Abstract:
An air control door with stratification feature is provided. The door includes a mixing section comprised of air guides that define spaced apart air passages. In a mixed mode application, where mixing of both hot and cold air streams is desired, the air control door directs the two air streams into each other, thereby promoting mixing of such air streams and reducing air stratification. By integrating a mixing section with the air control door, the present invention reduces the size, number and complexity of components required to reduce air stratification to an acceptable level.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to a heating and ventilation unit and/or a heating, ventilation and air conditioning unit for a motor vehicle, particularly to a unit comprising a housing with air ducts for supplying, and air doors for controlling, air to the interior of the motor vehicle. An air control door made according to the present invention is particularly advantageous for promoting the mixing of hot and cold air streams and reducing air stratification within a ventilation unit.  
       BACKGROUND OF THE INVENTION  
       [0002]     Conventional heating and ventilation units and/or heating, ventilation and air conditioning units (collectively “ventilation units”) of the present type are configured to mix cold or temperate air with heated air generated in a heater core. Due to various factors, hot and cold airflows through the air ducts can become stratified: cold air streams remain separate from hot air streams. In some cases, an undesirably large temperature gradient across the outlet openings of the ventilation unit can arise, which gradient can be felt by the occupants of the motor vehicle and cause discomfort. In the case of defrosting or demisting, the temperature gradient across the panel can lead to non-uniform defrosting effects. Vehicle manufacturers generally specify that the air temperature of panel outlets must remain below those of the defrost and floor outlets, and that the defrost and floor outlets remain at similar temperatures. It is, however, not desirable to have too large a temperature gradient between cooler outlets (panel) and warmer outlets (defrost, floor).  
         [0003]     Air doors within a ventilation unit are used to control the various airflows. When a “full hot” condition is required, the air doors shut off airflow from non-heated air sources. Conversely, when a “full cold” condition is required, the air doors shut off airflow from the heated air source. In “medium mode” conditions, when temperature other than “full hot” or “full cold” is required, the air doors may be positioned to allow heated and non-heated air streams, in varying degrees, to pass through the ventilation unit. Undesirable air stratification commonly occurs during “medium mode” operation. Although the air doors allow passage of both hot and cold air streams, a conventional air door does not promote the mixing of such air streams.  
         [0004]     Prior art approaches to reducing air stratification include stratification baffles that are either integrated into the housings or inserted into the housings as separate parts. These devices, although useful to reducing stratification, increase the tooling complexity and manufacturing costs of the ventilation units. Moreover, these stratification devices are present in the air stream even when not required (full hot and full cold modes), thereby causing undesirable pressure drops, which in turn leads to reduced airflow and increased noise.  
         [0005]     Although certain of these approaches and devices have successfully reduced air stratification, there remains a need to promote the mixing of air streams in order to reduce air stratification in a more efficient manner.  
       SUMMARY OF THE INVENTION  
       [0006]     An air control door with integrated stratification feature is provided. The door includes an integral mixing section comprised of air guides that define spaced apart air passages. The mixing section of the door is operable in a medium mode and is positioned such that hot and cold air streams intersect in a space proximate to the mixing section.  
         [0007]     In a preferred embodiment, the air guides of the mixing section are exposed to two air streams only in a medium mode of operation. The air guides are shaped to direct one air stream, and the spaced apart air passages, which are defined by the air guides, direct a second air stream. The mixing section causes the two streams to intersect and mix, thereby reducing air stratification. This arrangement has the particular advantage of promoting the mixing of different air streams while simultaneously controlling the flow rate of air through different ventilation components.  
         [0008]     The main body of the air control door is shaped in a manner that accomplishes the desired control of the air streams as is known in the prior art. In a highly preferred embodiment, the main body of the air control door is barrel shaped. In such an embodiment, the mixing section also may be barrel shaped, i.e., the air guides are curved and generally follow the same radius as the remainder of the door. The barrel shape of these highly preferred embodiments of the invention insure that the air streams efficiently pass over and through the main body of the air control door or the mixing section. It is noted, however, that the mixing section may have a different radius than the remainder of the door or an entirely different shape.  
         [0009]     The air guides, in a preferred embodiment, include integrated channels through which an airflow, or a portion thereof, may travel. These channels direct a first air stream, and portions thereof, into the region of the ventilation unit in which a second air stream passes, which in turn promotes a more desirable mixing profile. The air guides may be varied in size and/or number. For example, instead of three air guides, which in turn may define, for example, two air passages, an embodiment of the invention may include four air guides, which defines, for example, three air passages.  
         [0010]     In yet further embodiments, the size and shapes of the air guides may vary. Embodiments of a door made according to the invention may include, for example, three air guides in which two of the surfaces are identical in shape or size, but a third is different than the other two in shape or size or both. The shape of the air guides determines the mixing characteristics and thus may be tailored to a particular application. For example, in certain embodiments of the invention, the transverse cross-section of a channel is generally u-shaped. In yet another embodiment, semi-circular walls form the transverse cross-section of a channel. Alternatively, or in addition to, the width of the channel within an air guide can remain constant or may narrow as the channel extends from the main body of the door. It should be noted, however, that although the air guides of the described embodiments generally include channels for directing an air stream, including portions thereof, the air paths of the ventilation unit can be designed such that these channels are not needed to promote the mixing of the air streams. In these alternative embodiments, the air guides do not include channels, but instead may be flat or fin-shaped.  
         [0011]     Further objects, features and advantages of the invention will become apparent from the detailed description of the preferred embodiments that follows, particularly when considered in conjunction with the attached figures of drawing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Exemplary embodiments of the invention are given below with reference to the drawings, in which:  
         [0013]      FIG. 1  is an exterior perspective view of a ventilation unit for a motor vehicle;  
         [0014]      FIG. 2  is a simplified interior cross-section of the ventilation unit of  FIG. 1  showing hot and cold airflows through the unit when an air control door made according to the present invention is set in a medium mode;  
         [0015]      FIG. 3  is a simplified interior cross-section of the ventilation unit of  FIG. 1  showing an air control door made according to the present invention as set in full cold mode;  
         [0016]      FIG. 4  is a simplified interior cross-section of the ventilation unit of  FIG. 1  showing an air control door made according to the present invention as set in full hot mode;  
         [0017]      FIG. 5  is a perspective view of an embodiment of an air control door made according to the present invention showing airflows through and around the door when the door is oriented for medium mode operation;  
         [0018]      FIGS. 6-8  are perspective views of various embodiments of an air control door made according to the present invention;  
         [0019]      FIG. 9  is a side elevation of a door assembly according to the embodiment illustrated in  FIG. 6 ;  
         [0020]      FIG. 10  is a perspective view of the door assembly of  FIG. 9 ;  
         [0021]      FIG. 11  is a perspective view of an embodiment of an air control door made according to the present invention;  
         [0022]      FIG. 12  is a side elevation of the air control door as illustrated in  FIG. 1 ;  
         [0023]      FIG. 13  is a side elevation of a door assembly made according to the embodiment of an air control door as illustrated in  FIG. 11 ;  
         [0024]      FIG. 14  is a perspective view of the door assembly as illustrated in  FIG. 13 ;  
         [0025]      FIGS. 15-16  are perspectives views of an embodiment of an air control door made according to the present invention;  
         [0026]      FIG. 17  is a side elevation of the door illustrated in  FIGS. 15-16 ;  
         [0027]      FIGS. 18-19  are perspectives views of an embodiment of an air control door made according to the present invention; and  
         [0028]      FIG. 20  is a side elevation of the door illustrated in  FIGS. 18-19 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0029]      FIG. 1  is an exterior perspective view of a ventilation unit  1  that may be used in a motor vehicle. As is known in the art, the ventilation unit  1  includes a blower  2  that causes air to circulate throughout the unit and into the passenger compartment of a motor vehicle. The ventilation unit typically further includes an evaporator  4 , a heater assembly  5 , a demist outlet  6 , defrost outlet  7 , panel outlets  8 , and floor outlet  3  (collectively “air outlets”). As air from blower  2  passes over or through the evaporator  4 , it is cooled. Likewise, air is warmed as blower  2  forces it over or through the heater assembly  5 . Through a selection of appropriate doors and controls, warm and cool air is passed through all or some of the air outlets.  
         [0030]     It is desirable from time to time to reduce or completely stop the “cold” air stream, i.e., air that passes through or over the evaporator but not the heater assembly, from exiting through an air outlet. When the ventilation unit is operated in this configuration, it is said to be in a “full hot” mode. Likewise, it is desirable from time to time to reduce or completely stop an air stream that passes through the heater core, i.e., the “hot” air stream, from exiting through an air outlet. When the ventilation unit is operated in this configuration, it is said to be in a “full cold” mode. Between these two extremes, the ventilation unit permits cold and hot air streams to pass to appropriate air outlets. When the ventilation unit is operated in this configuration, it is said to be in a “medium” mode.  
         [0031]     As is known in the art, air doors are employed in ventilation units to control the various air streams. These doors block the cold air stream in full hot mode and allow only heated air to pass. They likewise block the hot air stream in full cold mode and allow air that has passed only over or through the evaporator to pass. In medium mode, these doors allow varying proportions of hot and cold air streams to pass depending on the desired temperature in the passenger compartment.  
         [0032]      FIGS. 2-4  illustrate an air control door  9  according to the present invention with the position of door  9  determined by its degree of rotation along an axis directed perpendicularly to the illustrated cross sections.  FIG. 2  illustrates door  9  set in a medium mode,  FIG. 3  illustrates door  9  set in full cold mode, and  FIG. 4  illustrates door  9  set in full hot mode. As is evident from the cross-sections illustrated in  FIGS. 2-4 , door  9  includes a hub at its pivot point. The cross-section of main body  23  of door  9  in the illustrated embodiments is semi-circular in shape, and, for these preferred embodiments, door  9  thus has a cylindrical or “barrel” shape.  
         [0033]     In a medium mode, as illustrated by the arrows in  FIG. 2 , the cold air stream mixes with the hot air stream. The two air streams flow through a housing  11  defined by housing walls  12  and  13  before exiting through air outlets  14 - 16 . In contrast, as illustrated in  FIG. 3 , the cold air stream, but not the hot air stream, exits through air outlets  14 - 16 .  FIG. 4  illustrates the opposite condition in which the hot air stream, but not the cold air stream, is permitted to exit through air outlets  14 - 16 .  
         [0034]     Door  9  includes edges  17  and  18 , which interface with various portions of the housing in order to block an airflow or airflows. In full cold mode, as illustrated in  FIG. 3 , door  9  is rotated such that a door edge  17  contacts an end stop portion  20  of housing  11  and door edge  18  contacts an end stop portion  19  of housing component  21 . Through the contact of these door edges with the housing, door  9  effectively blocks hot air from exiting through outlets  14 - 16 . In full hot mode, as illustrated in  FIG. 4 , door  9  is rotated such that door edge  17  contacts an end stop portion  19  of housing component  21 , and door edge  18  contacts end stop portion  22  of housing  11 . Through the contact of these edges and stops, door  9  effectively blocks the cold air stream from exiting through outlets  14 - 16 .  
         [0035]     In certain embodiments of the invention, the mixing section  10  of door  9  does not contact one of a plurality of air streams in either full hot or full cold modes. In highly preferred embodiments of the invention, mixing section  10  extends from between 10 to 90 percent of the prescribed path traveled by the main body  23  of door  9  from end stop to end stop. In such embodiments, the mixing section is in contact with a plurality of air streams through most of the possible rotation of door  9 , but it does not interface with the air streams in the remaining rotational travel. This arrangement insures that the mixing section is placed in the path of an airflow only when it is needed, thereby minimizing the pressure drop across the mixing section when it is unneeded. For similar reasons, in certain embodiments of the invention, mixing section  10  extends laterally across only a portion of door  9 . In highly preferred embodiments of the invention, mixing section  10  extends from between 10 to 90 percent of the width of door  9 .  
         [0036]      FIG. 5  is a perspective view of an air control door  9  according to a preferred embodiment. Door  9  includes a mixing section  10  comprised of three air guides  24 , which in turn define two spaced apart air passages  25 . Air mixing section  10  is integrally formed, attached or molded to door  9 . In a preferred embodiment, air guides  24  include at least two air control surfaces, one of which contacts a first air stream and the other contacts a second air stream. Door  9  further includes edges  17  and  18 , which mate with the housing as described above.  FIG. 5  includes five arrows that illustrate the paths of two airflows at the mixing section  10 . A hot airflow, indicated by the three parallel arrows, passes over and through the top of the door  9  whereas a cold airflow passes through the two spaced apart passages  25 . The separate airflows, as directed by air guides  24 , thus intersect and mix.  
         [0037]      FIG. 6  illustrates an embodiment of an air control door similar to the door illustrated in  FIG. 5 . Air mixing section  10  includes three air guides  24 , which each include a channel  26  defined by channel walls  27 - 29 . Door  9  further includes hubs  30  and  31 , which lie along the same axis and permit door  9  to be rotatably mounted to the ventilation unit. In the embodiment of  FIG. 6 , hub  30  is different than hub  31 . In this embodiment, hub  30  is configured to interconnect with a second door whereas hub  31  is configured to interconnect with the housing of the ventilation unit. Persons of skill in the art will readily appreciate that hub  30  could also be identical to hub  31 .  
         [0038]     Door  9 , once mounted to ventilation unit  1 , rotates to permit air to flow in varying degrees as is illustrated, for example, in  FIGS. 2-4 . A distal surface of main body  23  of door  9  is curved and generally follows a constant radius. Unlike the mixing section  10 , the distal surface of main body  23  blocks air from passing. In the embodiment of  FIG. 6 , the distal surface of an air guide channel wall  29  is also curved and, for ease of illustration, is shown as generally following the same constant radius as the distal surface of main body  23 . Channel wall  29 , however, need not follow the same radius or be curved at all.  
         [0039]     Depending on the dimensions of the air guides  24  and the spaced apart air passages  25 , a portion of air from the first air stream is directed into channels  26  instead of air passages  25 . A second air stream is forced through the spaced apart passages  25  and immediately mixes with the portion of the first air stream that does not flow through channels  26 . Subsequently, the partially mixed air streams intersect and mix with the air passing through channels  26 . Air guides  24 , with or without a channel, thus control a portion of the first air stream as to how and where it mixes with the second air stream.  
         [0040]      FIG. 7  is an alternative embodiment of an air control door  9  made according to the present invention. In this embodiment, door  9  is larger than the doors of prior embodiments. Consequently, the mixing section  10  requires four air guides  24 , which in turn define three spaced apart air passages  25 . As with the embodiment of  FIG. 6 , air guides  24  include channels  26  defined by channel walls. Although door  9  is larger than the doors of prior embodiments, it is noted that the number of air guides on any size door, such as the door size indicated in  FIG. 6 , may be decreased or increased depending on the desired mixing characteristics. An increase in the cumulative surface area of the air guides increases the pressure drop of the various air streams in the vicinity of the mixing section  10 .  
         [0041]      FIG. 8  is yet another embodiment of an air control door  9  made according to the present invention. In contrast with the embodiments of  FIGS. 6 and 7 , the air guides in the mixing section of the embodiment of  FIG. 8  are not identical. A central air guide  32  is larger than two surrounding air guides  24 , which collectively define two spaced apart air passages  25 . In this embodiment, the mass flow rate and mixing characteristics of the two air streams will be different than in the previously described embodiments. A person of skill in the art will appreciate that air guides  24  alternatively may be larger than the central air guide  32  and/or surrounding air guides  24  need not be identically shaped. Likewise, a person of skill in the art will appreciate that the same mixing section may employ more than three air guides that differ in shape or size. A larger air guide, such as air guide  32 , can be substituted for one or more of the air guides  24  in the embodiment of  FIG. 7 , for example.  
         [0042]     A side elevation of a door assembly  34  is illustrated in  FIG. 9  and a perspective view of such assembly is illustrated in  FIG. 10 . In this ganged relationship, a second air control door  33  is combined with a first air control door  9  to make door assembly  34 . As illustrated, hubs  35  and  36  of a second door  33  are reversed when compared with hubs  30  and  31  of a first door  9 . The two inner hubs  30  and  35  permit the interconnection of the two doors  9  and  33 , and the two outer hubs  31  and  36  permit the connection of the door assembly  34  with the housing of ventilation unit  1 . Although the door assembly  34  in  FIGS. 9 and 10  generally adheres to the embodiment of a door  9  as illustrated in  FIG. 6 , it should be understood that different embodiments of the doors, such as the embodiments of  FIGS. 7-8  as previously described, may be combined to form an appropriate door assembly. In addition, as will be appreciated by a person of skill in the art, three of more doors may be combined to form an appropriate door assembly depending on the size and requirements of the ventilation unit.  
         [0043]     Yet another embodiment of door  9  is illustrated in  FIGS. 11 and 12 . In this embodiment, mixing section  10  includes air guides  37  having a generally semi-circular transverse cross-section. A person of skill in the art will realize, however, that the curvature need not be exactly circular or semicircular, and may instead, be aerodynamically shaped or curved in such a way as to minimize pressure drop. The transverse cross-section of air guides  37  includes channel walls  40  that define channels  39 . Distal surface  41  of air guide  37  may adhere to the shape of the distal surface of main body  23  of door  9 , as is illustrated in  FIG. 11 , or may adhere to a different shape. For example, the radius of curvature of the distal surface  41  of air guide  37  may be larger or smaller than the radius of curvature of the main body  23 . Alternatively, distal surface  41  may be straight. The mixing section of this embodiment further includes spaced apart air passages  38  defined by air guides  37 . Notches  43  in a guide surface  42  further define the air, passages  38 . In the embodiment of  FIGS. 11 and 12 , notch  43  is generally u-shaped and further includes radial surfaces  44  integrated into guide surface  42 . The presence and shaping of notch  43 , including radial surfaces  44 , promotes desirable mixing of the two air streams.  
         [0044]     A side elevation of a door assembly  42 , which is comprised of two doors made according to the embodiment of  FIGS. 11 and 12 , is illustrated in  FIG. 13 . A perspective view of such assembly  42  is illustrated in  FIG. 14 . In a manner analogous to the embodiments of  FIGS. 9 and 10 , a second air control door  33  is combined with a first air control door  9  to make door assembly  42 . As illustrated, hubs  35  and  36  of a second door  33  are reversed when compared with hubs  30  and  31  of a first door  9 . As with the door assembly described in connection with  FIG. 9  and  10 , it should be understood that different embodiments of the doors may be combined to form an appropriate door assembly depending on the size and airflow needs of a particular ventilation unit.  
         [0045]      FIGS. 15 through 17  illustrate a embodiment of an air control door in which mixing section  10  includes air guides  46  having a channel  48  defined by channel walls  49 - 51 . The width of channel  48  varies as the channel extends from the main body. Air guides  46 , in a longitudinal cross-section, are thus trapezoidal in shape, as illustrated in  FIG. 17 . In this embodiment, mixing section  10  further includes spaced apart air passages  47  defined by air guides  46 . As illustrated in  FIG. 16 , a distal surface  52  of channel wall  49  is curved and, as illustrated, generally adheres to the shape of main body  23  of door  9 . As with the prior embodiments, the shape of distal surface  52  need not be the same as or even similar to the shape of main body  23 . For example, the radius of the curvature of the air guide&#39;s distal surface may be larger or smaller than the radius of curvature of main body  23 .  
         [0046]      FIGS. 18 through 20  illustrate yet additional embodiments of an air control door made according to the present invention. In these embodiments, air guides  53  include channels  55  (defined by channel walls  56 - 58 ) that progressively narrow along u-shaped transverse cross-sections. In comparison to the air guides illustrated in the embodiments of  FIGS. 15-17 , the width of channels  55  vary at a non-uniform rate as the channel extends from the main body.  FIG. 20 , which is a side elevation of this embodiment of door  9 , illustrates the non-linear rate of change for the width of channels  55 . In this embodiment, mixing section  10  also includes spaced apart air passages  54  defined by air guides  53 . The distal surface  59  of channel wall  56  is curved and, as illustrated, generally follows the shape of main body  23  of door  9 . As with the prior embodiments, however, the shape of distal surface  59  need not be the same as or similar to the shape of distal surface  23 . For example, the air guide&#39;s distal surface may be straight and not curved.  
         [0047]     Each of the different shapes of the channels in the previously described embodiments causes air to flow differently over and through the mixing section  10  of door  9 . By using different transverse and longitudinal shapes for the air guides, an HVAC designer has increased control over the mixing characteristics of two or more air streams. By shaping the air guides in an aerodynamically desirable manner, it is also possible to minimize pressure drop and noise generated by the air stream moving over and through the air guides. In the various embodiments, for example, the portion of an air stream that passes through the channels will be directed downstream with a greater velocity than air that does not pass through channels. By varying the shape and/or width of the channels, the mass flow rate through the channel, as well as the velocity of the air, can be controlled. The portion of a first air stream that passes through a channel will thus mix with the second air stream in a location downstream from the location of where the remainders of the air streams mix.  
         [0048]     Alternative embodiments of the invention (not illustrated) that are within the scope of the invention include channels that are integrated into the main body  23  of door  9 . In these embodiments, the channels direct a different air stream than the channels in the air guides as described above. It is also contemplated that the air guides need not include channels at all. Instead, in such embodiments, the mixing section includes projections that direct an airflow but are not channel shaped, e.g., flat or fin-like projections. Various permutations and combinations of channels, or the absence of channels, in both air guides and door surfaces are possible and made known to persons of skill in the art by reference to the foregoing written description and attached drawings. Finally, although the foregoing included a description of the preferred embodiments with reference to a single mixing section  10  integrated with the main body of door  9 , persons of skill in the art will also appreciate that additional mixing sections could be added. For example, door  9  can include a first mixing section at one end of its rotational travel and a second mixing section at the other end of its rotational travel.  
         [0049]     It will be apparent that further modifications may be made to the invention, and that some or all of the advantages of the invention may be obtained. Also, the invention is not intended to require each of the above-described features and aspects or combinations thereof. In many instances, certain features and aspects are not essential for practicing other features and aspects. The invention should only be limited by the appended claims and equivalents thereof, since the claims are intended to cover other variations and modifications even though not within their literal scope.