Energy consumption of a multiple zone heating, ventilating and air conditioning system for a vehicle and method

A vehicle includes a controller configured to determine when an HVAC system is providing at least one of heating, ventilating and air conditioning to a primary zone and to determine when a drivetrain is providing energy to a power source or the power source is providing surplus energy to the drivetrain, and in response, to activate a low cost energy mode wherein the HVAC system is operated to provide the at least one of heating, ventilating and air conditioning to at least one secondary zone.

FIELD OF THE INVENTION

The invention relates to Heating, Ventilating and Air Conditioning (HVAC) systems for vehicles and more specifically to improving the efficiency of a vehicle with a multiple zone HVAC system.

BACKGROUND AND SUMMARY

A multiple zone HVAC system may be included in a vehicle to provide heating, ventilating and air conditioning to at least one zone within or about a cabin or cargo hold of the vehicle. Heating, ventilating and air conditioning may include other processes, such as dehumidifying, i.e., maintaining a constant temperature while removing moisture, air filtering, or other processes for affecting a climate or environment of the vehicle.

The cost of energy to operate a multiple zone HVAC system may be defined as a parameter of vehicle efficiency. More specifically, for any given road trip, a vehicle may have a maximum attainable fuel efficiency which may be compromised by energy costs associated with operation of the multiple zone HVAC system. Exemplary embodiments may leverage the use of low cost energy, such as free energy or surplus energy, when available, to advantageously operate the HVAC system, and further, may also inhibit the consumption of energy by the HVAC system when the cost of such energy is high.

According to an embodiment of the invention, a vehicle includes a power source including a drivetrain arranged to receive energy from and provide energy to the power source, a heating, ventilating and air conditioning (HVAC) system arranged to receive energy from the power source, a plurality of zones arranged to controllably receive at least one of heating, ventilating and air conditioning from the HVAC system, the plurality of zones including a primary zone and at least one secondary zone and, a controller operable to determine when the HVAC system is providing at least one of heating, ventilating and air conditioning to the primary zone and to determine when the drivetrain is providing energy to the power source or the power source is providing surplus energy to the drivetrain, and in response, to activate a low cost energy mode wherein the HVAC system is operated to provide the at least one of heating, ventilating and air conditioning to the at least one secondary zone.

According to another embodiment, a method of operating a heating, ventilating and air conditioning (HVAC) system in a vehicle having a plurality of zones arranged to receive heating, ventilating and air conditioning from the HVAC system, including a primary zone and at least one secondary zone, the vehicle having a power source arranged to provide energy to the HVAC system and a drivetrain arranged to receive energy from and provide energy to the power source includes the steps of determining if the HVAC system is providing at least one of heating ventilating and air conditioning to the primary zone and determining at least one of the following conditions, the drivetrain is providing energy to the power source or the power source is providing surplus energy to the drivetrain and in response, activating a low cost energy mode wherein the HVAC system is operated to provide the at least one of heating, ventilating and air conditioning to the at least one secondary zone.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of a vehicle10according to the present invention is illustrated schematically inFIG. 1. Vehicle10includes a power source12arranged to provide motive energy26, such as mechanical or electrical energy, to a drive train14for, among other purposes, propelling vehicle10. Motive energy26may be produced by power source12through the consumption of a fuel such as a petroleum based fuel if power source12takes the form of an internal combustion engine, or as another example, as electricity if power source12takes the form of a battery. Vehicle10also includes a multiple zone HVAC system16arranged to receive accessory energy24from power source12, for example, HVAC system16may operate by mechanical or electrical accessory energy24received from power source12.

As shown inFIG. 1, the power source12may be arranged to receive free energy28from drivetrain14during certain periods of operation of vehicle10. Free energy28is considered to be “free” in the sense that it is not directly derived from the consumption of an onboard stored fuel such as the aforementioned petroleum based fuel or electricity. According to exemplary embodiments, free energy28may be derived from the kinetic energy associated with coasting or downhill movement of vehicle10. Alternatively, or in combination therewith, free energy may be derived from devices incorporated to the drivetrain which harvest energy from vehicle waste heat, or energy from solar or wind or other sources. As may be appreciated from the above discussion, the flow of free energy28to power source12from drivetrain14may occur in addition to or in place of the motive energy26delivered by power source12to drivetrain14.

As further shown inFIG. 1, vehicle10may, during certain periods of operation, provide surplus energy29from power source12to drivetrain14. For example, if power source12takes the form of an internal combustion engine, and if a load is applied to power source12in order to heat an exhaust after treatment system (not shown) of the engine, then the excess energy created as a consequence of the heating procedure may be considered to be surplus energy29. As another example, if power source12is being operated in a first brake specific fuel consumption (BSFC) mode, it may be determined that a second BSFC mode may be more efficient regardless of whether the second mode results in surplus energy29being delivered from power source12to drivetrain14. As yet another example, motive energy26provided to drivetrain14may be greater than the energy needed to accelerate or propel vehicle10at a rate called for by an operator. Such energy may be considered to be surplus energy29.

Vehicle10may also include a controller18which may, among other functions, determine when low cost energy, such as free energy or surplus energy is available for use as accessory energy24to operate HVAC system16. More specifically, controller18may determine when free energy28is being received by power source12from drivetrain14or when surplus energy29is being received by drivetrain14from power source12. As shown inFIG. 1, controller18may be operatively connected to multiple zone HVAC system16, power source12, and drivetrain14. Controller18is shown as a single device but may comprise several onboard or remote devices associated with the operation of vehicle10. Further, controller18may include devices, sensors, and control logic for detecting a state or condition or measuring an aspect of operation of vehicle10to determine when power source12is receiving free energy28from drivetrain14or when power source12is providing surplus energy to drivetrain14. For example, if power source12takes the form of an internal combustion engine and vehicle10is travelling downhill and if the engine is rotating at a speed above idle despite a lack of depression of an accelerator pedal (not shown), then controller18may determine that power source12is receiving free energy28from drivetrain14. As another example, if power source12takes the form of a battery and vehicle10is provided with one or more traction motors (not shown) arranged for regenerative braking, then power source12may be determined to be receiving free energy28from drivetrain14during braking of vehicle10. As another example, drivetrain14may incorporate a measuring device15, such as an ammeter (not shown) or dynamometer (not shown), between the power source12and drivetrain14to determine when drivetrain14is providing free energy28to or receiving surplus energy29from power source12. As yet another example, drivetrain14may be provided with solar panels (not shown) and power source12may be determined to be receiving free electrical energy28from drivetrain14during day time. One of ordinary skill in the art will appreciate the myriad solutions available for determining when free energy28is being provided by drivetrain14to power source12or when surplus energy29is being provided by power source12to drivetrain14.

When controller18determines that power source12is receiving free energy28from drivetrain14, or when controller18determines that power source12is delivering surplus energy to drivetrain14, a low cost energy mode may be activated for vehicle10. More specifically, controller18may include control logic and/or sensors for determining whether a low cost energy mode based on free energy or surplus energy may be activated. For example, controller18may activate the low cost energy mode if free energy28is being received by power source12from drivetrain14while multiple zone HVAC system16is being operated. Other characteristics of the vehicle10and the accessories thereof may be included in determining whether low cost energy is sufficiently available to activate the low cost energy mode. For example, controller18may determine that the free energy28being provided to the power source12from the drivetrain14or the surplus energy29being supplied by the power source12to the drivetrain14fails to conform to a criterion, and in response, may inhibit activation of the low cost energy mode. For example, controller18may determine that the free energy28being received by power source12or the surplus energy29being received by drivetrain14is below a certain horsepower or wattage threshold and in response, inhibit activation of the low cost energy mode.

Further, during certain periods of operation of vehicle10, it may be advantageous to limit the consumption of accessory energy24by HVAC system16if vehicle efficiency would be excessively diminished. Thus, in addition to determining whether low cost energy is available for operating HVAC system16, controller18may further determine whether the cost of accessory energy24from power source12to operate HVAC system16is greater than a threshold cost. The threshold cost may be pre-established or dynamically calculated. For example, if providing accessory energy24to HVAC system16would require operating the power source12at a brake specific fuel consumption (BSFC) level below a certain threshold then controller18may determine that the cost of accessory energy24exceeds the threshold cost. As another example, if controller18determines that providing accessory energy24to HVAC system16may cause the temperature of a thermostat13(FIG. 1) for a power source cooling fan (not shown) to rise above a threshold temperature, then controller18may determine that the cost of accessory energy consumption by HVAC system16is above the threshold cost.

The rate of consumption of accessory energy24by HVAC system16may also be used in determining whether the threshold cost is exceeded. The rate of consumption of accessory energy24by HVAC system16may be established by direct measurement, for example, a measuring device17such as an ammeter (not shown) or dynamometer (not shown), may be disposed between the power source12and HVAC system16to provide information regarding the rate of consumption of accessory energy24by HVAC system16. Alternatively, the rate of consumption of accessory energy24by HVAC system16may be inferred from empirical data. For example, known conditions of vehicle operation such as temperatures, pressures, mass flow rates and fuel consumption may be used to calculate the rate of consumption of accessory energy24by HVAC system16. If, for example, the rate of consumption of accessory energy24by HVAC system16exceeds the rate at which free energy28is delivered to power source12, controller18may determine that the cost of accessory energy24exceeds the threshold cost.

Upon determining that the cost of accessory energy24is above the threshold cost, controller18may inhibit energy consumption of HVAC system16. In other words, if controller18determines that operation of HVAC system16would result in excessively diminished vehicle efficiency, then controller18may reduce or suspend the delivery of accessory energy24to HVAC system16. Alternatively, or in combination, controller18may also operate HVAC system16with reduced functionality or performance. For example, if HVAC system16is being operated to provide a heating, ventilating or air conditioning function to a primary zone as well as a defrost function to a windshield or window of vehicle10, controller18may turn off the heating, ventilating or air conditioning to the primary zone while maintaining operation of the defrost function. Controller18may resume normal operation of the HVAC system16according to, for example, a preset length of time, or as another example, amelioration of the high cost condition. An operator may be provided with the option of overriding the controller18to maintain normal operation of HVAC system16regardless of the loss to vehicle efficiency.

FIG. 2illustrates an exemplary layout of a duct system40of multiple zone HVAC system16according to an exemplary embodiment of the invention. Duct system40may include an air mover42such as an electric fan (not shown) to flow air across a heat exchanger44towards a plurality of valves46,48,50,52and54each of which may control the flow of air to a respective zone56,58,60,62and64of vehicle10. Heat exchanger44may include several devices such as a heater coil20through which coolant heated by power source12may circulate for heating the ducted air and an evaporator22through which a working fluid may circulate for cooling the ducted air. Duct system40may also include at least one return66to allow air flow from zones56,58,60,62and64towards air mover42. HVAC system16may also include a valve68for allowing ambient air70to enter air mover42for delivery to one or more of the zones56,58,60,62and64of HVAC system16.

A working fluid system30of multiple zone HVAC system16according to an exemplary embodiment of the invention is shown inFIG. 3. System30may include a compressor32for compressing a working fluid to flow through a cooling condenser34. System30may also include an air mover36such as an electric fan (not shown) for moving air across the condenser to further cool the working fluid. After exiting condenser34, the working fluid may flow through an expansion valve38for expanding and reducing the temperature of the working fluid prior to flowing through evaporator22. The evaporator22may thereby cool the ducted air flowing through heat exchanger44(FIG. 2).

FIG. 4illustrates a cabin72of a vehicle10in the form of a tractor-trailer combination vehicle according to an exemplary embodiment. Cabin72includes zones56,58,60,62and64corresponding to the zones56,58,60,62and64shown inFIG. 2. More specifically, zone56is associated with a driver area, zone58is associated with a passenger area, zone60is associated with a front windshield, zone62is associated with a driver side sleeper area and zone64is associated with a passenger side sleeper area. It should be noted that the zone layout illustrated inFIG. 3is exemplary and that a zone may be defined anywhere in or about vehicle10. For example, a zone may be defined by an armrest, a headrest, an area within a cargo hold, an area exterior of the vehicle such as a roof of a tractor or trailer, an exterior surface of the windshield, a side mirror, an area between a tractor and trailer, etc.

As further shown inFIG. 4, multiple zone HVAC system16may include an HVAC system interface74operatively connected to multiple zone HVAC system16and controller18. Interface74may allow one or more zones56,58,60,62, and64of multiple zone HVAC system16to be selected as primary zones. HVAC system interface74may also allow one or more of the remaining zones56,58,60,62and64, i.e., zones which have not been selected as primary zones, to be selected as secondary zones. Alternatively, each zone not selected as a primary zone may be automatically selected as a secondary zone by HVAC system16. Further, HVAC system16may include temperature sensors (not shown) to provide temperature information for each zone56,58,60,62and64to interface74. Zone temperature information may be used by interface74and HVAC system16to provide thermostatic control of the heating, ventilating and air conditioning process provided to each zone56,58,60,62, and64.

HVAC system interface74may allow a driver or occupant to select a thermostatically controlled heating, ventilating or air conditioning process to be provided by HVAC system16to one or more of the selected primary zones of zones56,58,60,62and64without providing such heating ventilating or air conditioning process to the remaining zones56,58,60,62and64. For example, a driver or occupant may select thermostatically controlled cooling to be provided to driver zone56without providing such cooling to secondary zones58,60,62, and64. In accordance with such a selection, HVAC system16may open valve46(FIG. 2) and close each of valves48,50,52and54during the thermostatically controlled cooling of driver zone56.

An increase in fuel economy may be realized by reducing the number of primary zones selected to receive heating, ventilating or air conditioning from HVAC system16. However, and as shown inFIG. 4, the primary and secondary zones in the cabin may be exposed to one another, and thus, the heating, ventilating or air conditioning process or processes applied to the one or more selected primary zones may be compromised by the secondary zones. For example, heat transfer from one or more secondary zones into the one or more selected primary zones may cause a decrease in the time interval between periods of operation of HVAC system16during thermostatic control of the one or more primary zones. This frequent on/off cycling of the HVAC system16may contribute to wear of various components of HVAC system16and, if such cycling is audible, may also contribute to driver fatigue.

One solution to this problem may be provided by modifying the control of HVAC system16when the zones56,58,60,62and64are differentiated between primary and secondary zones. For example, HVAC system16may include logic for providing disproportionate control of a parameter in the one or more primary zones when the cabin72is differentiated between primary and secondary zones. For example, controller18may include control logic and/or sensors to determine if HVAC system16is being operated to provide thermostatically controlled cooling to one or more primary zones, and in response, reduce the temperature at which HVAC system16ends a cooling cycle of the one or more primary zones. This solution may reduce cycling of the HVAC system16, however, the relatively large temperature changes in the thermostatically controlled primary zone may be discomforting to the driver and may also compromise the fuel efficiency gains achieved by differentiating the cabin into controlled primary and non-controlled secondary zones.

Exemplary embodiments according to the present invention may provide solutions to the aforementioned problems. More specifically, if HVAC system16is being operated to provide heating, ventilating or air conditioning to at least one primary zone56,58,60,62, and64and if it is determined that free energy28is being provided by drivetrain14to power source12or surplus energy is being provided by power source12to drivetrain14, then a low cost energy mode may be activated and HVAC system16may be operated to provide heating, ventilating or air conditioning to at least one of the remaining secondary zones56,58,60,62, and64. It is particularly advantageous to provide heating ventilating or air conditioning to one or more of the secondary zones when such low cost energy is available since the accessory energy24(FIG. 1) used to operate HVAC system16may be provided without a significant loss to vehicle efficiency. For example, during the low cost energy mode, HVAC system16may be powered by energy derived from the kinetic energy of the vehicle during coasting or downhill travel, regenerative braking, or other sources, as previously described. Moreover, and as will be described further below, since the low cost energy mode allows for the secondary zones to be controlled the same as or differently than the primary zones, gains in vehicle efficiency may be realized without compromising the comfort or convenience of a driver or occupant of vehicle10.

Consider again the above described example wherein a driver has operated interface74to select thermostatically controlled cooling to be provided to driver zone56without such cooling being provided to secondary zones58,60,62, and64. In view of this example, a method100according to an exemplary embodiment of the invention will be described in reference toFIG. 5. In step102, it may be determined whether HVAC system16is being operated. In step104, it may be determined whether the cost of accessory energy24is above a threshold, as previously described. If the cost of accessory energy24is acceptable, then the method may skip to step112.

In step106, controller18may determine whether to inhibit consumption of accessory energy24by HVAC system16. The extent to which the consumption of accessory energy24is inhibited may be proportional to the extent that the use of such energy would reduce the efficiency of vehicle10. Thus, if the cost of accessory energy24greatly exceeds the threshold, controller18may entirely suspend the delivery of accessory energy24to HVAC system16according to step106. Such circumstances may arise, for example, where the entirety of the energy production of power source12is in demand for providing motive energy26to drivetrain14to ascend a particularly steep grade. In other circumstances, accessory energy24may be less costly to vehicle efficiency and thus, it may be determined that merely decreasing the functionality or performance of HVAC system16according to step108may be adequate to maintain a desired level of vehicle efficiency. Thus, for example, the duty cycle of compressor32(FIG. 3) may be reduced or the speed of air mover42(FIG. 2) may be limited to preserve accessory energy24. As previously described, the accessory energy24being provided to HVAC system16may be in use to provide a critical function, such as a defrost function of a front windshield of vehicle10, or an operator may override a determination to inhibit consumption of accessory energy24. Accordingly, in such circumstances, accessory energy24may continue to be provided to HVAC system16regardless of the relatively high cost of such energy to vehicle efficiency and the method may skip to step112.

In step112, it may be determined whether HVAC system includes at least one primary zone and at least one secondary zone and whether HVAC system is being operated to provide heating, ventilating or air conditioning to only the at least one selected primary zone. Since, in the present example, HVAC system is providing thermostatic cooling to only driver zone56, the method may proceed to steps114and116wherein it is determined whether the drivetrain14is providing free energy to power source12, or whether the power source12is providing surplus energy29to the drivetrain14, respectively, and as previously described.

In step118, it is determined whether to activate the low cost energy mode. Step118may be determined based on the affirmative determination of step112in combination with step114or step116. Alternatively, other aspects of the operation of vehicle10and the accessories thereof may be included in determining whether to activate the low cost energy mode or inhibit activation of the low cost energy mode. For example, controller18may include control logic and data, such as route information, as well as sensors, such as a GPS sensor (not shown), for predicting or anticipating the duration of time or distance that low cost energy may be available to HVAC system16and based on such predictions or anticipation control the activation of the low cost energy mode. In exemplary embodiments, vehicle route information may be correlated with vehicle speed information and GPS sensor information to control activation of the low cost energy mode. Thus, for example, controller18may determine that vehicle10is approaching a downhill road grade and that the grade extends in excess of a threshold distance, and in response, activate the low cost energy mode.

According to exemplary embodiments, the heating ventilating or air conditioning process applied to the secondary zone or zones and the manner in which the process is controlled during activation of the low cost energy mode may be determined by inputs to the HVAC system interface74by a driver or occupant, or alternatively, may be determined automatically by HVAC system16or controller18. For example, and as will be described further below, HVAC system16may include selectable settings, such as automatic, maximum and thermostatic. The automatic setting may be a default setting, i.e., selected by HVAC system16in the absence of a selection by a driver or occupant. Alternatively, in the absence of a setting selection by a driver or occupant of vehicle10, HVAC system16may inhibit activation of the low cost energy mode.

If the automatic setting is selected, then the method100ofFIG. 5may proceed to step120. In step120, HVAC system16may automatically provide the process and control being applied to the primary zone56to the secondary zones58,60,62and64. Thus, with regard to the above described example, HVAC system16may open each of valves48,50,52, and54(FIG. 2) during activation of the low cost energy mode to provide cooling to each of the secondary zones58,60,62, and64. Note that during the automatic setting, the cooling provided to each of the secondary zones58,60,62, and64will cycle on and off according to the thermostatic control of the primary zone56. According to this exemplary embodiment, since the thermostatic control of the primary zone56remains unchanged, and particularly the on and off cycling of air mover42, activation of the low cost energy mode may be advantageously imperceptible to the driver or occupants in the primary zones.

Alternatively, and as further shown inFIG. 5, if the maximum setting is selected, the method100proceeds to step122. In the maximum setting, like the automatic setting, HVAC system16may open each of valves48,50,52, and54(FIG. 2) to provide the heating, ventilating or conditioning being provided to each primary zone to each of the secondary zones58,60,62, and64. However, in the maximum setting, HVAC system16may be operated such that the heating, ventilating or air conditioning is provided continuously, as opposed to thermostatically, to the primary and secondary zones. Thus, with regard to the above described example, during activation of the low cost energy mode, each of the zones56,58,60,62, and64may be cooled below the temperature set for thermostatic control of the primary zone56. Note that, advantageously, cooling of the primary zone56may continue to be thermostatically controlled by HVAC system16during activation of the low cost energy mode in the maximum setting by modulation of valve46according to the temperature set at HVAC system interface74. Providing extra cooling to the secondary zones58,60,62, and64while maintaining thermostatic control of the primary zone56during activation of the low cost energy mode may further increase vehicle efficiency and at the same time, improve cabin comfort and reduce driver fatigue.

During extended periods of activation of the low cost energy mode in the maximum setting, the continuous operation of HVAC system16may result in an unacceptable temperature change in the primary and/or secondary zones. Accordingly, HVAC system16may include a “thermostatic” setting as shown in step124ofFIG. 5. HVAC system interface74may allow a driver or occupant to select the thermostatic setting and additionally, to set the temperature at which the heating, ventilating or air conditioning process provided by HVAC system16to the selected secondary zones is thermostatically controlled during activation of the low cost energy mode. For example, if driver zone56is provided with thermostatic cooling according to a first temperature, then each of secondary zones58,60,62, and64may be provided with cooling during activation of the low cost energy mode according to a thermostatically controlled second temperature. The second temperature may be lower than the first temperature. Advantageously, HVAC system16may modulate each of valves46,48,50,52and54to accommodate the differences in thermostatic control between the primary and secondary zones during activation of the low cost energy mode in the thermostatic setting.

In each of above described automatic, maximum, and thermostatic settings, valve68(FIG. 2) may be modulated by HVAC system16during activation of the low cost energy mode to provide ventilation of ambient air70(FIG. 2) in addition to cooling or heating of the primary and secondary zones. Further, vehicle10may include occupancy sensors (not shown) operatively connected between each of zones56,68,62and64and HVAC system16. Thus, with regard to the above-described example, if one or more secondary zones, such as zone62and zone64associated with the cabin sleeping area are occupied then HVAC system16may modulate valves52and54(FIG. 2) to prevent HVAC system16from providing extra cooling or heating to such occupied zones. HVAC system16and/or controller18may also include logic to provide for continuous operation of air mover36(FIG. 3) during activation of the low cost energy mode to maintain condenser34as close to ambient temperature as possible during activation of the low cost energy mode.

The invention has been described in terms of preferred principles, embodiments, and componentry; however, those skilled in the art will understand that some substitutions may be made without departing from the scope of the invention as defined by the appended claims.