Patent Publication Number: US-2018029443-A1

Title: System for multi-zone vehicle heating

Description:
FIELD OF THE INVENTION 
     The present disclosure generally relates to vehicle heating systems, and more particularly, to vehicle heating systems for multi-zone heating control. 
     BACKGROUND OF THE INVENTION 
     Conventional vehicles use waste heat from a combustion engine as the sole source of heating for the passenger compartment. However, Battery Electric Vehicles (HEV) may have intermittent access to waste heat such that they may require additional heat sources. Plug-in Hybrid Electric Vehicles (PHEV) may further compound this issue by running with the combustion engine off for significant periods of time. The disclosure provides for systems and methods to heat the passenger compartment without relying solely on engine waste heat. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present disclosure, a vehicle heating system is disclosed. The heating system comprises an engine configured to heat a coolant and an electric heater configured to heat the coolant. A coolant supply valve is configured to selectively direct the coolant to the engine and a plurality of heat exchangers are configured to receive the coolant. The system further comprises at least one heat exchanger control valve configured to selectively allow the coolant to flow to one of the heat exchangers. 
     According to another aspect of the present disclosure, a hybrid vehicle heating system is disclosed. The system comprises an engine configured to heat a coolant and an electric heater configured to heat the coolant. A coolant supply valve is configured to selectively circulate the coolant through the engine in response to a temperature of the coolant in the engine. The system further comprises a plurality of heater cores configured to receive the coolant and at least one heater control valve configured to direct the coolant to one of the heat cores. 
     According to yet another aspect of the present disclosure, a vehicle heating system is disclosed. The system comprises an engine configured to heat a coolant and an electric heater configured to heat the coolant. The system further comprises a plurality of heat exchangers are configured to receive the coolant and a controller in communication with the electric heater and the engine. The controller is configured to control a coolant supply valve configured to selectively direct the coolant to the engine and control at least one heat exchanger control valve to selectively allow the coolant to flow to one of the heat exchangers. 
     These and other aspects, objects, and features of the present disclosure will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic representation of a hybrid vehicle; 
         FIG. 2  is a schematic view of a vehicle heating system for multi-zone heating; 
         FIG. 3  is a schematic view of a vehicle heating system for multi-zone heating demonstrating a plurality of heating loops; 
         FIG. 4A  is a process diagram demonstrating a method for controlling a heating process for a vehicle; 
         FIG. 4B  is a flow chart demonstrating a subroutine for the heating process of  FIG. 4A  for controlling a Heater Core Isolation Valve (HCIV); 
         FIG. 4C  is a flow chart demonstrating a subroutine for the heating process of  FIG. 4A  for controlling an engine temperature subroutine; and 
         FIG. 5  is a process diagram demonstrating a method for controlling an electric heating process for a vehicle in accordance with the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As required, detailed embodiments of the present disclosure are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to a detailed design and some schematics may be exaggerated or minimized to show function overview. 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 disclosure. 
     As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. 
     The following disclosure describes a heating system that may be utilized in a hybrid vehicle. The heating system may provide for improved passenger comfort while maintaining a high level of operating efficiency for the vehicle. In some embodiments, the system may provide for a multi-zone heating system that may selectively generate heat from an electric heater or utilize waste heat from a combustion engine to heat a passenger compartment. An exemplary application of the system may be in the form of full size passenger vehicles (e.g. sport utility vehicles (SUVs, vans, full size cars, etc) that may be equipped with hybrid drive systems. 
       FIG. 1  illustrates a hybrid electric vehicle (HEV)  10  powertrain configuration and control system. A power split hybrid electric vehicle  10  may be a parallel hybrid electric vehicle. The HEV configuration as shown is for purposes of example only and is not intended to be limiting as the present disclosure applies to HEVs, PHEVs, or other vehicle types of any suitable architecture. As demonstrated in  FIG. 1 , the powertrain configuration may comprise two power sources  12 ,  14  that are connected to the driveline. The power sources may include a combination combustion engine generator subsystem and an electric drive system. The engine and generator may comprise a planetary gear set connecting the generator to the engine. The electric drive system may comprise an electric motor subsystem, a generator subsystem, and a battery subsystem. The battery subsystem may correspond to an energy storage system for the generator and the motor. 
     The speed of the charging of the generator  18  may vary based on the engine output power split between an electrical path and a mechanical path. In a vehicle  10  with a power split powertrain system, the engine  16  may require either the generator torque resulting from engine speed control or the generator brake torque to transmit its output power through both the electrical and mechanical paths (split modes) or through the all-mechanical path (parallel mode) to the drivetrain for forward motion. During operation using the second power source  14 , the electric motor  20  may draw power from the battery  26  and provide propulsion independently of the engine  16  for forward and reverse motions. This operating mode may be called “electric drive,” electric-only mode, or EV mode. 
     The operation of the power split powertrain system, unlike conventional powertrain systems, may integrate the two power sources  12 ,  14  to work together seamlessly to meet the driver&#39;s demand without exceeding the system&#39;s limits (such as battery limits). Additionally, the demand may be met while optimizing the total powertrain system efficiency and performance. In order to function in this way, coordination control between the two power sources  12 ,  14  is needed. As shown in  FIG. 1 , there is a hierarchical vehicle system controller (VSC)  28  that may perform the coordination control for the power split powertrain system. Under normal powertrain conditions (no subsystems/components faulted), the VSC  28  may interpret the driver&#39;s demands (e.g. PRND and acceleration or deceleration demand). Based on the driver&#39;s demands and powertrain limits, the VSC  28  may then determine a wheel torque command. The VSC  28  may also determine the torque each power source needs to provide in order to meet the driver&#39;s torque demand and to achieve an operating point (torque and speed) of the engine. 
     In some embodiments, the battery  26  may be implemented in a rechargeable configuration (shown in phantom). The rechargeable configuration may utilize a receptacle  32  which may be connected to a power grid or other outside electrical power source. In this way, the battery  26  may be charged by the outside electrical power source via a battery charger/converter  30 . 
     As described herein, the vehicle  10  may be operated in an electric mode (EV mode). In the EV mode, the battery  26  may provide all of the power to the electric motor  20  to operate the vehicle  10 . In addition to the benefit of saving fuel, operation in EV mode may enhance the ride comfort through lower noise and better driveability. For example, some driveability characteristics may include smoother electric operation, lower noise, vibration, and harshness (NVH), and faster response. Operation in EV mode may also provide environmental benefits by limiting emissions and improving fuel economy. 
     A Plug-in Hybrid Electric Vehicle (PHEV) may share characteristics of both an internal combustion engine and a battery electric vehicle. For example, a PHEV may have a driving range in which propulsion is provided only by an electric motor  20  powered from a battery pack  26 . Once the battery pack  26  charge has been depleted to a predetermined level, the engine  16  may be started. The engine  16  may provide power to propel the vehicle and to recharge the battery pack  26 . In electric only mode, the engine  16  may be inactive. Since the engine  16  is inactive, heat may not be generated and consequently, engine heat may not be utilized to heat the passenger compartment. A PHEV may start the engine  16  in response to a need for passenger heating. This, however, may interfere with the electric only operation and may impact fuel economy and emissions. 
     Referring now to  FIG. 2 , a heating system  34  for providing heat to a passenger compartment for a PHEV is shown. The system  34  may provide two sources to heat coolant for heating the vehicle  10 . For example, as discussed in reference to  FIG. 1 , the vehicle system controller (VSC)  28  may utilize heat from the engine  36  to heat the coolant as in a conventional ICE vehicle. Additionally, when the heat from the engine  36  is insufficient, the VSC  28  may provide heat via an electric heater  38 . The electric heater  38  may be similar to that utilized in a battery electric vehicle system and may correspond to a high voltage electric heater. Having multiple sources of heat may provide for flexibility during normal operating conditions and some redundancy during fault mode operation. 
     The system  34  may allow the coolant from either the engine  36  or the electric heater  38  to flow through at least one heater core  48 . The at least one heater core  48  may correspond to a heat exchanger configured to deliver heated air to a passenger compartment of the vehicle  10 . A Heater Core Isolation Valve (HCIV)  42  may provide for the VSC  28  to select the source of heated coolant to be the engine  36  or the electric heater  38 . Though discussed in reference to the VSC  28 , various controllers, circuits, and/or processors may communicate to control the various tasks described herein. Accordingly, the primary control described in reference to the various control methods and systems discussed herein is the VSC  28 . However, it may be understood that various control circuits may be in communication with the VSC  28  to provide for the various controls and functions discussed herein. 
     The VSC  28 , discussed in reference to  FIG. 1 , may determine the heating mode based on the passenger-heating request and the status of the various components in the heating system. Based on the passenger heating request, a desired coolant temperature of the heater core  40  is generated by or provided to the VSC  28  ( FIG. 1 ). In operation, the goal of the heating system  34  may be to maintain the temperature of the heater core  40  at the desired temperature in the most fuel efficient manner possible. In this way, the system  34  may optimize operation such that efficiency is maintained without sacrificing the comfort of the passengers of the vehicle  10 . 
     The electric heater  38  may be a positive temperature coefficient (PTC) type heater. PTC heating elements may be constructed with small ceramic stones that have self-limiting temperature properties. These properties may include a fast heating response time and the ability to automatically vary wattage to maintain a pre-defined temperature. As such, PTC heaters may be a selected for providing controlled electrical heat to a vehicle cabin. Though a PTC heater is discussed specifically in reference to the electric heater  38 , various types of heaters may be incorporated into the system  34  without departing from the spirit of the disclosure. 
     The system  34  may further comprise at least one auxiliary water pump  43 . The at least one auxiliary water pump  43  may be configured to force coolant to flow through the heating system  34 , which may comprise a plurality of coolant paths or heating loops  44 . The heating loops may correspond to a plurality of climate zones  46 , which may provide for independent climate control for various regions of the vehicle. Additionally, one or more temperature sensors  46  may be in connection with the heating loops to identify a coolant temperature at one or more stages of the heating loops. In general, during operation the coolant flows through at least one heater core  48  that allows heat to be transferred from the coolant to air entering the passenger compartment. The heat may be transferred from the coolant and may flow into the at least one heater core  48  using a blower  50  to pass air over the heater core  48  and into the passenger compartment. 
     The system  34  may further comprise a water pump  52  configured to force fluid to flow through the engine  36 . The water pump  52  may be electrically or mechanically driven. In certain modes, the water pump  52  may force fluid through the heating system  34  components as well. The system  34  may further comprise a radiator  54  configured to dissipate heat in the coolant. A flow path of the coolant may be controlled by the heating system  34  in response to an input from a thermostat  56 . In this way, the heating system may control the flow of coolant between the radiator  54  and the engine  36  based on a temperature of the coolant identified by the thermostat  56 . 
     In some embodiments, the system  34  may comprise a degas bottle  58  which may act as a coolant reservoir. Additionally, the degas bottle  58  may remove air from the coolant, and provide pressure relief. The cooling system may further include an exhaust gas recirculation (EGR) system  60  that recirculates a portion of the engine&#39;s exhaust gas back to the engine cylinders. Though specific components are discussed in reference to the heating system  34  for the vehicle  10 , various components may be utilized to facilitate various functions of the heating system  34  as discussed herein. Accordingly, the system  34  may be tailored to suit various applications without departing from the spirit of the disclosure. 
     During operation, the VSC  28  may control the flow and temperature of the coolant based on a desired climate. The desired climate may be input by a passenger of the vehicle  10  via a user interface. In an exemplary embodiment, the user interface may be configured to receive the desired temperature for a plurality of climate zones  46  in the vehicle  10 . For example, the climate zones  46  may correspond to a fore portion and an aft portion of the passenger compartment. The fore portion may correspond to a front seat region while the aft portion may correspond to a rear seat region. Accordingly, each of the climate zones  46  may correspond to front climate region and one or more additional climate regions of the vehicle. In some embodiments, the climate zones  46  may correspond to a driver-side and passenger side, a storage region and passenger compartment, etc. 
     Each of the climate zones  46  may be configured to receive heat from the one or more heating loops  44 . For example, the VSC  28  may control the flow of the coolant to each of a first heating loop  44   a  and a second heating loop  44   b.  In this configuration, the VSC  28  may control the climate of each of a first zone  46   a  and a second zone  46   b  by controlling the flow of the coolant to each of the heating loops  44 . In addition to controlling the flow of the coolant to each of the heating zones  46 , the VSC  28  may further control the HCIV  42  to control the source of heated coolant from the engine  36  and/or the electric heater  38 . 
     As discussed in reference to  FIG. 1 , during different periods of operation of the vehicle  10 , the VSC  28  may identify whether the engine coolant is sufficiently warm to supply heated coolant to one or more of the first heater core  48   a  and a second heater core  48   b.  The VSC  28  may identify an engine coolant temperature (ECT) via an ECT sensor  64  configured to monitor the ECT in an engine coolant loop  70  for the engine  36 . The engine coolant loop  70  is demonstrated in  FIG. 3  and corresponds to a coolant circulation path of the coolant formed when the HCIV  42  is closed. Accordingly, the VSC  28  may be configured to control the HCIV  42  to isolate an electric heating loop  72  from the engine coolant loop  70 . In this way, the system  34  may selectively supply heated coolant to the heater cores  48  from the electric heater  38  independent of the engine  36  and the corresponding engine coolant. 
     The engine coolant loop  70  may pass through the engine  36  via an inlet  76  and be released via an outlet  78 . The outlet  78  may be in fluid communication with a Bypass and the radiator  54 . In this configuration, the thermostat  56  may control whether the coolant flows through the radiator  54  to disburse heat or bypasses the radiator  54  to maintain/build heat. The thermostat  56  is in fluid communication with the water pump  52 , which may return the coolant to the inlet  76 . In this configuration, the water pump  52  may also supply the coolant to one or more of the heat cores in response to the engine temperature being greater than a temperature of the coolant output from the heater cores  48 . 
     The electric heat loop  72  may be selectively isolated from the engine coolant loop  70  via the HCIV  42 . In the closed configuration, the coolant may pass from the HCIV  42  to the electric heater  38 . From the electric heater  38 , the coolant may pass through at least one electric loop temperature gauge  80 . The at least one electric loop temperature gauge  80  may correspond to a first electric loop temperature gauge  80   a  that may be positioned upstream of the heater cores  48 . The coolant may be drawn from the electric heater  38  through at least one auxiliary pump  82  and at least one zone control valve  84  to selectively supply heated coolant to the first heater core  48   a  and/or the second heater core  48   b.  Accordingly, the zone control valves  84  may correspond to heat exchanger coolant supply valves for the heater cores  48 . Following the heater cores  48 , the coolant may pass through a second electric loop temperature gauge  80   b  and return to the HCIV  42 . In this configuration, the VSC may control the auxiliary pumps  82  and the zone control valves  84  to supply heated coolant to each of the heat cores  48  to independently heat the zones  46 . 
     The VSC  28  may control the electric heater  38  to heat the coolant in response to a mode of operation of the system  34 . The various modes of operation are discussed further in reference to  FIG. 3 . The VSC  28  may activate the electric heater in response to a temperature of the coolant. The temperature of the coolant during electric only operation of the vehicle  10  may be measured and communicated to the VSC  28  as it passes through at least one of the first electric loop temperature gauge  80   a  and/or the second electric loop temperature gauge  80   b.  Such a coolant temperature may be referred to as a heater coolant temperature (HCT), which is further discussed in reference to  FIG. 4 . In this configuration, the VSC  28  may control the system  34  to supply heat to each of the zones  46  during periods of electric only operation. 
     Referring now to  FIGS. 2 and 3 , the VSC  28  may control the HCIV  42  to selectively combine the engine coolant loop  70  with the electric heat loop  72  to supply heated coolant to the heater cores  48  via a combined coolant loop  90 . The combined coolant loop  90  may typically be activated by the VSC  28  when the engine coolant temperature is sufficient to satisfy a demand for heat from the first heater core  48   a  and the second heater core  48   b.  The VSC  28  may identify the coolant temperature via the ECT sensor  64  and compare it to a heater core output requirement to identify whether to activate the electric heat loop  72  or the combined heat loop  90 . Accordingly, the VSC  28  may selectively utilize heat generated by the engine  36  or utilize heat generated by the electric heater  38  to heat the heater cores  48 . 
     Additionally, the VSC  28  may selectively control the flow of the coolant to each of the heater cores  48  based on a heating demand of an occupant of the vehicle  10 . For example, the VSC  28  may be in communication with one or more heating zone valves  84  and configured to control the heating zone valves  84  to selectively supply the coolant to the first heater core  48   a  and/or the second heater core  48   b.  The VSC  28  may control the first heat zone valve  84   a  to activate heated coolant to be supplied to the first heater core  48   a  via a first heating zone loop  44   a.  Accordingly, the VSC  28  may be operable to selectively activate the first heating zone  46   a  in response to a passenger request via the user interface. When the first heat zone valve  84   a  is active, the VSC  28  may further control a first blower  50   a  such that heated air is delivered to the first zone  46   a  in the passenger compartment of the vehicle  10 . In this way, the VSC  28  may supply coolant heated by either the engine  36  and/or the electric heater  38  to the first heater core  48   a  to heat the first zone  46   a.    
     The VSC  28  may further be configured to control the second heat zone valve  84   b  to activate heated coolant to be supplied to the second heater core  48   b  via a second heating zone loop  44   b.  The VSC  28  may be operable to selectively activate the second heating zone  46   b  in response to a passenger request via the user interface. When the second heat zone valve  84   b  is active, the VSC  28  may further control a second blower  50   b  such that heated air is delivered to the second zone  46   b  in the passenger compartment of the vehicle  10 . In this way, the VSC  28  may supply coolant heated by either the engine  36  and/or the electric heater  38  to the second heater core  48   b  to heat the second zone  46   b.    
     The electric heat loops  72  and the combined heat loops  90  of the system  34  may correspond to coolant flow paths that deliver the coolant to one of the heater cores  48 . A first combined heat loop  90   a  may be formed by the following path: coolant flowing from the engine  36  to the HCIV  42 , from the HCIV  42  into the first heater core  48   a  via a first auxiliary pump  82   a  and the first heat zone valve  84   a,  and from the first heater core  48   a  back to the engine  36  via the thermostat  56 . A second combined heat loop  90   b  may be formed by the following path: coolant flowing from the engine  36  to the HCIV  42 , from the HCIV  42  into the second heater core  48   b  via a second auxiliary pump  82   b  and the second heat zone valve  84   b,  and from the second heater core  48   b  back to the engine  36  via the thermostat  56 . Accordingly, the heating system  34  may comprise a plurality of combined heating loops  90  that may be selectively activated by the VSC  28  when the engine  36  is operating. 
     Additionally, when the engine  36  is not operating, the VSC  28  may heat the zones  46  of the passenger compartment with the electrical heat loops  72 . A first electric heat loop  72   a  may be formed by the following path: coolant drawn from the HCIV  42  through the first heat zone valve  84   a  in the open position via the first auxiliary pump  82   a,  into the first heater core  48   a  from the first heat zone valve  84   a,  and back to the HCIV  42  from the first heater core  48   a.  A second electric heat loop  72   b  may be formed by the following path: coolant drawn from the HCIV  42  through the second heat zone valve  84   b  in the open position via the second auxiliary pump  82   b,  into the second heater core  48   b  from the second heat zone valve  84   b,  and back to the HCIV  42  from the second heater core  48   b.  Accordingly, the heat system  34  may provide for a plurality of combined heat loops  90  for operation when the engine is discharging heat and a plurality of electric heat loops  72  for operation when the engine  36  is not discharging sufficient heat to heat the coolant. 
     In some embodiments, the system  34  may comprise additional controllers that may be configured to control one or more of the processes described herein. For example, in some embodiments, the electric heater  38  may correspond to a high voltage heater. The electric heater  38  may be controlled by a heat controller  92 , which may be in communication with a user interface  94 . In this configuration, the heat controller  92  may be in communication with the VSC  28  and configured to control and communicate a heating instruction received from a passenger of the vehicle  10  via the user interface  94 . 
     The system  34  may further comprise at least one ambient air temperature gauge  96 . The ambient air temperature gauge may be in communication with at least one of the controller  92  and the VSC  28 . The ambient air temperature gauge  96  may be configured to identify an air temperature of air passing over the heater cores  48  via the blowers  50 . In some applications, the system  34  may comprise a first ambient air temperature gauge  96   a  configured to measure the air temperature of air entering the first blower  50   a  and a second ambient air temperature gauge  96   b  configured to measure the air temperature of air entering the second blower  50   b.  Accordingly, the system may be operable to determine the temperature of ambient air supplied to the heater cores  48  to estimate a heat load or heat demand of the coolant. 
     Referring now to  FIGS. 4A, 4B, and 4C , various diagrams demonstrating an exemplary operating method  100  for the system  34  are shown. Beginning in reference to  FIG. 4A , the climate control or heating of the vehicle  10  may be initialized in response to a vehicle startup sequence or the receipt of a climate adjustment to a user interface of the vehicle  10  ( 102 ). In response to the initializing of the climate control, the VSC  28  may select the zone(s)  46  for climate control of the vehicle  10 . The VSC  28  may select the zone(s)  46  in response to a heat setting, which may be selected by a passenger of the vehicle  10  via the user interface ( 104 ). Based on the heat setting requested, the VSC  28  may continue to control each of the blowers  50  and the valves  84  to selectively output the heat to the zones  46  of the vehicle  10 . 
     In response to a request for heat to the first zone  46   a,  the VSC  28  may control the heating system  34  as follows: activate the first blower  50   a  to a level commensurate to the requested heat, deactivate or maintain an idle state of the second blower  50   b,  open the first heat zone valve  84   a,  and close the second heat zone valve  84   b  ( 106 ). In response to a request for heat to the second zone  46   b,  the VSC  28  may control the heating system  34  as follows: activate the second blower  50   b  to a level commensurate to the requested heat, deactivate or maintain an idle state of the first blower  50   a,  close the first heat zone valve  84   a,  and open the second heat zone valve  84   b  ( 108 ). In response to a request for heat to the first zone  46   a  and the second zone  46   b,  the VSC  28  may control the heating system  34  as follows: activate the first blower  50   a  to a level commensurate to the requested heat, activate the second blower  50   b  to a level commensurate to the requested heat, open the first heat zone valve  84   a,  and open the second heat zone valve  84   b  ( 110 ). 
     As discussed in reference to  FIGS. 2 and 3 , the VSC  28  of the system  34  may also control the HCIV  42  and the engine  36  to ensure that the temperature of the coolant supply for the heater core(s)  48  if sufficient to provide heated coolant to suit the operating demand. Accordingly, the VSC  28  may determine the HCIV control position by activating a Control Position Subroutine for the HCIV  42  ( 112 ). The HCIV control subroutine is discussed further in reference to FIG.  4 B. Additionally, the system  34  may selectively activate the engine  36  to supply heated coolant to the heater cores  48 . An engine control subroutine may be activated by the VSC  28  to determine an engine on/off condition ( 114 ). The engine control subroutine is further discussed in reference to  FIG. 4C . 
     Referring now to  FIG. 4B , the HCIV control subroutine  120  may be initialized by the VSC  28  in response to a heating request to supply heat to one or more of the climate zones  46  of the vehicle  10 . The HCIV control subroutine  120  may be configured to identify whether the engine coolant temperature measured by the ECT sensor  64  is sufficient to heat the coolant to supply heat to the heater cores  48 . As discussed previously, during some periods of operation, the engine  36  may be idle. Accordingly, the HCIV  42  may isolate the electric heat loops  72  to prevent cooling of the coolant by the engine  36 . 
     Once initialized, the VSC  28  may apply the HCIV control subroutine  120  to identify a total blower demand (TB) of the system  34 . The total blower demand (TB) may be calculated as a total blower cooling rate of the first blower  50   a  and the second blower  50   b  ( 122 ). The blower flow rate of each of the blowers  50  may be approximated as a scalar value corresponding to a blower setting of the blowers  50  and summed. For example, the scalar value may correspond to a control value for each of the blowers  50  that may range from 0 to 10 or low to high with some intermediate level of precision ranging therebetween. Such a blower setting may be set by the system  34  based on a temperature differential between an ambient temperature AT of each climate zone  46  compared to a user temperature setting for each of the respective climate zones. 
     The control subroutine may continue to determine the ambient temperature of the passenger compartment or each of the zones  46  of the vehicle  10 . The ambient temperature AT may be identified by the VSC  28  in step  124  based a temperature signal from at least one temperature gauge  96  in the passenger compartment of the vehicle  10 . Accordingly, the VSC  28  may be operable to determine the total blower demand TB and the ambient temperature AT to infer or calculate a coolant output temperature (HC Out ) of the coolant output from the heater cores  48  in step  126 . 
     The coolant output temperature (HC Out ) may be determined as the difference between the heater coolant temperature (HCT) and the heat demand of the heater cores  48  of each of the climate zones  46 . The heater coolant temperature (HCT) may be identified by the VSC  28  as a temperature signal from the first electric loop temperature gauge  80   a.  Equation 1 demonstrates the equation for the coolant output temperature (HC Out ) as the difference between the heater coolant temperature (HCT) and the heat demand of the climate zones. 
         HC   Out =HCT−funct( AT, TB )   (eq. 1)
 
     Accordingly, based on equation 1, the VSC  28  may calculate the coolant output temperature (HC Out ) as the difference between the heater coolant temperature (HCT) and a function of the ambient temperature and the total blower demand TB. Based on the coolant output temperature (HC Out ), the system  34  may control an instruction of the HCIV  42 . 
     In some embodiments, the VSC  28  may comprise the second electric loop temperature gauge  80   b.  In such systems, the VSC  28  may measure the coolant output temperature (HC Out ) from a second coolant temperature of the second electric loop temperature gauge  80   b.  As previously discussed in reference to  FIGS. 2 and 3 , the heater coolant temperature HCT may be measured and communicated to the VSC  28  as it passes through the first electric loop temperature gauge  80   a  and/or the second electric loop temperature gauge  80   b.  Accordingly, the HCIV control subroutine may provide for a flexible control solution for various vehicles. 
     With the coolant output temperature (HC Out ) calculated, the VSC  28  may compare the coolant output temperature (HC Out ) with the engine coolant temperature ECT ( 128 ). As discussed in reference to  FIGS. 2 and 3 , the engine coolant temperature ECT may be communicated to the VSC  28  from the ECT sensor  64 . If the engine coolant temperature ECT is greater than the coolant output temperature (HC Out ), the VSC  28  may control the HCIV  42  to activate the heating loops  44  to supply heated coolant to the heater cores  48  ( 130 ). If the engine coolant temperature ECT is not greater than the coolant output temperature (HC Out ), the VSC  28  may control the HCIV  42  to activate the electric only heat loops  72  such that the electric heater  38  supplies heat to the heater cores  48  ( 132 ). Accordingly, the system  34  may provide for efficient operation by utilizing the heat of the engine  36  to supplement or supply heat for the system  34  when the engine coolant temperature is sufficient. 
     Referring now to  FIG. 4C , the VSC  28  may be configured to activate the engine climate control subroutine  140  depending on a heat demand of the system  34 . Depending on a heating demand HD of the heat cores  48  of the system  34 , the VSC  28  may activate the engine  36  to supplement a heat supplied by the electric heater  38 . In some embodiments, heat generated by the engine  36  may be necessary to heat the vehicle  10  if the heating demand (HD) of the heater cores  48  exceeds maximum electric heat supply threshold (EMax). 
     In step  142 , the method may determine the total blower demand (TB) of the system  34 . The total blower demand (TB) may be calculated as a total blower cooling rate of the first blower  50   a  and the second blower  50   b  ( 122 ). As discussed in reference to  FIG. 4B , the blower flow rate of each of the blowers  50  may be approximated as a scalar value corresponding to a blower setting of the blowers  50  and summed. The engine climate control subroutine  140  may continue to determine the ambient temperature of the passenger compartment or each of the zones  46  of the vehicle  10  ( 144 ). The ambient temperature (AT) may be identified by the VSC  28  in step  144  based a temperature signal from at least one temperature gauge  96  in the passenger compartment of the vehicle  10 . Accordingly, the VSC  28  may be operable to determine the total blower demand TB and the ambient temperature AT to estimate the heating demand (HD) of the system  34 . 
     The heating demand (HD) is calculated as a function of the ambient temperature AT and the total blower demand (TB) ( 146 ). The heating demand (HD) may be similar to the heat demand of the heater cores  48  of each of the climate zones  46  applied in step  126 . The functions may differ in steps  126  and  146  in that each function may be weighted differently or include a different constant to adjust operating behavior of the corresponding control schemes. Accordingly, based on the heating demand, the system  34  may selectively activate the engine  36  to assist the electric heater  38  in supplying heat to meet the heating demand (HD). 
     To determine if operation of the engine  36  is required to supply heat to meet the heating demand (HD), the subroutine  140  may compare the heating demand (HD) to the maximum electric heat supply threshold (EMax) ( 148 ). If HD is less than EMax, the engine  36  may be deactivated because the electric heater  38  has sufficient power to provide for the heating demand (HD) ( 150 .) If HD is not less than EMax, the subroutine  140  may continue to step  152  to compare the heater coolant temperature (HCT) to a heater coolant temperature target (HCT Target). If HCT is greater than the HCT Target, the engine  36  may be deactivated because there is not yet a need for heat from the engine  36  to heat the coolant. If HCT is not greater than the HCT Target, the engine  36  may be activated by the system  34  to supply heat to the coolant to satisfy the heating demand (HD) ( 154 ). 
     As discussed in reference to  FIG. 4 , exemplary embodiments of the system  34  were discussed in reference to the operation of the HCIV  42  and the engine  36  to supply heat to the heater cores  48 . Referring now to  FIG. 5 , a control routine  170  for the electric heater  38  is discussed demonstrating a method for controlling the temperature of the plurality of climate zones  46  with the electric heater  38 . The heat controller  92  discussed in reference to  FIG. 3  may be configured to control the electric heater  38  and may further be communication with the VSC  28  to integrate the control of the various systems and methods described herein. 
     Once initialized, the control routine  170  may determine if heat is requested for the vehicle  10  ( 172 ). If heat is not request, the heat controller  92  may remain at step  172  until heat is requested. If heat is requested, the VSC  28  and the heat controller  92  may determine if the heat is requested in first zone  46   a  ( 174 ). In response to a request for heat to the first zone  46   a,  the heat controller  92  may control the heating system  34  as follows: activate the first blower  50   a  to a level commensurate to the requested heat, deactivate or maintain an idle state of the second blower  50   b,  open the first heat zone valve  84   a,  and close the second heat zone valve  84   b  ( 176 ). If heat is not requested in only the first zone  46   a,  the control routine  170  may determine if heat is requested in second zone  46   b  ( 178 ). 
     In response to a request for heat to the second zone  46   b,  the VSC  28  and the heat controller  92  may control the heating system  34  as follows: activate the second blower  50   b  to a level commensurate to the requested heat, deactivate or maintain an idle state of the first blower  50   a,  close the first heat zone valve  84   a,  and open the second heat zone valve  84   b  ( 180 ). If heat is not only requested in only one of the first zone  46   a  or the second zone  46   b,  the routine  170  may continue to heat the first zone  46   a  and the second zone  46   b.  In response to a request for heat to the first zone  46   a  and the second zone  46   b,  the VSC  28  and the heat controller  92  may control the heating system  34  as follows: activate the first blower  50   a  to a level commensurate to the requested heat, activate the second blower  50   b  to a level commensurate to the requested heat, open the first heat zone valve  84   a,  and open the second heat zone valve  84   b  ( 182 ). 
     After identifying the zones  46  that are operating, the control routine  170  may determine the total blower demand (TB) for the system  34 . The total blower demand (TB) may be calculated as a total blower cooling rate of the first blower  50   a  and the second blower  50   b  ( 184 ). As discussed in reference to  FIG. 4B , the blower flow rate of each of the blowers  50  may be approximated as a scalar value corresponding to a blower setting of the blowers  50  and summed. The engine climate control subroutine  140  may continue to determine the ambient temperature of the passenger compartment or each of the zones  46  of the vehicle  10 . The ambient temperature (AT) may be identified by the heater controller  92  in step  144  based a temperature signal from at least one temperature gauge  96  in the passenger compartment of the vehicle  10 . 
     Based on the total blower demand (TB) and the ambient temperature (AT), the heat controller  92  may determine the coolant output temperature (HC Out ). The coolant output temperature (HC Out ) may be determined as the difference between the heater coolant temperature (HCT) and the heat demand of the heater cores  48  of each of the climate zones  46 . The heater coolant temperature (HCT) may be identified by the heat controller  92  and/or the VSC  28  as a temperature signal from the first electric loop temperature gauge  80   a.  Accordingly, based on equation 1, the VSC  28  may calculate the coolant output temperature (HC Out ) as the difference between the heater coolant temperature (HCT) and a function of the ambient temperature and the total blower demand TB. 
     The routine  170  may further identify a control error in the heater coolant temperature (HCT) ( 188 ). The control error may be calculated as the difference between a coolant temperature target (HCT Target) and the heater coolant temperature (HCT). In this way, the routine  170  may compare the response of the heater coolant temperature (HCT) to various settings and inputs into the electric heater  38 . Based on the calculation of coolant output temperature (HC Out ) and the control error, the VSC  28  and the heat controller  92  may control an input to the electric heater  38  to ensure that the heater operates to accurately heat the passenger compartment of the vehicle  10  ( 190 ). 
     Additionally, the control routine for the electric heater  38  may identify an operating mode of the vehicle  10  (e.g. electric-only mode, combustion hybrid mode, etc.) to control the electric heater  38 . For example, if the battery  26  is diminished, the VSC  28  may control the engine  36  to activate to assist in propulsion of the vehicle  10 . Under such circumstances, the engine coolant temperature (ECT) would likely heat to a level such that it may be utilized to heat the coolant as a result of the engine coolant temperature (ECT) being greater than the coolant output temperature (HC Out ). Accordingly, the various routines and methods (e.g.  120 ,  140 ,  170 , etc.) discussed herein may provide comprehensive operational instructions to controlling the system  34 . 
     The system  34  may also incorporate a Cold Engine Lock Out (CELO) feature. A CELO feature may inhibit operation of the blowers  50  until the coolant has reached a certain threshold. The system  34  may request that the engine  36  be turned on to assist in heating the coolant. Once the coolant has achieved a certain threshold, the fan speed of the blower  50  may be increased to allow heated air to flow into the passenger compartment. 
     For the purposes of describing and defining the present teachings, it is noted that the terms “substantially” and “approximately” are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The term “substantially” and “approximately” are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.