WO2006040323A1

WO2006040323A1 - Vehicle part made of a non-yieldable material, method and mould for the production of said part

Info

Publication number: WO2006040323A1
Application number: PCT/EP2005/055167
Authority: WO
Inventors: Frédéric Charnoz; Thierry Renault; Jacques Heinry
Original assignee: Cadence Innovation
Priority date: 2004-10-11
Filing date: 2005-10-11
Publication date: 2006-04-20
Also published as: FR2876307B1; EP1809468A1; FR2876307A1

Abstract

The part, (2) particularly for a vehicle, has two main surfaces (6, 8) arranged opposite each other and comprises at least one non-yieldable material (10) extending from one surface to the other, in addition to at least one yieldable plastic material (12) extending from one surface to the other. The invention also discloses a method and mould (30) for manufacturing said part.

Description

VEHICLE PIECE HAVING NON-FLUABLE MATERIAL, METHOD AND MOLD FOR THE PRODUCTION OF SUCH A PIECE

The invention relates to at least partially plastic parts, in particular for a motor vehicle, and in particular but not exclusively the underbody parts.

It is known from EP-649 736 in the name of the applicant a motor vehicle part made by forming in a mold a stack comprising two skins made of thermoplastic material and a foam material extending between the skins. Each of these three materials is not fluable.

We will call this stack in the following a sandwich structure. The sandwich structure makes it possible to manufacture pieces that are both light and very rigid. For example, a base piece such as a motor underbody or an aerodynamic screen conventionally made of reinforced thermoplastic material is stampable with 20 to 30% glass fibers and having a thickness of 2 mm, has a weight per meter. square of 2.2 kg. The same part made by means of a 5 mm sandwich structure may have a weight per square meter of between 1.4 and 1.7 kg and a much greater rigidity. The same applies to injected polypropylene parts possibly reinforced with glass fibers.

The shaping of these sandwich structures in a mold does not involve any creep of material and can be related in its main principles to a stamping operation of a sheet. This implies that the blank of material placed in the mold must cover the latter integrally. It is even better to use blanks approximately 2 to 3 cm beyond the entire periphery of the workpiece. The material that protrudes from the mold can be cut directly into the mold or taken up again. This implies, however, that the material falls required for forming the part are substantial. They can represent a few percentages of the mass of the piece for a rectangular piece, or even 35 to 40% of its mass for a piece of complex shape. In the latter case, the cost price of the part is relatively high. When this cost price becomes prohibitive, it is preferred to use conventional molding solutions such as the compression of solid thermoplastic materials, that is to say dense or fluable, or injection techniques.

An object of the invention is to provide a part having the advantages of the sandwich structure but having a reduced cost.

For this purpose, there is provided according to the invention a part, especially for a vehicle, having two main faces opposite to each other and comprising at least one non-flowable material extending from one to the other of the two face, the part further comprising at least one flowable plastic material extending from one to the other of the two faces.

The part according to the invention may also have at least one of the following characteristics:

the one or one of the non-flowable materials comprises a plastics material;

the one or one of the non-flowable materials comprises a material other than a plastic material;

the one or one of the non-flowable materials is alveolar; the one or one of the non-flowable materials comprises a weave;

it comprises a single non-flowable material extending from one to the other of the two faces;

the or each non-flowable material occupies a medial part of the part when it is seen in plan; the or each flowable material extends around the periphery of the part;

the or each fluidizable material occupies at least one part fixing part;

the or each non-flowable material occupies a surface of the piece larger than the area occupied by the or each flowable material; the non-flowable and flowable materials comprise an identical material; it comprises a zone of mutual overlapping of the non-flowable and flowable materials; and

- the room is a piece of bedrock.

Also provided according to the invention a method for manufacturing a part, especially for a vehicle, in which at least one non-flowable material and at least one flowable plastic material are assembled so that the non-flowable material (s) extend from one to the other of two main faces of the part opposite to each other and that the fluable material or materials extend from one to the other of the two faces. The method according to the invention may also have at least one of the following characteristics:

- The materials are assembled during the shaping of the piece;

immobilizing the or each non-flowable material before compressing the or each flowable material; the one or each non-flowable material is cut during the shaping;

- the materials are shaped, then the materials are assembled; and

several parts of flowable material are assembled to the same part of non-flowable material.

Finally, there is provided according to the invention a mold for manufacturing a part, in particular for a vehicle, comprising at least a first zone arranged to shape at least one non-flowable material so that the non-flowable material or materials extend. from one to the other of two opposite major faces of the workpiece and at least one second zone arranged to shape at least one flowable plastic material so that the flowable material or materials extend from one to the other. other of the two main faces.

The mold according to the invention may also have at least one of the following characteristics:

the first and second zones of the part are arranged to generate different shaping pressures from each other;

- He understands : - a matrix ; and

first and second punches each mounted movable relative to the die so that the first punch can be immobilized relative to the die while the second punch is moving closer to the die; the first punch is mounted on the second punch; and

- It comprises at least one spring bearing on the second punch to solicit the first punch in the direction of the matrix.

Other features and advantages of the invention will become apparent in the following description of a preferred embodiment and variants given as non-limiting examples with reference to the accompanying drawings in which:

- Figure 1 is a perspective view of a part according to a preferred embodiment of the invention;

FIG. 2 is a view similar to FIG. 1 showing the sandwich structure blank that would be necessary to integrally produce the part of FIG. 1;

- Figure 3 is a view similar to Figure 1 showing in hatched form the location of the sandwich structure in the part of Figure 1;

- Figure 4 is a view similar to Figure 3 showing an alternative embodiment;

- Figures 5, 6 and 7 are three partial views in vertical section of a mold according to a preferred embodiment of the invention illustrating three steps in the manufacture of the part of Figure 1; and

- Figures 8 and 9 are two perspective views of principle illustrating two variants.

FIG. 1 illustrates a part 2 according to a preferred embodiment of the invention. This is a base piece for a motor vehicle. This piece is in this case a refit under engine. It could also be an aerodynamic screen. With reference to FIG. 2, assuming that this part is made by means of the sandwich structure over its entire surface, the one or more Foam blanks should have a larger surface area than the part. This blank 4 has been illustrated in FIG. 2. As it is a rectangular blank, it is easy to observe that the falls will be numerous, which will make the cost of the piece relatively high. This is why the part according to the invention comprises at least two materials, namely at least one non-flowable material and at least one flowable material. The part 2 comprises two main faces 6 and 8 opposite one another on both sides of the room. In the parts 12 comprising flowable material, this material extends from one to the other of the two faces 6, 8. In the part 10 comprising the non-flowable materials, these form a stack extending from the one to the other of the two faces.

FIG. 3 shows with hatching the part 10 of the part formed with non-flowable materials in a first embodiment. This part consists of the sandwich structure, namely and as illustrated in FIG. 8, a stack of three layers comprising two skins 50 made of thermoplastic material between which a cellular thermoplastic material 52, for example with a honeycomb structure, extends. bee. Each of these three materials is non-flowable in this arrangement. As seen in Figure 3, the portion 10 has a rectangular planar shape and occupies a medial portion of the workpiece without extending to any of the peripheral edges of the workpiece. Furthermore, the part comprises a portion 12 of solid material, dense, and flowable. This material is here a stampable thermoplastic material reinforced by glass fibers. This part extends around the part 10 and forms the periphery of the piece by constituting a frame. It is within this part 12 that are provided fixing areas 14 of the room 2 to the rest of the vehicle. The flowable material forming the portion 12 is in fact particularly suitable for constituting the complex shapes of the geometry of the part, such as the technical fixing zones. Part 10 comprising the non-flowable materials extends over a larger area of the workpiece than the portion 12 of flowable material. Preferably, the base materials used to form the non-flowable materials 10 and the flowable material 12 will be identical thermoplastics, such as polypropylene, polyamide or polyethylene terephthalate (PET). In the case of this fairing, one can thus obtain a part consisting of:

- 0.6 m ² sandwich structure with a thickness of 5 mm and high rigidity. The share of falls in the cellular material is reduced to 0.

- 0.15 m ² of flowable material that fills the periphery areas of the part and integrates the attachment points.

Knowing that in the embodiment of Figure 3 the part 12 of dense material makes the room relatively heavy, it is preferred to manufacture the part 2 as shown in the variant of Figure 4. On it, it is observed that again , the greater part of the part which corresponds to its median part is formed by means of the sandwich structure 10. For this, a blank 22 of sandwich structure is used whose dimensions exceed those of the middle part of the piece without however covering certain areas of the periphery. Moreover, several parts 12 of the periphery of the part are formed by means of several blanks 16 of flowable material such as reinforced thermoplastic material which can be stamped. As shown in Figure 4, the blanks 16 arranged in the mold for this purpose are for example 5 in number. In this variant, the parts 12 are therefore discontinuous with each other. The peripheral edge of the finished part is formed partly by the sandwich structure 10 and partly by the flowable material 12. Compared with the example of FIG. 3, the area occupied by the flowable material 12 is thus reduced, which makes the piece lighter. Admittedly, this leads to the generation of a few drops in the cellular material, in particular to generate certain edges of the part, but these falls are limited. Knowing that the piece thus manufactured is much more rigid than a part made entirely of flowable material, the number can be reduced. This piece is also much lighter than the part made entirely of flowable material.

FIGS. 5 to 7 illustrate a mold for manufacturing the part of FIG. 1. The mold according to this principle will allow the parts of FIGS. 3 or 4 to be made as desired.

The mold 30 comprises a matrix 32 extending in the lower part and two punches 34, 35 extending above the matrix. The mold comprises a cavity 36 delimited between the die and the punches for forming the workpiece. Each of the punches 34 and 35 is movably mounted with respect to the sliding die 32 in the vertical direction 38. The means ensuring this mobile assembly for the punch 35 have not been illustrated and are conventional. In the present example, the first punch 34 is mounted on the second punch 35. It is movable with respect to the latter and is slidably guided along the direction 38 in a cavity 40 formed in the underside of the punch 35.

The mold comprises at least one spring 42, and preferably several, extending in the vertical direction and a lower end bears on an upper face of the first punch 34 and an upper end bears against a lower face of the second punch 35. Thus, the spring 42 urges the first punch 34 towards the die by resting on the second punch 35.

The assembly formed by the first punch 34 and the portion of the matrix 32 extending facing constitutes in the mold a forming zone of the portion 10 associated with the sandwich structure. Furthermore, the assembly formed by the second punch 35 and the other parts of the facing matrix constitutes a zone of the mold dedicated to forming the parts 12 of flowable material.

To produce the piece, the sandwich structure 10 comprising the cellular material is deposited on the central part of the matrix 32 and at the periphery one or more sections of flowable material 12. The sandwich structure extends opposite the first punch 34 while the material fluidable extends opposite the second punch 35 at the periphery of the structure 10.

The crew formed by the first punch 34 and the second punch 35 is then lowered. During this descent, the first punch 34 remains stationary relative to the second punch 35. It then comes into contact with the sandwich structure 10 before the second punch 35 does not come into contact with the flowable material 12 as illustrated in FIG. 6. This contact causes the sandwich structure 10 to be pinched and therefore immobilized relative to the matrix. The first punch 34 then remains stationary relative to the die 32 while the descent of the second punch 35 which comes into contact with the flowable material 12 continues and the springs 42 press down. The flowable material 12 compressed between the second punch 35 and the matrix 32 flows at the periphery of the material 10 without migrating to the upper and lower faces of the material 10 which are pinched between the first punch 34 and the die 32.

By virtue of such an arrangement, the pressure exerted between the first punch 34 and the matrix may be relatively small, for example of the order of 10 × 10 ⁵ Pa, whereas, between the second punch 35 and the matrix 32, it may be much more high and for example between 200 and 250.10 ⁵ Pa.

During molding, at the boundary between the materials 10 and 12 is generated a mutual overlap area in which the thickness of the piece is formed by the assembly of the flowable and non-flowable materials. In this zone, the materials are welded in the mold by the action of temperature and pressure. This welding is facilitated by the fact that the materials are formed by the same basic material. As can be seen, the part is formed by means of a single forming step in a common mold receiving the materials.

The material 12 will generally be in the form of rectangular bars 16 that will be available in the mold preferably after a preliminary heating step, as well as for the sandwich structure. Of Preferably, the sections of material 12 will always be arranged in zones of the mold corresponding to parts of the part intended to be formed by this material once they have been shaped. The creep of the material makes it possible to plug the areas not covered by the material before closing the mold. One advantage of the prior nipping of the sandwich structure before causing the flow of the material 12 is to confine it in a specific area of the mold to avoid a lack of material during the creep of the material 12. It should be noted that projection techniques of material could possibly make it possible to dispense with prior nipping of the sandwich structure. Although this has not been illustrated in FIGS. 5 to 7, provision may be made to cut off during the closing of the mold the excess portions of the sandwich structure that are not intended to form part of the part 2, as in FIG. example of Figure 4.

In another embodiment of the method of the invention, it may be possible in a first step to mold to shape the sandwich structure for forming part 10 of the part. Independently of this and in a second step, the flowable material 12 may be shaped in another mold. In a third step, the portion 10 is assembled with the part or parts 12 by a conventional assembly method such as welding. {by vibration, ultrasound, laser, mirror, ...), by gluing or by mechanical assembly (screw, clip, rivet, ...). In particular, it will be possible in the context of this second embodiment to form parts 12 separately from each other to relate them independently of each other on the part 10. Alternatively, it could be provided to manufacture the parts 12 of flowable material by extrusion compression, injection or other.

In all these embodiments, knowing that the preheating times of the materials 10 and 12 are different, it will be possible to use two different furnaces. The invention makes it possible to take advantage of the advantages of the sandwich structure (weight gain compared to molded parts with a material dense) and higher stiffness, which in turn reduces the number of attachment points of the part to its support on the vehicle. The invention makes it possible to avoid significant falls in material. The flowable material 12 will make technical parts of the room such as fixing areas, legs, etc.

FIG. 8 illustrates an alternative embodiment of the part 2 according to the invention. This is an exploded perspective view illustrating the structure of parts 10 and 12. In part 10 is found the sandwich structure comprising two skins 50 of thermoplastic material and a honeycomb material 52, for example honeycomb s' extending between the two skins. At part 10, the skins are intended to form the main faces 6 and 8 of the part. The parts 12 are made of a reinforced thermoplastic material stampable as before. In the present example, the honeycomb portion 52 is formed not of thermoplastic material but of a material other than a plastic material. This is cardboard or paper.

In the alternative embodiment of Figure 9, the parts 12 are unchanged and still made of a flowable thermoplastic material. This time, the portion 10 is constituted by means of a fabric 54 comprising strands of thermoplastic material forming for example weft son, interwoven with strands of glass fibers forming for example warp son. Such a product is sold by the company Vétrotex under the name Twintex. No other layer is superimposed on this fabric which is intended to form the main faces 6 and 8 of the part at the level of the portion 10. Alternatively, several layers of this fabric may be superimposed between them. It is also possible to replace this fabric 54 with the material called Symalite and marketed by Quadrant. Symalite also has a slightly porous character. Twintex and Symalite materials are non-flowing. In both variants of Figures 8 and 9, the part and its manufacture are, moreover, in accordance with what has been described above with reference to Figures 1 and 3 to 7.

The invention is aimed in particular at the case where several non-flowable materials (for example two in number) are stacked so that this stack extends from one to the other of the main faces 6, 8 of the part to form part 10, this stack consisting solely of non-flowable materials.

Of course, we can bring to the invention many changes without departing from the scope thereof.

In the sandwich structure, it will be possible to replace the honeycomb layer with a foam.

The invention is not limited to vehicles and extends to the most varied fields. The invention may be used in aircraft, etc.

Claims

1. Part, (2) in particular for a vehicle, having two main faces (6, 8) opposite to each other and comprising at least one non-flowable material (10) extending from one to the other both sides, characterized in that the piece further comprises at least one flowable plastic material (12) extending from one to the other of the two faces.

2. Part according to the preceding claim, characterized in that the or one of the non-flowable materials comprises a plastic material.

3. Part according to any one of the preceding claims, characterized in that the or one of the non-flowable materials comprises a material other than a plastic material.

4. Part according to any one of the preceding claims, characterized in that the or one of the non-flowable materials is cellular.

5. Part according to any one of the preceding claims, characterized in that the or one of the non-flowable materials comprises weaving.

6. Coin seioπ any one of the preceding claims, characterized in that it comprises a single non-flowable material extending from one to the other of the two faces.

7. Part according to any one of the preceding claims, characterized in that the or each non-flowable material (10) occupies a central part of the part when it is seen in plan.

8. Part according to any one of the preceding claims, characterized in that the or each flowable material (12) extends at the periphery of the workpiece.

9. Part according to any one of the preceding claims, characterized in that the or each flowable material (12) occupies at least one fixing portion (14) of the workpiece.

10. Part according to any one of the preceding claims, characterized in that the or each non-flowable material (10) occupies a surface of the workpiece greater than the area occupied by the or each flowable material (12).

11. Part according to any one of the preceding claims, characterized in that the non-flowable and fluabie materials comprise an identical material.

12. Part according to any one of the preceding claims, characterized in that it comprises a mutual overlapping zone of non-flowable and flowable materials.

13. Part according to any one of the preceding claims, characterized in that the part (2) is a base piece.

14. A method of manufacturing a workpiece (2), especially for a vehicle, characterized in that at least one non-flowable material (10) and at least one flowable plastic material (12) are assembled so that the material or materials non-flowing fluids extend from one to the other of two main faces (6,8) of the part opposite to each other and that the fluable material or materials extend from one to the other other of the two faces.

15. Method according to the preceding claim, characterized in that the materials are assembled during the shaping of the workpiece.

16. A method according to any one of claims 14 or 15, characterized in that immobilizes the or each non-flowable material (10) before compressing the or each flowable material (12).

17. A method according to any one of claims 14 to 16, characterized in that the cutting or each non-flowable material (10) during shaping.

18. Process according to claim 14, characterized in that the materials are shaped and then the materials are assembled.

19. A method according to any one of claims 14 or 18, characterized in that assembling several parts of flowable material (12) to the same part of non-flowable material (10).

20. A mold (30) for manufacturing a part, particularly for a vehicle, comprising at least a first zone arranged to shape at least one non-flowable material so that the non-flowable material or materials (10) extend from one to the other of two opposite major faces of the part, characterized in that it comprises at least a second zone arranged to shape at least one flowable plastic material (12) so that the flowable material or materials extend from one to the other of the two main faces (6,8).

21. Mold according to the preceding claim, characterized in that the first and second zones of the part are arranged to generate different shaping pressures from one another.

22. Mold according to any one of claims 20 to 21, characterized in that it comprises:

a matrix (32); and

first and second punches (34,35) each mounted movable relative to the matrix so that the first punch (34) can be immobilized with respect to the matrix while the second punch (35) approaches the matrix ( 32).

23. Mold according to the preceding claim, characterized in that the first punch (34) is mounted on the second punch (35).

24. Mold according to any one of claims 22 to 23, characterized in that it comprises at least one spring (42) resting on the second punch (35) for biasing the first punch (34) towards the die (32).