Drag reduction accessory for vehicles and long vehicles

Abstract

The invention relates to a vehicle (2) drag reduction accessory (1) comprising: - a flexible, deployable, streamlined pouch (100) designed to reduce vehicle drag, - a mounting structure (400) for the pouch at a rear end of the vehicle, having at least one passive airflow inlet (410) for directing airflow (F2) into the pouch, so as to deploy the pouch from a folded to a deployed configuration and to maintain the pouch in the deployed position. According to the invention, the opening forms a slot located at the rear of the vehicle, and the mounting structure includes an airflow guidance surface extending convexly from the front edge (411) of the slot into the pouch. Figure for the abstract: Fig. 5

Description

Title of the invention: Drag reduction accessory for vehicles and long vehicles

[0001] The present invention relates, in general, to the field of vehicles and more particularly to vehicles with trailers.

[0002] The invention relates more particularly to a vehicle drag reduction accessory comprising: - a flexible pouch deployable from a folded configuration to a deployed configuration in which the pouch is streamlined to reduce vehicle drag, - a pouch attachment structure to a rear end of the vehicle, the attachment structure having at least one passive intake opening for a flow of air in relative motion with respect to the vehicle, from outside the pouch to inside the pouch, so as to deploy the pouch from its folded configuration to its deployed configuration and to maintain the pouch in its deployed configuration.

[0003] The invention finds a particularly advantageous application for improving the aerodynamics of long vehicles, especially vehicles with trailers.

[0004] The term "trailer" refers to a large transport unit located at the rear of a vehicle's traction unit, for example, a rectangular cargo unit such as a semi-trailer attached to a tractor. The term "long vehicle" includes heavy goods vehicles and trucks, as well as public passenger transport vehicles such as coaches or buses, and motorhomes. This term also includes trains, for example, freight trains transporting containers.

[0005] A similar accessory, described above, is already known from US patent 2013 / 076068. This accessory reduces tail drag (sometimes referred to as "tail drag") at the rear of a vehicle, particularly a truck. The streamlined shape of the bag, in its deployed configuration, allows the airflow generated by the vehicle's movement and flowing along the vehicle's side walls to continue flowing laminarly along the bag, thereby reducing tail turbulence and thus lowering drag. To ensure sufficient airflow to deploy the bag passes through the intake openings, these openings are positioned to protrude from the vehicle's side walls, in the direction that they are located upstream of a rear end wall of the vehicle and have a frontal cross-section transverse to the vehicle's direction of travel. The accessory is also attached to the vehicle's side walls.

[0006] According to this arrangement, the accessory therefore increases the vehicle's frontal area, that is, the vehicle's cross-sectional area, particularly at the rear. This presents two major drawbacks. Firstly, from an aerodynamic point of view, increasing the vehicle's frontal area increases the vehicle's wind resistance and therefore limits the advantage provided by the accessory. Secondly, from a road safety point of view, it is inadvisable, or even prohibited, to use accessories that increase the vehicle's cross-sectional area.

[0007] To overcome the drawbacks of the aforementioned known accessory, the present invention proposes an accessory that can be positioned entirely at the rear of the vehicle, that is, without increasing the vehicle's frontal area. In other words, the accessory can be positioned longitudinally along the overall length of the vehicle.

[0008] More specifically, according to the invention, an accessory is proposed as defined in the introduction: - wherein the opening forms a slot located, in a front-to-rear direction of the vehicle, at the rear of the rear end of the vehicle, said slot having a front edge and a rear edge, the front edge being closer to the vehicle than the rear edge in said front-to-rear direction, and - wherein the fastening structure comprises an airflow guiding surface, said guiding surface extending convexly from the front edge of the slot towards the interior of the pocket.

[0009] Thanks to the slot positioned downstream of the rear end of the vehicle, i.e. behind the vehicle, the accessory can be mounted on the vehicle in such a way that it does not increase the vehicle's cross-section at the rear end. In other words, it does not protrude laterally (or upwards) from the rear end.

[0010] Remarkably, the airflow guidance surface ensures efficient deployment of the pocket despite the specific positioning of the slot. Indeed, the guidance surface takes advantage of the air's viscosity, allowing the airflow (flowing along a side wall of the vehicle) to follow the curved profile of the guidance surface thanks to the boundary layer phenomenon. The guidance surface thus directs the airflow into the pocket without the slot presenting a surface transverse to the airflow, and therefore without changing the vehicle's frontal area. Thanks to the guidance surface, the airflow can thus rush into the pocket through the slot and pressurize it to deploy.

[0011] The accessory according to the invention, in its deployed configuration, allows a reduction of 8% or more in the vehicle's SCx, that is, its drag coefficient multiplied by its frontal area. Consequently, the accessory according to the invention allows a reduction of more than 8% in the energy consumption required to move the vehicle.

[0012] Other features of the accessory according to the invention are as follows: - the guiding surface extends over the entire height of the slot; - at the front edge of the slot, the guide surface is tangent to an external side wall of the vehicle; - the fixing structure includes an additional concave surface extending opposite the guide surface and from the rear edge of the slot towards the inside of the pocket; - the distance between the guide surface and the complementary surface increases along the guide surface from the slot towards the inside of the pocket; - the fixing structure includes a front chassis comprising the front edge of the slot and a rear chassis comprising the rear edge of the slot, the rear chassis being adapted to be mounted on the front chassis at an adjustable distance from the front chassis so that the distance between the front edge of the slot and the rear edge of the slot is adjustable; - a pocket edge is removably attached to the rear frame of the fixing structure; - the width of the slot is between 1 cm and 15 cm and in which the height of the slot is greater than 50% of the height of a rear end wall of the vehicle; - the fixing structure has, transversely to the front-rear direction of the vehicle, dimensions less than or equal to those of a rear end wall of the vehicle; - the pouch includes an outer envelope and internal shape-maintaining partitions connecting different parts of the outer envelope together; - the device includes mechanical return means designed to automatically return the pouch from its deployed configuration to its folded configuration when the relative speed of the airflow, with respect to the vehicle, is less than a non-zero threshold value; - the mounting structure is articulated to allow the opening of a rear door of the vehicle.

[0013] The invention also proposes a long vehicle whose rear end is equipped with a drag reduction accessory as mentioned above.

[0014] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0015] On the attached drawings:

[0016] [Fig.1] is a schematic perspective view of a long vehicle according to the invention equipped with a drag reduction accessory according to the invention in which the flexible pocket of the accessory is in its folded configuration;

[0017] [Fig.2] is a schematic perspective view of a rear part of the vehicle of the [Fig.l] in which the accessory's flexible pocket is in its deployed configuration;

[0018] [Fig.3] is a schematic perspective view of a rear part of the vehicle of the [Fig.l] in which the accessory is pivoted to allow the rear door of the vehicle to be opened;

[0019] [Fig.4] is a schematic exploded perspective view of the reduction accessory of the drag of [Fig. 1] in its deployed configuration; and

[0020] [Fig.5] is a view similar to that of [Fig.2] with a partial tear-off of the drag reduction accessory.

[0021] In the following description, by convention, the terms "front" and "rear" will be used with reference to the vehicle, the front corresponding to the cab or driver's compartment of the vehicle, while the rear corresponds to the end of the vehicle opposite the driver's compartment. The terms "top" and "bottom" will be used with reference to the vertical direction of the vehicle in the operating position. The term "side" will be used with reference to the left and right sides of the vehicle, as opposed to the term "center," which will be used with reference to an orientation toward the middle of the vehicle.

[0022] Figures 1 to 5 show a drag reduction accessory 1 according to the invention, hereinafter referred to as accessory 1. Accessory 1 is designed to be mounted on a vehicle, typically a long motor vehicle comprising a large rear volume, for example, of parallelepiped shape, for the transport of goods or persons. As shown in the figures, accessory 1 is here mounted on an articulated vehicle 2 comprising a tractor 21 and a trailer 22 of generally rectangular parallelepiped shape coupled to the tractor 21 ([Fig. 1]). The trailer 22 generally defines a rear transport volume of the vehicle 2 which may be integral with the rest of the vehicle or attached to it. As clearly shown in [Fig.[l] In the described embodiment of the invention, the trailer 22 comprises a longitudinal upper wall, two parallel longitudinal side walls 22A extending along the longitudinal upper wall, and two parallel end walls, including a rear end wall 22B. These five external walls internally delimit a loading volume and externally an overall volume. As shown in [Fig. 3], the rear end wall 22B includes, in particular, a rear door 23 allowing the trailer 22 to be opened to access the loading volume.

[0023] Accessory 1 is designed to be mounted at a rear end of vehicle 2. In the example shown in the figures, accessory 1 is designed to be mounted on the rear end wall 22B of the trailer 22 of vehicle 2.

[0024] As shown in [Fig. 4], accessory 1 comprises two main elements: - a pocket 100; and - a 400 fixing structure for attaching the 100 pocket to vehicle 2.

[0025] The pocket 100 is made of a flexible material so that it can be deployed from a folded configuration ([Fig. 1]) to an deployed configuration ([Fig. 2]), and, conversely, be folded back from its deployed configuration to its folded configuration. The pocket 100 thus forms a retractable envelope.

[0026] In its folded configuration, the pocket 100 is arranged to occupy a limited space. As shown in [Fig. 1], it then has a substantially flat shape that increases the vehicle's length very little (the pocket then protrudes only slightly from the rear of the vehicle). The pocket 100 is typically positioned in its folded configuration for parking the vehicle 2 or for opening and closing the rear door 23 of the trailer 22 of vehicle 2.

[0027] In its deployed configuration, the pocket 100 is profiled to reduce the drag of the vehicle 2. The pocket 100 then forms an appendage extending in continuity with the overall volume of the vehicle 2 in a front-to-back direction Al corresponding, in the example of the figures, to a horizontal direction going from the front to the rear of the vehicle 2 in a manner substantially parallel to the longitudinal side walls 22A of the trailer 22.

[0028] The term "profiled" refers to the fact that, in its deployed configuration, an external surface 101 of the pocket 100 has a three-dimensional shape specifically designed to reduce turbulence at the rear of the vehicle 2 when the latter is in motion. Indeed, as described in the introduction, airflows generated by the movement of the vehicle 2 and flowing laminarly along the trailer 22 (for example, those referenced Fl in [Fig. 5]) also flow laminarly along the pocket 100.

[0029] As shown in [Fig. 5], in its deployed configuration, the pocket 100 has a tapered shape that narrows in the front-to-back direction AL. Transversely to the front-to-back direction AL, the pocket 100 has dimensions that decrease in the front-to-back direction AL. At its front end (i.e., at the rear end wall of the vehicle), the pocket 100 has dimensions substantially equal to those of the rear end wall 22B of the trailer 22 of vehicle 2. The dimensions of the pocket 100 decrease towards its rear end until a terminal zone 102, which is here substantially flat and rectangular (Figures 2 and 5). The cross-sections of the pocket 100 They are rectangular, with heights and widths decreasing towards the rear. Terminal zone 102 can, for example, accommodate signaling elements, blind spot indicators, speed limit discs, reflective strips, reflectors, or markings.

[0030] Preferably, the pouch 100 is made of a textile material, which gives it suitable strength and flexibility. As shown in [Fig. 4], it has an outer shell 110 and internal shape-maintaining partitions 120 connecting different parts of the outer shell 110. The outer shell 110 is concave and thus delimits an internal volume of the pouch 100 (which varies depending on the pouch configuration), hereinafter referred to as the inside of the pouch. The internal partitions 120 form a network; some internal partitions 120 extend vertically while others extend horizontally. As shown in Figures 2 and 4, the outer shell 110 comprises a plurality of panels 111 sewn together. The internal partitions 120 have openings 121, here with a circular outline ([Fig.4]), in order to even out the air pressure inside the pocket 100.

[0031] According to the front-to-back direction Al, the pocket 100 has a length which is for example between 5 cm and 50 cm in its folded configuration, and a length which is for example between 50 cm and 500 cm in its deployed configuration.

[0032] The transition of the pouch 100 from its folded to its deployed configuration relies on the movement of the vehicle 2. As clearly shown in [Fig. 5], the accessory 1 has passive intake openings 410 for airflow in relative motion with respect to the vehicle 2, from the outside of the pouch 100 to the inside of the pouch 100. The relative movement of the airflow results primarily from the forward movement of the vehicle 2 (in air that is not necessarily in motion). These incoming airflows (for example, those referenced F2 in [Fig. 5]) pressurize the inside of the pouch 100, which, beyond a pressure threshold, deploys.The fact that the air intake is "passive" means that the airflow is admitted into the pocket through the openings 410 solely by virtue of the relative velocity of the airflow with respect to the vehicle 2, as opposed to an air intake which would be active using, for example, devices powered by an energy source, such as an air compressor, to deploy the pocket.

[0033] These openings 410 are more specifically provided in the mounting structure 400. The mounting structure 400 is described as installed at the rear of the vehicle 2.

[0034] As shown in [Fig. 4], the fastening structure 400 comprises: - a front chassis 200 shaped to be mounted on the rear end wall 22B of the trailer 22 of vehicle 2, and - a rear chassis 300 shaped to be mounted on the front chassis 200 and to carry the pouch 100.

[0035] From front to rear, the front chassis 200 includes a mounting panel 210 on the vehicle 2, a female support plane 220 and two lateral front profiles 230.

[0036] In the example shown in figures 1 to 5, the mounting panel 210 comprises a first vertical flap 211 and a second vertical flap 212 arranged side by side and of substantially equal rectangular dimensions.

[0037] The first vertical flap 211 is pivotally mounted about a vertical axis along a lateral edge 22C of the rear end wall 22B of the trailer 22 of vehicle 2 ([Fig. 4]). The first vertical flap 211 is equipped for this purpose with an articulated fork 213 of the mounting structure 400, which allows the first vertical flap 211 to be attached to said rear end wall 22B. This articulated fork 213 comprises a vertical rod arranged along a lateral edge 211A of the first vertical flap 211 and two prongs gripping the rear end 22B of the trailer 22 at the top and bottom. As shown in [Fig. 3], this articulation between the mounting panel 210 and the vehicle 2 allows the accessory 1 of the rear door 23 of vehicle 2 to be offset, thus opening the latter.

[0038] Advantageously, the two vertical flaps 211, 212 are also hinged to each other along their central edge 21IB, 212B (opposite their lateral edges 21IA, 212A). Finally, the second vertical flap 212 is pivotally mounted about a vertical axis and at its lateral edge 212A along a lateral edge 220A of the female support plane 220 by means of another fork 214. As shown in [Fig. 3], this double hinge of the mounting panel 210, with respect to itself and with respect to the female support plane 220, allows, once the accessory 1 is offset from the rear door 23, the accessory 1 to be stored along the longitudinal side wall 22A of the trailer 22.

[0039] Of course, when the accessory 1 is in use (i.e., when the vehicle is moving), the second vertical flap 212 is secured to the vehicle 2 by means of retainers (not shown) that can be disengaged. Preferably, the second vertical flap 212 is secured to the vehicle 2 along the lateral edge 212A of the second vertical flap 212 and a lateral edge 22C of the rear end wall 22B of the trailer 22 of vehicle 2. Similarly, the first vertical flap 211 is secured to the female support plate 220 by means of retainers (not shown) that can be disengaged, preferably along the lateral edge 211A of the first vertical flap 211. Thus, the accessory 1 does not move away from the rear end wall 22B of the trailer 22 of vehicle 2 in an uncontrolled manner.

[0040] The other elements of the front chassis 200, namely the female support plane 220 and the two front profiles 230, are rigid, in contrast to the mounting panel 210 which is hinged.

[0041] The female support plate 220 has the shape of a plate folded at the top and bottom. The female support plate 220 thus comprises a flat, solid, vertical central portion 221, and two returns 222 projecting from the central portion 221, at approximately 90 degrees to it, towards the rear. The two returns 222 thus form horizontal bands.

[0042] The female support plane 220 thus defines a recessed housing 223 in which are arranged the two front profiles 230 which are fixed to the female support plane 220. As clearly shown in [Fig.4], the two front profiles 230 are symmetrical with respect to a vertical front-rear plane PI, only one front profile 230 is described thereafter.

[0043] The front profile 230 is positioned along a lateral edge 220A of the female support plane 220. As shown in [Fig. 4], it has the shape of a vertical tube, extending along the entire length of the female support plane 220, from one of its returns 222 to the other, and has an overall triangular cross-section. The front profile 230, however, has one curved face. It thus comprises three faces: a first flat face 231 extending along the central portion 221 of the female support plane 220, a second flat face 232 extending in the front-to-back direction A1, and a third curved face 233 connecting the first face 231 and the second face 232.

[0044] The third face 233 of the front profile 230 extends rearward in a curved manner from a lateral edge 233A of the front profile 230 to a central edge 233B of the front profile 230. The third face 233 has a convex curvature. In other words, the third face 233 is curved about an axis located in front of the third face 233 in the front-to-rear direction AL. As shown in Figures 4 and 5, the third face 233 is particularly tangent to the front-to-rear direction Al at the lateral edge 233A of the front profile 230. In the example shown in the figures, this means that the third face 233 is tangent to the longitudinal side wall 22A of the trailer 22 of the vehicle 2 ([Fig. 5]).

[0045] The radius of curvature of this third face 233 depends on the speed of the vehicle 2 at which we want the accessory 1, when the pocket 100 is deployed, to best reduce the drag of the vehicle 2.

[0046] From back to front, the rear chassis 300 includes a rear frame 310 for attaching the pocket 100, a male support plane 320 and two lateral rear profiles 330.

[0047] The back frame 310 connects the pocket 100 to the mounting bracket 400. The back frame 310 has a relatively thin rectangular perimeter 311 compared to its central recess 312. For mounting the pocket 100, the back frame 310 has a flared groove (not shown) extending along its entire perimeter 311. An edge 103 of the pocket 100 is inserted into this groove by means of piping. The edge 103 of the pocket 100 and the groove thus form a A dovetail joint in which the edge 103 of the pocket 100 forms a tenon and the rib of the perimeter 311 of the back frame 310 forms a mortise. The pocket 100 is thus mounted removably on the back frame 310, which allows, for example, easy replacement of the pocket 100 in case of wear.

[0048] The rear frame 310 is fixed to the male support plane 320.

[0049] The male support plate 320 has the shape of a plate folded at the top and bottom. The male support plate 320 thus comprises a flat, partially hollowed, vertical central portion 321, and two returns 322 projecting forward from the central portion 321 at approximately 90 degrees to it. The two returns 322 thus form horizontal bands. The recesses allow the passage of the return means 500 for the pocket 100 described later.

[0050] The male support plate 320 is designed to be mounted on the female support plate 220. Advantageously, the male support plate 320 is more specifically designed to be mounted in the female support plate 220 at an adjustable mounting distance. In other words, the male support plate 320 can be mounted on the female support plate 220 closer to or further from the latter depending on the front-to-back direction AL. This allows the position of the rear chassis 300 relative to the front chassis 200 to be adjusted along the front-to-back direction Al and thus, as will become apparent later, the size of the openings 410.

[0051] This mounting of the male support plane 320 in the female support plane 220 is done at the level of their respective returns 322, 222.

[0052] The returns 322 of the male support plate 320 are shaped to fit together, within the assembly clearance, between the returns 222 of the female support plate 220 (hence their respective names of "male" and "female" support plates). Each return 322 of the male support plate 320 extends into contact with the corresponding return 222 of the female support plate 220. The returns 322 of the male support plate 320 and the returns 222 of the female support plate 220 are then in contact with each other over a length, along the front-to-back direction A1, which is greater or lesser depending on the assembly distance.

[0053] To secure the male support plate 320 to the female support plate 220, the returns 322, 222 are for example fixed to each other by means of screw-nut assemblies, the returns 322, 222 having several holes aligned in the front-back direction Al to choose the mounting distance.

[0054] The male support plane 320 thus defines a recessed housing 323 in which are arranged the two rear profiles 330 which are fixed to the male support plane 320. As clearly shown in [Fig.4], the two rear profiles 330 are symmetrical with respect to the vertical front-rear plane PI, only one rear profile 330 is described thereafter.

[0055] As shown in [Fig. 4], the rear profile 330 is positioned along a lateral edge 320A of the male support plane 320. It has the shape of a vertical tube, extending along the entire length of the male support plane 320, from one of its returns 322 to the other, and having an overall triangular cross-section. The rear profile 330, however, has a curved face. It thus comprises three faces: a first flat face 331 extending along the central part 321 of the male support plane 320, a second flat face 332 extending in the front-to-back direction A1, and a third curved face 333 connecting the first face 331 and the second face 332.

[0056] Thus, the third face 333 of the rear profile 330 extends rearward in a curved manner from a lateral edge 333A of the rear profile 330 to a central edge 333B of the rear profile 333C. The third face 333 has a concave curvature. In other words, the third face 333 is curved about an axis located in front of the third face 333 in the front-to-back direction AL

[0057] As shown in [Fig. 5], the rear profile 330 is complementary to the corresponding front profile 230 in that the third concave face 333 of the rear profile 330 extends opposite the third convex face 233 of said front profile 230. As shown in Figures 4 and 5, the front profile 230 and the rear profile 330 extend parallel and vertically. "Vertically" here means that the profiles 230 and 330 extend in a direction forming an angle of less than 15 degrees with the vertical direction.

[0058] As can be clearly seen in [Fig. 5], the fastening structure 400 thus comprises two passive airflow inlet openings 410 from the outside to the inside of the pocket 100, each forming a slot 410, that is to say, a narrow and elongated opening. As shown in [Fig. 5], these two slots 410 are substantially vertical in the sense that their dimension in the vertical direction, corresponding to their height, is much greater than their dimension in the front-to-back direction Al, corresponding to their width.

[0059] Each slot 410 is defined between the front profile 230 and the rear profile 330 facing it. Each slot 410 is more specifically delimited, at the front, by the lateral edge 233A of the front profile 230, which then defines a front edge 411 of the slot 410, and, at the rear, by the lateral edge 333A of the rear profile 330, which then defines a rear edge 412 of the slot 410. The front edge 411 of each slot 410 is closer to the vehicle 2 than the rear edge 412 of the slot 410 in the front-to-rear direction A1; it thus corresponds to the first edge of the slot 410 that an airflow sliding over a longitudinal side wall 22A of the trailer 22 of the vehicle 22 encounters. The front edge 411 and the rear edge 412 of each slot 410 are parallel. Each slot 410 is further delimited, at the top and bottom, by the edges of the returns 222, 322 of the female and male support planes 220, 320.

[0060] For each slot 410, the third convex face 233 of the front profile 230 then forms a guiding surface for an airflow that extends convexly from The front edge 411 of the slot 410 towards the inside of the pocket 100. The third concave face 333 of the rear profile 330 forms a complementary surface to the guiding surface which helps to reduce turbulence at the slot 410. The guiding surface and the complementary surface thus form a conduit which extends from the slot 410 and opens towards the inside of the pocket 100.

[0061] As clearly shown in [Fig. 5], some of the air flowing along the longitudinal side walls 22A of the trailer 22 of vehicle 2 enters the slots 410. These airflows F2 correspond overall to the boundary layer of the air flowing along the longitudinal side walls 22A of the trailer 22 of vehicle 2, that is, to the air flowing closest to said longitudinal side walls 22A. These airflows F2 exhibit a certain degree of adhesion to said longitudinal side walls 22A and therefore, by continuity, to the guide surfaces. The guide surfaces thus direct these airflows F2 towards the interior of the pocket 100 for its deployment and maintenance in the deployed configuration. Once the pocket 100 is placed in its deployed configuration, the airflows Fl flowing along the longitudinal side walls 22A of the trailer 22 of the vehicle 2 then slide by continuity over the external surface 101 of the pocket 100.These F2 airflows correspond in particular to the air flowing slightly away from the aforementioned longitudinal lateral walls 22A, i.e. beyond the boundary layer. The airflow is then laminar and the base turbulence is greatly reduced.

[0062] The distance between the front edge 411 and the rear edge 412 of each slot 410, i.e., the width of the slot 410, is, for example, between 1 cm and 15 cm. This distance can be adjusted, in particular, by modifying the aforementioned mounting distance. Advantageously, increasing the width of the slots 410 allows for greater airflow and thus reduces the threshold speed of the vehicle 2 at which the pocket 100 deploys. Conversely, reducing the width of the slots 410 increases this threshold speed of the vehicle 2.

[0063] The length of the front edge 411 and the rear edge 412 of each slot 410 in the vertical direction, i.e., the height of the slot 410, is greater than 50% of the height of the rear end wall 22B of the trailer 22 of vehicle 2. Preferably, the height of the slot 410 is greater than 70% of the height of the rear end wall 22B of the trailer 22 of vehicle 2.

[0064] Preferably, for each slot 410, the distance between the guiding surface and the complementary surface, measured for example parallel to the front-to-back direction A1, increases from the slot 410 towards the inside of the pocket 100. In other words, the guiding surface and the complementary surface form a conduit that flares towards the inside of the pocket 100. Advantageously, this allows, by venturi effect, an increase in the pressure at the outlet of the channel (i.e., in the pocket 100) by relative to the duct inlet (i.e., at slot 410). This facilitates the deployment of pocket 100. For this reason, the curvature of the third face 333 of the rear profile 330 is less than the curvature of the third face 233 of the front profile 230.

[0065] As shown in [Fig. 4], the mounting structure 400 has, transversely to the front-to-rear direction A1, dimensions less than or equal to those of the rear end wall 22B of the trailer 22 of vehicle 2. The same is true for the pocket 100. Transversely to the front-to-rear direction A1, the slots 410 are located in particular in the frame of the rear end wall 22B of the trailer 22 of vehicle 2. Thus, the accessory 1 does not increase the frontal area of ​​vehicle 2.

[0066] As shown in [Fig. 4], the accessory 1 also includes return means 500 designed to automatically return the pocket 100 from its deployed configuration ([Fig. 2]) to its folded configuration ([Fig. 1]). These return means 500 are mechanical means comprising a weight 501, pulleys 502, and cables 503. The pulleys 502 are mounted on the male support plate 320 of the rear frame 300 of the mounting structure 400. The cables connect the weight 501 to the pocket 100 and more specifically to the end zone 102 of the pocket 100. Between the two, the cables 503 rest on the pulleys 502 and pass through the recesses in the male support plate 320.

[0067] When the pocket 100 is in its deployed configuration and the pressure inside the pocket 100 falls below a threshold pressure, the ballast 501 descends vertically under the effect of its weight, which brings the rear end of the pocket 100, i.e. the terminal zone 102 of the pocket 100, towards the fixing structure 400 and thus folds the pocket 100 down. The terminal zone 102 includes, for example, reinforcements ensuring its rigidity, the cables 503 then being fixed to these reinforcements.

[0068] In practice, this threshold pressure also corresponds to a (non-zero) threshold velocity of the airflows in relative motion around the vehicle 2 below which the weight of the ballast 501 becomes greater than the force generated by the pocket 100 on the cables 503. Consequently, since these airflows are mainly set in relative motion with respect to the vehicle 2 by the forward movement of the vehicle 2, this threshold pressure also corresponds to a (non-zero) threshold velocity of the vehicle 2.

[0069] Conversely, thanks to the return means 500, the pouch 100 is maintained in its folded configuration until the pressure inside the pouch 100 exceeds said threshold pressure. Consequently, in practice, the return means 500 maintain the pouch 100 in its folded configuration as long as the vehicle 2 does not reach said threshold speed of vehicle 2.

[0070] Thus, it is intended to be possible to select the threshold speed of vehicle 2 above which the pocket is deployed and below which the pocket is retracted. For this purpose, it is possible, for example, to adjust the mass of the ballast 501 of the return means 500 and / or the width of the slots 410 via the mounting distance. The threshold speed of vehicle 2 is, for example, 50 km / h. The threshold speed of vehicle 2 is, for example, selected so that the pocket 100 is deployed only when vehicle 2 is traveling at high speed, for example on a motorway.

[0071] The invention is not limited to the embodiment described and represented and any variant in accordance with the attached claims could be envisaged.

[0072] In particular, the number of slots in the mounting structure may differ from two. For example, the mounting structure may include two slots on each side, the height of each slot being slightly less than half the height of the rear end wall of the vehicle. The shape of the slots may also vary; for example, the front and rear edges may not be parallel.

[0073] The mounting structure does not necessarily comprise two chassis adjustable relative to each other but may comprise a single chassis. The slots then have a fixed width. The threshold speed of vehicle 2 for changing the configuration of the pocket can still be adjusted via the mass of the ballast.

[0074] The mounting structure may also not include rear profiles or may include rear profiles lacking their third curved face. Although air intake is less efficient, particularly without the additional surfaces, airflow is still directed into the pocket through the guide surfaces.

[0075] The accessory may also not include mechanical return means. For example, the folding of the pocket can be achieved by making the internal partitions of the pocket from elastic material.

Claims

Demands

1. A vehicle (2) drag reduction accessory (1) comprising: - a flexible pouch (100) deployable from a folded configuration to a deployed configuration in which the pouch (100) is streamlined to reduce the drag of the vehicle (2), - a mounting structure (400) for the pouch (100) to a rear end of the vehicle (2), the mounting structure (400) having at least one passive intake opening (410) for an airflow (F2) moving relative to the vehicle (2), from the outside of the pouch (100) to the inside of the pouch (100), so as to deploy the pouch (100) from its folded configuration to its deployed configuration and to maintain the pouch (100) in its deployed configuration, characterized in that the opening (410) forms a slot (410) located, along a front-to-rear direction (A1) of the vehicle (2), at the rear of the rear end of the vehicle (2),said slot (410) having a front edge (411) and a rear edge (412), the front edge (411) being closer to the vehicle (2) than the rear edge (412) in said front-to-rear direction (A1), and in that the fastening structure (400) comprises an airflow guiding surface (F2), said guiding surface extending convexly from the front edge (411) of the slot (410) towards the interior of the pocket (100).

2. Accessory (1) according to claim 1, wherein the guiding surface extends over the entire height of the slot (410).

3. Accessory (1) according to claim 1 or 2, wherein, at the front edge (411) of the slot (410), the guide surface is tangent to an external side wall (22A) of the vehicle (2).

4. Accessory (1) according to any one of claims 1 to 3, wherein the fastening structure (400) comprises a complementary concave surface extending opposite the guide surface and from the rear edge (412) of the slot (410) into the interior of the pocket (100).

5. Accessory (1) according to claim 4, wherein the distance between the guide surface and the complementary surface increases along the guide surface from the slot (410) towards the inside of the pocket (100).

6. Accessory (1) according to any one of claims 1 to 5, wherein the fastening structure (400) comprises a front frame (200) including the front edge (411) of the slot (410) and a rear frame (300) including the rear edge (412) of the slot (410), the rear frame (300) being adapted to be mounted on the front frame (200) at an adjustable distance from the front frame (200) such that the distance between the front edge (411) of the slot (410) and the rear edge (412) of the slot (410) is adjustable.

7. Accessory (1) according to claim 6, wherein a pocket edge (100) is removably attached to the rear frame (300) of the fastening structure (400).

8. Accessory (1) according to any one of claims 1 to 7, wherein the width of the slot (410) is between 1 cm and 15 cm and wherein the height of the slot (410) is greater than 50% of the height of a rear end wall (22C) of the vehicle (2).

9. Accessory (1) according to any one of claims 1 to 8, wherein the fastening structure (400) has, transversely to the front-rear direction (Al1) of the vehicle (2), dimensions less than or equal to those of a rear end wall (22C) of the vehicle (2).

10. Accessory (1) according to any one of claims 1 to 9, wherein the pocket (100) comprises an outer cover (110) and internal shape-maintaining partitions (120) connecting different parts of the outer cover (110) together.

11. Accessory (1) according to any one of claims 1 to 10, comprising mechanical return means provided (500) to automatically return the pouch (100) from its deployed configuration to its folded configuration when the relative velocity of the airflow (F2), with respect to the vehicle (2), is less than a non-zero threshold value.

12. Accessory (1) according to any one of claims 1 to 11, wherein the fastening structure (400) is articulated to permit the opening (410) of a rear door (23) of the vehicle (2).

13. Long vehicle (2) having the rear end (22B) equipped with a drag reduction accessory according to any one of claims 1 to 12.

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