Patent Publication Number: US-2022234418-A1

Title: Air conditioning recirculation mode for vehicle

Description:
TECHNICAL FIELD 
     The embodiments disclosed herein are related to control of air flow in a vehicle with a sunroof. 
     BACKGROUND 
     Vehicles are commonly equipped with air conditioning systems so as to provide comfort to the vehicle&#39;s driver and passengers on hot summer days. An air conditioning system includes an air compressor which is powered by the vehicle&#39;s motor, for driving a highly-volatile refrigerant through a system that includes a condenser, an expansion valve and an evaporator, as is well known. In a typical vehicle air conditioning system, fresh outside air is brought into the system and cooled down, after which it is blown into the vehicle cabin. 
     Several conditions influence the performance and efficiency of an air conditioning system, such as ambient temperature and humidity. Under hot, humid ambient conditions, the air conditioning system performs work to cool down and remove moisture from the fresh air to obtain a desired temperature and humidity within the vehicle. This fresh air is continually being added to the already-cooled air in the vehicle cabin. Since air is continually flowing in, the air conditioning system creates a positive pressure within the vehicle cabin, and so the already-cooled and dried air is continually seeping out of the vehicle cabin, resulting in air cooling losses. Thus, the air conditioning must perform constant work just to maintain a desired level of temperature and humidity within the vehicle cabin. 
     However, a vehicle air conditioning system is powered by the vehicle engine, and so the increased operation of the air conditioning system contributes to the engine load, which results in the consumption of additional fuel, thereby reducing fuel efficiency. It has therefore been previously contemplated to recirculate the already-cooled air in the vehicle cabin into the air conditioning system. This approach maintains the temperature and humidity level of already-cooled air, and reduces the cabin air cooling losses, and thereby reduces the load of fresh air coming into the system. In a “recirculation” mode, dampers may be closed to prevent introduction of fresh air into the vehicle, and rather draws air from the passenger compartment. 
     However, applying vehicle recirculation to aid in cooling with a sunroof tilted open, as is often the case when a vehicle passenger compartment is extremely hot, may lead to a loud wind noise level specifically in the passenger cabin from 0-10 kHz, mainly above 500 Hz. 
     With standards and regulations governing clean air and fuel conservation, it is highly desirable to reduce fuel consumption wherever possible, particularly if this goal can be attained without a reduction in performance or end-user expectations. It would be highly desirable to control the amount of recirculated air, and/or provide a mixture of recirculated and fresh air, for the purpose of reducing noise in the passenger cabin. 
     APPLICATION SUMMARY 
     The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. 
     According to one aspect, a method of operating an HVAC system of a vehicle, the HVAC system having a control unit for controlling the HVAC system and an air recirculation unit operable in an automatic mode or a manual mode, includes determining if a sunroof is applied to the vehicle, determining if the control unit can determine whether the sunroof is open or closed, determining if the sunroof is open or closed, and changing an operating condition of the air recirculation unit in the automatic mode from a first operating level to a second operating level if the sunroof is determined to be open. 
     According to another aspect, a method of operating a vehicle including an HVAC system having a control unit and an air recirculation unit operable in an automatic mode includes determining if a sunroof is applied to the vehicle, determining if the control unit can determine whether the sunroof is open or closed, determining if the sunroof is open or closed, and changing an operating condition of the air recirculation unit in the automatic mode from a first operating level to a second operating level if the sunroof is determined to be open. 
     According to yet another aspect, an HVAC system for a vehicle includes a control unit for controlling the HVAC system, and an air recirculation unit controlled by the control unit and operable in an automatic mode and a manual mode, wherein in the automatic mode, the air control unit is operable to determine if a sunroof is applied to the vehicle, determine if the control unit can determine whether the sunroof is open or closed, determine if the sunroof is open or closed, and change an operating condition of the air recirculation unit in the automatic mode from a first operating level to a second operating level if the sunroof is determined to be open. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is top perspective view of a portion of vehicle with an open sunroof. 
         FIG. 2  is a side perspective view of a portion of a vehicle with a tilted open panoramic sunroof. 
         FIG. 3  is a schematic view of an HVAC system and power window system of a vehicle. 
         FIG. 4  is a flowchart of a method of controlling an air recirculation unit of the HVAC system of the vehicle. 
         FIG. 5  is a graph illustrating the results of an Example A of operation of the method of  FIG. 4 . 
         FIG. 6  is a graph illustrating the results of an Example B of operation of the method of  FIG. 4 . 
     
    
    
     The figures depict various embodiments for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the embodiments described herein. 
     DETAILED DESCRIPTION 
       FIG. 1  is a top view of a vehicle  10  that includes a sunroof  12  in a roof  14  of the vehicle  10 . A sunroof  12  is a movable panel that is operable to uncover a window opening  16  in the roof  14 , which allows light and/or fresh air to enter a passenger compartment  18  of the vehicle  10 . The sunroof  12  may be either manually operated or motor driven, and the sunroof  12  may be available in many shapes, sizes, and styles. A sunroof  12  of the spoiler type, also described as a tilt-and-slides, and illustrated in  FIG. 1 , combines the features of a pop-up-type sunroof with those of a sliding roof system. The sunroof  12  may tilt to vent, as illustrated in  FIG. 2 , and slide open above the roof  14 , as illustrated in  FIG. 1 , requiring little headroom or roof length. A sunroof  12  of the spoiler type typically do not provide as large an window opening  16  as other roof systems, but offer the convenience of a self-storing panel. Most sunroofs  12  of the spoiler-type are electric, with optional features like integrated sun shades and express open/close. A sunroof  12  of the inbuilt-type has a panel which slides between the metal roof  14  and interior headliner (not-shown) in the passenger compartment  18 , requiring some loss of headroom but providing a full window opening  16  in the roof  14 . Any sunroof  12  that is inbuilt slides inside the roof  14 , while some also include a rear venting feature (see pop-up), and/or express open/close functions. An Inbuilt sunroof  12  may not fit every vehicle  10 , as the panel must slide and store completely within the vehicle roof. Historically, a sunroof  12  inbuilt was a metal sunroof panel painted to match the vehicle roof  14 , but now most are glass-panel systems with sliding sunshades 
     Panoramic roof systems  20 , as illustrated in  FIG. 2  are a type of large or multi-panel sunroof  12  which offer openings above both the front and rear seats and may be operable or fixed glass panels. Large operable window openings  16  are often accomplished with inbuilt, top-slider (tracks in the top of the roof  14 ), or spoiler-type mechanisms. 
     The vehicle may also be equipped with a heating, ventilation, and air-conditioning (“HVAC”) system  22 , schematically illustrated in  FIG. 3 . The HVAC system  22  includes a heating unit  24  for heating air, an air conditioning unit  26  for cooling and dehumidifying air, and a recirculation unit  28  for controlling the mix of fresh air and recirculated from the passenger compartment  18  moving through the HVAC system  22 . Using the recirculation unit  28  helps to cool the vehicle  10  as quickly as possible when it is warm outside of the vehicle  10  and the air conditioning unit  26  of the HVAC system  22  is on. The recirculation unit  28  recirculates the cool air produced by the air conditioning unit  26  and delivered to the passenger compartment  18  and reduces the flow of fresh air from outside of the vehicle  10 . If fresh air from outside the vehicle  10  that is much warmer in the summer is used, the air conditioning unit  26  must work continuously to cool the hot air from the outside when pulling it into the vehicle  10 , creating undue wear-and-tear on the air conditioning unit  26  and reducing fuel economy as a result. 
     Additionally, the recirculation unit  28  may be effective to reduce the flow of polluted air from another vehicle into the passenger compartment  18 , such as when following another vehicle with combustion or muffler problems. 
     The HVAC system  22  may also be equipped with a control unit  30  that includes an automatic setting that allows the user  32 , such as the driver, to select a temperature for the vehicle  10  while the control unit  30  controls the HVAC system  22  to operate in an automatic mode. Alternatively, the user  32  of the vehicle  10  may make manual selections as to temperature control, fan speed, and recirculation. 
     Finally, the recirculation unit  28  may be used to determine the source of vented air moving through the vehicle  10  when the HVAC system  22  is off, or additionally when the selected temperature does not require operation of either the heating unit  24  or the air conditioning unit  26 . 
     Based on increased wind noise, logic was created to limit recirculation operation when the sunroof  12  is open, as illustrated in either  FIG. 1 or 2 , and the vehicle  10  is in an automatic mode for operation of the HVAC system  22 . The HVAC system  22  may not be using the air conditioning unit  26  or heating unit  24 , or, more likely, the HVAC system  22  is turned off in order to choose the source of vented air, either from outside of the vehicle  10  or recirculated air from the passenger compartment  18 . This is particularly necessary, but not limited to, when the sunroof  12  applied to the vehicle is of the panoramic-type, and the user  32  selects a panorama tilt mode, as illustrated in  FIG. 2 . The logic may improve the overall decibel (“dB”) level when the user  32  chooses the panorama tilt mode. This logic only applies when auto recirculation is chosen, and will limit recirculation operation to a specified value, which in the examples disclosed below and in  FIGS. 5-6 , may be set to approximately 70%. The user  32  may still chose manual 100% recirculation regardless of sunroof  12  position. 
     The method  34  of operation of the control unit  30  while controlling the air HVAC system  22  in a vehicle  10  and controlling the air recirculation unit  28  in an automatic mode, as illustrated in  FIG. 4 , is as follows. First, the control unit  30  determines whether a sunroof  12  is applied to the vehicle  10  in step  36 . The step  36  is necessary as not all trim levels of a vehicle  10  may have an applied sunroof  12 , but the control unit  30  of the HVAC system  22  may be common across all trim levels. 
     Next, in step  38  the control unit  30  determines if the HVAC system  22  can determine whether the sunroof  12  is open or closed. It may be possible that the connection between control unit  30  and the either the power window system  40  or the sunroof  12  are not connected. This lack of connection may be present from the factory, which thus yields the same result every time. Alternatively, the lack of a connection may be transient or the result of disconnected or broken bus  42  or some other part failure. 
     If the control unit  30  can determine if the sunroof  12  is open or closed, the next step  44  is to actually make the determination whether the sunroof  12  is open or closed. The final step  46  of the base method  34  is to change an operating condition of the air recirculation unit  28  in the automatic mode from a first operating level  70  to a second operating level  72  if the sunroof  12  is determined to be open. The first operating level  70  of the recirculation unit  28  shown in Example A,  FIG. 5 , and shown in Example B,  FIG. 6 , is for the recirculation unit  28  in a fully closed state, i.e. full recirculation of air from the passenger compartment  18  and outside fresh air completely blocked. 
       FIG. 5  illustrates the effect of the method  34  for Example A, in which the second operating level  72  is approximately 70%, in which the recirculation unit  28  is 70% closed and 30% open to fresh air from outside of the vehicle  10 . In Example A, a reduction in passenger compartment  18  noise level, with passenger compartment  18  noise measured at a frequency of 5 kHz, the sunroof  12  in a tilt condition, and the vehicle  10  moving at 100 kph, was measured from 58.2 dB to 56 dB when moving from the first operating level  70  to the second operating level  72 . As further shown, moving to a third operating level  74  of 30%, in which the recirculation unit  28  is 30% closed and 70% open to fresh air from outside the vehicle  10  only provided a further reduction in passenger compartment  18  noise to 55.8 dB. In a fourth operating level  76 , with a fully open recirculation unit  28  with 100% fresh air, the passenger compartment  18  noise level only dropped to 55.7 dB. Thus, the greatest impact was movement from the first operating level  70  to the second operating level  72 . 
       FIG. 6  illustrates the effect of the method for Example B, in which the second operating level  72  is approximately 70%, in which the recirculation unit  28  is 70% closed and 30% open to fresh air from outside of the vehicle  10 . In Example B, a reduction in passenger compartment  18  noise level, with passenger compartment  18  noise measured at a frequency of 5 kHz, the sunroof  12  in a tilt condition, and the vehicle  10  moving at 100 kph, was measured from 56.7 dB to 54.2 dB when moving from the first operating level  70  to the second operating level  72 . As further shown, moving to a third operating level  74  of 30%, in which the recirculation unit  28  is 30% closed and 70% open to fresh air from outside the vehicle  10  only provided a further reduction in passenger compartment  18  noise to 54 dB. In a fourth operating level  76 , with a fully open recirculation unit  28  with 100% fresh air, the passenger compartment  18  noise level rose back to 54.2 dB. Thus, the greatest impact in Example B, as with Example A, was movement from the first operating level  70  to the second operating level  72 . 
     While the examples above indicate improvement in the 1-5 kHz range, improvements may be found in bands ranging from 0-10 kHz. 
     Additional steps may further be applied to the method  34  of operation of the control unit  30  illustrated in  FIG. 4 . The next step may be include maintaining the operating condition of the air recirculation unit  28  at the first operating level  70  if the sunroof  12  is not applied to the vehicle  10 . If the sunroof  12  is not applied, there is no need to adjust the recirculation unit  28 . 
     Next, the method  34  of operation of the control unit  30  includes maintaining the operating condition of the air recirculation unit  28  at the first operating level  70  if the control unit  30  cannot determine whether the sunroof  12  is open or closed. Thus, the failsafe operation is to maintain the first operating level  70  in the event the control unit  30  cannot determine if the sunroof  12  is open. 
     Additionally, the method  34  of operation of the control unit  30  may include the step  52  maintaining the operating condition of the air recirculation unit  28  at the first operating level  70  if the sunroof  12  is determined to be closed. 
     The control unit  30  may continue to check if the sunroof  12  is open or closed in step  54 . If the control unit  30  determines that the sunroof  12  has moved from closed to open, the control unit  30  may move the air recirculation unit  28  from the first operating level  70  to the second operating level  72  through repeating the method  34 . If the control unit  30  determines that the sunroof  12  has moved from open to closed, the control unit  30  returns the air recirculation unit  28  to the first operating level  70  from the second operating level  72  in step  56 . If the control unit  30  determines that the sunroof  12  remains open, the control unit maintains the air recirculation unit in the second operating level  72  in step  58 . 
     Finally, the method  34  of operation of the control unit  30  may be overridden by user  32  of the vehicle  10  overriding the automatic mode of the HVAC system  22  by manually selecting air recirculation by pressing button  60 , in which case the air recirculation unit  28  is returned to the first operating level  70  from the second operating level  72 . 
     Reference in the specification to “one embodiment” or to “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment. The appearances of the phrase “in one embodiment” or “an embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
     In addition, the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the embodiments, which is set forth in the claims. 
     While particular embodiments and applications have been illustrated and described herein, it is to be understood that the embodiments are not limited to the precise construction and components disclosed herein and that various modifications, changes, and variations may be made in the arrangement, operation, and details of the methods and apparatuses of the embodiments without departing from the spirit and scope of the embodiments as defined in the appended claims.