Patent Publication Number: US-8535002-B2

Title: HVAC diffuser with mounting receptacle for variable blower control

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to an automotive heating, ventilation, air conditioning (HVAC) system having an electrically controlled blower motor, and, more specifically, to structures for obtaining even diffusion of air simultaneously with improving cooling of the blower controller. 
     In a typical automotive HVAC system, a blower delivers fresh or recirculated air to heat exchangers (e.g., an evaporator) which is then distributed to the passenger cabin via ducts. A diffuser couples the air stream from the blower to the evaporator. Due to space requirements, the diffuser turns the air stream for delivery to the evaporator. The blower/diffuser combination produces a high speed, non-uniform flow that tends to produce high flows on the outer periphery of the diffuser due to centrifugal forces. 
     A uniform velocity distribution at the diffuser outlet and in the evaporator is very desirable to ensure efficient evaporator performance, higher air flow, and reduced noise generation as the air passes through the evaporator core. Various vanes and wall guides have been added to the diffuser to improve the uniformity of the air flow. One example is U.S. patent application publication 2010/0074743A1 of Jairazbhoy et al, entitled “Air Diffuser for a HVAC System,” which is hereby incorporated by reference in its entirety. 
     The diffuser is normally made as a molded plastic part. It has not been possible to make interior vanes of sufficient height extending from a corresponding wall due to limitations in the molding process and limitations associated with handling of the part after molding (e.g., breakage of the vanes). Therefore, vanes can affect the air flow near to the diffuser walls but are less able to affect air flow at the center of the diffuser. Furthermore, the die draw of the molding process does not allow vanes to extend from walls that are perpendicular to one another (i.e., vanes cannot extend from both the curved outer peripheral wall and either of the transverse (i.e., floor and ceiling) walls in the same molded section). 
     For similar reasons, wall guides have a greater influence on air flow in the regions of the walls. Known vanes and wall guides may be insufficient to obtain a desired uniformity of a diffused air stream when it becomes necessary to manipulate flow at the core, central portion of the diffuser. 
     The typical automotive HVAC system allows a user to select a rotating speed of the blower via a switch or dial. A variable blower control (VBC) module is an electronic controller that is mounted to the outside of the diffuser between the blower and the evaporator. Cooling fins penetrate the diffuser wall so that they benefit from the air flow within the diffuser. The VBC module has been conventionally mounted on a relatively flat exterior surface of the diffuser wall. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, a diffuser is provided for an automotive heating, ventilation, air conditioning (HVAC) system, wherein the HVAC system includes a blower and a variable blower control (VBC) module having a plurality of cooling fins. An inlet receives air flow from the blower. An outlet is downstream from the inlet. An enclosed passageway is provided between the inlet and the outlet for forming a diffused air stream at the outlet. The enclosed passageway has a plurality of peripheral walls for guiding the air stream between the inlet and the outlet, including a curved outer peripheral wall corresponding to a region with a tendency for a high flow as a result of centrifugal effects. One of the peripheral walls includes a VBC receptacle formed as a depression into the peripheral wall having a substantially flat mounting surface and a first sloped side at an upstream end of the VBC receptacle to shape a portion of the diffused air stream. The flat mounting surface includes a plurality of cooling fin receiving slots arranged to receive the cooling fins, whereby the cooling fins extend into an interior of the diffused air stream. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view showing a blower, diffuser and evaporator of an automotive HVAC system. 
         FIG. 2  is a cross section showing a conventional mounting of a VBC module to a diffuser. 
         FIG. 3  perspective view showing the interior of a diffuser with guide vanes secured to the inner surface of the diffuser. 
         FIG. 4  is an outside, perspective view of the VBC receptacle of the present invention. 
         FIG. 5  is an inside, plan view of cooling fins projecting into the diffuser air stream from the VBC receptacle. 
         FIG. 6  is a side cross section through another embodiment of the VBC receptacle. 
         FIG. 7  is an end view of another embodiment of a diffuser with a VBC receptacle in the outer peripheral wall. 
         FIG. 8  is a plan view showing an alternative orientation of the cooling fins with respect to a diffuser wall. 
         FIG. 9  is a plan view showing an alternative aerodynamic profile of a cooling fin. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Cooling fins of conventionally mounted VBC modules did not function as effective vanes because of incorrect placement and/or insufficient penetration into the air stream. Cooling fin materials (e.g., aluminum) would be too expensive to merely increase their heights beyond what is required for cooling purposes. 
     The present invention employs a recessed receptacle in the diffuser wall for mounting the VBC heat sink cooling fins. The receptacle itself protrudes into the diffuser. The cooling fins extend into the central portion of the diffuser to act as a set of vanes, influencing the flow in the core of the diffuser and resulting in improved evaporator coverage, velocity distribution, pressure drop, air flow, &amp; aerodynamic noise. 
     The receptacle can also be placed in the outer peripheral wall of the diffuser with the cooling fins substantially horizontal, permitting guidance of the flow upwards or downwards as desired, a capability not present in prior art vertical vanes or wall guides. An outer cooling fin of the VBC heat sink can also be used as a vane in conjunction with a wall, a wall guide, or a molded guide vane to accelerate or decelerate flow as it passes through the gap. This is accomplished by a changing the cross section between the fin and the corresponding wall, wall guide, or vane along the length of the fin (i.e., using the Bernoulli Effect). 
     Referring to the top view of  FIG. 1 , a portion of an automotive HVAC system  10  has an air flow path or stream from a blower  11  with a motor-controlled bladed wheel through a diffuser  12  to an evaporator  13 . Diffuser  12  has an inlet generally indicated at  14  and an outlet  15 . Diffuser  12  creates an enclosed passageway between inlet  14  and outlet  15  which is enclosed by a plurality of peripheral walls that guide the air stream. The walls include a curved outer peripheral wall  16  and an inner peripheral wall  17 . “Outer” and “inner” are relative to the curved path of the air stream through diffuser  12 . Because of the curve, curved outer peripheral wall corresponds to a region with a tendency for a high flow as a result of centrifugal effects. Correspondingly, the region adjacent inner wall  17  tends to have a lower flow and a lower pressure. Walls  16  and  17  are vertical in the top view of  FIG. 1 , and are sometimes referred to as side walls. Upper and lower transverse walls that extend between walls  16  and  17  are sometimes referred to as the ceiling and floor, respectively. 
       FIG. 2  represents one placement of a prior art VBC module. A receptacle  18  includes raised sides  20  around a flat mounting surface  21  to create a space  22  for receiving the VBC module. Raised sides  20  function to create a protected location for the VBC module which is inserted into space  22  so that its cooling fins pass through slots  23 . A dashed line  24  shows the region where the cooling fins of the VBC module heat sink enter the air stream within the diffuser. In prior art devices, the cooling fins have not affected the central regions of the air stream. 
       FIG. 3  shows prior art vanes for shaping an air stream in a manner that helps achieve a well diffused air stream at the diffuser exit. Outer peripheral wall  16  and inner peripheral wall  17  are joined by a transverse wall  25  and a transverse wall  26  to provide the enclosed passageway of the diffuser. A set of vanes  27  extends from outer peripheral wall  16  and a vane  28  extends from transverse wall  26 . In a plastic injection-molded unit formed from two half-shells joined together (as is the typical construction), it is not possible to form vanes that extend in right angles after final assembly since the draw directions must be parallel. In order to provide vanes  27  and  28 , one of them must comprise a separate component. Thus, vanes  27  are a separate molded part that is assembled into a receiving hole in wall  16 . Vanes  27  may be capable of being formed with a greater height than vanes that are integrally molded with the diffuser, however, manufacturing and assembly costs associated with a separate subcomponent are undesirable. 
       FIG. 4  shows a first embodiment of the present invention for mounting a VBC module in a manner that achieves improved manipulation of the air stream. A diffuser includes an upper transverse wall  30  and a curved outer peripheral wall  31 . A VBC receptacle  32  is formed as a depression into transverse wall  30  and has a substantially flat mounting surface  33 . Receptacle  32  has a first sloped side  34  at the upstream end of receptacle  32 , a downstream side  35 , and lateral sides  36  and  37 . Flat surface  33  has a plurality of cooling fin receiving slots  38 - 40  that are arranged to receive the cooling fins of the VBC module. By virtue of receptacle  32  being made as a depression into the diffuser, the cooling fins extend into an interior region of the air stream. 
     Two different aspects of the receptacle of the present invention can be used to separately manipulate the air stream. As shown in  FIG. 5 , cooling fins  42 - 44  extend into the core of the air stream between outer wall  31  and an inner peripheral wall  41 . Cooling fins  42 - 44  function as vanes for directing flow as desired. For example, the alignment of the longitudinal sides of cooling fins  42 - 44  with respect to the impinging air flow can be selected so that a portion of the air flow can be redirected. 
     In a second mechanism, sloped side  34  redirects airflow away from the upper transverse wall in order to shape a portion of the diffused air stream. Sloped side  34  may be generally parallel with the flow direction of the air stream or may be rotated in a manner to redirect the air flowing over sloped surface  34  toward the inner peripheral wall. 
       FIG. 6  shows another embodiment for the receptacle. A diffuser  50  has a curved outer peripheral wall  51  and an upper transverse wall  52  into which a VBC receptacle  53  is sunk. A generally flat mounting surface  54  is coupled to a first sloped side  55 . A sidewall  56  of receptacle  53  provides part of the enclosure for the VBC module. A plurality of slots  57  are provided in flat mounting surface for receiving the cooling fins of the VBC module so that they extend into the position shown at  58 . A mounting structure  59  is provided for coupling diffuser  50  to an evaporator. 
       FIG. 7  shows an embodiment wherein the VBC receptacle is provided on the outer peripheral wall. Thus, a diffuser  60  has an outer peripheral wall  61  and an inner peripheral wall  62  joined by upper transverse wall  63  and lower transverse wall  64 . A diffuser exit  65  is adapted to be coupled to an evaporator housing. 
     VBC receptacle  66  is formed as a depression into outer peripheral wall  61 . An upstream side  67  is sloped in order to shape a portion of the diffused air stream, in particular by directing airflow away from outer peripheral wall  61  which is a region with a tendency for a high flow. Thus, a portion of the diffused air stream is shaped so that flow is increased in (i.e., redirected to) regions with a tendency for a lower flow. Downstream side  68  and lateral sides  70  and  71  of receptacle  66  have relatively little effect on the airflow. Cooling fins  72  extend deep into the air stream for optimal cooling and can optionally be shaped to further redirect a corresponding portion of the diffused air stream at the exit  65 . 
       FIG. 8  illustrates an additional technique for using the VBC receptacle and cooling fins for shaping the diffused air stream. Receptacle  80  is disposed in close proximity to a wall  81 , which may be either an outer wall, inner wall, or transverse wall. Receptacle  80  has a flat mounting surface  82  and a sloped upstream side  83 . Cooling fin receiving slots  84  are oriented so that when the cooling fins are inserted they shape a respective portion of the diffused air stream by functioning as guide vanes within the air stream. In particular, at least one cooling fin receiving slot  84  may be oriented so that the cooling fin is slanted with respect to wall  81 . Specifically, one end of slot  84  is at a distance  85  from wall  81  while the other end of slot  84  is at a distance  86  from wall  81 . Thus, an air path  87  between the cooling fin and wall  81  has a variable cross-section from its beginning to end. The changing cross-section modifies the velocity of the portion of the air stream passing between the cooling fin and wall  81 . An increasing cross-section reduces the velocity while a decreasing cross-section increases the velocity. The modified velocity is selected in a manner that improves the even diffusion of the diffused air stream at the outlet. 
       FIG. 9  shows another embodiment of a flat mounting surface  90  having cooling fin receiving slots  91 - 93 . Velocity of a portion of the air stream can be modified by using a cooling fin having an aerodynamic profile. Slot  91  may be shaped in correspondence to the aerodynamic profile of the cooling fin. The aerodynamic profile may have the cross-sectional shape of an airplane wing, for example. The slot and the cooling fin do not necessarily have the same profile. Likewise, the cross-section profile of the cooling fin could change along its height.