VEHICLE BODY GROOVE WITH UPSTREAM HERRINGBONE EDGE

Abstract

VEHICLE BODYWORK GROOVE WITH UPSTREAM EDGE IN HERRINGBONE The invention relates to a motor vehicle bodywork (2), comprising two adjacent bodywork elements (4, 6) forming, adjacent to them, a groove (8) transverse to a main airflow direction when the motor vehicle is moving, the two adjacent bodywork elements (4, 6) comprising an upstream bodywork element (4) and a downstream bodywork element (6), said groove (8) being delimited, upstream, by a downstream edge (4.1) of the upstream bodywork element (4) and, downstream, by an upstream edge (6.1) of the downstream bodywork element (6); wherein the downstream edge (4.1) of the upstream bodywork element (4) has, in the extent of the upstream bodywork element, a herringbone profile with points directed towards the upstream edge (6.1) of the downstream bodywork element (6). (Figure to be published with the abstract: Figure 1)

Description

Title of the invention: VEHICLE BODY GROOVE WITH UPSTREAM HERRINGBONE EDGE Technical field

[0001] The invention relates to the field of motor vehicle bodies, more particularly to the field of managing aerodynamic noise from motor vehicle bodies. Prior art

[0002] The published patent document FR 2 910 863 A1 relates to a device for reducing aerodynamic noise generated in a cavity formed by a groove between two bodywork elements of a motor vehicle. This device comprises a perforated wall arranged in the cavity and connected to a sound absorption cavity. This device is interesting but has a drawback of complexity and cost of implementation, in particular in the context of mass production.

[0003] The published patent document FR 2918016A1 relates to another device for reducing aerodynamic noise generated in a cavity formed by a groove between two bodywork elements of a motor vehicle. This other device comprises one or more blocks made of elastically deformable material, such as foam in particular, forming a separation in the cavity. This or these blocks are fixed to one of the two bodywork elements. Similar to the device of the previous teaching, this device is interesting but has a drawback of complexity and cost of implementation, in particular in the context of mass production.

[0004] The aerodynamic noise reduction devices of the aforementioned teachings seek to reduce by absorption the aerodynamic noise generated in the cavity formed by the groove between the two adjacent bodywork elements. They do not make it possible to reduce the generation or production of these aerodynamic noises. Presentation of the invention

[0005] The invention aims to overcome at least one drawback of the aforementioned state of the art. More particularly, the invention aims to reduce the aerodynamic noise generated in the cavity formed by a groove between the two adjacent bodywork elements.

[0006] The subject of the invention is a motor vehicle body, comprising two adjacent body elements forming, at their adjacency, a groove transverse to a main direction of air flow when the motor vehicle is moving, the two adjacent body elements comprising a body element upstream and a downstream bodywork element, said groove being delimited, upstream, by a downstream edge of the upstream bodywork element and, downstream, by an upstream edge of the downstream bodywork element; remarkable in that the downstream edge of the upstream bodywork element has, in the extent of the upstream bodywork element, a chevron profile with points directed towards the upstream edge of the downstream bodywork element.

[0007] The downstream edge of the upstream body element corresponds to the upstream edge of the groove. Similarly, the upstream edge of the downstream body element corresponds to the downstream edge of the groove.

[0008] The downstream edge of the groove, that is to say the upstream edge of the downstream bodywork element, is advantageously generally straight or rectilinear. It is understood that it may have a slight curvature, inherent in the usually complex shape of the motor vehicle bodywork. The concept of a straight or rectilinear profile is thus to be understood on the scale of the chevrons of the upstream profile of the groove, that is to say the downstream edge of the upstream bodywork element.

[0009] According to an advantageous embodiment of the invention, the groove has a width in the main direction of air flow, the chevron profile covering at least part of the width of the groove.

[0010] The width of the groove, in the main direction of air flow, is advantageously delimited, upstream, by an upstream wall of the groove adjacent to the upstream bodywork element, and downstream, by the downstream edge of the groove, i.e. the upstream edge of the downstream bodywork element.

[0011] According to an advantageous embodiment of the invention, the overlap of the width of the groove by the chevron profile is greater than or equal to 1 / 3.

[0012] According to an advantageous embodiment of the invention, the overlap of the width of the groove by the chevron profile is greater than or equal to 1 / 2.

[0013] According to an advantageous embodiment of the invention, the overlap of the width of the groove by the chevron profile is greater than or equal to 3 / 4.

[0014] According to an advantageous embodiment of the invention, the chevron profile is formed integrally with the upstream bodywork element.

[0015] According to an advantageous embodiment of the invention, the chevron profile is formed on an element attached to the upstream bodywork element.

[0016] According to an advantageous embodiment of the invention, at least one of the upstream bodywork element and the downstream bodywork element is an opening.

[0017] According to an advantageous embodiment of the invention, the upstream bodywork element is a roof and the downstream bodywork element is a rear flap.

[0018] The invention also relates to a method for reducing aerodynamic noise produced in a groove in the body of a motor vehicle, said groove being transverse to a main direction of air flow when the motor vehicle moves, and delimited, upstream, by a downstream edge of an upstream bodywork element and, downstream, by an upstream edge of a downstream bodywork element; remarkable in that said method comprises providing at the downstream edge of the upstream bodywork element a chevron profile with points directed towards the upstream edge of the downstream bodywork element, the motor vehicle bodywork being according to the invention.

[0019] The measures of the invention are advantageous in that they significantly reduce the production of aerodynamic noise in the bodywork grooves of motor vehicles, particularly in frequency ranges where the human ear is most sensitive, in particular between 500 and 1000 Hz. Furthermore, the measures of the invention can be easily implemented, in particular by forming the chevron profile directly in the bodywork element or by attaching to the bodywork element an element with the previously formed chevron profile, in particular by plastic molding.

[0020] Compared to the aforementioned state of the art, the invention is advantageous in that it reduces the production of aerodynamic noise, meaning that it can be combined with state of the art solutions consisting of absorbing the aerodynamic noise produced. Brief description of the drawings

[0021] [Fig. 1] is a perspective view of a vehicle body showing a groove whose upstream edge has a herringbone profile, in accordance with the invention;

[0022] [Fig.2] is a geometric representation of the herringbone profile of [Fig.l];

[0023] [Fig.3] is a graphical representation of the noise measured in the passenger compartment of the motor vehicle of [Fig.l] in the presence of the chevron profile at the upstream edge of the groove and this for different overlap rates. Detailed description

[0024] [Fig.l] is a perspective representation of a vehicle body provided with a groove between two body elements whose upstream edge has a chevron profile, in accordance with the invention.

[0025] The motor vehicle body 2 comprises two adjacent body elements 4 and 6, forming at their adjacency, that is to say at the place where they are adjacent, a groove 8, also commonly called a caesura. This groove extends transversely to the motor vehicle and thus transversely to a main direction of air flow along the body of the motor vehicle when the latter is moving forward. In the description which follows, the concepts of flow orientation such as “downstream” and “upstream” are to be understood with reference to this main direction of air flow along the body of the vehicle au- car.

[0026] The bodywork element 4 is upstream of the groove 8 and comprises a downstream edge 4.1 delimiting, upstream, the groove. The bodywork element 6 is downstream of the groove 8 and comprises an upstream edge 6.1 delimiting, downstream, the groove 8.

[0027] In this case, the upstream bodywork element is a roof panel and the downstream bodywork element 6 is a rear trunk flap of the motor vehicle bodywork 2.

[0028] A portion of the groove 8 is illustrated enlarged in the detail rectangle in [Fig.l]. It can be seen that the downstream edge 4.1 of the upstream bodywork element 4 has a herringbone profile with points directed downstream, i.e. towards the upstream edge 6.1 of the downstream bodywork element 6. The presence of this herringbone profile substantially modifies the interaction between the flow and the groove 8 and, therefore, substantially reduces the production of aerodynamic noise in the groove 8 in question.

[0029] The volume of the groove 8 is visible by the sectional view showing an upstream wall 8.1 and a downstream wall 8.2, both directed in directions transverse to a mean plane of connection of the upstream 4 and downstream 6 bodywork elements, at the level of the groove 8. In this case, taking into account the fact that this connection plane is close to a horizontal plane, the upstream 8.1 and downstream 8.2 walls extend mainly downwards. In the specific case where the groove 8 is located between a roof panel and a rear trunk flap, the upstream wall 8.1 is integral with the body of the vehicle, more particularly still forms part of a rear roof crossmember, and the downstream wall 8.2 forms part of the rear trunk flap, more particularly still forms part of a lining of the rear trunk flap. We can observe the presence of a lip seal 8.3 with a U-shaped section fixing zone fitting a joining groove of the upstream wall 8.2 with another bodywork element, and a contact zone, forming a hollow and deformable circular section flange, in contact with a support zone of the downstream wall 8.2. The groove 8 thus has a certain depth, due in particular to various construction constraints, rigidity and sealing of the motor vehicle bodywork 2, this depth being conducive to the development of aerodynamic noise.

[0030] Each chevron forms two portions 4.1.1 and 4.1.2 of the downstream edge 4.1 of the upstream bodywork element 4, which converge downstream. The main flow, along the outer surface is modified via the two portions 4.1.1 and 4.1.2 of the downstream edge 4.1 of the upstream bodywork element 4. These two portions are inclined relative to the direction of the main flow, which corresponds to the longitudinal direction of the motor vehicle bodywork 2, these inclinations being contrary or opposite. The two inclined portions will generate two counter-rotating secondary vortices, illustrated in the detail circle in [Fig.l]. These counter-rotating secondary vortices have the effect of reducing the interaction with the groove and its excitation, thus reducing the noise generated by the mixing layer and its interaction with the groove.

[0031] The groove may be located between two openings such as between a front door and a rear door adjacent to the front door, or between a rear door and a rear body wing adjacent to the rear door. These are non-exhaustive and non-limiting examples.

[0032] [Fig.2] details the geometry of the chevron profile of the upstream trailing edge of the groove, formed by the downstream edge 4.1 of the upstream bodywork element 4.

[0033] The groove has a width Lc, in the main direction of flow symbolized by the arrow Vo, and the chevron profile 4.1 has a width L, also in the direction Vo, which is less than or equal to the width Lc. In the case of [Fig.2], the rate of coverage of the width of the groove by the chevron profile, corresponding to L / Lc, is of the order of 3 / 4. Each of the two portions 4.1.1 and 4.1.2 of the chevron profile is advantageously straight and inclined at an angle α and [3, respectively, relative to the direction Vo. These angles α and [3 are advantageously between 0° and 90°, preferably between 10° and 60°, even more preferably between 15° and 45°. It is however understood that the two portions 4.1.1 and 4.1.2 of the chevron profile may not be rectilinear but rather curved. The chevron profile may have a pitch e, that is to say a chevron length, along said profile, which is constant.The connections between the two portions 4.1.1 and 4.1.2 of the chevron profile can form non-zero radius R2 and R3 roundings. The radius Ri results in a distance e' between each pair of directly adjacent chevrons.

[0034] It is understood that these parameters may be constant along the herringbone profile or vary along said profile. It is also understood that the herringbone profile does not necessarily extend over the entire length of the groove 8. It may in fact extend only over a fraction of this length, such as for example at least 70%, preferably at least 80% of the length of the groove 8.

[0035] Acoustic tests were carried out and gave the results illustrated graphically in [Fig.3].

[0036] [Fig. 3] shows different curves of the noise level measured inside the vehicle under given travel conditions, expressed in decibels dB as a function of the frequency in Hz. Curve 10 corresponds to the noise in a motor vehicle body without a chevron profile according to the invention, while curves 12 and 14 correspond to the noise in a motor vehicle body provided with a chevron profile according to the invention. The two curves 12, which are almost identical, correspond to an overlap of the width of the groove by the chevron profile of 1 / 3 and 1 / 2, respectively, while curve 14 corresponds to a re- 1 / 1 coverage, i.e. total.

[0037] A notable reduction in the noise level can be observed over a frequency range between 500 and 1000 Hz, by comparing curves 12 and 14 with the reference curve 10, i.e. with the overlaps of 1 / 3, 1 / 2 and 1 / 1. It is interesting to note that the overlap of 1 / 3 already provides a substantial reduction in aerodynamic noise.

Claims

Claims

1. Motor vehicle body (2), comprising two adjacent body elements (4, 6) forming, at their adjacency, a groove (8) transverse to a main direction of air flow when the motor vehicle is moving, the two adjacent body elements (4, 6) comprising an upstream body element (4) and a downstream body element (6), said groove (8) being delimited, upstream, by a downstream edge (4.1) of the upstream body element (4) and, downstream, by an upstream edge (6.1) of the downstream body element (6); characterized in that the downstream edge (4.1) of the upstream body element (4) has, in the extent of the upstream body element, a herringbone profile with points directed towards the upstream edge (6.1) of the downstream body element (6).

2. A motor vehicle body (2) according to claim 1, wherein the groove (8) has a width (Lc) in the main airflow direction, the chevron profile covering at least part of the width (Lc) of the groove (8).

3. Motor vehicle body (2), according to claim 2, in which the overlap of the width (Lc) of the groove (8) by the chevron profile is greater than or equal to 1 / 3.

4. Motor vehicle body (2), according to claim 2, in which the overlap of the width (Lc) of the groove (8) by the chevron profile is greater than or equal to 1 / 2.

5. Motor vehicle body (2), according to claim 2, in which the overlap of the width (Lc) of the groove (8) by the chevron profile is greater than or equal to 3 / 4.

6. Motor vehicle body (2), according to one of claims 1 to 5, in which the chevron profile is formed integrally with the upstream body element (4).

7. Motor vehicle body (2), according to one of claims 1 to 5, in which the chevron profile is formed on an element attached to the upstream body element (4).

8. Motor vehicle body (2), according to one of claims 1 to 7, in which at least one (6) of the upstream body element (4) and of the downstream body element (6) is an opening.

9. Motor vehicle body (2), according to one of claims 1 to 8, in which the upstream body element (4) is a roof and the downstream bodywork element (6) is a rear flap.

10. Method for reducing aerodynamic noise produced in a groove (8) of a motor vehicle body (2), said groove being transverse to a main direction of air flow when the motor vehicle is moving, and delimited, upstream, by a downstream edge (4.1) of an upstream body element (4) and, downstream, by an upstream edge (6.1) of a downstream body element (6); characterized in that said method comprises providing at the downstream edge (4.1) of the upstream bodywork element (4) a chevron profile with points directed towards the upstream edge (6.1) of the downstream bodywork element, the motor vehicle bodywork (2) being according to one of claims 1 to 9.

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