Open roof construction for a vehicle

0001The invention relates to an open roof construction.

0002In an open roof construction of the type to which the present invention relates, which comprises a panel whose rear edge can be pivoted upward and downward (a so-called tilt panel), objectionable noises, in particular whistling noises, are produced in the open position of the panel. Said noises, which depend on the pivoting angle and the driving speed of the vehicle, among other things, are produced especially (but not exclusively) during the first stage of pivoting the panel from the closed position to an open position. The noises that are produced are highly objectionable to the occupants of the vehicle. The cause of said objectionable noises is to be found inter alia in the underpressure which is generated above the roof of the vehicle as a result of the air flow over the panel, which causes the air to be drawn out from the interior of the vehicle through the gap that is formed at the location of the upwardly pivoted rear edge of the panel.

0003In the past attempts have already been made to prevent the occurrence of said objectionable noises. Thus <patcit id="pcit0001" dnum="DE4016791"><text>German patent no. 4016791</text></patcit> discloses an open roof construction for a vehicle in accordance with the preamble of the main claim, wherein the means for locally influencing the air flow are made up of a strip projecting downwards near the rear edge of the panel, on the free ends of which projections are present for influencing the air flow. The function of the strip provided with projections is to disturb coherent flow structures through the aforesaid gap. The means used in this prior art solution having a substantially two-dimensional shape (after all, with a minimum dimension in the direction of flow), whose dimension in a direction perpendicularly to the panel surface is considerable. Accordingly, one drawback of this prior art solution is the fact that the obstruction in the gap that is formed by said means needs to be compensated by a greater pivoting movement of the rear edge of the panel if it is desired to maintain an unchanged effective gap between the rear edge of the panel and the roof of the vehicle. Such increased pivotability, however, makes it necessary to adapt the technical construction of the panel (in particular the parts thereof that are to effect the movement of the panel) with all the concomitant drawbacks thereof (among which an increased space requirement for construction parts, higher cost, etc.).

0004It is an object of the present invention to provide an open roof construction of the type referred to in the introduction, by means of which the occurrence of objectionable noises can be prevented while avoiding the related drawbacks of the prior art.

0005In order to accomplish that objective, the open roof construction according to the invention is characterized in that said three-dimensional body consists of a tetrahedron, one surface of which coincides with the underside of the panel, with one corner point of said surface pointing in the direction of flow, or in a direction opposite thereto. In the former orientation of said surface, the tetrahedron has a windward surface, which surface diverges in the direction of flow with respect to the panel surface, with two mutually converging (in the direction of flow) leeward surfaces adjoining said surface. The transition edges between said one diverging surface and said two converging surfaces produce the swirling effect. In the other orientation there are two mutually diverging windward surfaces, and one leeward surface, which converges with respect to the panel surface.

0006In a preferred embodiment of the open roof construction according to the invention the height of the three-dimensional body, measured in a direction perpendicularly to the panel, is in the order of three times the thickness of the panel. In this way the obstruction of the flow that is caused by the three-dimensional body is minimized, so that hardly any adaptation of the pivoting height of the rear edge of the panel is required or desired, if at all.

0007Furthermore it is advantageous with regard to the generation of swirls if said three-dimensional body includes at least one windward surface (i.e. facing towards the air flow) and at least one leeward surface (i.e. facing away from the air flow). The generation of swirls will take place at the transition between the two surfaces.

0008There are several possibilities within this framework. One possible embodiment is characterized by the fact the three-dimensional body includes sharp transition edges between a respective windward surface and a respective leeward surface on its rear side, seen in the direction of flow, which edges include an angle with the direction of flow.

0009Partially as a result of said angle (which may have any desired value), swirls are generated in the air flow at the location of said sharp transition edges, which swirls lead to the formation of so-called vortex streets. The dimensions of said vortex streets depend on the location on the transition edge where the swirls are generated, so that a large range of frequencies (as regards the objectionable background noises that occur) is covered and such objectionable background noises can be prevented from occurring over the entire frequency range. Also the total swirling of the exiting air flow in the case of small panel openings contributes to this.

0010In another variant the three-dimensional body includes windward surfaces and leeward surfaces, which surfaces gradually blend into one another. A sharply defined transition edge is lacking in this variant, but the (gradual) transition between the two surfaces can nevertheless lead to the generation of swirls.

0011Generally a number of three-dimensional bodies will be arranged beside and/or behind each other. Said bodies may or may not be arranged adjacently to each other thereby.

0012It is possible to attach the aforesaid three-dimensional bodies to an existing panel afterwards, but it is also possible to form said bodies thereon during the production stage already. In the latter case it is preferable for the three-dimensional body to be integral with the panel. Thus the three-dimensional body may form part of the so-called panel encapsulation, which forms the underside (interior side) of the panel.

0013The invention will now be explained in more detail with reference to the drawing, which shows a number of embodiments of the open roof construction according to the invention. <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a schematic side view of an embodiment of the open roof construction not belonging to the invention;</li><li><figref idref="f0001">Fig. 2</figref> is a larger-scale, perspective view of a detail of another embodiment not belonging to the invention;</li><li><figref idref="f0001">Fig. 3</figref> shows, likewise on a larger scale, a detail of an embodiment according to the invention;</li><li><figref idref="f0002">Fig. 4</figref> shows yet another embodiment not belonging to the invention;</li><li><figref idref="f0002">Fig. 5</figref> shows a variant of the embodiment of <figref idref="f0001">Fig. 2</figref>; and</li><li><figref idref="f0002">Fig. 6</figref> shows an embodiment not belonging to the invention which includes windward surfaces and leeward surfaces, which surfaces gradually blend into one another.</li></ul>

0014<figref idref="f0001">Fig. 1</figref> shows an open roof construction for a vehicle, comprising a roof opening 1 which can be closed by means of a panel 2, whose rear edge 3 can be pivoted upward and downward. Means 4 for locally influencing the air flow 5 are provided on the underside of said panel, near said rear edge. Said air flow 5 is produced as a result of an underpressure being generated above roof 6, which causes air to be drawn from the interior of the vehicle through the gap 7 that is present between rear edge 3 of the panel and roof 6. The presence of said means 4 leads to the air flow 5 being locally influenced.

0015The detail views of <figref idref="f0001 f0002">Figs. 2 - 6</figref> show the open roof construction in a direction obliquely upwards and rearwards (in the direction of rear edge 3) from a location under panel 2. Thus <figref idref="f0001">Fig. 2</figref> shows the inner side of panel 2 and the rear edge 3 thereof. Disposed near rear edge 3 is a strip 8 extending substantially transversely to panel 2, which strip has a zigzag rear edge 9. The bottom face 10 of strip 8, which is shown on the upper side in <figref idref="f0001">Fig. 2</figref>, forms a windward surface, which is separated from leeward surfaces 12 on the rear side of strip 8. An arriving air flow 13 will cause swirls 14 at the location of transition edge 11. The magnitude of said swirls 14 depends on the location where they are generated. In the illustrated example the magnitude of the swirls over edge 11 increases towards the rear (in the direction of the rear edge 3 of panel 2).

0016The swirls being generated effectively prevent the production of objectionable background noises, such as whistling noises, at the location of gap 7.

0017<figref idref="f0001">Fig. 3</figref> shows an embodiment of the open roof construction according to the invention. In a view comparable to that of <figref idref="f0001">Fig. 2</figref> the three-dimensional bodies 15, in this case in the form of tetrahedrons, can be distinguished. A first surface 16 of each tetrahedron coincides with the underside of panel 2. A corner point 17 of said surface 16 points in the direction of flow (i.e. in the direction of the rear edge 3 of panel 2).

0018As a result of this orientation of tetrahedron 15, another surface 18 thereof forms a windward surface, which diverges with respect to panel 2 and which is separated from two leeward surfaces 20 and 21 by transition edges 19. Swirls 22 are generated at the transition edges 19, which swirls help to prevent objectionable background noises, such as whistling noises, being produced.

0019As the figure shows, several three-dimensional bodies may be arranged in side-by-side relationship on panel 2. In contrast to what the figure shows, it is not always necessary for said bodies to be placed adjacently to each other. Furthermore it is conceivable for such three-dimensional bodies to be arranged one behind another, seen in the direction of flow.

0020In one variant (not shown) the bodies are turned through 180 degrees, so that exactly the opposite side of the bodies faces towards the air flow (corner point 17 points in a direction opposed to the direction of flow). Surfaces 20 and 21 are the windward surfaces and surface 18 is the leeward surface in that case. Edges 19 continue to provide the swirling effect, however.

0021The height of the three-dimensional bodies, measured in a direction perpendicularly to the panel, is generally in the order to three times the thickness of panel 2.

0022<figref idref="f0002">Fig. 4</figref> shows three-dimensional bodies 23 not belonging to the invention arranged in side-by-side relationship, which bodies each include three windward surfaces 24-26 and one leeward surface 27. It is in particular the transition edge 28 between surfaces 26 and 27 that provides the swirling effect in this case, although it cannot be ruled out that also the transition edges 29 between the respective surfaces 24, 25 on the one hand and surface 26 on the other hand contribute thereto.

0023The variant according to <figref idref="f0002">Fig. 5</figref>, which is derived from that of <figref idref="f0001">Fig. 2</figref>, comprises a zigzag rear 11 edge 11 as well as a zigzag front edge 30. As a result, a certain swirling effect can also occur at the location of edge 30.

0024<figref idref="f0002">Fig. 6</figref> finally shows an embodiment not belonging to the invention wherein there is no sharp transition between windward and leeward surfaces. In order to explain the shape of the three-dimensional body that is shown in <figref idref="f0002">Fig. 6</figref>, three sections 32-34 thereof are shown by way of illustration. The direction of flow is indicated by arrow 35. The transition between windward surfaces and leeward surfaces will be located near the place where the body has its largest cross-sectional area 33, and consequently the main part of the swirling effect will take place at that location.