Abstract:
The present invention generally relates to an HVAC door and method of use for an HVAC system in a vehicle, and more specifically to an airflow distribution door for use in a vehicle climate control system configured to suppress flutter of the door.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to an HVAC door for use in an HVAC system in a vehicle, and more specifically to an airflow distribution door for use in a vehicle climate control system configured to suppress flutter of the door in use. 
       BACKGROUND OF THE INVENTION 
       [0002]    HVAC door assemblies in vehicle climate control or HVAC systems provide air distribution functionality for the vehicle user. However, the varying pressures within a vehicle HVAC system can cause unsteady forces which lead to vortex shedding, door vibration or flutter, which ultimately leads to noise resonating throughout the HVAC system as well as less than peak performance of air distribution. HVAC systems are generally closed systems which will amplify noise which is created within the system. Vortex shedding is defined as an unsteady flow of air that is caused by air movement past a blunt or bluff object. The airflow past such an object will create alternating low pressure vortices and the object, such as an HVAC door, will tend to movement toward a zone of lower pressure, which causes the door to vibrate and flutter. 
         [0003]    HVAC doors are a relatively large hinged-free type plate, and can be classified as two-dimensional bluff body in aerodynamics. In the airflow passages, it is a bluff structure which results into large vortex shedding or wakes generated by the door as airflows over the exposed sides of the door. This is especially true at high airflow and pressure conditions, and the vortex shedding/wakes can generate large unsteady forces, even locked-in flutters which have the potential to violently damage the bluff door structural integrity. For this reason, the vortex shedding effects have to be controlled to reduce the amplitude of the fluctuating lift as well as the drag on the door. 
         [0004]    The present invention is designed to deliberately introduce airflow disruption such that unsteady forces in an HVAC system become less variable and resonant load frequencies on the HVAC door have negligible amplitudes. 
       SUMMARY OF THE INVENTION 
       [0005]    One aspect of the present invention includes an HVAC door assembly for a use in a vehicle&#39;s HVAC system wherein the door includes a first surface and a second surface. At least the first surface or the second surface, or both, include a planar portion and a non planar portion wherein the non planar portion includes undulations such that a cross section of the non-planar portion defines a sinusoidal wave pattern. 
         [0006]    Another aspect of the present invention includes an HVAC door assembly for a vehicle climate control system wherein the door includes a first surface and a second surface. The first surface of the HVAC door has a planar frame portion with a seal disposed on the periphery of the planar frame portion. The seal is configured to seal the door to a housing in the vehicle climate control system. The door further comprises a non-planar portion on the first surface which includes a plurality of air flow disrupting projections extending outwardly from the planar portion which are configured to disrupt the flow of air over the door and thereby suppress door flutter. 
         [0007]    Yet another aspect of the present invention includes a method of suppressing HVAC door flutter in a vehicle HVAC system which includes providing an HVAC door with a three-dimensional topographic surface capable of disrupting a moving airstream. The topographic surface then disrupts the airstream to provide a steady air force flow over the HVAC door. The steady flow of air reduces the vortex shedding, vibration, flutter, and noise in the HVAC system. 
         [0008]    These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    In the drawings: 
           [0010]      FIG. 1  is a cross-sectional view illustrating a vehicle climate control system; 
           [0011]      FIG. 2  is a top plan view of an HVAC door in accordance with one embodiment of the invention; 
           [0012]      FIG. 3  is a bottom perspective view of the HVAC door of  FIG. 2 ; 
           [0013]      FIG. 4  is a top perspective view of the HVAC door of  FIG. 2 ; 
           [0014]      FIG. 4A  is a fragmented perspective view of the HVAC door of  FIG. 4 ; 
           [0015]      FIG. 5  is a cross-sectional view of the HVAC door of  FIG. 2 , taken along line X; 
           [0016]      FIG. 6  is a top plan view of an HVAC door in accordance with another embodiment of the present invention; 
           [0017]      FIG. 7  is a bottom perspective view of the HVAC door of  FIG. 6 ; 
           [0018]      FIG. 8  is a top perspective view of the HVAC door of  FIG. 6 ; 
           [0019]      FIG. 9  is a cross-sectional view of the HVAC door of  FIG. 6 , taken along line XI; 
           [0020]      FIG. 10  is a top plan view of an HVAC door in accordance with another embodiment of the present invention; 
           [0021]      FIG. 11  is a bottom perspective view of an HVAC door of  FIG. 10 ; 
           [0022]      FIG. 12  is a top perspective view of the HVAC door of  FIG. 10 ; 
           [0023]      FIG. 13  is a cross-sectional view of the HVAC door of  FIG. 10 , taken along line XII; 
           [0024]      FIG. 14  is a top plan view of an HVAC door in accordance with yet another embodiment of the present invention; 
           [0025]      FIG. 15  is a bottom perspective view of the HVAC door of  FIG. 14 ; 
           [0026]      FIG. 16  is a top perspective view of the HVAC door of  FIG. 14 ; and 
           [0027]      FIG. 17  is a cross-sectional view of the HVAC door of  FIG. 14 , taken along line XIII. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]    For the purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in following specification, are simply exemplary embodiments. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be construed as limiting, unless expressly stated otherwise. 
         [0029]    Referring to  FIG. 1 , the reference numeral  2  generally designates a vehicle HVAC climate control unit or air conditioning/heating unit, which is generally disposed in the inner area of an instrument panel located in the front part of a vehicle compartment. The climate control unit  2  includes a casing  11  defining a series of airflow passages and chambers for directing air toward a vehicle compartment. The climate control unit further comprises a chamber  3  having a heat exchanger  12  and evaporator  13  disposed within the chamber  3 . The heat exchanger  12  and evaporator  13  work to heat and cool the air, respectively, before the air is delivered to various locations within the vehicle compartment. The climate control unit  2  further comprises an HVAC door  5  which, in this embodiment, directs airflow between the vehicle panel and floor. The panel/floor HVAC door  5  is a relatively large hinged-free type plate, which means that the door  5  has two sides: one which is connected to an actuator, such as a DC motor, and therefore has a hinged or pinned boundary condition, and another side which is in a free condition for directing air to the vehicle&#39;s panel or floor. The HVAC door can be made from a variety of materials such as a molded ABS resin or other like polymeric substance which is injection molded, vacuum formed or otherwise configured. The HVAC door  5  further includes a first front surface  7  and a second rear surface  6  and the door  5  is movable between a position A and a position B, as the door moves along a path indicated by the arrow C. When the door  5  is in position A, airflow is directed to the vehicle panel, as indicated by air pathway  15 . When the door  5  is in position A, air flowing along air pathway, indicated by solid arrow  15 , flows over the rear surface  6  of door  5 , causing reattaching sheer layers, indicated by arrows  9 , that generate vortex shedding forces which cause flutter. When the door is in position B, airflow is directed toward the lower part of the vehicle compartment along an air pathway, indicated by broken line arrow  14 , and air passes over the front surface  7  of door  5 , causing reattaching sheer layers, indicated by arrows  8 . These sheer layers can reattach to the HVAC door surface and cause the door to lift and flutter against the HVAC housing. 
         [0030]    Referring to  FIG. 2 , an illustrated embodiment of an HVAC door assembly  20  is shown having an upper first surface  22 , which includes a planar frame portion  24  having a seal  26  disposed thereon, and a non-planar body portion  28 . The planar flame portion  24  comprises a front wall  30 , side walls  32 ,  34 , and a rear wall  36 . Together, the front wall  30 , side walls  32 ,  34 , and rear wall  36  make up the planar frame portion  24  of the HVAC door  20  which surrounds non-planar body portion  28 . In this embodiment, the seal  26  is disposed on the entirety of planar frame portion  24  to form an airtight seal between the door  20  and an HVAC door housing in assembly. The rear wall  36  has a pivot member  38  disposed thereon, wherein the pivot member  38  further comprises a pivot actuator member  40  which is used to connect the HVAC door  20  to a vehicle climate control actuator for moving the door  20  between various open and closed positions about pivot point D to direct airflow to different locations within the vehicle compartment. The seal  26  is made of a resilient material, such as sealing foam, padding or other like polymeric material, which is used to seal door  20  to a housing in the vehicle climate control system  2  ( FIG. 1 ), such as a housing made up by the vehicle climate control casing  11 . 
         [0031]      FIG. 3  illustrates the lower surface  23  of the HVAC door  20 . Lower surface  23  has a seal  42  disposed on the outer periphery of lower surface  23 , and, in this embodiment, lower surface  23  is a planar surface. Seal  42  functions similarly to seal  26  in operation. As shown in  FIG. 3 , the HVAC door  20  pivots about pivot point D in a direction as indicated by arrow E between an open position (OP) and a closed position (CP). To prevent warping or twisting of the HVAC door, the lower surface or upper surface can include small ribs or a reinforcing wafer system to stiffen the door and increase the doors structural integrity. 
         [0032]    As shown in  FIG. 4 , the upper surface  22  of the HVAC door  20  has a non-planar body portion  28  disposed within planar frame portion  24  which includes a plurality of undulations  44  disposed thereon. In this embodiment, the non-planar portion  28  comprises over 50% of the upper surface. The undulations  44  are shown, in this embodiment, as wave undulations spaced laterally apart spanwise across the non-planar body portion  28  of the HVAC door  20 . The undulations  44  extend above the non-planar portion  24  of the HVAC door  20  to disrupt the airflow over the upper first surface  22  of the HVAC door  20 , thereby suppressing HVAC door flutter as further described below. 
         [0033]      FIG. 4A  illustrates a zoomed-in view of the HVAC door  20 , as shown in  FIG. 4 , which shows the planar frame portion  24  of the HVAC door  20  disposed between the upper seal  26  and lower seal  42  in configuration. 
         [0034]    As shown in  FIG. 5 , the undulations  44  comprise projections  46  and recesses  48 , such that from one projection to another projection, or from one recess to another recess, the cross-sectional view of the upper surface  22  of the HVAC door  20  defines a full sinusoidal wavelength. In the embodiment shown in  FIG. 5 , the non-planar portion  28  of upper surface  22  includes a uniform pattern of undulations  44  which are in the form of a sinusoidal wave pattern, wherein the projections  46  extend above the non-planar frame portion  24  of the upper surface  22  and the recesses  48  recess to the same plane as the planar frame portion  24 . 
         [0035]    Referring now to  FIGS. 6-9 , the illustrated embodiment of the vehicle HVAC door assembly  50  includes an upper first surface  52  ( FIG. 6 ) and a lower second surface  54  ( FIG. 7 ). The HVAC door  50  comprises a planar frame portion  56  ( FIGS. 7-9 ) disposed around the periphery of both the upper surface  52  and lower surface  54 . The upper surface  52  further comprises a non-planar portion  58  disposed within the planar frame portion  56 , wherein the non-planar portion  58  further comprises a plurality of airflow disrupting wave projections  60  extending outwardly from the plane of the planar frame portion  56 . Lower surface  54  of the HVAC door  50  similarly comprises projections  62  disposed in a non-planar portion  64  of the lower surface  54 , which are also capable of disrupting airflow passing over lower surface  54 . Projections  60  and projections  62  are laterally disposed in a spaced-apart relationship on upper surface  52  and lower surface  54 , respectively. Projections  60  and  62  are staggered in relation to each other on the upper and lower surfaces, such that, in the embodiment shown in  FIGS. 6-9 , the projections  60 ,  62  form a sine wave pattern between upper and lower surfaces  52 ,  54 , as shown in the cross-sectional view of the HVAC door  50  in  FIG. 9 . The HVAC door  50  of  FIGS. 6-9  has an upper seal  66  and a lower seal  68  disposed in either side of planar frame portion  56 , as well as a pivot member  70  having a pivot actuator flange  72  similar to the embodiment shown in  FIGS. 2-5 . 
         [0036]    Referring now to  FIGS. 10-13 , the illustrated embodiment of the vehicle climate control HVAC door assembly  80  includes a first door  82  and a second door  84 . Doors  82 ,  84  share a common pivot member  86  having a pivot actuator flange  88 . In the embodiment shown in  FIGS. 10-13 , the first and second doors  82 ,  84  of HVAC door  80  comprise upper sides  90  and lower sides  92 . The upper sides  90  comprise planar frame portions  94  and non-planar body portions  96 . The non-planar body portions  96  further comprise a plurality of projections  98  which are capable of disrupting airflow as air passes over upper surface  90  of the HVAC door  80 . As shown in  FIG. 13 , the projections  98  form a sinusoidal wave pattern when upper surface  90  is viewed in cross section. As shown in  FIG. 11 , lower surface  92  is planar and has a seal  100  disposed around its periphery. Similarly, the upper surface  90  of first and second doors  82 ,  84  has a seal  102  disposed on planar frame portion  94 . This double door design of the embodiment shown in  FIGS. 10-13  is designed to open and close two air pathways in a vehicle HVAC system. In assembly, the HVAC door  80  of this embodiment would be used in a vehicle HVAC system wherein a housing formed with side-by-side air pathways would correlate to the configuration of the HVAC door  80 , such that the seals  100  and  102  disposed on the upper surface  90  and lower surfaces  82  would align with the housing of the vehicle HVAC system to seal the dual HVAC system air pathways. 
         [0037]    Referring now to  FIGS. 14-17 , the illustrated embodiment of the HVAC door assembly  110  includes a planar frame portion  112  disposed around the periphery of the HVAC door  110  and a web portion  114  disposed within the planar frame portion  112 . The planar frame portion  112  has seals  116  and  118  disposed on either side of the planar frame portion  112  for use in sealing the HVAC door  110  to a housing in a vehicle climate control system. The web portion  114  includes sinusoidal wave form undulations  120  which give the cross section of the web portion  114  a sinusoidal wave pattern form ( FIG. 17 ). The embodiment shown in  FIGS. 14-17  further comprises a pivot member  122  and a pivot member actuator flange  124  similar to the pivot members and pivot actuator flanges described above for selectively moving the door  110  to varying positions to direct airflow. 
         [0038]    The embodiments disclosed herein include spanwise undulations of varying wave steepness. The wave steepness of the non-planar portions of the embodiments disclosed herein is a factor which is variable, depending on the airflow of the specific HVAC system in question. The wave steepness disrupts the airflow and reduces or suppresses vortices which cause HVAC door flutter in an HVAC system. Generally, an HVAC door is classified as a two-dimensional bluff body, such that it exhibits significant drag and strong vortex shedding in a high airflow field. Drag is the aerodynamic force resisting the motion of the object through the air that is produced by front and rear pressure differences and sharing between the fluid and solid surface. A vortex shedding frequency coincides with a door structural resonance, then “locked in” violent vibration can be induced, which can compromise the HVAC door structural integrity. The undulations, as found in the embodiments disclosed herein, breaks up the pressure differential, such that a constant and steady air force is distributed over the HVAC door surfaces, and door flutter is, thereby, suppressed. When the vortex shedding effects are controlled by undulated wave patterns in the HVAC door, the amplitude of the fluctuating lift, as well as the drag forces on the HVAC door are reduced, such that noise and vibration can be suppressed in the HVAC system. While the embodiments shown herein include sinusoidal wave patterns, it is contemplated that persons of skill in the art will appreciate that other three dimensional geometric figures will also cause the disturbance in airflow needed to weaken the vortex shedding features. 
         [0039]    It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.