Abstract:
A HVAC system for reducing the level of air rush and blower noise escaping into the interior of the vehicle when the HVAC system is operating in the recirculation mode. The HVAC system includes a recirculation door having an acoustically transparent portion that enables a component of the air rush and blower noise to pass through the recirculation door to the vehicle exterior instead of entering the vehicle cabin or interior through the recirculation air inlet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a motor vehicle climate control system; and, more specifically to an apparatus that reduces air rush noise transmitted into the vehicle cabin or passenger compartment during operation of the system.  
         [0004]     2. Description of Related Art  
         [0005]     A motor vehicle climate control system or heating, ventilation air-conditioning (HVAC) system typically utilizes a blower to move and control airflow through the system. Air rush noise occurring in the HVAC system, especially when the blower is operated at high speeds; i.e., producing maximum airflow, is a customer comfort concern. In most vehicles, the operating mode generating the highest noise level is the recirculation mode with a high blower setting. The recirculation mode of the HVAC system draws air from the interior of the vehicle cabin or passenger compartment.  
         [0006]     To operate the HVAC system in the recirculation mode, a recirculation door closes the fresh air inlet and opens the recirculation inlet enabling the HVAC system to draw air from the vehicle interior. Drawing air from the interior of the cabin not only provides a direct path for the inlet related noise but also traps other blower noises within the vehicle interior. Current recirculation doors used in climate control systems are a solid barrier of very stiff plastic or ABS material having a very low noise transmission loss. As a result, when the system is operating in the recirculation mode, it is almost 2-4 decibels louder than when operating in the fresh air mode.  
         [0007]     One reason for the increased noise level is that when the recirculation door covers the fresh air inlet it prevents air rush and blower generated noise from escaping through the fresh air inlet to the exterior of the vehicle. Accordingly, closing the fresh air inlet audibly increases the noise level a perceptible amount as compared to operating the HVAC system in a fresh air mode, that is, when the recirculation door closes the recirculation air inlet and the fresh air inlet is open providing a path for noise to escape to the exterior of the vehicle.  
         [0008]     It would be desirable to provided a recirculation door that enables passage of at least a portion of the air rush and blower noise to the vehicle exterior when the climate control system is operating in the recirculation mode.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides a HVAC system for reducing air rush and blower noise escaping into the interior of the vehicle when the HVAC system is operated in the recirculation mode. The apparatus includes an acoustically transparent recirculation door that transmits a component of the air rush and blower noise to the vehicle exterior when the system is operating in the recirculation mode.  
         [0010]     The acoustically transparent recirculation door includes forming a portion of the recirculation door from an acoustically transparent material. In particular, that portion of the recirculation door that operates to close the fresh air inlet includes an acoustically transparent material. When the recirculation door closes the fresh air inlet, air is drawn into the climate control system through the open recirculation air inlet. Providing the recirculation door with an acoustically transparent material enables noise generated during operation of the HVAC system to pass through that portion of the recirculation door positioned adjacent to the fresh air inlet and out the fresh air inlet to the exterior of the vehicle.  
         [0011]     According to one aspect of the invention, the recirculation door may include a plurality of acoustically transparent apertures, the apertures positioned adjacent to the fresh air inlet when the recirculation door closes the fresh air inlet. The acoustically transparent apertures enabling at least a portion of the air rush and blower noise to pass through the recirculation door to the vehicle exterior. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic view of a climate control system utilizing a recirculation door according to the present invention.  
         [0013]      FIG. 2  is an enlarged, exploded view of a recirculation door according to the present invention.  
         [0014]      FIG. 3  is a cross-sectional view of a recirculation door according to the present invention.  
         [0015]      FIG. 4  is an enlarged cross-sectional view of a recirculation door according to the present invention illustrating an aperture therein having a acoustically transparent member positioned in the aperture according to one embodiment of the present invention.  
         [0016]      FIG. 5  an enlarged cross-sectional view of a recirculation door according to the present invention illustrating an aperture therein having a acoustically transparent member positioned in the aperture according to an additional embodiment of the present invention.  
         [0017]      FIG. 6  illustrates a recirculation door according to the present invention placed such that the recirculation air inlet is closed and the fresh air inlet is open.  
         [0018]      FIG. 7  illustrates a recirculation door according to the present invention placed such that the recirculation air inlet is open and the fresh air inlet is closed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Referring now to the drawings,  FIG. 1  shows a climate control assembly, seen generally at  10 , of a type typically used with an automotive vehicle. The climate control assembly  10  includes a housing or case  12  including a heater core  14 , an evaporator core  16  and a blower motor  18  driving a blower wheel  20 . A blower inlet  22 , having a fresh air inlet  24  and a recirculation air inlet  26  is located near the blower wheel  20 . The fresh air inlet  24  is typically located such that when the fresh air inlet  24  is open, the climate control assembly  10  draws air from outside the vehicle passenger compartment. The recirculation air inlet  26  is located within the vehicle passenger compartment and when the recirculation air inlet  26  is open, the climate control assembly  10  draws air from inside the vehicle passenger compartment. Accordingly, air, drawn in through either the fresh air inlet  24  or the recirculation air inlet  26 , flows in the direction shown by the arrow  28 . The blower inlet  22  includes a recirculation door  30  that operates to open and close the respective fresh air inlet  24  and recirculation air inlet  26 .  
         [0020]     In operation, air drawn in through either the fresh air inlet  24  or the recirculation air inlet  26 , in the direction of the arrow  28 , is forced by the blower wheel  20  through the evaporator core  16  and heater core  14  to a distribution plenum  32 . From the distribution plenum  32  the air is directed either to the defrost nozzles  34  or heater outlet  36  when the heater core  14  is used to heat the airflow. When the evaporator core  16  operates to cool the airflow, the distribution plenum  32  directs the air through air-conditioning ducts  38  to air-conditioning outlets  40  located in the vehicle dashboard. When operating in the air-conditioning mode, a drain  42  operates to drain condensation and corresponding moisture from the system  10 .  
         [0021]     Turning to  FIG. 2 , there is shown a recirculation door  30  in accordance with the present invention. The recirculation door  30  includes an arcuate door panel  44  configured to fit adjacent the arcuate shaped blower inlet  22 . A pair of arm members  46  support the door panel  44  on a bushing  48 . The bushing  48  is disposed over a rod or shaft (not shown) whereby the door panel  44  swings back and forth in between first and second positions. In the first position, the door panel  44  closes the recirculation air inlet  26  and opens the fresh air inlet  24 . In the second position, the door panel  44  closes the fresh air inlet  24  and opens the recirculation air inlet  26 . A suitable drive mechanism operates to move the recirculation door  30  between the first and second positions.  
         [0022]     As illustrated in  FIGS. 2-4 , the door panel  44  includes an acoustically transparent portion  50  and an acoustically opaque or non-transparent portion  52 . As used herein, the term acoustically transparent means allowing the passage of sound waves with minimal reflection. In the preferred embodiment, a portion of the door panel  44  is formed of an acoustically opaque material, such as polypropylene or nylon. Accordingly, the nontransparent or acoustically opaque portion  52  of the door panel  44  is formed of a rigid material that prevents the flow of air and sound waves through the door panel  44 . When the acoustically opaque or nontransparent portion  52  of the door panel  44  is placed adjacent the recirculation air inlet  26 , it closes the recirculation air inlet to prevent airflow and noise transmission through the recirculation air inlet  26 .  
         [0023]     The acoustically transparent portion  50  of the door panel  44  includes a plurality of apertures  54 . The apertures allow the sound waves or noise to pass through the acoustically transparent portion  50  of the door panel  44 . To prevent airflow through the acoustically transparent portion  50  of the door panel  44 , an acoustically transparent member or layer  56  is placed in the apertures  54 . As shown herein, the acoustically transparent member or layer  54  is a thermoplastic or polyester member placed in the apertures  56  located in the acoustically transparent portion  50  of the door panel  44 . Mylar®, manufactured by DuPont Teijin Films of Hopewell, Va., is one type of thermoplastic or polyester member suitable for use as an acoustically transparent member or layer. It should be understood that the acoustically transparent member or layer  56  operates as an airflow barrier to prevent airflow through the apertures  54  well allowing noise or sound waves to pass through the apertures  54  located in the arcuate door panel  44 . Thus, when the acoustically transparent portion  50  of the door panel  44  is placed adjacent the fresh air inlet  24 , the acoustically transparent member or layer  56  allows air rush and blower noise, specifically the sound waves generated by operation of the blower and the air moving through the system, to pass through the apertures  54  rather than being reflected back into the vehicle interior through the recirculation inlet  26 .  
         [0024]     As illustrated in  FIG. 3 , the acoustically transparent member or layer  56  is secured within the apertures  54  located in the door panel  44 . The apertures  54  includes sloped or beveled sidewalls  58  to redirect sound waves striking the surface of the door panel  44  through the acoustically transparent member  56 . Maximizing, the number of apertures  54  located in the door panel  44  increases the overall surface area of the door panel  44  formed of the acoustically transparent member  56 . Increasing the surface area formed of the acoustically transparent member  56  correspondingly increases amount of sound or noise that passes through the acoustically transparent portion  50  of the door panel  44 .  
         [0025]     Accordingly, since the strength, rigidity and ability to resist airflow forces of the acoustically transparent layer or member  56  varies, the ratio of the acoustically transparent member or layer  56  to the overall area of the acoustically transparent portion  50  of the door panel  44  will vary. Specifically, the acoustically transparent portion  50  of the door panel  44  includes the acoustically transparent member or layer  56  and a portion of the door panel  44  that provides support for the acoustically transparent member or layer  56 . The invention contemplates that the acoustically transparent portion  50  of door panel  44  utilized the greatest amount or surface area of acoustically transparent member or layer  56 . As set forth above, one approach is a plurality of apertures located in the acoustically transparent portion  50  of the door panel  44 . Another approach may include a honeycomb type construction formed of a plurality of thinwall cells, each cell supporting an acoustically transparent member or layer  56  secured and supported within each cell.  
         [0026]     In addition, the door panel  44  may include a seal member  60  placed on one or both sides of the door panel  44 . Generally, the seal member  60  is made of a compressible material, such as foam. Suitable foams for use with recirculation doors are known and include for example polyester and polyurethane foams. Such foams also function to reduce any noise reflected back into the housing or case  12  of the climate control assembly  10 .  
         [0027]     As illustrated in  FIG. 4 , the acoustically transparent member or layer  56  is molded within the door panel  44 . The sidewalls  58  of the apertures  54  are configured to funnel sound waves through the acoustically transparent member  56 . In this embodiment, the acoustically transparent member or layer  56  is a thin film molded into the door panel  44  during the manufacturing process. Once again, the acoustically transparent portion  50  of the door panel  44  supports the acoustically transparent member or layer  56 . Accordingly, the acoustically transparent portion  50  of the door panel  44  located adjacent the fresh air inlet  24 , when the recirculation door  30  is placed in the recirculation mode, supports the acoustically transparent member or layer  56  adjacent the fresh air inlet  24  thereby allowing passage of noise or sound waves while preventing airflow.  
         [0028]      FIG. 5  illustrates an alternative embodiment of the recirculation door  30  wherein the acoustically transparent member or layer  56  is secured, typically through an adhesive, on one side  62  of the door panel  44  such that the acoustically transparent member or layer  56  covers the apertures  54 . As with the previous embodiment, a compressible seal member  60 , such as a polyester or polyurethane foam, may be placed over the door panel  44  and correspondingly next to the acoustically transparent member or layer  56 . The compressible seal member  60  also provides support for the acoustically transparent member or layer  56  and helps reduce noise transmission within the climate control assembly  10 .  
         [0029]      FIG. 6  illustrates the climate control assembly  10  operating in the fresh air mode, where air is drawn in, as illustrated by the arrow  60 , through the fresh air inlet  24  for distribution through the housing or case  12  and ultimately through the defroster,  34  heater outlet,  36  or A/C outlets  40 . In the fresh air mode, the recirculation door  30  is located at a fresh air position wherein the acoustically opaque or nontransparent portion  52  of the door panel  44  covers the recirculation air inlets  26 . Accordingly, as illustrated in  FIG. 6 , resultant air rush noise along with noise generated from the blower and blower motor noise, illustrated by noise vectors  66 , generated in the housing or case  12  strikes the acoustically opaque portion  50  of the door panel  44  and is reflected outward through the fresh air inlet  24 .  
         [0030]     Conversely, as illustrated in  FIG. 7 , placing the recirculation door  30  in the recirculation mode results in air, as illustrated by the arrow  68 , being drawn in through the recirculation air inlets  26 . When positioned in the recirculation mode, the acoustically transparent portion  50  of the door panel  44  is placed adjacent to and closes the fresh air inlet  24 . Accordingly, air rush noise along with blower and blower motor noise, illustrated by noise vectors  70 , generated in the housing or case  12  strikes the acoustically transparent portion  50  of the door panel  44  wherein at least a portion of the noise travels through the acoustically transparent portion  50  of the door panel  44  and out the fresh air inlet  24 . Accordingly, the acoustically transparent portion  50  of the door panel  44  reduces the noise being reflected back into the vehicle operating compartment through the recirculation air inlet  26 .  
         [0031]     While  FIGS. 3-6  illustrate one type of acoustically transparent recirculation door  30 . Accordingly, the recirculation door  30  of the present invention includes an acoustically transparent portion  50  and an acoustically opaque portion  52 . Both portions functioning to reduce the noise level of the climate control assembly  10  by channeling or directing noise generated by the system outwards towards the fresh air inlet  24  and vehicle exterior rather than towards the recirculation air inlet  26  and ultimately the vehicle interior.  
         [0032]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.