WO2008012435A2

WO2008012435A2 - Lining element, especially for the interior of a motor vehicle, and method for producing same

Info

Publication number: WO2008012435A2
Application number: PCT/FR2007/001279
Authority: WO
Inventors: Jonathan Cassaro
Original assignee: Faurecia Interieur Industrie
Priority date: 2006-07-26
Filing date: 2007-07-25
Publication date: 2008-01-31
Also published as: WO2008012435A3; FR2904253A1; FR2904253B1

Abstract

The invention relates to a lining element comprising a base element (18) consisting of a rigid plastic material, a flexible skin (16) covering the base element (18) and having a substantially constant thickness, and a foam layer (20) inserted between the base element and the skin. The lining element comprises a main region (12) in which the skin and the base element define a cavity containing foam, and a marginal region comprising continuous passages (24) which connect the cavity to the edge of the lining element. The dimension of the passages which extends parallel to the adjacent edge is much longer than the dimension of same extending in the direction of the thickness, and the filling rate for filling said passages with foam is less than 1. The invention can be applied to the inner lining of motor vehicles.

Description

The present invention relates to a method of manufacturing trim elements, in particular for a vehicle interior, and the trim elements obtained by its implementation. implemented.

The invention essentially relates to dressing elements made by a high precision injection process, in which a flexible skin is carried by a base member with the interposition of a foam. At the boundaries of the covering member, the soft skin is applied against a portion of the base member by the foam in certain areas, and in other areas the base member and the skin are superimposed and are in contact. The invention particularly relates, in this context, the problem posed by the realization of marginal portions of trim elements in which the skin and the base member are superimposed and are intended to be inserted into a groove. EP-1,580,077 has already considered this problem. According to this document, the marginal area in which the skin and the base element are superimposed comprises channels in which the foam is present, so that in these channels the skin is held on the base member and, these channels, the skin is free. According to this document, this marginal zone is extended towards the edge, but does not normally open to the outside from which it is separated. Alternatively, small section channels allow evacuation of the air expelled by the injected foam and, possibly also a small amount of foam, the outlet of the foam may indicate that the injection operation e is completed.

According to the method described in the aforementioned document, as it is possible that the channels formed in the marginal zone are not filled, for example by trapping air, it is the observation of the foam outlet by the ventilation channels. which normally determines the end of injection. This operation therefore requires the attention of a operator, who must most often observe a whole edge and not just a location, the foam can go out sometimes to one end of this edge, sometimes to the other end. In this process, there is foam that exceeds and can dirty the elements of dressing.

It has been found that this problem is particularly present when the closing angle of the two parts of molds which carry the skin and the base element is less than 40 'with respect to the demolding direction. So that the skin can not be driven, it is necessary to increase the width of the marginal zone, and thus the cost of the elements.

It would be desirable to make such cladding elements without increasing the width of the marginal area, and without an operator having to watch the time of the release of excess foam. This result must be obtained without the risk of insufficient injection, that is to say without trapping air that could interfere with the contact of the base element and the skin. According to the invention, this result is obtained by carrying out continuous passages throughout the marginal zone, between the injection cavity and the outside. These continuous passages have a dimension in a direction parallel to the adjacent edge much greater than their dimension in the direction of the thickness. These passages are sufficient to allow the evacuation of all the air expelled by the advance of the foam. In addition, the filling rate of these continuous passages by the foam is less than 1, so that the foam does not appear at the edge of the room, while remaining greater than 0.2, so that it does not There is no cavity due to a filling fault outside the marginal area. These results are obtained when, under the injection conditions, the pressure loss created during the flow of the foam forming fluid in the continuous passages is sufficiently high for this injected fluid to enter a significant part of these passages.

More specifically, the invention relates to a cladding element, of the type which comprises a basic element of rigid plastic material, a flexible skin covering the base member and having a substantially constant thickness, and a foam layer interposed between the base member and the skin, the dressing element having a main zone in which the skin is spaced apart from the base member and the skin and the base member delimit between them a cavity containing foam, and a marginal zone in which the skin and the base member are in at least partial contact, marginal area having continuous passages connecting the cavity to the edge of the trim element; according to the invention, the continuous passages have a dimension in a direction parallel to the adjacent edge much greater than their dimension in the direction of the thickness, and the filling rate of the continuous passages by the foam is less than 1.

In an advantageous embodiment, the continuous passages delimit sinuous paths.

In a variant, the degree of filling of the continuous passages by the foam varies in the marginal zone, in the direction of the edge, and reaches at least locally a value greater than 0.7.

In an advantageous embodiment, the section of the continuous passages decreases between their nearest portions of the main zone and the outer edge of the cladding element.

In a variant, the continuous passages are delimited by projections formed on the base element on the side intended to be in contact with the flexible skin.

In one embodiment, the projections occupy a larger portion of the surface of the base member near the edge than the main zone side.

For example, the continuous passages have a sinuous shape because the projections are staggered on the base member. Preferably, the average filling ratio does not exceed 0.8.

The invention also relates to a method of manufacturing a dressing element object of the preceding paragraphs, of the type which comprises the production of the base element and the skin, the arrangement of the skin and the base element in the cavity of a mold, the closing of the mold with application of the skin against the marginal zone of the base member, and injecting a foam-forming fluid between the base member and the skin. According to the invention, the method comprises, prior to the injection of the foam-forming fluid into the cavity of the dressing element, the determination of the relationship between, on the one hand, the parameters of injection of the fluid. of the foam, the geometrical parameters of the continuous passages, and the dynamic viscosity parameter of the foam-forming fluid, and secondly the degree of filling of the continuous passages by the foam-forming fluid, and the selection of values parameters such that, at the end of the injection, the degree of filling of the continuous passages by the foam-forming fluid is greater than 0.2 but less than 1, and, during the injection, the use of the values selected parameters. In one embodiment, determining the relationship between the parameters and the degree of filling comprises realizing the marginal area of the base element so that it delineates specific geometric property passages, and then empirically determining at least one parameter chosen from the injection parameters and the dynamic viscosity parameter giving a degree of filling of the continuous passages by the foam-forming fluid greater than 0.2 but less than 1. For example, the parameter of injection is selected from the pressure and the duration of injection.

In one variant, the empirical determination of at least one parameter comprises the variation of the dynamic viscosity by variation of the injection temperature.

Advantages of the invention are that, despite the low height of the passages, their large dimension in a direction parallel to the edge makes it possible on the one hand to obtain excellent evacuation of the gases from the mold, and on the other hand to form a sufficient volume for the injection operation to be interrupted automatically, or at least without an observer having to monitor the exit of foam from the passages. In addition, the marginal area may keep a small width. Other features and advantages of the invention will be better understood on reading the following description of exemplary embodiments, with reference to the appended drawings, in which: FIG. 1 is a diagrammatic section of an element of FIG. cladding made by the method of the invention; Figure 2 is a sectional view of the circled portion of Figure 1; Figure 3 is a section of the circled portion of Figure 1, in a variant; FIG. 4 shows an example of a base element surface intended to be in contact with the skin of a covering element; and Figure 5 shows a base element surface variant. Figure 1 is a section of a portion of a trim element, including the interior of a vehicle.

The covering element 10 has a main zone 12 and a marginal zone 14. In the main zone 12, a flexible skin 16, for example polyolefin skin, is kept at a distance from a base element 18 formed of a rigid plastic material, for example polyolefin, by a foam layer 20 introduced by injection into a mold in which the skin 16 and the base member 18 have been previously positioned. FIG. 2 is an enlargement of the circled portion 22 of FIG. 1. It is noted that in the marginal zone 14, the base element 18 is not in continuous and total contact with the skin 16. 24. On the section of FIG. 2, the reference 24 seems to designate cavities, but these are in fact continuous passages, as indicated for example in FIG. 4. On this one, it is noted that passages 24 are delimited between projections 26 arranged in staggered rows. So passages 24 are continuous passages connecting the cavity formed between the skin 16 and the base member 18 in the main zone 12, outside the edge.

In this context, the term "continuous" in the expression "continuous passages" indicates that, in the marginal zone, paths of passage of foam merge locally; for example, the foam forming fluids of two adjacent paths passing on either side of a protrusion can regroup after the protrusion. According to the invention, the filling rate of these passages 24 by the foam is between 0.2 and less than 1. This last value simply indicates that, during manufacture, the foam does not come out and does not cause soiling . On the other hand, it is desirable that this level be high, at least in certain parts along the edge, so that the skin is well held against the base element.

It is conceivable that the continuous and numerous passages 24 defined between the projections 26 facilitate ventilation, that is to say the evacuation of the air driven by the foam-forming fluid when it is injected into the cavity included between the skin 16 and the base member 18.

The geometric properties of the passages 24, which are essentially, in the particular case of Figure 4, the height of the projections 26, their section, their spacing, their arrangement, staggered or not, etc. determine geometrical parameters of the passages such as the section, the length and the sinuosity of the passages. The values of these geometrical parameters are selected to cause the creation, during the flow of the foam-forming fluid, of a pressure drop sufficiently large that, at the end of the injection, the filling rate of the passages continuous by the foam is less than 1, that is to say that the injected fluid has not reached the edge of the base member 18. This feature can be easily observed on the trim elements obtained by the implementation of the process, since it is sufficient to spread the skin, pulling out parts of foam, to determine how far the foam has entered the marginal area.

FIG. 5 shows an arrangement in which the pressure loss created during the flow of the foam-forming fluid is greater than in the case of FIG. 4. This greater pressure drop is obtained because the projections occupy most of the surface, so that the passages have a reduced section, and, moreover, they are especially much more sinuous, as indicated by the reference 24 '. This result is obtained by simple elongation of the projections 26 'or, compared with FIG. 4, by two-to-two connection of the projections 26.

FIGS. 2, 4 and 5 show embodiments in which the base element 18, 18 'delimits passages with projections of constant height. This characteristic is not essential. Figure 3 shows an example in which the passages have a varying height or depth.

Thus, the essential features of the invention are on the one hand the fact that there are continuous passages between the main zone and the outside in all the marginal zone part which is intended to be introduced into a support groove. the lining element, and that these passages create a pressure drop sufficiently high that, after the injection of the foam - forming fluid, the filling rate of the passages by the foam is less than 1. that this rate does not reach anywhere 1, and that the foam does not come out at the edge, it is desirable that the average filling rate does not exceed 0.8.

The pressure drop in the passages depends on many parameters. These parameters firstly comprise the parameters of the injection itself, in particular the pressure used and the duration of the injection, and the fact that the injection may optionally be staged.

Other paramount parameters are obviously the geometrical parameters of the continuous passages, in particular δ their length, their section, their sinuosity, in a manner known to those skilled in the art.

Finally, other essential parameters for the determination of this pressure drop are fixed by the intrinsic properties of the injected fluid, essentially its dynamic viscosity, and by the pressure used.

It is conceivable that one can act on any of the above parameters to determine the conditions of implementation of the method. However, since the geometrical properties of the continuous passages are essentially fixed by the configuration of the base element, it is desirable that this configuration of the base element is initially set, and that the other parameters are modulated in the same manner. necessary. Such parameters that can be modulated are the pressure and the duration of injection, possibly the creation of several injection phases, at different pressures and / or with different durations. Another parameter that can be modulated is the dynamic viscosity of the injected fluid, since this viscosity is very dependent on the injection temperature. A simple adjustment of the injection temperature is a convenient option during the implementation of the method.

It is therefore conceivable that the skilled person has many possibilities for this implementation.

Since it is desirable for the skin to be held over most of the width of the marginal zone, it is desirable that the pressure drop which is opposite to the fluid advance along the continuous passages be relatively low. on the side of the main zone and bigger and bigger towards the outside. In this way, the foam may be present near the outer edge, without ever reaching it.

In the embodiments described above, this result can be obtained when the projections 26, 26 'of FIGS. 4 and 5 are denser or of larger section near the edge than near the main zone. Note that the implementation of the method of the invention does not require any modification of the equipment normally used, since the modifications may be limited to the single basic element.

Claims

A cladding element of the type comprising: a base member (18, 18 ', 18 ") of rigid plastic material, a flexible skin (16) covering the base member (18, 18', 18") and having a substantially constant thickness, and a layer (20) of foam interposed between the base member and the skin, the dressing member having a main zone (12) in which the skin is at a distance from the element base (18, 18 ', 18 ") and the skin and the base element delimit between them a cavity containing foam, and a marginal zone (14) in which the skin (16) and the base element (18, 18 ', 18 ") are in at least partial contact, the marginal zone (14) having continuous passages (24, 24', 24") connecting the cavity to the edge of the cladding element, characterized in that that the continuous passages have a dimension in a direction parallel to the adjacent edge much greater than their dimension in the direction of the thickness, and the filling rate of the passes Continuous ages (24, 24 ', 24 ") by the foam is less than 1.

2. cladding element according to claim 3, characterized in that the continuous passages (24, 24 ', 24 ") delimit sinuous paths.

3. cladding element according to one of claims 1 and 2, characterized in that the degree of filling of the continuous passages (24, 24 ', 24 ") by the foam varies in the marginal zone (14) in the direction edge and at least locally reaches a value greater than 0.7.

4. Cladding element according to any one of claims 1 to 3, characterized in that the section of the continuous passages (24, 24 ', 24 ") decreases between their nearest parts of the main zone (12) and the outer edge of the trim element.

5. Cladding element according to one of claims 1 to 4, characterized in that the continuous passages (24, 24 ', 24 ") are delimited by projections (26, 26 ') formed on the base member on the side intended to be in contact with the flexible skin (16).

6. cladding element according to claim 5, characterized in that the projections (26, 26 ') occupy a larger part of the surface of the base element near the edge than the side of the main zone.

7. cladding element according to any one of the preceding claims, characterized in that the average filling rate does not exceed 0.8.

8. A method of manufacturing a trim element according to any one of the preceding claims, of the type which comprises: the embodiment of the base element (18, 18 ', 18 ") and the skin (16) the arrangement of the skin (16) and the base element (18, 18 ', 18 ") in the cavity of a mold, the closing of the mold with application of the skin (16) against the marginal zone of the base element, and the injection of a foam-forming fluid between the base element (18, 18 ', 18 ") and the skin (16), characterized in that it comprises, prior to injecting the foam-forming fluid into the cavity of the dressing element, determining the relationship between, on the one hand, the injection parameters of the foam-forming fluid, the geometric parameters of the continuous passages (24), , 24 ', 24 "), and the dynamic viscosity parameter of the foam-forming fluid, and secondly the degree of filling of the continuous passages (24, 24', 24). ") by the foam-forming fluid, and the selection of parameter values such that, at the end of the injection, the degree of filling of the continuous passages (24, 24 ', 24") with the formation fluid foam is greater than 0.2 but less than 1, and during the injection, the use of the values of the parameters thus selected.

9. Method according to claim 8, characterized in that the determination of the relationship between the parameters and the degree of filling comprises forming the marginal zone of the base member (18, 18 ', 18 ") to delimit passages (24, 24', 24") of determined geometric properties, and then empirically determining at least a parameter chosen from the injection parameters and the dynamic viscosity parameter giving a degree of filling of the continuous passages by the foam-forming fluid greater than 0.2 but less than 1.

10. The method of claim 9, characterized in that the empirical determination of at least one parameter comprises the variation of the dynamic viscosity by variation of the injection temperature.