Abstract:
An air outlet, in particular for a motor vehicle, includes at least one air guide element in a flow duct for inducing a swirl in the airflow on introduction of air into the air outlet from an air duct and a flow body embodied along the longitudinal axis of the flow duct.

Description:
FIELD OF THE INVENTION 
     The invention relates to an air diffuser, in particular for a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     In motor vehicles, the supply of conditioned air into the passenger compartment is often felt by the passengers to be an unpleasant sensation if this feed takes place in the form of a concentrated jet which strikes the passengers&#39; bodies. This is the case in particular if the space within the passenger compartment is restricted. 
     To avoid a concentrated jet, it is known to provide a large number of small outlet openings for example in the center console, in the roof or in the B/C pillars. Outlet openings of this type are in widespread use in particular in means of public transport, such as buses, railway carriages or aircraft. However, the provision of a large number of outlet openings is relatively expensive. 
     EP 1 223 061 A2 has disclosed an air diffuser, in particular for vehicle air-conditioning, having a frame, a plurality of lamellae, which are arranged such that they can pivot about a first axis, and, at least one coupling element, to which each of the lamellae is coupled, the coupling element being adjustable relative to the first axis between a neutral position, in which the lamellae are parallel to one another, and a comfort position, in which at least some of the lamellae can be pivoted in opposite directions to one another. The air diffuser is arranged in front of an air duct from which an air stream emerges; the direction of this air stream can be set with the aid of the air diffuser. The air stream can be made to fan out with the aid of the lamellae which have been pivoted in opposite directions to one another, so as to produce a divergent air stream in which the flow velocities are lower than in an air stream with a constant cross section, so that even with a high throughput of air it is possible to prevent the emerging air stream from coming into contact with a vehicle passenger at a high velocity. However, even an air diffuser of this type still leaves something to be desired. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved, in particular less expensive, air diffuser, which as a result of its outflow characteristic provides the maximum possible comfort in the passenger compartment. 
     According to the invention, an air diffuser, in particular for a motor vehicle, is provided with at least one air-guiding element which is arranged in a flow duct and imparts a swirl to the air stream as it passes from an air duct into the air diffuser, a flow body being formed along the longitudinal center axis of the flow duct. The flow body is preferably of solid configuration with a circular cross section, although for reasons of weight or material saving the flow body may also be of hollow configuration, although the air stream should not be able to flow through it. The air diffuser in this case distributes the air over a very large area, resulting in a complete absence or at least a minimization of drafts. 
     It is particularly advantageous for an air diffuser of this type to be arranged shortly after a bend, since in this case, if no swirl is imparted to the air stream, a very irregular flow profile is present in the air diffuser, which gives rise to a draft effect which can be virtually or completely eliminated by the application of a swirl. This allows an air diffuser of this type to be more versatile in use, since even if the air diffuser is in an unfavorable position, for example just after a bend, a draft effect can be avoided or at least minimized, thereby considerably enhancing comfort. 
     To optimize the way in which the air stream is swirled up as it emerges from the air diffuser, the flow body and/or the flow duct in which the flow body is arranged has a cross section which, in the longitudinal direction of the flow duct, changes over the longitudinal direction. 
     It is preferable for the air-guiding element arranged in the air diffuser to be of helical configuration. In this case, it is also possible for a plurality of helically configured air-guiding elements to be provided at equidistant intervals from one another and in the form of a multi-lead thread. 
     It is preferable for the pitch of the air-guiding element(s) to be constant, but it is also possible for this pitch to change in particular in the air inlet region of the air diffuser or in the outlet region thereof. For example, the pitch may in particular be greater in the inlet region than in the outlet region. In a further advantageous configuration of an air diffuser, the latter has an air-guiding element pitch which increases or decreases in the direction of flow. The swirl imparted to the flow can be influenced by the change in cross section in the flow path and the resulting acceleration or deceleration of the flow. 
     To increase passenger comfort, the air diffuser preferably has a direction-setting device, so that the mean direction of flow of the air stream which emerges in diffuse form from the air diffuser can be set. 
     It is preferable for the air diffuser with direction-setting device to have an outer flow duct, in which case the direction-setting device is arranged in the outer flow duct. In this case, it is preferable for the flow body to be formed in the direction-setting device along the longitudinal center axis of the inner flow duct. The air-guiding element for generating swirl is preferably arranged helically around the flow body. 
     The outer flow duct preferably has a cross section which widens as seen in the direction of air flow, thereby boosting the diffusion of the air stream. 
     It is preferable for all the pivot axes of the direction-setting device to be arranged centrally with respect to the longitudinal extent of the inner flow duct. However, in particular in the case of relatively large adjustment angles, it may be expedient for this point to be offset toward the direction of the air stream. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the text which follows, the invention is explained in detail on the basis of three exemplary embodiments with variants, in part with reference to the drawing, in which: 
         FIG. 1  diagrammatically depicts the cross section of an air diffuser in accordance with the first exemplary embodiment, 
         FIG. 2  shows a section on line II-II in  FIG. 1 , 
         FIG. 3  diagrammatically depicts the cross section of an air diffuser in accordance with the second exemplary embodiment, 
         FIG. 4  shows a section on line IV-IV in  FIG. 3 , 
         FIG. 5  diagrammatically depicts the cross section of an air diffuser in accordance with the third exemplary embodiment, and 
         FIG. 6  shows a section on line VI-VI in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     An air diffuser  1  by means of which conditioned air coming from an air-conditioning system can be fed with a swirl to a passenger compartment has, in its swirl zone, a flow duct  2  with a circular cross section which, in its longitudinal center axis, has a flow body  3  with a guiding element  4 . The flow body  3 , which is solid in form, has a circular cross section, and the guiding element  4  extends helically in the radial direction with a constant pitch between flow body  3  and inner lateral surface  5  of the flow duct  2 . 
     The air which is fed to the air diffuser  1  via an air duct (not shown) has a type of screw motion imparted to it by the guiding element  4 , so that the air stream enters the passenger compartment with a swirl and therefore in diffuse form. On account of the absence of a spot jet, the diffuse air stream is not considered an unpleasant sensation even if it comes into contact with a passenger. 
     According to a variant of the first exemplary embodiment which is not illustrated in the drawing, the air diffuser has two guiding elements, which are each formed in the same way as the air-guiding element  4  of the first exemplary embodiment but are arranged offset through 180° with respect to one another. 
       FIGS. 3 and 4  show the second exemplary embodiment, according to which what is provided is an air diffuser  1  with a flow body  3  and flow duct  2  whose shape deviates from the corresponding components in the first exemplary embodiment. The solid flow body  3  and the flow duct  2  have a contour which deviates from the cylindrical shape and influences the outlet characteristic of the air stream so as to optimize the way in which the swirl is imparted. In the present case, the flow body  3  has a streamlined thickened portion  11  in a region before the outlet region, and the flow duct  2  has a widened portion  12  in the outlet region. 
     According to a variant of the second exemplary embodiment which is not shown in the drawing, the flow body in the outlet region has a thickened portion which approximately corresponds to the increase in the diameter of the flow duct in the outlet region, following a profile corresponding to that of the second exemplary embodiment. The widening in the cross section of flow with a slight diversion outward (and inward on leaving the flow duct) in the outlet region of the air diffuser in this case makes a contribution to swirling of the air stream and therefore to optimizing the diffusion of the air stream as it emerges. 
     The air diffuser  1  in accordance with the third exemplary embodiment is in two-part form. The air diffuser  1  has an outer flow duct  21  which widens toward its end lying in the direction of air flow and also has a direction-setting device  22 . The shape of the direction-setting device  22  substantially corresponds to that of the air diffuser  1 , i.e. it has an inner flow duct  2  with a circular cross section, a flow body  3  running in the longitudinal center axis of the flow duct  2  and a guiding element  4 , this inner flow duct  2  together with flow body  3  and guiding element  4  being mounted such that it can pivot over a small angle in any desired direction within the outer flow duct  21 , so that the main outlet direction of the air stream which emerges in diffuse form can be set within a certain angular range. The direction-setting device  22  according to the third exemplary embodiment is configured in such a manner that the inner flow duct  3  is mounted in its center, so that in the event of any desired pivoting movement the associated pivot axis runs through this center point. 
     An air diffuser according to the exemplary embodiments described above is suitable in particular for conditions in which space is limited and in which it is necessary to feed air into the passenger compartment without the risk of a draft when the air comes into direct contact with a passenger. Suitable applications are in particular air diffusers in the B/C pillars, although an air diffuser of this type may also be used at any other desired positions in a vehicle, aircraft, ship or any desired air-conditioned space. 
     To control the air stream, it is possible for a flap to be arranged in front of the air diffuser; this flap can be actuated by means of an operating device arranged in the passenger compartment. In its simplest possible form, the flap may simply have an open and shut position, whereas in its most complicated form it can provide continuously variable adjustment of the air stream. 
     LIST OF REFERENCE DESIGNATIONS 
     
         
           1  Air diffuser 
           2  Flow duct 
           3  Flow body 
           4  Guiding element 
           5  Inner lateral surface 
           11  Thickened portion 
           12  Widened portion 
           21  Outer flow duct 
           22  Direction-setting device