Dynamic system for reducing the drag and lift of a motor vehicle

Abstract

The invention relates to a dynamic drag and lift reduction system (100) for a vehicle comprising: - at least two air injection devices (110) located respectively upstream of the two wheel arches of a wheel assembly, each air injection device comprising at least one injector provided with an injection nozzle opening into a slot formed in the front portion of the corresponding wheel arch; - an air pump (120) capable of injecting pressurized air into said injectors to which it is fluidly connected; - an anemometer (130) capable of measuring the relative wind speed impacting said vehicle; and - a control unit (150) capable of autonomously controlling, via said pump, the pulsed air flow exiting the injector(s) of each air injection device as a function of the relative wind speed transmitted by said anemometer. Figure to be published with the abbreviation: Fig. 2

Description

Title of the invention: Dynamic system for reducing the drag and lift of a motor vehicle Technical field

[0001] The present invention relates generally to the aerodynamics of motor vehicles. It relates in particular to a system for reducing the aerodynamic drag and lift of such a motor vehicle. Prior art

[0002] Motor vehicles, when moving, are subjected to a certain number of forces which oppose their progress. These forces are in particular solid friction, that is to say the contact of the wheels with the ground, and aerodynamic friction, such as for example the friction of the air on the walls of the vehicle body.

[0003] In addition to these frictions, motor vehicles are subject to a third source of forces which also oppose their progress. These forces are the aerodynamic forces exerted on the vehicle through regions of overpressure and depression. Indeed, at high speed, these forces become dominant compared to the others and play an essential role in the consumption and stability of the vehicle.

[0004] These aerodynamic forces are essentially generated by the depressions created by the separations, recirculations and longitudinal vortices of the air. The recirculations and therefore the low pressure regions are significant at the rear of the vehicle and particularly at the rear window and trunk. Indeed, the air flows at the rear of motor vehicles are complex and, in general, there is a balance between the separations and the longitudinal vortices.

[0005] The devices used in automotive aerodynamics intervene on the separation which takes place at the rear of the vehicle, in particular in the region of the connection between the roof and the rear window, on the one hand, and the rear window and the trunk, on the other hand.

[0006] While the largest depressions and the main vortex structures and separations are indeed generated at the rear of the motor vehicle, the region of the wheels and wheel arches is also a critical area. In fact, the air flow rushes into the wheel arch and very often a separation is observed downstream of it.

[0007] There is also always a significant wake behind the vehicle's wheels and the wake from the front wheels meets the rear wheels and modifies their wake. The wake The airflow of the wheels and the airflow in the wheel arches also act directly on the airflow at the underbody of the vehicle, thus modifying the flow of air exiting from under the vehicle and thereby modifying the structure of the airflow over the rear of the motor vehicle.

[0008] Thus, the region of the wheels and wheel arches is a very sensitive region for the aerodynamics of the vehicle and manufacturers estimate that these regions contribute on average 15% of the value of the air penetration coefficient of the motor vehicle.

[0009] In order to reduce the drag and lift generated at the wheels of a motor vehicle, document EP 1 508 510 A2 proposes arranging, upstream of each wheel arch of the vehicle, a scoop arranged below the underbody and comprising an inlet directed towards the front of the vehicle.

[0010] This scoop is connected by a conduit to a vertically oriented slot provided on the external edge of said wheel arch in front of the corresponding wheel, so as to create a vertical air curtain offset laterally from this wheel.

[0011] The creation of this fluid fairing thus makes it possible to prevent the air circulating around the vehicle from entering a part of the wheel arch and to limit the creation of significant recirculation and complex flow zones which are detrimental to the drag and lift of the vehicle. This scoop also makes it possible to protect the corresponding wheel from the impact of the incident air and therefore to reduce the separation regions around this wheel.

[0012] The effectiveness of such a scoop, however, proves to be very limited, particularly at high speed. This type of device is also ineffective in improving the flow of air around the front wheels when the vehicle is turning. Statement of the invention

[0013] The present invention therefore aims to improve the situation.

[0014] To this end, it proposes a dynamic system for reducing the drag and lift of a motor vehicle, characterized in that it comprises: - at least two air injection devices installed respectively upstream of the two wheel arches of a set of wheels of said vehicle, each said air injection device comprising at least one injector provided with an injection nozzle opening onto a slot made in the front portion of the corresponding wheel arch; - an air pump capable of injecting pressurized air into said injectors to which it is fluidically connected; - an anemometer capable of measuring the relative wind speed impacting said vehicle; and - a control unit capable of autonomously controlling the said pump pulsed air flow rate leaving the injector(s) of each air injection device as a function of the relative wind speed transmitted by said anemometer.

[0015] The invention makes it possible to generate at each wheel arch of said wheel set a pulsed air flow adapted to the relative wind experienced by the vehicle which will be added to the external air flow impacting the vehicle to optimize the flow of air around the corresponding wheel and thus avoid the creation of complex recirculation and flow zones which are detrimental to the drag and lift of the vehicle.

[0016] According to preferred characteristics of said dynamic drag and lift reduction system according to the invention: - said control unit is configured so that said pulsed air flow varies according to an increasing function of the relative wind speed; - the injector(s) of each said air injection device are configured so that the pulsed air flow generated by this air injection device impacts the corresponding wheel over its entire width, overflowing laterally on either side of the latter; the injector(s) of each said air injection device are configured so that the pulsed air flow generated by this air injection device impacts the corresponding wheel over its entire width, overflowing laterally on either side of the latter; - the injection nozzle of each said injector is flat and configured so that this injector generates a horizontal jet through said corresponding slot over a predetermined angular sector; - each said air injection device comprises several injectors arranged parallel to each other at regular intervals in the same horizontal plane; - said system also comprises a wind vane capable of measuring the orientation of the relative wind impacting said vehicle, the flow of pulsed air leaving the injector(s) of each air injection device also being a function of said orientation of the relative wind transmitted by said wind vane; - the injector(s) of the same said air injection device are fixedly mounted on a support integral with the body structure of said vehicle; - said system comprises a steering angle sensor capable of measuring in real time the steering angle of the wheels of a wheel set of said vehicle, said supports of the injectors associated with these wheels being mounted to move relative to the body structure of the vehicle via a motorized mechanism controlled by said control unit, the latter being configured to cause the movement of these supports when said wheels steer so that the position of the injectors associated with each of these wheels remains fixed in the reference frame of this wheel; and / or - said system comprises two said air injection devices located respectively upstream of the two wheel arches of the front wheel set, as well as two other said air injection devices installed respectively upstream of the two wheel arches of the rear wheel set.

[0017] The invention also relates, in a second aspect, to a motor vehicle comprising such a dynamic system for reducing drag and lift. Brief description of the drawings

[0018] The description of the invention will now be continued by the detailed description of several exemplary embodiments, given below for illustrative but non-limiting purposes, with reference to the appended drawings, in which: - [Fig.l] represents a schematic view from below of a motor vehicle equipped with a dynamic drag and lift reduction system according to the invention; - [Fig.2] is a functional diagram of the dynamic drag and lift reduction system according to the invention; - [Fig.3] represents a schematic perspective view illustrating the installation, upstream of a wheel arch of the vehicle, of one of the air injection devices comprising the dynamic drag and lift reduction system according to the invention; and - [Fig.4] represents a view similar to [Fig.l] but in which the front wheels are turned at a predetermined angle relative to the longitudinal axis of the vehicle. Description of the embodiments

[0019] [Fig.l] represents a bottom view of a motor vehicle 1.

[0020] We define with respect to this vehicle 1 an orthogonal reference frame XYZ comprising three axes perpendicular two by two, namely: - an X axis, defining a longitudinal, horizontal direction, - a Y axis, defining a transverse, horizontal direction, which with the X axis defines a horizontal XY plane, and - a Z axis, defining a vertical direction, perpendicular to the horizontal XY plane.

[0021] In the remainder of the description and with reference to the reference defined above, the terms “longitudinal” or “longitudinally” will refer to a direction parallel to the X axis, the terms “transverse” or “transversely” will refer to a direction parallel to the Y axis, and the terms “vertical” or “vertically” will refer to a direction parallel to the Z axis.

[0022] On the other hand and by convention, the terms "lower", "upper", "front" and "rear" will be understood in relation to the general orientation of the vehicle. The terms "lower" and "low" will indicate a greater proximity to the ground in the vertical direction than the terms "upper" or "high". The term "front" will indicate a positioning oriented towards the front of a vehicle in the horizontal direction and the term "rear" will indicate a positioning oriented towards the rear of a vehicle in the same horizontal direction.

[0023] Finally, the terms “external” and “internal” will be used to define the relative position of an element with reference to the median vertical longitudinal plane of the vehicle 1. The element closest to this plane will thus be described as internal as opposed to the other element further away from this same plane which will be described as external.

[0024] The motor vehicle 1 conventionally comprises two front wheels 2 mounted on a front axle not shown, as well as two rear wheels 3 mounted on a rear axle not shown.

[0025] The front wheels 2 (respectively rear 3) are installed in corresponding front wheel arches 4 (respectively rear 5) which form recesses extending back from the front and rear wings of the vehicle body 1.

[0026] According to the invention, the vehicle 1 further comprises a dynamic drag and lift reduction system 100, the functional diagram of which is shown in [Fig.2].

[0027] This dynamic drag and lift reduction system 100 comprises two air injection devices 110 located respectively upstream of the two front wheel arches 4, as well as two other air injection devices 110 located respectively upstream of the two rear wheel arches 5.

[0028] The invention is however not limited to this configuration and the system may comprise only two air injection devices installed upstream of the two rear wheel arches 5 or only two air injection devices installed upstream of the two front wheel arches 4.

[0029] Each air injection device 110 comprises at least one injector 111 provided with an injection nozzle opening onto a slot 6 formed in the front portion of the corresponding wheel arch 4, 5 (as illustrated by [Fig. 3] for one of the front wheel arches 4) and extending transversely over at least the major part of the width of this wheel arch.

[0030] Each air injection device 110 advantageously comprises several injectors 111 (preferably between two and five) arranged parallel side by side at regular intervals in the same horizontal plane.

[0031] The injector(s) 111 of the same air injection device 110 are fixedly mounted on a support 112 secured to the body structure of the vehicle.

[0032] The injection nozzle of each injector 111 is advantageously flat and configured so that this injector 111 generates a horizontal jet through the corresponding slot 6 over a predetermined angular sector.

[0033] The injector(s) 111 of each air injection device 110 are further preferably configured so that the pulsed air flow generated by this device air injection 110 impacts the corresponding wheel 2, 3 over its entire width, extending laterally on either side of the latter.

[0034] As illustrated in [Fig.2], the system 100 also comprises an air pump 120 supplied by an air intake, not shown, arranged on the vehicle 1 (for example in the engine compartment behind the grille) and capable of injecting pressurized air into the injectors 111 fluidly connected to this pump 120 by flexible pipes 113.

[0035] Still with reference to [Fig.2], this system 100 further comprises: - an anemometer 130 comprising for example a Pitot probe installed on the roof of the vehicle 1 and capable of measuring the speed of the relative wind impacting this vehicle 1 (this relative wind being the vector resultant of the speed wind generated by the movement of the vehicle and the real wind); and - a steering angle sensor 140 capable of measuring in real time the steering angle of the wheels 2 of the front axle of the vehicle.

[0036] The system 100 finally comprises a control unit 150, preferably consisting of the vehicle's BSI (for "Intelligent Service Box") also called VSM (for "Vehicle Supervisor Module" in English) in common terminology, and connected, via the on-board electronic network of the vehicle 1, to the anemometer 130 and to the steering angle sensor 140.

[0037] The control unit 150 is capable of autonomously controlling, via the pump 120, the flow of pulsed air leaving the injector(s) 111 of each air injection device 110 as a function of the relative wind speed transmitted by the anemometer 130, so as to generate at each front 4 and rear 5 wheel passage a flow of pulsed air which will be added to the flow of external air impacting the vehicle to optimize the flow of air around the corresponding wheel 2, 3 and thus avoid the creation of complex recirculation and flow zones which are detrimental to the drag and lift of the vehicle.

[0038] Advantageously, the control unit 150 is configured so that this flow of pulsed air leaving the injector(s) 111 varies according to an increasing function of the relative wind speed.

[0039] The control unit 150 may, for example, determine the value of this pulsed air flow rate leaving the injector(s) 111 from a correspondence table stored in a memory of this control unit 150.

[0040] Alternatively, the control unit 150 could also determine this value of the pulsed air flow rate by calculation from an affine or polynomial function of second or third degree stored in a memory of this control unit 150.

[0041] Advantageously, the supports 112 carrying the injector(s) 111 of the air injection devices 110 associated with the front wheels 2 are mounted to be mobile (for example example rotation and translation) with respect to the body structure of the vehicle via a motorized mechanism controlled by the control unit 150.

[0042] The latter is then configured to cause the movement of these supports 112 when the front wheels 2 turn so that the position of the injectors 111 associated with each of these front wheels 2 remains fixed in the frame of reference of this wheel 2, as illustrated by [Fig.4].

[0043] Such movement kinematics thus allows the flow of pulsed air generated by each injection device 110 associated with a front wheel 2 to continue to impact the entire width of this wheel 2 when the vehicle 1 steers by extending laterally on either side of the latter, so as to ensure optimal efficiency of the system according to the invention 100.

[0044] According to an alternative embodiment not shown, the system 100 may also comprise a wind vane capable of measuring the orientation of the relative wind imparting said vehicle 1, the flow of pulsed air leaving the injector(s) 111 of each air injection device 110 then also being a function of this orientation of the relative wind transmitted by said wind vane.

[0045] Other variant embodiments are of course conceivable and it is recalled in this respect that the present invention is not limited to the embodiments described and shown, but also encompasses all variant embodiments within the reach of those skilled in the art.

Claims

Claims

1. Dynamic drag and lift reduction system (100) of a motor vehicle (1) characterized in that it comprises: - at least two air injection devices (110) located respectively upstream of the two wheel arches (4, 5) of a wheel set of said vehicle (1), each said air injection device (110) comprising at least one injector (111) provided with an injection nozzle opening onto a slot (6) formed in the front portion of the corresponding wheel arch (4, 5); - an air pump (120) capable of injecting pressurized air into said injectors (111) to which it is fluidically connected; - an anemometer (130) capable of measuring the speed of the relative wind impacting said vehicle (1);and - a control unit (150) capable of controlling autonomously and via said pump (120) the flow of pulsed air leaving the injector(s) (111) of each air injection device (110) as a function of the relative wind speed transmitted by said anemometer (130).;

2. System (100) according to claim 1, characterized in that said control unit (150) is configured so that said pulsed air flow varies according to an increasing function of the relative wind speed.

3. System (100) according to one of claims 1 or 2, characterized in that the injector(s) (111) of each said air injection device (110) are configured so that the pulsed air flow generated by this air injection device impacts the corresponding wheel (2, 3) over its entire width, overflowing laterally on either side of the latter.

4. System (100) according to one of claims 1 to 3, characterized in that the injection nozzle of each said injector (111) is flat and configured so that this injector generates a horizontal jet through said corresponding slot (6) over a predetermined angular sector.

5. System (100) according to one of claims 1 to 4, characterized in that each said air injection device (110) comprises several injectors (111) arranged parallel side by side at regular intervals in the same horizontal plane.

6. System (100) according to one of claims 1 to 5, characterized in that it also comprises a weather vane capable of measuring the orientation of the relative wind impacting said vehicle (1), the flow of pulsed air leaving the or injectors (111) of each air injection device (110) also being a function of said relative wind orientation transmitted by said weather vane.

7. System (100) according to one of claims 1 to 6, characterized in that the injector(s) (111) of the same said air injection device (110) are fixedly mounted on a support (112) integral with the body structure of said vehicle (1).

8. System (100) according to claim 7, characterized in that it comprises a steering angle sensor (140) capable of measuring in real time the steering angle of the wheels (2, 3) of a wheel set of said vehicle, said supports (112) of the injectors (111) associated with these wheels (2, 3) being mounted movably relative to the body structure of the vehicle (1) via a motorized mechanism controlled by said control unit (150), the latter being configured to cause the movement of these supports (112) when said wheels (2; 3) steer so that the position of the injectors (111) associated with each of these wheels (2, 3) remains fixed in the frame of reference of this wheel (2, 3).

9. System (100) according to one of claims 1 to 8, characterized in that it comprises two said air injection devices (110) located respectively upstream of the two wheel arches (4) of the front wheel set, as well as two other said air injection devices (110) located respectively upstream of the two wheel arches (5) of the rear wheel set.

10. Motor vehicle, characterized in that it comprises a dynamic drag and lift reduction system according to one of claims 1 to 9.

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