PATENT ABSTRACT
An apparatus for heating a passenger compartment of a vehicle having an engine room defining a ram airflow path, an engine located in the engine room, and a cooling pack located in the ram airflow path for dissipating waste heat generated by the engine is described. The apparatus includes a fan positioned in the ram airflow path, the fan responsive to a control signal to operate in at least two modes relative to the ram airflow path. The apparatus also includes a controller responsive to at least one sensor and configured to generate the control signal to operate the fan in a first mode when the detected one or more operating conditions are in a first state and to operate the fan in a second mode when the detected one or more operating conditions are in a second state.

PATENT DESCRIPTION
FIELD OF THE INVENTION 
       [0001]    The present invention pertains to the field of heating a passenger compartment in a vehicle, and more particularly to controlling a fan providing airflow to a heat exchanger. 
       BACKGROUND 
       [0002]    Internal combustion engines in vehicles produce heat during operation. A heat exchanging system can be provided to ensure the engine is kept below a certain temperature. For example, a heat exchanging system can include a radiator to dissipate heat produced by the engine and a condenser to dissipate heat produced by an air conditioning system. Forced convection is often used to transfer heat away from the radiator and condenser using airflow provided by at least one of an electric fan, an engine-driven fan, and ram airflow resulting from the movement of the vehicle. 
         [0003]    Under certain circumstances, for example, when an ambient air temperature outside the vehicle is cold, it is desirable to dissipate less heat than the heat exchanging system is designed to dissipate. A heat exchanging system for a diesel engine is particularly susceptible to dissipating more heat than desirable when the ambient air temperature is cold and ram airflow is high (e.g., when the vehicle is travelling fast) because diesel engines generally do not produce as much heat as gasoline engines. In response, a driver of diesel engine truck will often place a grille cover, such as a fabric or plastic sheet, over at least a portion of the grille of his vehicle during the winter in order to reduce the ram airflow passing over the heat exchanging system. 
       SUMMARY 
       [0004]    In one disclosed embodiment, an apparatus for heating a passenger compartment of a vehicle having an engine room defining a rain airflow path, an engine located in the engine room, and a cooling pack located in the ram airflow path for dissipating waste heat generated by the engine is provided. The apparatus includes a heater configured to provide heated air to the passenger compartment. The heater is in thermal communication with the engine to transfer waste heat from the engine to the passenger compartment. A sensor is configured to detect one or more operating conditions of the vehicle. A fan is positioned in the ram airflow path, and the fan is responsive to a control signal to operate in at least two modes relative to the ram airflow path. A controller is responsive to the sensor and configured to generate the control signal to operate the fan in a first mode when the detected one or more operating conditions are in a first state and to operate the fan in a second mode when the detected one or more operating conditions are in a second state. 
         [0005]    In another embodiment, an apparatus for heating a passenger compartment of a vehicle having an engine room defining a ram airflow path and an engine located in the engine room is provided. The vehicle includes a sensor configured to detect one or more operating conditions of the vehicle. A heater is configured to provide heated air to the passenger compartment, and the heater thermally is coupled to the engine. A cooling pack in the ram airflow path is thermally coupled to the engine, and the cooling pack includes at least one of a radiator and a condenser. A fan is positioned in the ram airflow path adjacent the cooling pack, and the fan is responsive to a control signal to operate in a forward direction in which the fan moves air in a direction of the ram airflow path, and a reverse direction in which the fan moves air in an opposite direction of the ram airflow path. A controller is responsive to the sensor and configured to generate the control signal to operate the fan in the forward direction when the detected one or more operating conditions are in a first state and to operate the fan in the reverse direction when the detected one or more operating conditions are in a second state. 
         [0006]    In another embodiment, a method for heating the passenger compartment of a vehicle having an engine room defining a ram airflow path, a fan located in the ram airflow path, an engine, and a heater configured to heat the passenger compartment using waste heat of the engine is provided. The method includes detecting one or more operating conditions of the vehicle including at least one of a passenger compartment heat demand and a heater heat capacity, driving the fan in a forward direction when the detected operating conditions are in a first state, and driving the fan in a reverse direction when the detected operating conditions are in a second state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
           [0008]      FIG. 1  is a partially exploded perspective view of a vehicle and a reversible fan; 
           [0009]      FIG. 2  is a schematic diagram of an engine room; 
           [0010]      FIG. 3  is a flowchart of communication between a sensor, a controller, and a fan; and 
           [0011]      FIG. 4  is a flowchart of a logic of the of  FIG. 3  controller. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]      FIGS. 1-4  illustrate a heat exchanging system according to the present invention. 
         [0013]      FIG. 1  illustrates a heating system  10  in a vehicle  12 . While the illustrated vehicle  12  is a sedan, the heating system  10  can also be used in trucks, buses, sports cars, and other types of vehicles. The heating system  10  provides warm air to a passenger compartment  14 . The system  10  includes components located in an engine room  16  of the vehicle. While the illustrated engine room  16  is located underneath a hood of the vehicle  12 , the engine room can be located at another location, e.g., beneath a passenger compartment. 
         [0014]    As illustrated in  FIGS. 1 and 2 , the engine room  16  includes a fan  18 . The fan  18  can be positioned directly inside a grille  19  of the vehicle  12 . Alternatively, the fan  18  can be positioned at another location in the engine room  16 , such as spaced from the grille  19  with a cooling pack between the fan  18  and the grille  19 , or at another location in fluid communication with the engine room  16 . The fan  18  can be an electric fan powered by a vehicle battery or another power source. The fan  18  can be a variable speed fan capable of producing a continuous range of airflow speeds, or the fan can produce only a certain number of airflow speeds, e.g., two or three speeds. Additionally, the fan  18  can be rotatable in two directions to produce airflow in two opposing directions, i.e., airflow in a direction toward a rear of the vehicle  12  (i.e., a normal airflow path  36 ) and airflow toward a front of the vehicle  12  (i.e., a reverse airflow path  38 ). The fan  18  can include, for example, a brushless motor controlled by pulse width modulation (PWM). 
         [0015]    As further illustrated in  FIG. 2 , an ambient air sensor  20  is located on the vehicle  12  outside the engine room  16 . The sensor  20  can be positioned at a suitable location for measuring an ambient air temperature external the vehicle  12 , such as on a bumper of the vehicle  12 , underneath the vehicle  12 , or elsewhere on the vehicle  12 . The air sensor  20  can be located internally, e.g., inside the engine room  16 , so long as the sensor  20  is able to obtain a substantially accurate ambient air temperature measurement. 
         [0016]    Also as illustrated in  FIG. 2 , an engine room temperature sensor  22  is positioned in the engine room  16 . Alternatively, the engine room temperature sensor  22  can be positioned at another location in which the sensor  22  can obtain a measurement of a temperature indicative of the temperature of the heat exchanging system  10 . For example, the sensor  22  can be positioned in a conduit between the engine compartment  16  and the passenger compartment  14  in order to obtain an indirect measurement of the engine room  16  temperature. Moreover, the temperature of the engine room  16  may vary depending on the exact location in which a measurement is taken, and the position of the sensor  22  should be taken into consideration in operating the system  10 . For example, positioning the sensor  22  close to an engine  24  can result in a higher temperature reading than positioning the sensor  22  away from the engine  24 , and the heat exchanging system  10  should be controlled accordingly as is described in greater detail below. 
         [0017]      FIG. 2  also illustrates the engine  24  in the engine room  16 . The engine  24  can be a gasoline internal combustion engine, a diesel internal combustion engine, an electric motor, a hydrogen fuel cell, or another device that produces heat during operation. 
         [0018]      FIG. 2  additionally illustrates a cooling pack and a heater  26  in thermal communication with the engine  24 . The cooling pack can include a radiator  28 , a condenser  30 , and/or other heat exchangers for transferring heat from engine coolant, engine oil, transmission oil, and/or other fluids to an ambient environment. The cooling pack can include discrete heat exchangers, e.g., a separate radiator  28  and condenser  30 , or the cooling pack can be an integral unit including a radiator, condenser, and additional heat exchangers. Moreover, the cooling pack can include just one heat exchanger, e.g., only one of the condenser  28  and the radiator  30 . The cooling pack is positioned in a ram airflow path  34 , such as at a location on the opposing side of the fan  18  from the grille  19  as shown, or between the fan  18  and the grille  19 . 
         [0019]    The ram airflow path  34  is a path for air entering the engine room  16  while the vehicle  12  is traveling. For example, the ram airflow path  34  can include a path through the grille  19  or another air inlet positioned to receive air as the vehicle  12  travels. The ram airflow path  34  extends into the engine room  16 , and the exact geometry of the path  34  depends on the size and location of the grille  19  and/or other air inlets, the cooling pack, the engine  24 , and other vehicle  12  parts in the engine room  16 . The ram airflow path  34  need not be a single, continuous line; the path  34  can include branches and junctions where air streams diverge and converge, respectively. The ram airflow path  34  is generated during forward travel of the vehicle  12 , and therefore the path  34  is generally aligned with the normal fan airflow  36  and opposed by the reverse fan airflow  38 . 
         [0020]    The heater  26  is a heat exchanger, e.g., a radiator, in thermal communication with the engine  24  and the passenger compartment  14 . A fan can produce an airflow for forcing convective heat transfer from the heater  26  to the passenger compartment  14  through a series of ducts. A thermostat can be included within at least one of the ducts to regulate the operation of the heater  26 , for example, by opening to allow heated air to flow from the heater  26  to the passenger compartment  14  or closing to prevent heated air to flow. While the heater  26  is illustrated in the engine room  16 , the heater  26  can alternatively be positioned at another location, e.g., between the engine room  16  and passenger compartment  14 . 
         [0021]    A heater temperature sensor  32  can be used to measure the temperature of the heater  26 . The heater temperature sensor  32  can be positioned to contact the heater  26  or at another location in which the sensor  32  can obtain a measurement of a temperature indicative of the temperature of the heater  26 , such as in an airflow from the heater  26  to the passenger compartment  14 . 
         [0022]    Also as illustrated in  FIG. 2 , the passenger compartment  14  includes a heater control  40 . The heater control  40  is a control for generating a heat demand signal, which can include a demand to heat the passenger compartment  14  to a specific objective (e.g., 72° F.) or subjective (e.g., “Low”, “Medium”, or “High”) temperature. In addition or alternative to the heater control  40 , the heat demand signal be produced in consideration of the ambient air temperature as measured by the ambient air temperature sensor  20  or another temperature, e.g., the temperature of the engine room  16 , engine  24 , or heater  26 , as is discussed below in greater detail. 
         [0023]    A controller  42 , as shown in  FIG. 2 , is in communication with the ambient air temperature sensor  20 , the engine room temperature sensor  22 , the heater temperature sensor  32 , the heater control  40 , and an engine temperature sensor  44  positioned to measure the temperature of the engine  24 . The controller  42  generally includes a CPU, a memory and other peripheral circuits. Note that sensors  20 ,  22 ,  32 , and  44  and heater control  40  are not all necessary. The controller  42  can operate from the input of a single sensor, e.g., the heater sensor  32 , if desired. However, more accurate control may be obtainable with the use of multiple sensors. While the controller  42  is illustrated as being positioned in the engine room  16 , the controller  42  can be located elsewhere in the vehicle  12 . 
         [0024]    Operation of the heat exchanging system  10  is shown in  FIGS. 3 and 4 . As shown in step S 1  of  FIG. 3 , one or more of the sensors  20 ,  22 ,  32 ,  44  and the heater control  40  can generate respective signals α and transmit the signals α to the controller  42 . Additional sensors can detect other vehicle operating conditions, such as the speed and/or acceleration of the vehicle  12 , a rotational speed of the engine  24 , a time the engine  24  has been operating, or a signal corresponding to airflow into the engine room  16 , and output of the additional sensors can also be included in the signals α. As shown in step S 2 , the controller  42  receives the signal(s) α, determines the proper control mode of the fan  18 , and outputs a signal β corresponding to the fan control mode. The logic employed by the controller  42  will be discussed later in reference to  FIG. 4 . Referring still to  FIG. 3 , in step S 3  the fan  18  receives the signal β output by the controller  42  and rotates accordingly. 
         [0025]      FIG. 4  illustrates the logic employed by the controller  42  in controlling the fan  18 . In step S 4 , the controller  42  determines a heat capacity of the heater  16 . The heat capacity of the heater  16  can be based on the signal output by the heater sensor  32  corresponding to the temperature of the heater  16 . That is, the hotter the heater  16 , the greater the heat capacity of the heater  16 . Additionally, since the heater  16  is in thermal communication with the engine  24 , the controller  42  can determine the heat capacity based on another temperature, e.g., the temperature of the engine  24  or the temperature of the engine room  16 . Alternatively, the heater capacity can be estimated based on one or more of the ambient temperature, the rotational speed of the engine  24 , the speed of the vehicle  12 , and the time the engine  24  has been operating. 
         [0026]    In step S 5  of  FIG. 4 , the controller  42  determines the passenger compartment heat demand. As described above, the heat demand can be a function of the heater control  40  setting. In addition or alternative to the heater control  40 , the heat demand signal be produced in consideration of the ambient air temperature as measured by the ambient air temperature sensor  20  or another temperature, e.g., the temperature of the engine room  16 , engine  24 , or heater  26 , into consideration. For example, the controller  42  can determine that the heat demand is high when the ambient temperature is low. Additionally, since there is a relationship between the ambient air temperature and the engine room  16 , engine  24 , and heater  26  temperatures, the controller  42  can take these temperatures into consideration. As an example of the controller  42  taking multiple settings into consideration, the controller  42  can be configured to calculate a heat demand based on vehicle operating conditions excluding the heater control  40  setting and to control the fan  18  on the basis of a heat demand calculated from measured temperatures, unless the calculated heat demand is lower than the setting of the heater control  40 . 
         [0027]    As shown in step S 6  of  FIG. 5 , the controller  42  determines whether the heater  16  can provide sufficient heat to the passenger compartment  14  to meet the heat demand. The determination can include a calculation including only the heat demand (e.g., whether the heat demand is greater than a predetermined value), a calculation including the heat demand and the heat capacity (e.g., whether the heat demand is greater than the heat capacity, or whether the heat demand is greater than the heat capacity plus a threshold value), or a calculation including the heat demand and at least one of the operating conditions. The predetermined value and threshold value can be determined experimentally or calculated based on the design of the heat exchanging system  10  and vehicle  12 . 
         [0028]    If the heat capacity is sufficient to heat the passenger compartment  14 , the controller rotates the fan  18  to produce normal fan airflow  36  as shown in step S 7 . Depending on the fan  18 , the normal fan airflow  36  speed can be varied continuously or as a step function, e.g., between two discrete speeds. Additionally, the controller  42  can stop rotation of the fan  18  in step S 7 , for example, if the engine  24  is adequately cooled without the normal fan airflow  36  provided by the fan  18 . However, if the heat capacity is insufficient to heat the passenger compartment, the controller rotates the fan  18  to produce reverse fan airflow  38  as shown in step S 8  of  FIG. 5   
         [0029]    Reverse fan airflow  38  is airflow in a direction opposing the direction of ram airflow  34  as described above. Reverse fan airflow  38  can cancel out at least a portion of the ram airflow  34 , thereby reducing the forced convection of heat away from the cooling pack when the vehicle  12  is travelling. As a result, the cooling pack transfers less heat from the engine  24  to the ambient environment, causing the engine  24  to heat faster. As the heat of the engine  24  increases, the amount of heat transferred from the engine  24  to the heater  26  increases. Thus, rotating the fan  18  to produce reverse fan airflow  38  increases the heat capacity of the heater  26 . 
         [0030]    Additionally, reverse fan airflow  38  can also be beneficial when the vehicle  12  is idle. For example, if the ambient temperature is greater than the engine room temperature, reverse fan airflow  38  can draw relatively warmer air over the cooling pack to increase the engine temperature. Regardless of the vehicle  12  speed, operation of the fan  18  increases the load on the engine  24  and as a result increases the rate at which the engine  24  produces heat. Reverse fan airflow  38  can continue for a predetermined time, or the controller  42  can determine the rotational velocity of the fan  18  at predetermined intervals. 
         [0031]    As described above, by monitoring the operating conditions of a vehicle and controlling a fan positioned adjacent a cooling pack accordingly, the heat capacity of a heater can be increased. An increased heat capacity enables the heater to more quickly meet a heat demand of a passenger compartment. Thus, the passenger compartment can be warmed to a comfortable temperature more quickly than without a reversible fan. Additionally, the system allows more accurate control of the fan when the fan is rotating in a normal direction. 
         [0032]    Conventional grille covers should be installed or removed according to ambient air temperature fluctuations, which can be frequent during transitional times between seasons or when driving a long distance. Moreover, a conventional grille cover may be desirable when an engine initially starts, but after running for a period of time the engine may heat up to the point that a grille cover is no longer necessary. The system as described above can react to changing conditions, eliminating the need for a grille cover and its associated disadvantages. 
         [0033]    While the invention has been described in connection with what is presently considered to be the most practical embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.