Aerodynamic device for a motor vehicle

Abstract

Aerodynamic device for a motor vehicle. Aerodynamic device (5) for a motor vehicle (1), characterized in that it comprises: - a structure (13) intended to be fixed to a vehicle body, - a first diffuser (11) movable relative to the structure by means of a pivot joint about a first axis (Y1) between a folded position and an unfolded position, - a second diffuser (12) movable relative to the first diffuser by means of a sliding joint along a second axis (A2) between a folded position and an unfolded position, and - an actuation mechanism comprising a shaft (21) movable in rotation relative to the structure about a third axis (Y3) parallel to the first axis, and at least one arm (22) connecting the second diffuser to the shaft. Figure for the abstract: Figure 4

Description

Title of the invention: Aerodynamic device for a motor vehicle. Technical field of the invention

[0001] The invention relates to an aerodynamic device for a motor vehicle. The invention also relates to a motor vehicle comprising such an aerodynamic device. The invention further relates to a method of operating such an aerodynamic device. Prior art

[0002] Air resistance significantly impacts the energy consumption of a motor vehicle. In order to offer fuel-efficient vehicles with long ranges, manufacturers seek to improve the aerodynamic drag coefficient (Cd), while also offering attractive and functional vehicle designs.

[0003] In particular, the airflow between the ground and the underbody of a vehicle generates turbulence that negatively impacts the aerodynamic drag coefficient. To limit this turbulence, motor vehicles are known to include a diffuser arranged on the rear part of the vehicle's underbody. The effectiveness of diffusers known from the prior art is only significant above very high speeds and are therefore generally reserved for sports cars. Such diffusers are thus of little use for ordinary vehicles intended for use on public roads, where the maximum speed is limited.

[0004] Active aerodynamic devices are also known, that is, aerodynamic devices comprising movable elements designed to be deployed above a certain speed. Active aerodynamic devices are generally very complex and / or insufficiently efficient. Presentation of the invention

[0005] The object of the invention is to provide an aerodynamic device for a motor vehicle remedying the above disadvantages and improving the aerodynamic devices known in the prior art.

[0006] More specifically, a first object of the invention is a simple aerodynamic device to manufacture, effectively reducing the coefficient of air penetration of a vehicle, and capable of integrating discreetly and harmoniously into the silhouette of a vehicle. Summary of the invention

[0007] The invention relates to an aerodynamic device for a motor vehicle, the aerodynamic device comprising: - a structure designed to be attached to a vehicle body, - a first diffuser that is movable relative to the structure via a pivot joint around a first axis between a folded position and an unfolded position, - a second diffuser movable relative to the first diffuser by means of a sliding link along a second axis between a folded position and an unfolded position, and - an actuation mechanism comprising a shaft movable in rotation relative to the structure around a third axis parallel to the first axis, and at least one arm connecting the second diffuser to the shaft.

[0008] The actuation mechanism may further include an electric motor configured to rotate the shaft around the third axis.

[0009] The first diffuser may include an external face intended to be visible from outside the vehicle, and the first diffuser may cover the second diffuser when the first diffuser and the second diffuser are in the folded position.

[0010] The second diffuser can be positioned in line with the first diffuser when the first diffuser and the second diffuser are in the unfolded position.

[0011] The at least one arm may include a first end rigidly fixed to the shaft and a second end fixed to the second diffuser by means of a pivot joint about a fourth axis, parallel to the first axis.

[0012] The aerodynamic device may include at least one sliding linkage means arranged at an interface between the first diffuser and the second diffuser.

[0013] The invention also relates to a motor vehicle comprising an aerodynamic device as defined above, the aerodynamic device being arranged in a lower rear part of the vehicle.

[0014] The first diffuser and the second diffuser can extend substantially horizontally in line with the underside of the vehicle when they are in the unfolded position.

[0015] The aerodynamic device can be housed inside a housing formed below a rear bumper of the vehicle, the first diffuser closing said housing when it is in the folded position.

[0016] The invention also relates to a method of using an aerodynamic device as defined above, the method of use comprising: - detecting the vehicle's speed, then - comparing the speed of movement with a predefined speed threshold, then - if the speed of movement is greater than or equal to the predefined speed threshold, the automatic rotation of the shaft of the aerodynamic device so as to move the first diffuser and the second diffuser into their unfolded position. Presentation of the figures

[0017] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0018] Fig. 1 is a schematic view of the rear of a motor vehicle equipped with an aerodynamic device according to an embodiment of the invention, the aerodynamic device being in a folded configuration.

[0019] Fig. 2 is a schematic side view of a rear part of the vehicle, with the aerodynamic device in its folded configuration.

[0020] Fig. 3 is a schematic side view of the rear part of the vehicle, with the aerodynamic device in its unfolded configuration.

[0021] Fig. 4 is a perspective view of the aerodynamic device in the unfolded position.

[0022] Fig. 5 is a perspective view of the aerodynamic device in the folded position.

[0023] Fig. 6 is a perspective and cross-sectional view along a longitudinal and vertical plane of the aerodynamic device in the unfolded position.

[0024] Fig. 7 is a side view of the aerodynamic device in the unfolded position.

[0025] Fig. 8 is a top view of the aerodynamic device in the unfolded position. Detailed description

[0026] Figure 1 schematically illustrates a motor vehicle 1 according to an embodiment of the invention. Vehicle 1 may be a passenger vehicle, in particular a city car, a compact car, a minivan, a sedan, a coupe, or an SUV. Vehicle 1 may also be an electric vehicle. It may therefore include a battery capable of supplying electrical energy to an electric motor. The range of vehicle 1 may thus be limited by the battery capacity.

[0027] The vehicle 1 comprises a rear end including a trunk lid 2 framed by lighting devices 3G, 3D, a rear bumper 4, and an aerodynamic device 5 according to one embodiment of the invention. The bumper is positioned below the trunk lid 2. The aerodynamic device 5 is positioned between the bumper 4 and a subframe 6 of the vehicle. The aerodynamic device 5 preferably extends over a large portion of the vehicle's width, for example, at least 50%, or even at least 70%, of the vehicle's width. According to an embodiment not shown, the aerodynamic device extends over the entire width of the rear bumper 4. The aerodynamic device 5 can extend in width up to the height of the left rear wheel 7G and right rear wheel 7D of the vehicle.

[0028] In this document, the X-axis designates the longitudinal axis of a vehicle. When moving forward in a straight line, the vehicle progresses from rear to front in a direction parallel to its longitudinal axis. The X-axis is oriented from the front to the rear of the vehicle, that is, in the direction of reverse. The Y-axis designates the transverse axis of the vehicle. The Y-axis is oriented from left to right, left and right being defined from the perspective of a driver of the vehicle. The Z-axis designates the axis perpendicular to the X-axis and the Y-axis. The vehicle is assumed to be resting on a horizontal surface. The Z-axis is a vertical axis, oriented from bottom to top. The X, Y, and Z axes form an orthogonal coordinate system. This same coordinate system, defined with reference to a vehicle, will also be used to describe the aerodynamic device 5, even when considered outside the vehicle, since it is intended for mounting in a specific orientation within the vehicle.

[0029] The aerodynamic device 5 is an active device, meaning that it comprises movable elements between at least two positions, each position producing a different aerodynamic effect. In particular, the aerodynamic device is movable between a folded configuration, schematically illustrated in Figures 1 and 2, and an unfolded configuration, schematically illustrated in Figure 3. The aerodynamic device 5 is intended to be controlled by an electronic control unit, which will be described in detail later.

[0030] The aerodynamic device 5 comprises a first diffuser 11 movable between a folded and an unfolded position, a second diffuser 12 movable between a folded and an unfolded position, and a structure 13 fixed to the vehicle body. The structure 13 is therefore fixed in the vehicle's frame of reference. The structure 13 may be fixed directly to the vehicle body or indirectly, that is, by means of one or more rigid components themselves fixed to the vehicle body, said components being sufficiently robust to support the weight of the aerodynamic device 5. The structure 13 may include a frame, for example, a metallic one. The two diffusers 11 and 12 may each comprise a plate, preferably at least roughly rectangular or trapezoidal in shape. Each plate may be made of plastic and / or composite fibers.

[0031] The aerodynamic device 5 can be housed in a compartment 8 of the vehicle. The compartment 8 can be positioned below the rear bumper 4. In the folded position, the aerodynamic device 5 is retracted and presents only one face extending rearward and upward in line with the rear bumper 4 and the underbody 6 of the vehicle. This face corresponds to an external face 111 of the first diffuser 11. Thus, when the first diffuser 11 is in the folded position, it closes the compartment 8 in which the aerodynamic device 5 is housed. The structure 13 and the second diffuser 12 are then completely masked by the first diffuser. 11. Advantageously, the outer face 111 of the first diffuser may include a decorative surface, for example a colored layer harmonized with the color of the vehicle's body. The outer face 111 is preferably smooth.

[0032] In its folded configuration, the aerodynamic device 5 produces no particular aerodynamic effect or a very slight aerodynamic effect, and blends discreetly into the vehicle's silhouette. In particular, the aerodynamic device does not impede the vehicle's maneuverability. The aerodynamic device is not likely to strike an obstacle when the vehicle is reversing.

[0033] In the unfolded, or in other words, deployed, position, the two diffusers 11, 12 extend substantially horizontally towards the rear of the vehicle, in line with the vehicle's underbody 6. In this configuration, the aerodynamic device extends the underbody towards the rear, which has the effect of improving the vehicle's drag coefficient. Substantially horizontal is preferably understood to mean any angle between +20° and -20° around the horizontal plane.

[0034] The first diffuser 11 is movable relative to the structure 13 by means of a pivot joint about a first axis Y1 between its folded and unfolded positions. A pivot joint is a mechanical joint comprising a single degree of rotational freedom. The first axis Y1 is preferably an axis parallel to the transverse axis Y. The first axis Y1 extends at the level of a lower edge of the first diffuser 11, substantially at the level of the vehicle's underbody 6. As mentioned previously, the folded position is a position in which the first diffuser 11 extends obliquely upwards and backwards, and the unfolded position is a position in which the first diffuser 11 extends substantially horizontally. The first diffuser 11 can therefore rotate approximately 45° between its folded and unfolded positions.

[0035] The second diffuser 12 is movable relative to the first diffuser 11 by means of a sliding joint along a second axis A2 between its folded and unfolded positions. A sliding joint is a mechanical joint comprising a single translational degree of freedom. The second axis A2 is preferably an axis perpendicular to the transverse axis Y. Since the first diffuser 11 is movable relative to the structure 13, the second axis A2 is also movable relative to the structure 13. When the first diffuser is in the unfolded position, the second axis A2 extends substantially parallel to the longitudinal axis X. The folded position of the second diffuser 12 is a position in which the second diffuser is superimposed on the first diffuser 11. The unfolded position of the second diffuser 12 is a position in which the second diffuser is positioned in line with the first diffuser 11, in particular towards the rear of the first diffuser.In the unfolded position, a front portion. The second diffuser can remain superimposed on the first diffuser, while a rear portion of the second diffuser is positioned behind the rear edge of the first diffuser. The extension of the first diffuser 11 by the second diffuser 12 makes the aerodynamic device even more effective in improving the vehicle's drag coefficient.

[0036] Due to the sliding joint that connects the first diffuser 11 to the second diffuser 12, the two diffusers 11 and 12 always extend parallel to each other; they are always either both in the extended position, both in the folded position, or possibly both in an intermediate position between the extended and folded positions. In the extended position, the second diffuser 12 is positioned slightly above the first diffuser 11.

[0037] The aerodynamic device 5 further includes an actuation mechanism configured to move the diffusers 11, 12 from their folded position to their unfolded position, and vice versa. The actuation mechanism comprises a shaft 21 that rotates relative to the structure 13 about a third axis Y3 parallel to the first axis Y1, and at least one arm 22 connecting the second diffuser 12 to the shaft 21. The actuation mechanism is thus configured to act directly on the second diffuser 12, and indirectly on the first diffuser 11. In particular, the actuation mechanism is configured to rotate the first diffuser 11 about the first axis Y1 via the second diffuser 12.

[0038] As illustrated by a dashed arc in [Fig. 2], a rotation of the shaft 21 and at least one arm 22 around the third axis Y3 causes the application of a force F on the second diffuser 12. The orientation of the force F varies during the rotation of the shaft 21. However, during this rotation, the force F includes at least a first component oriented perpendicular to the second axis A2. This first component is transmitted to the first diffuser 11 via a sliding linkage at the interface between the first diffuser and the second diffuser. The application of the second force F thus tends to rotate the first diffuser around the first axis YL. The force F also includes at least a second component oriented parallel to the second axis A2. This second component tends to slide the second diffuser 12 relative to the first diffuser 11 along the second axis A2.

[0039] It is therefore understood that to unfold the aerodynamic device, the shaft 21 is driven in rotation in a first direction of rotation identified by SI in [Fig. 2]. To fold the aerodynamic device, the shaft 21 is driven in rotation in a second direction of rotation, identified by S2 in [Fig. 3], and opposite to the first direction SL. Finally, the unfolding and folding of the two diffusers 11, 12 is relatively simple to execute since it only requires the rotation of the shaft 21 around the third axis Y3.

[0040] Figures 4 to 8 illustrate in more detail one embodiment of the aerodynamic device 5. The structure 13 comprises two brackets 13IG, 131D, connected by a cross member 132. The structure 13 further comprises a central reinforcing element 133. The brackets 13IG, 131D, the cross member 132, and the reinforcing element 133 can each be metallic components, in particular obtained by bending a sheet of metal. These components can be fastened together by fixing screws and / or by welding. The structure 13 is intended to be fixed to the vehicle body by fixing screws 134 cooperating with holes provided in the brackets 13IG, 131D, and in the reinforcing element 133.

[0041] The first diffuser is articulated relative to the structure by three pivot linkage means 31, 32, 33 positioned along a rear edge of the first diffuser 11 and at the lower ends of the brackets 13IG, 131D and of the reinforcing element 133. The three pivot linkage means 31, 32, 33 may advantageously include bearings to allow a particularly smooth rotation of the first diffuser around the first axis Yl.

[0042] The shaft 21 is pivotally mounted about the third axis Y3 between the two brackets 131G, 131D. The shaft 21 can also be supported by roller bearings. The shaft 21 comprises a tubular shape whose axis of revolution coincides with the third axis Y3. The third axis Y3 is offset relative to the first axis YL. In particular, the third axis Y3 is positioned above the first axis YL and further back relative to the first axis YL.

[0043] The actuation mechanism further comprises two identical arms 22. Alternatively, this number could, of course, be different. Each arm 22 comprises a first end 221 rigidly fixed to the shaft 21, i.e., by means of a fixed-type connection. Each arm 22 also comprises a second end 222, opposite the first end 221, fixed to the second diffuser 12 by means of a pivot connection about a fourth axis Y4. The fourth axis Y4 is parallel to the first axis Y1, and therefore also parallel to the third axis Y3. The fourth axis Y4 is movable in the frame of reference of the structure 13. Thus, the second end 222 of each arm 22 is intended to describe a circle centered on the third axis Y3 and whose radius is substantially equal to the length of the arms 22. The second diffuser 12 is articulated in rotation relative to the arms 22 by two pivot linkage means 34 positioned respectively at the level of the second end of each arm.

[0044] The second diffuser 12 is articulated relative to the first diffuser 11 by two sliding connection means 41 arranged at the interface between the first diffuser and the second diffuser. With reference to [Fig. 6], it can be seen that the means of Each sliding connection 41 may comprise a set of rollers 411, preferably mounted on roller bearings, cooperating with a profile element 412, for example, a profile element with a horizontal U-shaped cross-section. According to the embodiment shown, the rollers 411 are connected to the second diffuser 12, and the profile elements 412 are fixed to the first diffuser 11, in particular to an inner face of the first diffuser. Advantageously, the second diffuser 12 covers the rollers 411, which are thus not exposed to weathering and splashes. For this purpose, the second diffuser 12 advantageously comprises two protrusions 121 formed on an upper face of the second diffuser. The rollers 411 are confined between the first and second diffusers and are thus well protected. Alternatively, this arrangement could be reversed and / or the number of sliding connection means could be different.

[0045] The actuation mechanism further comprises an electric motor 23 configured to rotate the shaft 21 about the third axis Y3 in the first direction S1 or in the second direction S2. The electric motor 23 is fixed to the structure 13, in particular to the bracket 13IG. To limit the size of the aerodynamic device 5, the electric motor 23 can be oriented so that its rotor extends substantially parallel to the longitudinal axis X. A transmission means 24, including in particular a right-angle gearbox, is then interfaced with the electric motor 23 and the shaft 21.

[0046] The electric motor 23 can be controlled by an electronic control unit 25 (shown schematically in [Fig. 4]). The electronic control unit 25 is capable of receiving information relating to the speed of the vehicle 1, for example, provided by a speed sensor 26 mounted in the vehicle. The electronic control unit 25 is configured to compare the vehicle's speed with a first predefined speed threshold, for example, 100 km / h. Then, if the speed is greater than or equal to the first speed threshold, the electronic control unit 25 emits an electrical control signal that activates the electric motor 23 so as to rotate the shaft 21 in the first direction SI, that is, so as to move the first diffuser 11 and the second diffuser 12 into their unfolded position.Similarly, the electronic control unit 25 is configured to compare the vehicle's travel speed with a second predefined speed threshold, for example, 90 km / h. Then, if the travel speed is less than or equal to the second speed threshold, the electronic control unit 25 emits an electrical control signal that activates the electric motor 23 so as to rotate the shaft 21 in the second direction S2, that is, so as to move the first diffuser 11 and the second diffuser 12 into their folded position. Advantageously, the second threshold is strictly less than the . The first threshold is set to prevent the aerodynamic device from deploying and retracting unexpectedly when the vehicle's speed fluctuates around a given speed. To ensure the aerodynamic device is maintained, the electronic control unit can also command the electric motor to deploy the aerodynamic device when the vehicle is stationary.

[0047] Advantageously, the aerodynamic device 5 further comprises a means for detecting the folded and unfolded positions of the two diffusers 11, 12. This makes it possible to confirm that the two diffusers are indeed in the desired positions and to deactivate the electric motor 23. With reference to [Fig. 7], the detection means comprises, in particular, a first sensor 51 and a second sensor 52, both fixed to the structure 13, in particular to the bracket 131D. The first sensor 51 and the second sensor 52 are advantageously electrically connected to the electronic control unit 25. The detection means further comprises a contactor 53, fixed to a first end of the shaft 21. The contactor 53 cooperates with the first sensor 51 when the first diffuser and the second diffuser are in the unfolded position, and cooperates with the second sensor 52 when the first diffuser and the second diffuser are in the folded position.

[0048] In addition, the aerodynamic device 5 also includes a stop means defining the extended and retracted positions of the diffusers 11, 12. With reference to [Fig. 6], the stop means includes, in particular, a first stop 61 and a second stop 62, both fixed to the structure 13, in particular to the bracket 13IG. The stops 61, 62 may be, for example, rubber pads. The stop means further includes a raised element 63, fixed to a second end of the shaft 21. The raised element 63 cooperates with the first stop 61 when the first and second diffusers are in the extended position, and cooperates with the second stop 62 when the first and second diffusers are in the retracted position.

[0049] Figure 8 shows the horizontal surface formed by the combination of the two diffusers 11 and 12 in their extended position. This horizontal surface can have a length L1 greater than or equal to 400 mm along the longitudinal axis X and a width L2 greater than or equal to 1000 mm along the transverse axis Y. The aerodynamic device 5 thus provides a considerable surface area which significantly improves the drag coefficient Cx of the vehicle 1.

[0050] Thanks to the invention, a simple aerodynamic device is available that effectively reduces a vehicle's drag coefficient and can be discreetly and harmoniously integrated into the vehicle's silhouette. In particular, thanks to the invention, the gains in the drag coefficient (Cd) can be between 0.005 and 0.010. The invention thus makes it possible to reduce significantly reduces the vehicle's energy consumption, and therefore increases the vehicle's range.

Claims

Demands

1. Aerodynamic device (5) for a motor vehicle (1), characterized in that it comprises: - a structure (13) intended to be fixed to a body of the vehicle, - a first diffuser (11) movable relative to the structure by means of a pivot joint about a first axis (Y1) between a folded position and an unfolded position, - a second diffuser (12) movable relative to the first diffuser by means of a sliding joint along a second axis (A2) between a folded position and an unfolded position, and - an actuation mechanism comprising a shaft (21) movable in rotation relative to the structure about a third axis (Y3) parallel to the first axis, and at least one arm (22) connecting the second diffuser to the shaft.

2. Aerodynamic device according to the preceding claim, characterized in that the actuation mechanism further comprises an electric motor (23) configured to rotate the shaft (21) around the third axis.

3. Aerodynamic device according to any one of the preceding claims, characterized in that the first diffuser (11) comprises an external face (111) intended to be visible from outside the vehicle, and in that the first diffuser covers the second diffuser (12) when the first diffuser and the second diffuser are in the folded position.

4. Aerodynamic device according to any one of the preceding claims, characterized in that the second diffuser (12) is positioned in line with the first diffuser (11) when the first diffuser and the second diffuser are in the unfolded position.

5. Aerodynamic device according to any one of the preceding claims, characterized in that at least one arm (22) comprises a first end (221) rigidly fixed to the shaft (21) and a second end (222) fixed to the second diffuser by means of a pivot joint about a fourth axis (Y4), parallel to the first axis (Y1).

6. Aerodynamic device according to any one of the preceding claims, characterized in that it comprises at least one sliding linkage means (41) arranged at an interface between the first diffuser (11) and the second diffuser (12).

7. Motor vehicle (1), characterized in that it comprises an aerodynamic device according to any one of the preceding claims, the aerodynamic device being arranged in a lower rear part of the vehicle.

8. Vehicle according to the preceding claim, characterized in that the first diffuser (11) and the second diffuser (12) extend substantially horizontally in line with a subframe (6) of the vehicle when they are in the unfolded position.

9. Vehicle according to the preceding claim, characterized in that the aerodynamic device (5) is housed inside a housing (8) formed below a rear bumper (4) of the vehicle, the first diffuser (11) closing said housing when it is in the folded position.

10. A method of using an aerodynamic device (5) according to any one of claims 1 to 6, characterized in that it comprises: - detecting a speed of movement of the vehicle, then - comparing the speed of movement with a predefined speed threshold, then - if the speed of movement is greater than or equal to the predefined speed threshold, automatically rotating the shaft (21) of the aerodynamic device so as to move the first diffuser and the second diffuser into their unfolded position.

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