Abstract:
A motor vehicle with a wheel, a wheel case enveloping the wheel, and an air duct leading to the wheel case, wherein the air duct incorporates an adjustable element, which in a first position steers the air entering into the wheel case through the air duct into a gap between an inner flank of the wheel and an inner wall of the wheel case, and in a second position diverts the air by an outer flank of the wheel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 102014018990.2, filed. Dec. 18, 2014, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure pertains to a motor vehicle with a wheel, a wheel case enveloping the wheel, and an air duct leading to the wheel case. 
       BACKGROUND 
       [0003]    DE 10 2006 044 952 A1 describes an air duct in a motor vehicle with an inlet opening on the underbody and an outlet opening in the wheel case, through which air is introduced into the wheel case for cooling a brake. The cross section of the outlet opening extends predominantly in the transverse direction of the vehicle. Air that gets into the wheel case via the air duct when driving is for the most part deflected by the tread of the tire and diverted around the brake enveloped by the tire, and thus only contributes little to cooling the brake. In addition, the introduction of air increases the drag inside of the wheel case, which leads to a deterioration in the aerodynamics of the vehicle. 
       SUMMARY 
       [0004]    Embodiments of the invention improve the cooling of the brake as well as the aerodynamics of the vehicle in the area of the wheel. 
         [0005]    In an embodiment of the invention within a motor vehicle with a wheel, a wheel case enveloping the wheel, and an air duct leading to the wheel case, the air duct incorporates an adjustable element, which in a first position steers the air entering into the wheel case through the air duct into a gap between an inner flank of the wheel and an inner wall of the wheel case, and in a second position diverts the air by an outer flank of the wheel. 
         [0006]    The air steered into the gap between the inner flank of the wheel and inner wall of the wheel case in the first position of the adjustable element at least partially flows around a brake secured in a recess to the inner flank of the wheel, and is used to effectively cool the latter. If no air is needed for cooling the brake, the air is diverted past the outer flank of the wheel in largely the vehicle direction in the second position of the adjustable element, and there forms an air curtain. This air curtain diminishes the air turbulence arising inside of the wheel case due to the rotational movement of the wheel, and thereby improves the aerodynamics in the area of the wheel. 
         [0007]    The air duct can exhibit a closed cross section. 
         [0008]    An inlet opening of the air duct can lie in the front of the vehicle. As a result, the dynamic pressure that builds up ahead of the driving vehicle at the front can be partially diverted. 
         [0009]    Therefore, it would also be possible to utilize the dynamic pressure and forego the adjustable element, so that the outflowing air always cools the brake, and simultaneously forms an air curtain. The unfavorable effects on the aerodynamics caused by steering air into the wheel case are then at least partially diminished by the formed air curtain. 
         [0010]    The air duct can branch into a brake air duct, through which the air flows into the gap, and a side air duct, through which the air flows by the outer flank of the wheel. 
         [0011]    The air flow exiting the brake air duct can be directed against the inner flank of the wheel. This results in an effective cooling of the brake secured in the recess to the inner flank of the wheel. 
         [0012]    An outlet opening of the brake air duct in the wheel case can for the most part lie on the side of a plane facing the middle of the vehicle, which is perpendicular to the wheel axle during straight line travel, and touches the inner flank of the wheel. As a result, the air is steered in a targeted manner into the gap between the inner flank of the wheel and the inner wall of the wheel case, and an increase in the air circulating on the tread of the wheel that is unproductive in terms of cooling the brake is largely prevented. 
         [0013]    An outlet opening of the side air duct can lie in proximity to the outer flank of the wheel. 
         [0014]    The expansion of an outlet opening of the side air duct can be greater in the vertical than in the transverse direction of the vehicle. As a consequence, an expanded air flow can be generated in the vertical to form an air curtain that is closed over a large portion of the vertical expansion of the wheel case. 
         [0015]    The adjustable element can be positioned between the brake air duct and side air duct. The brake air duct can be open and the side air duct can be closed in the first position, while the side air duct can be open and the brake air duct can be closed in the second position. 
         [0016]    An actuator can bring the adjustable element into the first position given a delay of the vehicle. 
         [0017]    A control circuit can be provided for activating the actuator. The control circuit is advantageously connected with the brake or a braking system allocated to the brake, so as to control the actuator depending on brake activity. 
         [0018]    The amount of air that must be supplied through the brake air duct to sufficiently cool the brake depends on the intensity of a braking process. Therefore, the control circuit can be set up to determine the duration for which the adjustable element remains in the first position after a braking process has concluded as a function of the intensity of the braking process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
           [0020]      FIG. 1  is a schematic cross section through the anterior left front area of a motor vehicle; 
           [0021]      FIG. 2  is a view of the vehicle front; 
           [0022]      FIG. 3  is a perspective view of the air duct. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
         [0024]    In a schematic cross section along the cutting plane I-I on  FIG. 2  through the anterior left front area of a motor vehicle,  FIG. 1  shows a front wheel  1  in a wheel case  2  and a bumper cover  3  situated ahead of that in the traveling direction. An inner flank  4  of the wheel  1  exhibits a recess  5 , in which a brake  9  that acts on the wheel  1  is secured. 
         [0025]    As depicted in a view of the vehicle front  6 , an air duct  10  extends from the inlet opening  11  in the bumper cover  3  between an upper bumper crossbeam  12  and a lower bumper crossbeam  14  in the direction of the Wheel case  2 . The upper and lower bumper crossbeams  12 ,  14  are joined by side members with a bearing structure for the front section. On  FIG. 2 , the upper and lower bumper crossbeams  12 ,  14  are concealed by the bumper cover  3 , and thus denoted by dashed lines. If a radiator grille takes up part of the vehicle front, the inlet opening  11  can also lie in the radiator grille instead of in the bumper cover. 
         [0026]    As shown on  FIG. 1 , a front section  37  of the air duct  10  extends between the inlet opening  11  and a junction  13 , where the air duct  10  branches into a brake air duct  16  and a side air duct  17 . 
         [0027]    The brake air duct  16  extends between the junction  13  and an outlet opening  24 . This outlet opening  24  lies in the wheel case  2 , for the most part on the side of a plane A facing the middle of the vehicle, which lies perpendicular to the wheel axle  15  and touches the inner flank  4  of the wheel  1 . 
         [0028]    The side air duct  17  extends between the junction  13  and an outlet opening  29 . This outlet opening  29  lies at the outer edge of the wheel case  2 , adjacent to a front fender  30 . 
         [0029]    The front section  37 , brake air duct  16  and side air duct  17  are each comprised of tubular molded components made out of plastic with a cross section that is closed all around. 
         [0030]      FIG. 3  shows a perspective view of the air duct  10 . The outlet opening  29  is elongated like a slit in the vertical, so as to generate an air curtain, which covers the open side of the wheel case  2  as completely as possible. 
         [0031]    An adjustable element is secured to the junction  13  in the form of a flap  20  that can be swiveled around an axis  19 . In a first position, the flap  20  seals the side air duct  17  and releases the brake air duct  16 . In a second position, the flap  20  seals the brake air duct  16  and releases the side air duct  17 . A lever arm  21  of a mechanical actuator  23  (denoted by dashed lines on  FIG. 1 ) is secured to the axis  19  of the flap  20  above the junction  13 . The lever arm  21  is aligned in such a way as to run in about the transverse direction of the vehicle in the second position of the flap  20 . The end of the lever arm  21  carries a weight  22 . 
         [0032]    If the vehicle is moving forward, air flows through the inlet opening and into the air duct  10 . If the vehicle is traveling without the brakes applied, the flap  20  is in the second position, and an air flow  27  (denoted by a dashed arrow) streams through the side air duct  17 . As shown on  FIG. 1 , the longitudinal axis of a section  31  of the side air duct  17  located directly in front of the outlet opening  29  runs along a plane B lying perpendicular to the wheel axle  15  in the straight ahead traveling position, and touches the outer flank  32  of the wheel  1 . The air flow  27  is in this way largely diverted along the outer flank  32  of the wheel  1 . It forms an expanded air curtain that is closed over a large part of the vertical expansion of the wheel case, diminishing turbulences in the area of the wheel  1  and improving the aerodynamics. 
         [0033]    In the braking process, the inertia of the weight  22  of the actuator  23  exerts a force on the lever arm  21  in the traveling direction, so that the latter swivels and moves the flap  20  into the first position. Caused by the location of the outlet opening  24 , an air flow  33  (denoted by a dashed arrow) through the brake air duct  16  is steered into a gap  36  between the inner flank  4  of the wheel  1  and an inner wall  25  of the wheel case  2 . In order to steer this air flow  33  into the recess  5  of the wheel  1  and onto the brake  9  to the greatest extent possible, the longitudinal axis of a section  26  of the brake air duct  16  situated directly in front of the outlet opening  24  runs in the direction toward the brake  9 . The air flow  33  streaming toward the brake  9  serves to cool the brake  9 . However, it also leads to air turbulences in the wheel case  2 , which detract from the aerodynamics, A restoring element, for example a spring secured to the axis  19 , thus brings the flap  20  back to the second position after the braking process has ended, and the force of the weight  22  associated therewith has been eliminated. This ensures that the brake  9  is cooled while braking on the one hand, while minimizing the deterioration of aerodynamics associated therewith. The process of returning the flap  20  to the second position can be supported by the pressure exerted by the air flowing in through the inlet opening  11 . 
         [0034]    Instead of the inertia-controlled mechanical actuator  23 , the second embodiment on  FIG. 3  shows an actuator  34  designed as an electric motor. The actuator  34  is connected with a control circuit  35 . The control circuit  35  receives information about a braking process from a brake sensor. The brake sensor can be part of a braking system of the motor vehicle known in the art, e.g., a pressure sensor, which detects the hydrostatic pressure of a brake fluid circulating in the braking system. If a braking process is initiated, the control circuit  35  activates the actuator  34 , and the latter brings the flap  20  into the first position. 
         [0035]    The control circuit  35  is set up to determine the time for which the flap  20  is retained in the first position based on the intensity of the braking process and, when necessary, to keep the flap  20  in the first position for a bit longer even after the braking process has concluded. For example, the vehicle speed, brake fluid pressure while braking and duration of the braking process can be used to estimate the heat quantity released in the brakes  9 , and determine the time for which the flap  20  is retained in the first position proportionately to this heat quantity. At the end of the retention time, the actuator  34  is activated by the control circuit  35 , and brings the flap  20  into the second position. In the driving mode, the flap  20  then remains in this position until the next braking process, and the air steams through the side air duct  17  to form the aerodynamically advantageous air curtain. 
         [0036]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.