Abstract:
A temperature control apparatus for an interior of a motor vehicle having a temperature control loop circulating a heat-exchange fluid to a drivetrain component. A thermoelectric heat-pump (Peltier device) is disposed in the vehicle to heat or cool the desired area, and a fluid comfort control loop exchanges heat with the thermoelectric heat-pump and with the drivetrain temperature control loop, increasing the net amount of heating or cooling that can be delivered to the desired location by the thermoelectric heat-pump. The comfort control loop may branch from the drivetrain loop and carry a portion of the heat-exchange fluid carried in the drivetrain loop. Alternatively, the comfort control loop may carry a second heat-exchange fluid that remains separate from the heat-exchange fluid of the drivetrain loop and exchanges heat therewith in a heat exchanger.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a comfort control system for a vehicle that includes a thermoelectric heat pump (Peltier device) having a fluid temperature control loop, and specifically to such a system in which energy efficiency is improved by the exchange of heat energy between the temperature control loop and a second fluid temperature control loop that controls the temperature of a drivetrain component. 
       BACKGROUND 
       [0002]    Electric powered vehicles (including hybrid-electric vehicles, fuel cell vehicles, plug-in electric vehicles, etc.) have one or more drivetrain components that should be maintained within a desired operating temperature range for optimum performance. Examples of such drivetrain components are high-voltage batteries, electric machines (motors, generators, and/or combined devices), and transmissions. Under some operating conditions, a temperature control system is necessary to cool and/or heat the components to maintain them within the desired temperature range. 
         [0003]    It is known to provide a temperature control system in which a fluid (usually a liquid) is circulated to, through, or around the drivetrain component where the fluid removes (or adds) heat energy, and through a heat exchanger to reject (or absorb) heat energy to some other medium, usually ambient air. In this context, the term “heat exchanger” refers to any apparatus that may achieve the desired result of adding and/or removing heat to/from the fluid circulating in the control system. This heat exchange function may be performed by apparatus such as a fluid/fluid heat exchanger, a refrigerant-cycle heat pump, and a thermoelectric heat pump (also known as a Peltier device). 
         [0004]    Thermoelectric heat pumps are currently used in some automotive vehicles to cool and/or heat a storage compartment in order to store food or drinks at a desired temperature. It is also known to use thermoelectric heat pumps to heat and/or cool seats in the vehicle interior. In such “air conditioned seats,” the seating surface which contacts the seat occupant is typically perforated and a fan circulates air over the cold side of the Peltier cooler and blows the cooled or heated air out of the perforations in the seat skin. 
         [0005]    It has also been proposed to integrate a liquid heat exchanger with a thermoelectric heat pump. In this concept, a liquid working fluid passes through the heat pump. In heating mode, heat is pumped from the working fluid through the thermoelectric device into the passenger comfort air. In cooling mode, heat is rejected from the air into the liquid working fluid. 
       SUMMARY 
       [0006]    The object of the invention is to improve the overall energy efficiency of a motor vehicle, in particular an electric vehicle, by reducing or eliminating the need to use electric power to run a conventional heater or air conditioning unit to achieve a comfortable cabin temperature. 
         [0007]    According to a feature disclosed herein, an interior temperature control apparatus for a motor vehicle having a temperature control loop carrying a heat-exchange fluid to a drivetrain component comprises a thermoelectric heat-pump disposed in the vehicle, and a comfort control loop exchanges heat with the thermoelectric heat-pump and with the drivetrain temperature control loop. This increases the net amount of heating or cooling that can be delivered to the desired location by the thermoelectric heat-pump, thereby reducing the amount of electrical power that may otherwise be needed to run the climate control system. 
         [0008]    According to another feature disclosed herein, the comfort control loop branches from the drivetrain loop and carries a portion of the heat-exchange fluid carried in the drivetrain loop. 
         [0009]    According to another feature disclosed herein, the comfort control loop carries a second heat-exchange fluid that exchanges heat with the heat-exchange fluid of the drivetrain loop. 
         [0010]    According to another feature disclosed herein, an apparatus for passenger comfort control in a motor vehicle comprises a drivetrain component, a temperature control loop circulating a heat-exchange fluid to the drivetrain component, a thermoelectric heat-pump disposed in a passenger compartment of the vehicle, and a comfort control loop branching from the temperature control loop and carrying a portion of the heat-exchange fluid to the thermoelectric heat-pump. 
         [0011]    According to another feature disclosed herein, the passenger comfort control apparatus further comprises a HVAC system circulating air through the passenger compartment, and an electronic control unit controlling the HVAC system and the thermoelectric heat-pump. Integrating the control of the thermoelectric heat pump with the HVAC system achieves optimum energy management, thereby minimizing energy usage while maintaining a comfortable passenger environment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic system diagram of a thermoelectric comfort control system according to a first disclosed embodiment; 
           [0013]      FIG. 2A  is a schematic depiction of a thermoelectric heat pump with fluid a heat exchange fluid loop; 
           [0014]      FIG. 2B  is a schematic depiction of a Peltier element of the type used in a thermoelectric heat pump; and 
           [0015]      FIG. 3  is schematic system diagram of second embodiment of a thermoelectric comfort control system. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0017]    Referring to  FIG. 1 , a thermoelectric comfort control system for a vehicle includes one or more thermoelectric heat pumps  10  located in, on, or adjacent to a passenger compartment of a vehicle. In the depicted embodiment, thermoelectric heat pumps (TEHP) are located inside a passenger seat  12 , one in the seat bottom and one in the seat back. TEHPs may be provided at other locations within a passenger cabin where heating and/or cooling is required, such as beneath a seat, adjacent a foot-well area, behind a body trim panel (e.g., headliner or door trim), or behind the instrument panel. Further, TEHPs may be located within or adjacent to a storage compartment in order to heat and/or cool the storage compartment as may be required, for example, to store food or drinks at a desired temperature. 
         [0018]    TEHPs as described herein operate on the well-known Peltier effect in which a DC electric voltage is applied across pairs of n-type and p-type thermo elements to cause an electron flow and resulting heat transfer from a “cold side” to a “hot side” of the elements. Reversing the polarity of the DC voltage reverses the flow of electrons and results in a switching of the hot side and cool side. Accordingly, a single TEHP may be used either as a heating device or a cooling device by simply applying the appropriate voltage polarity. 
         [0019]    The following description primarily discusses the situation where TEHPs  10  are used to cool the vehicle interior. This should, however, not be construed to limit the scope of the present invention since, as noted above, TEHPs  10  may easily be operated to heat the vehicle interior if desired. 
         [0020]    A comfort control loop  14  circulates a heat exchange fluid through TEHPs  10 . Comfort control loop  14  may comprise hollow pipes or tubes that enter TEHPs and pass across one side of the Peltier devices to allow an exchange of heat energy between the fluid and the Peltier device, and exit the TEHP. In the embodiment depicted in  FIG. 1 , comfort control loop  14  branches off from a drivetrain temperature control loop  16  and carries a portion of the heat exchange fluid circulating through the drivetrain temperature control loop. 
         [0021]    The amount or portion of heat exchange fluid that is diverted from the drivetrain temperature control loop  16  to circulate through comfort control loop  14  may be regulated by one or more valves  18  that are preferably controlled by an electronic control unit (ECU)  20 , the operation of which will be further described below. A pump  19  may be provided to provide additional control over the amount and direction of the flow of fluid through comfort control loop  14 . 
         [0022]    Drivetrain temperature control loop  16  exchanges heat energy with one or more drivetrain components  22  and with a heat exchanger  24 . In an electrically powered vehicle, drivetrain components  22  may comprise one or more components such as a high-voltage battery, electric motors, generators, and power electronics (such as DC/DC or AC/DC converters). Under most vehicle operating conditions, such drivetrain components will generate excess heat when operating, so that the heat exchange fluid circulating in drivetrain temperature control loop  16  carries heat away from the components. Heat exchanger  24  may comprise one or more of a conventional liquid-to-liquid or liquid-to-air exchanger, a heat pump using a fluid refrigerant cycle, or a thermoelectric (Peltier) heat pump. In any event, the objective of drivetrain temperature control loop  16  and heat exchanger  24  is to heat or cool drivetrain component  22  as is necessary to maintain a desired operating temperature range. 
         [0023]    ECU  20  may receive signals or inputs from a variety of sensors and controls. Examples of such sensors include: cabin temperature sensor(s)  26 ; exterior temperature sensor(s)  28 ; and sensor(s)  32  monitoring conditions of drivetrain components  22 , heat exchanger  24 , or drivetrain temperature control loop  16 . Inputs may be made by a vehicle occupant using a climate control panel  30 . Such inputs may include desired temperature, fan speed, direction of air flow, or simply “heat” or “cool.” ECU  20  controls the condition of valve(s)  18  and/or pump  19  to regulate the direction and/or flow rate of heat exchange fluid to TEHPs  10 . ECU  20  preferably also controls the electric voltage/current/polarity applied to the Peltier elements within TEHPs  10 . By monitoring and/or controlling the basic parameters of the temperature and volume flow rate of the heat exchange fluid traveling through comfort control loop  14  and the voltage and polarity of the current applied to the Peltier devices and TEHPs  10 , ECU  20  controls the amount or level of heating and/or cooling supplied to vehicle interior and any occupants. 
         [0024]    Heat transfer from/to TEHPs  10  may be enhanced by one or more fans or other air movement devices (not shown) integrated with or located adjacent to the TEHPs to circulate air over the occupant/cabin side of the Peltier device. ECU  20  may also control the on/off condition and/or the speed of the fans. 
         [0025]    ECU  20  may also control other vehicle comfort control systems, such as an HVAC system  36 , and may have one or more automatic climate control operating modes. HVAC system  36  comprises apparatus for circulating heated, cooled, or otherwise conditioned air through the vehicle interior, such as a conventional air conditioning system and/or vehicle heater. Alternatively ECU  20  may be connected with a separate control device (not shown) for HVAC system  36  so that the two systems may operate in a coordinated manner. 
         [0026]    As shown schematically in  FIG. 2A , a possible embodiment of a TEHP  10  includes Peltier elements  50  arranged on opposite sides of a multi-tube conduit  52 . Conduit  52  is part of comfort control loop  14  and conducts heat exchange fluid in a direction into/out of the page. Fins  54  extend outwardly from Peltier elements  50  in both directions (up and down, as viewed in  FIG. 2A ), and the entire structure is contained in an air flow housing  56 . A fan  48  (or other air movement device) is positioned to force air (usually ambient air from the passenger cabin or other interior compartment of the vehicle) through air flow housing  56  and over fins  54 . The air flow exits TEHP  10  and passes into the portion of the vehicle interior that is being warmed or cooled by the system. 
         [0027]      FIG. 2B  shows, again in schematic form, an example of a Peltier element  50 . Each Peltier element comprises a p-type element  50   a  and an n-type element  50   b  electrically connected with one another and with a DC voltage source as shown. When the indicated polarity is applied, the side of element  50  in contact with conduit  52  (see  FIG. 2A ) becomes the hot side and the opposite side, in contact with fin  54 , becomes the cold side. 
         [0028]    On a warm day, when vehicle occupants are most likely to be using TEHPs  10  in a cooling mode, heat energy from the hot side of the Peltier elements passes to the heat exchange fluid in the comfort control loop  14  as it circulates through the TEHPs. Thus, the fluid carries heat out of the passenger compartment and travels to/through heat exchanger  24  along with the rest of the heat exchange fluid circulating through the drivetrain temperature control loop  16 . Also on such a warm day, drivetrain components  22  will usually generate excess heat that must be removed by the drivetrain loop  16  in order to maintain the drive train components within the desired operating temperature range. So heat exchanger  24  will be operating in a mode to cool the fluid circulating in drivetrain loop  16 . If heat exchanger  24  is a heat pump (refrigerant cycle or Peltier), it will be operated in a cooling mode, which is compatible with the need to cool the fluid reaching the heat exchanger from the comfort control loop  14 . 
         [0029]    Under colder ambient conditions, vehicle occupants are likely to be using TEHPs  10  in a heating mode, in which heat exchange fluid circulating though comfort control loop  14  passes over the cold side of the TEHPs. The fluid therefore exits TEHPs  10  cooler than when it entered and must gain heat energy before returning to the TEHPs. Under all but very cold ambient conditions, this need for heat energy will be met by the excess heat generated by drivetrain components  22 . Under very cold conditions, drivetrain components  22  may need to be warmed by the drivetrain temperature control loop  16  in order to stay within the desired operating temperature range. In this case, heat exchanger  24  will operate in a mode to warm the fluid circulating in drivetrain loop  16 , and the branching comfort control loop  14 . 
         [0030]    The direction in which the fluid flows through comfort control loop  14  may be controlled (using a bi-directional pump  19  or any other appropriate means) as necessary to divert working fluid from powertrain loop  16  at the location best suited for operation of the system. The flow direction may depend on many factors, such as ambient temperature, fluid temperatures, drivetrain component temperatures, commanded function of the TEHP, etc. 
         [0031]      FIG. 3  shows a second embodiment of a thermoelectric heat pump comfort control system in which heat is exchanged between the comfort control loop  114  and the drivetrain temperature control loop in a manner different from the embodiment of  FIG. 1 . In this second embodiment, drivetrain components  122  are oil-cooled components such as, for example, a mechanical transmission or an electric machine (generator, motor, or integrated motor/generator). The cooling oil is circulated through a primary drivetrain loop  116   a  to an oil-to-coolant heat exchanger  124   a  by a pump  23 . 
         [0032]    A secondary drivetrain cooling loop  116   b  contains a second heat exchange fluid that circulates through oil-to-coolant heat exchanger  124   a  and a second fluid-to-air heat exchanger  124   b . Comfort control loop  114  also passes through the oil-to-coolant heat exchanger  124   a  under pressure provided by a pump  38  controlled by ECU  20 . The heat exchange fluid circulating in comfort control loop  114  remains physically separate from both the primary and secondary drivetrain control loops  116   a  and  116   b  and may exchange heat with either or both of the fluids (oil and/or coolant) carried in those loops, depending on the interior configuration of oil-to-coolant heat exchanger  124   a . In this second embodiment, as with the first embodiment of  FIG. 1 , the comfort control loop exchanges heat with the drivetrain temperature control loop in order to increase the amount of heat that it is possible to efficiently transfer into (or out of) the desired portion of the vehicle cabin using thermoelectric heat pumps. 
         [0033]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.