Abstract:
An air flow mixing system for a vehicle air conditioning system having a distribution door to force air from a first air flow to mix with a second air flow of different temperature proximate a merging region in the air conditioning system. In one embodiment, the distribution door has an arcuate passageway or scoop to forcibly route air from the first airflow to the second airflow. In a second embodiment, the distribution door has at least one projecting channel to divide each of the first and second air flows into a plurality of alternating flow paths to promote heat transfer and mixing of the two airflows. In each embodiment, the pivoting distribution door facilitates heat transfer between the airflows resulting in a more even temperate airflow emerging from the merging region.

Description:
FIELD OF THE INVENTION 
   The present invention relates to the field of air conditioning systems, and more specifically to air mixing systems within air conditioning systems. 
   BACKGROUND TO THE INVENTION 
   Vehicle air conditioning systems are well known in the art. Such systems conventionally include an air duct, which is selectively connected to the external air or to the interior of the vehicle cabin, a fan for causing the air to flow, and an evaporator unit within the duct for cooling the air. The cold air output from the evaporator unit may be supplied directly to various outlets within the vehicle cabin or some of the cold air may be passed through a heating heat exchanger whose heated air output is mixed with the cold air to provide temperature control of the air output to the cabin. Diversion of the cold air through the heat exchanger is controlled by a so-called “blend door”, which in one extreme position causes all of the cold air to flow through the heat exchanger and in the opposite extreme position causes none of the air to flow through the heat exchanger. In intermediate positions different proportions of cold air and heated air can be provided. 
   As will be seen in  FIG. 1 , the cold airflow  22  is concentrated on one side of the air duct and the hot air  21  to the other side. 
   In modern vehicles, there are a number of air outlets into the vehicle cabin and these outlets are connected to the air duct by a corresponding number of output ducts. Two such ducts are shown in FIG.  1 . As will be seen with reference to  FIG. 1 , a first upper duct  41  is disposed on the side of the system which will tend to provide cold air and the second lower duct  42  is disposed on the side of the system which will tend to provide hot air. When the temperature of the upper duct  41  and lower duct  42  are different, this is known as bi-level stratification. 
   It is desirable to be able to provide air outlets which are all at substantially similar temperatures. This may not be possible in the prior art arrangements due to the above-mentioned spatial distribution of air temperature within the air conditioning system. 
   Attempts have been made to provide improved mixing of hot and cold air at the output of an air conditioning system; however, these attempts have caused unacceptable temperature stratification and pressure drops, as well as substantial increases in manufacturing costs due to complex parts and assemblies. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide improved mixing of air within an air conditioning system. 
   In accordance with this invention, the present invention provides a mixing structure that mixes different airflows more efficiently within a limited space. The present invention may be structured to guide more cold air to the floor registers and more hot air to the panel registers as compared to the conventional designs with the goal of reducing bi-level stratification. 
   Moreover, the invention may increase the hot air flow velocity to penetrate the cold airflow to thereby reduce bi-level stratification. 
   The present invention may also be structured to avoid a permanently installed cross flow baffle that generates pressure drop in the cold air path, whereby in all blend positions including a full-cold position. In such case, the stratification control door is rotated aside in the full-cold position. 
   According to a first aspect of the invention there is provided an air flow mixing system for a vehicle air conditioning system having a first conduit for a first air flow, a second conduit for a second air flow, an opening between said first and second conduits for merging said first and second air flows in a merging region and a common air channel for said merged air flows. The mixing structure comprising a first side upstream of said merging region, a second side upstream of said merging region, and a substantially arcuate or curved passageway leading from said first side to said second side for mixing said first and second air flows at the merging region. 
   In the preferred embodiment, the mixing structure comprises a distribution door having a cold air side and a hot air side upstream of said merging region, whereby the distribution door includes a substantially arcuate or curved passageway disposed between the hot air side and the cold air side for mixing these first and second air flows at the merging region. 
   According to a second aspect of the invention, there is provided a vehicle air conditioning system having a heat exchanger disposed in a first conduit for providing a first heated air flow, a second conduit for a second air flow, an opening between said first and second conduits for merging said first and second air flows in a merging region, and a mixing structure. The mixing structure comprising a first side upstream of the merging region, a second side upstream of the merging region that is opposite the first side, at least one projection projecting from the first side, and at least one channel respectively passing through the at least one projection and leading from the first side to the second side. The second aspect of the invention includes at least one air passage opening at openings into said merging region for dividing said first heated air flow at an inlet region into plural air flows leading to the merging region and at least one u-shaped opening facing the second airflow, whereby the first heated air flow and second air flow mix in said merging region. 
   Preferably, the mixing structure is formed as part of the mixing and/or distribution doors. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a cross-sectional view through a known vehicle air conditioning system; 
       FIG. 2  is a partial perspective view of an air conditioning system similar to FIG.  1  and incorporating a first embodiment of the distribution door of the invention; 
       FIGS. 3   a  and  3   b  illustrate partial top views showing convergence of the hot air flow and cold airflow at the mixing region with the distribution door shown in two different positions; 
       FIG. 4  is a front perspective view of the distribution door according to a first embodiment of the present invention in the form of a u-shaped hole or scoop in the door. 
       FIG. 5  is a rear perspective view of the distribution door of FIG.  4 . 
       FIG. 6  is a front perspective view of the distribution door according to an alternate embodiment of the present invention in the form of a cross-flow-channels door. 
       FIG. 7  is a rear perspective view of the distribution door of FIG.  6 . 
       FIG. 8  is a schematic sectional view of a vehicle air conditioning system incorporating the air-mixing device of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the Figures like reference numerals refer to like parts. 
   Referring first to  FIGS. 1 and 2 , an evaporator unit  1  has an input side  2 . Air is urged into the input side  2  of the evaporator  1  by the movement of a vehicle in which the air conditioning system is mounted, or by a fan ‘f’ (see FIG.  2 ). The evaporator  1  is disposed in an air duct  3  and the evaporator  1  has an output side  4  from which emerges cooled air. The output duct  3  extends to a throat portion  5  which co-operates with a blend door  10 . The blend door as shown in  FIG. 1  may be positioned in a central position to define a first conduit for cold air flow between the blend door  10  and first wall  11  of the duct  3  and a second conduit for air to be heated between the opposite wall  12  of the duct  3 . The second conduit leads to a heat exchanger core  20  which is supplied with hot water, for example from the engine of the vehicle, and which has an output side from which emerges a flow  21  of heated air. The flow  21  of heated air and a cool air flow  22  from the first conduit come together in a mixing region  24  of the duct  3 . Two distribution ducts,  41  and  42  are shown in FIG.  1  and these, as has previously been discussed supply air outlets in different parts of the vehicle cabin, e.g. panel or face and/or foot and/or defrost areas. 
   It would be understood by one skilled in the art that although some mixing of the hot and cold air flows will take place in the mixing region  24 , nonetheless the flow resistance caused by the heat exchanger core  20  will substantially reduce the velocity of the hot air and, as a result, on the extreme left of the duct  3 , as seen in the direction of flow, the cold air will predominate and, on the extreme right of the duct  3  as seen in the direction of flow, hot air will dominate. Thus distribution duct  41  is more likely to contain cool air and distribution duct  42  is more likely to carry warm air. Additionally, the specific arrangement of the system downstream of the mixing region  24  may vary considerably depending on the environment and application for the air conditioning system. 
   Referring now to  FIGS. 2 ,  3   a ,  3   b  and according to the teachings of the invention, a distribution door  100 ,  200  is disposed at the mixing region  24  to efficiently control distribution and stratification of the different airflows. The distribution door  100 ,  200  of the present invention may take different forms, and by way of example, the instant invention shows a u-channel door structure (see  FIGS. 4 and 5 ) and cross-flow-channels door (see FIGS.  6  and  7 ).  FIG. 8  further depicts a schematic representation of arrangement of the mixing device disposed in a vehicle air conditioning system. 
   With reference to  FIGS. 4 and 5 , the u-shaped channel door  100  is formed with a primary flap member  110  attached to a post  112  defining a pivot axis  101 . The primary flap member  110  has opposite sides  110   a ,  110   b . Projecting from the first side  110   a  of the flap member  110  is a u-shaped deflector/scoop  130  through which a u-shaped channel  120  passes. The u-shaped channel  120  is formed at the central portion of the primary flap member  110  and defines an arcuate opening spanning a variable or tunable angle which is tunable to about 0 to 90 degrees, typically approximately 30-70 degrees. Therefore, the u-shaped channel  120  has two opposite openings  120   a ,  120   b  oriented at about a 60 degree angle with respect to each other and an arcuate wall  120   c  connecting these two opposite openings. 
   When distribution door  100  is disposed in the hot air position shown in  FIG. 3   a , the primary flap member  110  will substantially, but not completely, block the flow of cold air (air path  22 ) and will permit the flow of heated air (air flow  21 ) to the mixing region  24 . The u-shaped channel  120  will divert a portion of the cold air-flow  22  towards the source of heated air (air flow  21 ) for mixture therewith before continuing to mixing region  24 . This causes a more violent clash or turbulence between the two airflows substantially increasing mixing and heat transfer between the two flows resulting in a more uniformed temperature air flow emerging from mixing region  24 . When the distribution door  100  is disposed in the cold air position shown in  FIG. 3   b , the primary flap member  110  will substantially block the flow of hot air (air path  21 ) and will permit unfettered flow of cold air (air flow  22 ) to the mixing region  24 . In the position shown in  FIG. 3   b , the u-shaped channel  120  will permit passage of a portion of the heated airflow  21  toward the mixing region  24 . 
   As will be understood by those of skill in the art, the distribution door  100  may be located at any intermediate position between the extreme positions shown in  FIGS. 3   a  and  3   b.    
   With reference to  FIGS. 6 and 7 , the cross-flow-channels door  200  is formed with a primary flap member  210  attached to a post  212  defining a pivot axis  201 . The primary flap member  210  has opposite sides  210   a ,  210   b . Formed on the primary flap member  210  is at least one u-shaped channel  220  defining an opening on the second side  210   b  of the flap member  210 . Projecting from the first side  210   a  of the flap member  210  is/are corresponding u-shaped deflector(s)  230  through which each u-shaped channel  220  passes. As shown in  FIG. 7 , the u-shaped deflectors  230  are shaped as scoops projecting from the first side  210   a.    
   In the preferred embodiment only one u-shaped channel  220  and deflector  230  is provided; however,  FIG. 6  shows three channels  220  and deflectors  230  for illustrative purposes of the invention. As understood by one of skill in the art, the specific number of channels  220  and deflectors  230  will vary depending on the application and system design. 
   When distribution door  200  is disposed in the hot air position shown in  FIG. 3   a , the primary flap member  210  partially block the flow of cold air (air path  22 ) with flow permitted through the channel(s)  220 . The u-shaped deflector(s)  230  permits deflected flow of heated air (air flow  21 ) around the u-shaped deflector(s)  230  and into the mixing region  24  (see airflow lines  21 ,  22  in FIG.  6 ). The u-shaped deflector(s)  230  and channel(s)  220  thereby interleave and co-mingle the paths of airflow  21 ,  22  in at least one or a plurality of alternating streams. By dividing the hot air flow  21  and cold air flow  22  into adjacent alternating flow paths, heat transfer and mixing between the two air flows  21 ,  22  is greatly enhanced. 
   When the distribution door  200  is disposed in the cold air position shown in  FIG. 3   b , the primary flap member  210  will primarily block the flow of hot air (air path  21 ) with partial flow of the hot air (air path  21 ) passing through the channels  220 . In the position of  FIG. 3   b , the distribution door  200  permits unfettered flow of cold air (air flow  22 ) to the mixing region  24 . 
   From the foregoing description, it will be understood by those of skill in the art that the distribution door  200  may be located at any intermediate position between the extreme positions shown in  FIGS. 3   a  and  3   b.    
   As described above, the present invention provides various mixing structures that commingle and interpose different airflows more efficiently within a limited space. For example, the present invention may be structured to guide more cold air to the floor registers and more hot air to the panel registers. Moreover, the invention may increase the hot air flow velocity to penetrate the cold airflow to thereby reduce bi-level stratification. 
   The present invention may also be structured to avoid a permanently installed cross flow baffle that generates pressure drop in the cold air path, whereby in all blend positions including a full-cold position. In such case, the stratification control door is rotated aside in the full-cold position. 
   While the foregoing invention has been shown and described with reference to several embodiments, it will be understood by those of skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of this invention. For example, although it is envisaged that the structures for mixing airflow will normally be made from plastics material, nevertheless it will also be possible to use metal if this should prove desirable.