FR2998838A1 - Method for manufacturing reinforcement for back of seat of automobile, involves heating set of strips by heating unit, where each of set of strips is embedded in plastic material with certain fibers extending over entire length from strips - Google Patents

Abstract

The method involves applying a set of strips (69) on a support (12) that is provided in a plastic material. The set of strips is heated by a heating unit such as infra-red radiation source, where each of the set of strips is embedded in another plastic material e.g. thermoplastic material, with certain fibers extending over an entire length from the strips. The heating of each of the set of strips is realized partly simultaneously with the application of strip on the support.

Description

B12077 - 3353 1.FR 1 SEAT FRAME AND MANUFACTURING METHOD THEREOF The present description relates to a seat frame, in particular a backrest frame or seat of a motor vehicle seat, and a method of manufacturing a seat frame. such a frame. DISCUSSION OF THE PRIOR ART A motor vehicle seat generally comprises a backrest articulated on a seat. The backrest and the seat each comprise a frame and a padding attached to the frame. It is known to make the reinforcement by assembling metal parts. To reduce the weight of the frame, it is also known to make the frame, at least in part, a plastic material. Publication WO 2010/101874 discloses a seat back frame of a motor vehicle made by a method of overmoulding a plastic material on reinforcing elements of a different material, for example a metallic material or a composite material. SUMMARY An embodiment is directed to a method of manufacturing a seat frame, comprising applying strips to a carrier made of a first plastic material, the strips being heated by a heating means, each strip comprising fibers embedded in a second plastic material, at least some fibers extending over the entire length of the strip. According to one embodiment, the heating means 5 comprises a laser, a source of infrared radiation or a source of hot air. According to one embodiment, the heating means comprises a laser. According to one embodiment, the heating of each strip is performed at least in part simultaneously with the application of the strip on the support. According to one embodiment, the second plastic material is a thermoplastic material. According to one embodiment, each strip is formed by juxtaposing fibers impregnated with the second plastic material, the method further comprising heating the second plastic material. According to one embodiment, the method comprises the following steps: a) forming the support by injection of the first plastic material into a mold; b) heating at least one band by laser; and c) applying the web to the support, steps b) and c) being performed at least in part simultaneously. According to one embodiment, the first plastic material and / or the second plastic material are selected from the group consisting of polyamide, polypropylene or acrylonitrile butadiene styrene. According to one embodiment, the method comprises the successive application of several bands at the same location of the support. According to one embodiment, the method comprises the formation of at least one surface imprint of the support and the application of at least one strip in the imprint.

B12077 - 3353 1.EN 3 Brief description of the drawings These and other features and advantages will be set forth in detail in the following description of particular embodiments in a non-limiting manner with reference to the accompanying figures in which: Figure 1 is an exploded view, partial and schematic, of an example of a backrest frame of a motor vehicle seat; Figure 2 is an exploded, partial and schematic view of an example of a composite material; Figure 3 is a partial sectional and schematic sectional view of an example of a mold containing the armature shown in Figure 1; Figure 4 is a schematic view of a manufacturing facility of an embodiment of a motor vehicle seat frame; Figure 5 is a partial sectional and schematic sectional view of a portion of the installation of Figure 4; and FIGS. 6 and 7 are respectively a top and a sectional view, partial and schematic, of an armature according to a variant at an intermediate stage during the manufacture of the armature. For the sake of clarity, the same elements have been designated with the same references in the various figures. Detailed Description In the remainder of the description, the terms "substantially", "approximately", "about" and "of the order of" mean "to within 10%". In addition, only the elements necessary for the understanding of the invention are represented. Figure 1 shows an example of a frame 10 of a motor vehicle seat back. The armature 10 comprises a support 12 made of a first material, in particular a first plastic material, and reinforcing elements 14, 16, 18 and 20 which are at least partly embedded in the support 12. The support 12 may have the form of a shell, as is B12077 - 3353 1.FR 4 shown in Figure 1, or a frame. The reinforcing elements 14, 16 are, for example, arranged along the lateral edges of the support 12. The reinforcing elements 18 and 20 are, for example, metal elements located at the joint of the backrest on the seat . The support 12 further comprises housing 22, 24 adapted to receive the pins of a headrest 26. The reinforcing elements 14, 16 are made of a second material different from the first material. By way of example, the reinforcing elements 14 and 16 are made of a composite material, comprising a second fiber-reinforced plastic material. This is, for example, a composite material comprising long fibers embedded in a matrix of the second plastic material. The composite material corresponds, for example, to the material marketed under the name CFRT by Baycomp. FIG. 2 represents an example of a composite material that can be used to produce the reinforcing elements 14 and 16. In this example, the composite material comprises a stack 27 of several sheets 28. By way of example, seven sheets 28 are represented in FIG. Figure 2. Each sheet 28 comprises a long layer of fibers 30 aligned next to each other substantially in the same direction and connected to each other by the second plastic material. In the stack of sheets 28, the continuous fibers 30 may be oriented in the same direction or in different directions. By way of example, in FIG. 2, each reinforcing element 14 and 16 is formed of a stack 27 of seven sheets for which the continuous fibers are oriented in the same direction with the exception of the sheet located in the middle of the stack 27 whose fibers are oriented at 90 ° with respect to the fibers of the other sheets 28. Conventionally, the reinforcing elements 14 and 16 35 are made before their integration into the frame 10. By title B12077 - 3353 1. For example, the reinforcing elements 14, 16 of composite material are made by a deformation process in press. In particular, in the case where the reinforcing elements 14, 16 are made of a plastic material reinforced with long fibers of the type shown in FIG. 2, the sheets 28 are applied against each other in a mold having the final shape. desired, and are heated so that the sheets 28 are deformed to the desired shape and adhered to each other. The deformation step is followed by a cutting step 10 to delimit the contour of the reinforcing elements 14 and 16. The reinforcement 10 can be made by an overmolding operation of the first plastic material on the reinforcing elements 14, 16 , 18, 20. FIG. 3 illustrates a step of an overmolding process and represents an example of a mold 40 that can be used for producing the armature 10. The mold 40 comprises lower mold parts 41, 42 and side 43, 44. An exemplary method of manufacturing the reinforcement by overmolding comprises the following steps: placing the reinforcing elements 14, 16, 18, 20 relative to the parts of the mold 41, 42, 43, 44; closing the mold 40 to delimit a cavity 45 in which the reinforcing elements 14, 16, 18, 20; injecting the first plastic material in the form of a more or less viscous liquid, the first plastic material spreading throughout the cavity 45 and at least partly overmoulding the reinforcing elements 14, 16, 18, 20; and removing the mold parts 42, 43, 44 to release the frame. Such an example of a method of manufacturing a seat frame or seat back has several disadvantages.

B12077 - 3353 1.EN 6 Indeed, the reinforcing elements 14, 16 made of composite material must be manufactured before the overmolding step. As a result, the shape of the reinforcing elements 14, 16 and the mechanical strength properties of the reinforcing elements 14, 16 are determined not only according to the desired mechanical reinforcing effect on the reinforcement but also taking into account constraints imposed by the method of manufacturing the reinforcing element and the overmolding process. In particular, the reinforcing elements 14, 16 must be able to be manipulated to be put in place in the mold 40. The mechanical strength of a reinforcing element 14, 16 increases especially with the number of sheets 28 composing the stack 37. As a result, the number of sheets 28 to be used to make each reinforcing member 14, 16 may be greater than would have been sufficient to achieve only the desired reinforcing effect. In addition, to allow handling and placement of the reinforcing members 14, 16 in the mold, the dimensions of the reinforcing members 14, 16 may be greater than would have been sufficient to achieve only the desired reinforcing effect. It may be necessary to use a quantity of composite material greater than the amount that would have been sufficient to obtain only the desired reinforcing effect. In addition, the manufacture of the reinforcing elements 14, 16 comprising a cutting step, a portion of the composite material is inevitably lost. In addition, the development of the overmolding process of the first plastic material on the reinforcing elements is a complex process. Indeed, it is necessary in particular to ensure that the first plastic material is spread throughout the cavity 45 of the mold. The presence of the reinforcing elements 14, 16 in the cavity 45, which are additional obstacles to the flow of the first plastic material can make more complex the development of overmolding process. In addition, the slightest change in the shape of the reinforcing elements 14, 16 leads to a further development of the overmoulding process. Indeed, it is then necessary to study how to place and maintain the modified reinforcing elements in the cavity 45 before the injection of the first plastic material and to study to what extent the modification of the reinforcing elements 14, 16 modifies the flow of the first plastic material in the cavity 45. The development time of a new method of manufacturing a reinforcement in the case of a modification of the reinforcing elements 14 and 16 is therefore long. An object of one embodiment is to overcome some or all of the disadvantages of the previously described methods. Another object of an embodiment is to arrange the reinforcement elements of the second material only at the locations of the support where they participate in a desired mechanical reinforcement. Another object of an embodiment is to reduce the losses of the second material constituting the reinforcing elements. Another object of one embodiment is to reduce the number of sheets of the composite material used to make reinforcing elements. Another object of an embodiment is to simplify the development of the overmolding process of the first plastic material. Another object of an embodiment is to reduce the development time of the armature manufacturing method when the reinforcing elements are modified. One embodiment comprises attaching the reinforcing elements, including in particular the second material, to the support made with the first material after the step of producing the support. The reinforcing elements comprising the second material are therefore not present in the mold during the manufacture of the support. The development of the injection process of the first plastic material in the mold to manufacture the support is simplified. In addition, modification of the reinforcing member does not result in modification of the overmoulding process. The development time of the method of manufacturing the armature is therefore reduced during modifications of the reinforcing elements. In addition, the reinforcing elements can be arranged on the support only where a mechanical reinforcement is desired. Losses of second material are therefore reduced. Each of these reinforcing elements is applied to the support in the form of strips of the second material. The length of the band depends on the dimensions of the area of the support to be reinforced. Several strips of the second material may be applied at the same location of the carrier to form a stack of tapes. Each strip is heated to allow its application on the support and its adhesion to the support. The first material forming the support is a plastic material, in particular a polymer, for example a thermoplastic or thermosetting polymer. By way of example, the first plastic material is a polyamide, a polypropylene or an acrylonitrile butadiene styrene (ABS). Preferably, the first plastic material is adapted to be shaped by injection molding. The support may be made by overmolding the first plastic material on the reinforcing elements 18 and 20 other than the reinforcing elements of the second material. The second material is a composite material comprising a second fiber reinforced plastic material. The second plastic material may be the same material as the first plastic material or a material different from the first plastic material. The second plastic material may be a polymer, for example a thermoplastic polymer or a thermosetting polymer. Preferably, the second plastic material is a thermoplastic material. By way of example, the second plastic material is a polyamide, a polypropylene or an acrylonitrile butadiene styrene. The composite material is, for example, reinforced with long fibers, also called continuous fibers. B12077 - 3353 1.FR 9 continuous fibers may be glass, carbon, aramid, copper, aluminum or steel fibers. The diameter of the fibers depends on the nature of these fibers. For example, for fiberglass, the fiber diameter is between 10 and 30 pin. By way of example, the second material is a thermoplastic material reinforced with long fibers. According to one embodiment, the first material is heated by the second material during the application of the second material to the first material. The second material tends to adhere to the first material, especially when it is applied, after being heated or while being heated, to the first material. The first material is preferably wettable by the second material. Preferably, the heating of the second material and the application of the second material to the first material are carried out simultaneously. This advantageously makes it possible to precisely control the quantity of heat supplied to the second material and the temperature of the second material when it is brought into contact with the first material.

According to one embodiment, the heating temperature of the second plastic material is between 215 ° C and 280 ° C, for example about 240 ° C. According to one embodiment, the heating temperature of the first plastic material is between 210 ° C and 240 ° C, for example about 225 ° C, at the interface with the second plastic material. Figure 4 shows an embodiment of an installation 50 for manufacturing seat frames. The installation 50 comprises a system 51 for applying a composite material of the type comprising a thermoplastic material reinforced with long fibers. The placement system 51 comprises a polyarticulate arm 52, for example of the six-axis robot type, mounted movably on a linear axis 54, an application head 56 mounted at the end 58 of the polyarticulate arm 52, storage means B12077 The polyarticulate arm 52 is adapted to move the applicator head 56 in three degrees of elevation of the fibers from the storage means 60 to the application head 62. freedom of translation and three degrees of freedom of rotation. The polyarticulate arm 52 is fixed by its base 64 on a carriage 66 slidably mounted on the linear axis 54, said linear axis may consist of two parallel rails fixed to the ground. The fiber application head 56, also called the fiber placement head, comprises an application roller 68 capable of applying a strip 69 of the composite material to the support 12 held by a holding device 70. The fibers, which are not visible in FIG. 4, are pre-impregnated with the second plastic material and are packaged in the form of coils. The storage means 60 are formed of a creel receiving the fiber reels. The creel is also mounted on a follower carriage 71, disposed on the rails 54 and mechanically connected to the carriage 66 carrying the polyarticulate arm 52. The installation 50 further comprises a control module, not shown, for controlling the movement of the carriage 66 and polyarticulate arm 52 and the operation of the application head 56, for example according to programmed sequences. The application system 51 may correspond to the system marketed by Coriolis Composites. FIG. 5 shows an embodiment of the placement head 56. The placement head 56 comprises a housing 72 in which is mounted the flexible application roll 68, a long fiber guide system 74, a system 76 of Fiber cutting and a system 78 for heating the second plastic material which impregnates the fibers, the systems 74, 76 and 78 not being shown in detail in FIG. 5. The application roller 68 is rotatably mounted between two plates of the casing. By way of example, it is made of an elastomeric material coated with a release material, for example Teflon. The fiber guiding system 74 is adapted to form a sheet of substantially parallel and substantially contiguous fibers and guide the sheet obtained in the direction of the application roll 68, the fibers being fed tangentially to the application roller 68. for example, system 74 includes rollers and guides. The cutting system 76 is adapted to cut the fibers so that the band 69 applied by the head 56 is at the desired length. For example, the cutting system 76 comprises at least one planar blade mounted at the end of the rod of a pneumatic cylinder, vis-à-vis a counter-tool. The pneumatic cylinder is adapted to move the blade between a rest position in which the blade is spaced from the fiber web and an active position in which the blade abuts against the counter-tool to cut the fibers. The heating system 78 is adapted to heat the second plastic material which surrounds the fibers so as to obtain at least a partial melting of this material before its application by the roller 68 on the support 12 or on a strip of the composite material already present on the the support 12.

By way of example, the heating system 78 is an infrared heating system, a hot air heating system or a laser heating system. Preferably, the heating system 78 is a laser heating system which advantageously provides a more localized heating action and better control of the resulting heating temperature. In particular, the use of a laser heating system facilitates the heating of the band 69 simultaneously with its application to the first material. The width of the roll 68 is greater than or equal to the maximum width of the band 69. The width of the band 69 is, for example, of the order of 2 mm to 120 mm, preferably 5 mm to 50 mm. According to one embodiment, the band 69 comprises the same number of son over the entire length of the band. As a variant, the width of the band 69 varies as the band 69 is applied.

In the present embodiment, the second plastic material is heated shortly before the moment when the fiber web is applied against the support 12. The second plastic material is then a thermoplastic material, for example a polymer. thermoplastic. One embodiment of a method for manufacturing the reinforcement comprises the following steps: manufacturing the support 12 of the first plastic material, in particular by molding the first plastic material, and possibly overmolding the first plastic material onto reinforcement elements, for example metal reinforcing elements; after demolding of the support 12, application of strips 69 of the composite material by the installation 50 described above at the locations of the support 12 where a mechanical reinforcement is desired. Depending on the desired reinforcement, several strips 69 may be applied successively in the same place to form a stack of several bands. The continuous fibers 20 of the strips of a stack of strips can be oriented in the same direction or in different directions. FIGS. 6 and 7 show a variant of a support 90 made of plastic material obtained after the step of manufacturing the support by molding and before the step of applying strips of the second material. Footprints 92 are provided on the surface of the support 90. Each footprint 92 is disposed at a location where it is intended to apply a reinforcing strip of the second material. By way of example, the depth of each cavity 92 corresponds to the desired thickness of the stack of strips of the second material which will be applied to the support 90. Therefore, after application of the strips of the second material, the outer surface of the resulting structure is substantially smooth. Particular embodiments have been described.

Various variations and modifications will be apparent to the man of the art. In particular, the first material may be a fiber-reinforced plastics material, for example short fibers.

Claims (10)

REVENDICATIONS1. A method of manufacturing a seat frame, comprising applying strips (69) to a carrier (12; 90) of a first plastic material, the strips being heated by a heating means (78), each band comprising fibers (75) embedded in a second plastic material, at least some fibers extending the entire length of the strip. The method of claim 1, wherein the heating means (78) comprises a laser, a source of infrared radiation, or a source of hot air. The method of claim 1 or 2, wherein the heating means (78) comprises a laser. 4. A method according to any of claims 1 to 3, wherein the heating of each strip (69) is performed at least in part simultaneously with the application of the strip on the support (12; 90). The method of any one of claims 1 to 4, wherein the second plastic material is a thermoplastic material. The method of claim 5, wherein each strip (69) is formed by juxtaposing fibers (75) impregnated with the second plastic material, the method further comprising heating the second plastic material. The method of any one of claims 1 to 6, comprising the steps of: a) forming the support (12; 90) by injection of the first plastic material into a mold (40); b) heating at least one strip (69) by laser; and c) applying the web to the support, steps b) and c) being performed at least in part simultaneously. 30 The process according to any one of claims 1 to 7, wherein the first plastic material and / or the second plastic material are selected from the group consisting of polyamide, polypropylene or acrylonitrile butadiene styrene. B12077 - 3353 1.EN 15 The method of any one of claims 1 to 8, comprising sequentially applying multiple strips (69) at the same location of the carrier (12; 90). A method according to any one of claims 1-5, comprising forming at least one impression (92) on the surface of the support (90) and applying at least one strip (69) in the footprint.