (23) 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 regulating loop (31) configured to control real time the pressure regulation organ (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) 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 displacement of the pressure regulation member (24) as a function of 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 regulation member (24) so ​​as to lower the pressure in the extruder (21) in real time,and when the measured pressure (Pmes) is lower than the 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.

3. 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).

4. Device (10) according to claims 2 and 3, wherein when the measured pressure (Pmes) is greater than said pressure setpoint (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 (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).

5. Device (10) according to any one of claims 2 to 4, wherein the pressure setpoint value (S) is between 50 bar and 300 bar, preferably between 60 bar and 120 bar.

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

7. Device (10) according to claim 6, 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).

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

9. 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).

10. 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 variable progressive along the circumferential carrier surface (5, 5') and defined by an amplitude (A) less than 60% of the nominal height (H_nom) 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 from 0Hz to at least 100Hz.

11. A method according to claim 10, wherein: - measured pressure values ​​(Pmes) are retrieved by the pressure sensor (24d); - the measured pressure value (Pmes) by the pressure sensor (24d) is compared with a pressure setpoint value (S); and - the displacement of the pressure regulating element (24) is controlled as a function of 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 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 device (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.

12. A 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. This 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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