FR2992241A1 - METHOD OF FORMING A METAL TUBE WITH FASTENING ON A FLANGE AND ASSEMBLY COMPRISING SUCH A TUBE - Google Patents

Abstract

A method of forming a metal tube (1) on an orifice (50) of a flange (5), the flange having a first face (51) and a second face (52), in a forming assembly comprising a die (2), a first punch (4) and a second punch (6), the first punch being movably mounted along the axis A against a return means (7), the method comprising: a- simultaneously the first and second punches, to form an end disc (12) intended to bear on the first face, b- continue the descent of the second punch by allowing the first punch to move back to form a projection bead (15) axial, c- continue the descent of the first and second punches to form a collar (13) bearing bearing on a second face.

Description

The present invention relates to processes for forming a metal tube with fixing on a flange and also relating to assemblies comprising such a tube fixed on a flange and also to assemblies comprising such a tube attached to a flange and also to assemblies comprising such a tube attached to a flange. a flask. It relates more particularly to a method and an assembly comprising a tube attached to a flange, such an assembly that can be used to manufacture a frame member or a motor vehicle seat frame. In the prior art, it is known to use a punch and a die to deformably join the end of a metal tube of circular section to an orifice of a flange. It is thus possible to form a collar serving as a shoulder and an end disc serving as a stop, the flange being sandwiched between the collar and the end disc in the vicinity of the orifice. This type of assembly effectively contributes to the strength of the seat structure and is put to use in the event of shock to the vehicle. Crash resistance criteria are becoming increasingly high for vehicles and therefore, it has become necessary to further increase the robustness of such assemblies. For this purpose, the invention provides a method of forming a metal tube of circular cross-section of axis A, the tube having an end zone to be deformed to fix it on an orifice of a flange, in a seat member, the flange having a first face and a second face, the method being implemented in a forming assembly comprising a die, a first punch and a second punch, the first punch being movably mounted according to the A-axis relative to the second punch against a return means, the tube being held in position by the die, an end zone of the tube being received in the orifice of the flange, the method comprising the steps: a- simultaneously lowering the first and second punches towards the die, to deform by radial expansion a first end portion of the tube, so as to form an end disc intended to bear against a first face of the flange, b- p bear the descent of the second punch by letting go the first punch to form a bead in axial projection protruding from the side of the first face of the flange and initiate the formation of a collar between the flange and the matrix, c- continue the descent of the first and second punches to the die to deform by radial expansion a second portion of the tube, to form a bearing collar bearing on a second face of the flange.

Thanks to these provisions, it is possible to increase the strength of an assembly obtained by such a method, in particular the resistance to forces experienced especially in the direction of the axis A of the tube. In particular, the presence of the bead has a beneficial effect on the resistance to efforts.

In various embodiments of the invention, one or more of the following provisions may also be used: in one aspect, during step c, the pressure is flange between the collar and the end disc; whereby the tube is immobilized both in translation and in rotation around the axis A; - In another aspect, the flange can be recalled to a reference position remote from the matrix by auxiliary return means; whereby the collar formation step is made more reliable; in another aspect, the outer diameter of the end disc may be between 1.3 times and 1.4 times the outer diameter D1 of the base tube; and in another aspect, the outer diameter of the collar may be between 1.3 times and 1.4 times the outer diameter of the base tube; so that the large bearing surfaces thus formed between the tube and the flange increase the resistance to efforts; in another aspect, the bead in axial projection protrudes from the end disc by at least 0.3 mm; so that the robustness of the end disk is thus increased; - In another aspect, the first punch may have a flared annular zone, which flares from the inside diameter of the tube outwardly to provide a space when the first punch is retracted for the formation of the bead. In addition, the invention also relates to an assembly comprising a metal tube formed on a flange having an orifice through which the tube passes, the tube comprising, after a forming and assembly operation: tubular of revolution about an axis A, - an end disc resting on a first face of the flange, - a collar resting on a second face of the flange, - a neck portion received in the orifice of the flange, arranged between the end disc and the collar, - an axial projection bead protruding from the side of the first face of the flange, interposed between the end disc and the neck portion, the flange being sandwiched between the collar and the end disk; whereby a very robust assembly is obtained with respect to the forces that can be experienced in the event of impact. According to various embodiments of the invention, it may further be possible to use, for such an assembly, one and / or the other of the arrangements described above for the method. The invention also relates to a vehicle seat comprising an assembly as described above. Other aspects, objects and advantages of the invention will appear on reading the following description of one of its embodiments, given by way of non-limiting example with the aid of the accompanying drawings in which: FIG. 1 is a partial perspective view of a seat cushion frame comprising an assembly according to one embodiment of the invention; FIG. 2 schematically shows a section illustrating an initial stage of the assembly process for producing 1 to 3, 4 and 5 show diagrammatically in section the successive steps of the assembly process for making the assembly used in the seat cushion of FIG. Fig. 6 is a cross-section of the assembly used in the seat cushion of Fig. 1. In the various figures, the same references denote like or similar elements. Figure 1 shows a seat frame of a motor vehicle seat. This seat frame usually comprises a right side flange 5 and a left side flange connected together by tubes 1, 1 ', 1 "In the example illustrated, the tube 1 directly connects the left and right flanges 5 while the tube 1 'connects the bodies of two connecting rods 5', respectively left and right, hinged to the lateral flanges, In addition, the tube 1 "connects the points of articulation of two connecting rods 5", respectively left and The invention described below relates to the attachment of an end of a tube (1, 1 ', 1 ") having an axis A on a part arranged transversely to the axis A at least in the vicinity of the end of a tube. The part on which the tube (1, 1 ', 1 ") is fixed may be a flange, a flange, a connecting rod, a structural plate, a piece of reinforcement of any kind, the term" flange "will therefore denote any part pierced on which the tube is assembled.This piece may be typically metallic, but it may also be a plastic part with high mechanical characteristics, or a part based on fiberglass or carbon fiber. (1,1 ', 1 ") is made of metal, steel or alloy, or aluminum with sufficient ductility to be able to undergo cold forming operations as will be described below. For example, one may opt for a high elasticity steel BFS 390B or a steel 'dualphase' DP600. In addition, the tube has an end zone 10 which has, at least in the vicinity of the attachment on the flange, a cylindrical shape of revolution, and preferably has a circular section. The outer diameter of the tube 1 may be between 10 mm and 40 mm, for example 20 or 25 mm. The thickness of the tube 1 may be 0.8 to 3 mm. As shown in FIGS. 2 to 6, the process used uses a forming assembly which comprises: a matrix 2 intended to hold the tube 30 firmly, for example by means of jaws (not shown), the die having a face upper 26, and a housing 25, - a first punch 4, with a symmetrical front portion 40 of revolution centered on the axis A, a diameter close to the inside diameter of the tube OD, 35 - and a second punch 6, arranged radially around the first punch 4, the second punch 6 being movable by press piston type displacement means (not shown). The first punch 4 is mounted movably along the axis A 5 relative to the second punch against at least one return means 7; this or these return means 7 may be made in the form of an elastic spring with a closed gas volume, or in the form of a mechanical spring. These return means 7 are supported on the one hand on a base 60 linked to the second punch 6 and on the other hand on the rear 47 of the first punch 4. These return means 7 recall the first punch 4 in the direction of the die 2 to a rest position in which a shoulder 41 before the first punch 4 bears against a rear reinforcement zone 61 of the second punch 6. The second punch 6 has on its underside 65 an annular recess 62 centered on the axis A and having an outer edge 63. In FIG. 2, the rest position is represented, before any deformation of the tube 1. It starts from a simple straight tube and of circular section having an outer surface la and is an inner surface lb, with an inside diameter denoted OD and an outside diameter denoted Dl. The tube 1 comprises an end zone 10 which is received in an orifice 50 of the flange 5, preferably a round bore. The inside diameter of said orifice is equal to or slightly greater than the outside diameter D1 of the tube. The flange extends, between the die 2 and the set of punches 4,6, substantially in a plane perpendicular to the axis A of the tube, at least in the vicinity of the orifice 50. The flange is disposed on auxiliary return means 75 remote from the upper face 26 of the matrix, which defines a reference position for the flange 5 (see Figs 2 and 3). The flange comprises a first face 51 facing upwards and a second face 52 facing downwards. The thickness of the flange may be low in the case of a metal part, that is to say between 0.5mm and 3mm, but it could be greater in the case of a plastic part without this does not pose a problem. In FIG. 3, which illustrates the state at the end of the first step noted a-, the simultaneous descent of the first and second punches 4,6 towards the matrix has been caused to deform by radial expansion a first end portion. of the tube, in order to form an end disk 12 intended to bear on a first face 51 of the flange. More specifically, the front end 19 of the tube is deflected by a flared annular zone 42 of the first punch 4, which area flares out from the inside diameter OD of the tube. The radial expansion continues until the front end 19 reaches the annular edge 63 of the recess 62. An end disc 12 extending perpendicular to the axis A is thus formed. Until this moment, the first punch 4 is still at its rest position relative to the second punch 6. In FIG. 4, which illustrates the state at the end of the second step marked b-, the descent was continued and the first punch 4 has moved back relative to the second punch 6, the return means 7 then being compressed. At the location of the flared zone 42 in the retracted position, a bead 15 is formed protruding from the end disc 12 upwards. In addition, a buckling occurs and a neck primer 18 is formed between the orifice 50 and the bottom of the housing 25. The presence of the front portion 40 of the first diameter punch OD which contacts the inner surface 1b of the tube prevents any bending of the tube inwards. On the other hand, the contact of the orifice 50 with the outer surface prevents it from deforming at this level, creating a neck region 14 on the tube. Therefore, a neck primer 18 is formed between the orifice 50 of the tube and the die 2.

The height available between the orifice 50 and the bottom of the housing 25 delimits the buckling zone which will form a collar in the next step, this height will be chosen substantially as being double the radial projection of the collar to be produced.

In FIG. 5, which illustrates the state at the end of the third step marked c-, the descent has continued and a collar 13 has been formed by completely folding the previously formed collar primer 18, the makes the compression of the auxiliary return means 75. Indeed, during the continuation of the downward movement, the second punch 6 comes to contact the upper face 51 of the flange and causes the flange 5 down until it abuts the upper surface 26 of the die, wherein the auxiliary biasing means 75 is compressed, and the collar is shaped in the annular housing 25 whose depth relative to the upper surface 26 is substantially twice tube thickness. The collar 13 comprises a first ring extending transversely to the axis A, a bend at 180 ° on its outside, then a second ring extending transversely to the axis A and pressed against the first. Below the collar 13, there remains a tubular portion 11 of undeformed revolution.

Above the collar 13, the neck section 14 has a non-deformed section relative to the base tube with an outer diameter D1. In addition, advantageously, the depths of the housing 25 and the recess 62 are chosen so as to come, at the end of the stroke, to press the flange between the collar and the end disk 12. The tube is then immobilized at the end of the stroke. translation and rotation about the axis A. It is also possible to provide an anti-rotation indentation by means of one or more notches provided at the orifice 50. It should be noted that the bead 15 protrudes from the disk end 12 of a dimension 'e' preferably greater than or equal to 0.3 mm, and even more preferably close to 0.5 mm. Advantageously, the outer diameter D3 of the end disc 12 can range from 1.3 to 1.4 times the outer diameter D1 of the base tube. Preferably, one opts for an outer diameter D3 of the end disc 12 close to 1.4 times the outer diameter D1 of the base tube. In addition, the outer diameter D2 of the collar 13 can range from 1.3 to 1.4 times the outer diameter D1 of the base tube. Preferably, one will also opt for an outside diameter D2 of the collar 13 close to 1.4 times the outer diameter D1 of the base tube. Thus, the contact surfaces between the flange and the deformed areas of the tube are thus large and contributes to improving the resistance to efforts. It should be noted that the method can be used elsewhere than in a seat, for example a backrest, or a headrest.

Claims (10)

REVENDICATIONS1. Process for forming a metal tube (1) of circular cross-section of axis A, the tube having an end zone to be deformed in order to fix it on an orifice (50) of a flange (5) in an element seat plate, the flange having a first face (51) and a second face (52), the method being implemented in a forming assembly comprising a die (2), a first punch (4) and a second punch (6), the first punch (4) being mounted movably along the axis A with respect to the second punch against return means (7), the tube being held in position by the die, a zone d end of the tube 15 being received in the orifice of the flange, the method comprising: a- simultaneously lowering the first and second punches 4,6 towards the matrix, to deform by radial expansion a first end portion of the tube, in order to 20 forming an end disk (12) intended to bear on a first face (51) of the flask, b- continue the descent of the second punch (6) by leaving the first punch (4) to retract to form a bead (15) in axial projection protruding from the side of the first face of the flange and to initiate the formation of a collar between the flange and the die, c- continue the descent of the first and second punches (4,6) towards the die to deform by radial expansion a second portion of the tube, to form a collar (13) of support coming from pressing on a second face (52) of the flange. 2. forming method according to claim 1, wherein during step c-, one just press the flange between the collar (13) and the end disc (12). 35 3. A forming method according to one of claims 1 to 2, wherein the flange (5) is returned to a rest position remote from the matrix by auxiliary return means (75). 4. forming method according to one of claims 1 to 3, wherein the outer diameter (D3) of the end disc (12) is between 1.3 times and 1.4 times the outer diameter (D1) of the tube base, and / or the outer diameter (D2) of the collar (13) is between 1.3 times and 1.4 times the outer diameter D1 of the base tube. 5. forming method according to one of claims 1 to 4, wherein the bead (15) in axial projection protrudes from the end disc (12) at least 0.3mm. 6. forming method according to one of claims 1 to 5, wherein the first punch has a flared annular zone (42), which flares from the diameter (OD) outwardly to provide a space during the retreat of the first punch for forming the bead (15). 7. An assembly comprising a metal tube (1) formed on a flange having an orifice through which the tube passes, the tube comprising, after a forming and assembly operation: a tubular portion (11) of revolution about an axis A, - an end disk (12) resting on a first face (51) of the flange, - a collar (13) resting on a second face (52) of the flange, - a collar portion (14) received in the orifice of the flange, arranged between the end disc and the collar, - a bead (15) in axial projection protruding from the side of the first face of the flange, interposed between the disc of the flange. end and the neck portion, the flange being sandwiched between the collar and the end disc. An assembly according to claim 7, wherein the outer diameter (D3) of the end disc (12) is between 1.3 times and 1.4 times the outer diameter D1 of the base tube, and / or the outer diameter (D2) of the collar (13) is between 1.3 times and 1.4 times the outer diameter D1 of the base tube. An assembly according to claim 7 or 8, wherein the axially projecting bead (15) protrudes from the end disc (12) by at least 0.3mm. 10. Seat for a motor vehicle comprising an assembly according to one of claims 7 to 9.