Automatic climate control system for vehicle

An automatic climate control system for a vehicle determines actual sun load and a virtual sun load based on prescribed virtual heat load data and the external air temperature. A controller is configured to compare the actual sun load to the virtual sun load to obtain an optimized sun load value, and to control the system based on this optimized sun load value. A method for automatically controlling the climate includes determining measured sun load, determining external air temperature, comparing the measured sun load to the virtual sun load based on prescribed virtual heat load data and the external air temperature to obtain an optimized sun load value, and controlling the system based on the optimized sun load value. The virtual sun load and/or the measured sun load are used to determine the optimized sun load value depending on lighting conditions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a climate control system. More specifically, the present invention relates to an automatic climate control system for an automotive vehicle passenger compartment, which utilizes measured sun load and/or virtual sun load depending on daylight conditions in controlling the system in order to optimize performance of the climate control system.

2. Background Information

For many years, automotive vehicles have been provided with climate control systems in order to provide a more comfortable environment for the driver and any passengers. In recent years, climate control systems have been provided that automatically adjust to maintain a desired cabin temperature of the driver and/or passengers.

One type of vehicle automatic climate control system uses ambient temperature sensors and sun load sensors to obtain information on exterior air temperature and solar energy load. The information gathered from the sensors is used in a logic control system to establish airflow data and outlet temperature for the temperature control system in the vehicle passenger compartment. The outside ambient air temperature sensor must be strategically placed so that it is positioned away from heat sources such as the engine of the vehicle. A common location for the ambient temperature sensor is behind the forward radiator grille. This provides fair performance at high vehicle speeds but relatively poorer performance at lower vehicle speeds and/or if the vehicle is traveling in the same direction as surface winds. The sun load sensor(s) are typically located in the upper vehicle dash surface. In this location the sun load sensor(s) may be subjected to shadows (shade), which can cause readings that are inconsistent with the actual solar energy load on the vehicle passenger compartment. Also, when so positioned, the sun load sensor(s) have poor directional sensitivity, i.e., the sensitivity of the sun load sensor(s) vary depending upon the sun angle, which varies seasonally as well as hourly.

U.S. Pat. No. 5,832,990 discloses a climate control system that takes into account airflow, as well as interior temperature, outlet temperature of the system and general comfort parameters while managing the total heat flux. This system uses thermodynamic interaction of the comfort parameters, the interior temperature, the outlet temperature and airflow, as well as other control variables, in accordance with a control logic to improve climate control. However, as in the case of the prior temperature control system, the control system of the '990 patent requires a sun load sensor and an ambient temperature sensor. Thus, this system suffers from some of the same deficiencies as the prior system.

U.S. Pat. No. 5,995,889 discloses a temperature control system that eliminates the need for an external ambient temperature sensor and sun load sensor(s) in order to overcome some of the problems with the prior systems using such sensors. This system regulates outlet temperature and blower speed automatically using a processor with stored control algorithms that rely upon data including virtual ambient temperature and virtual sun load heat flux. In certain driving situations such as when sun load sensors would be shaded, this system performs better than the prior systems utilizing sensors. However, it suffers from other deficiencies. In particular, in certain driving conditions such as when sun load sensors would be in direct sunlight (i.e. when direct sun load impingement on the passenger(s) is present), this system does not work as well as the prior systems utilizing sensors.

In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved automatic climate control system for a vehicle. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an automatic climate control system for an automotive vehicle, which maintains the desired cabin temperature when a sun sensor receives direct daylight (i.e. direct sunlight during daylight hours).

It is another object of the present invention to provide an automatic climate control system for an automotive vehicle, which maintains the desired cabin temperature even when a sun sensor is shaded such that it does not receive direct daylight (i.e. when it does not receive direct sunlight during daylight hours, but receives indirect daylight).

It is another object of the present invention to provide an automatic climate control system for an automotive vehicle, which maintains the desired cabin temperature when a sun sensor does not receive daylight (i.e. when it is substantially dark or at night time).

The foregoing objects can basically be achieved by providing an automatic climate control system for a vehicle that includes a cabin air regulating structure, a sun load sensor component, an external temperature sensor component and a controller. The cabin air regulating structure is configured to regulate airflow into a passenger compartment of the vehicle. The sun load sensor component is configured to measure actual sun load. The external temperature sensor component is configured to determine external air temperature. The controller is configured to compare the actual (measured) sun load to a virtual sun load based on prescribed virtual heat load data and the external air temperature to obtain an optimized sun load value, and to control the cabin air regulating component based on the optimized sun load value to maintain a desired cabin temperature.

The foregoing objects can also basically be attained by providing a method for automatically controlling the climate in a passenger compartment of a vehicle, which includes determining measured sun load, determining external air temperature, comparing the measured sun load to a virtual sun load based on prescribed virtual heat load data and the external air temperature to obtain an optimized sun load value, and controlling a cabin air regulating structure based on the optimized sun load value.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A selected embodiment of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiment of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

Referring initially toFIGS. 1-3, a vehicle V with an automatic climate control system10used to control the temperature within the passenger compartment11is illustrated in accordance with a the present invention. The automatic climate control system10of the present invention is designed to optimize passenger comfort (climate) regardless of the driving situation (e.g. at night, at initial start-up, in direct sunlight, in indirect sunlight or shade, etc.). Specifically, the automatic climate control system10of the present invention is designed to determine a virtual sun load VSL applied to the vehicle V, detect a measured sun load ASL indicated by sensor(s) applied to the vehicle V, and to compare the virtual sun load VSL and the measured sun load ASL depending on the driving conditions in order to obtain an optimized thermal sun load value TSL. The measured sun load ASL is representative value of the actual sun load. The climate control system10then controls the outlet airflow rate and regulates the outlet air temperature based on the optimized sun load value TSL, which is based on the virtual sun load VSL and/or the measured sun load ASL, depending on the driving conditions to optimize performance of the climate control system10, as explained below. Thus, the comfort of the passenger(s) within the passenger compartment11can be optimized.

The automatic climate control system10includes both heating and air conditioning components to regulate the temperature in the passenger compartment11. However, for the sake of simplicity, only the air conditioning components of the automatic climate control system10will be described and shown to explain the present invention. The automatic climate control system10basically includes a controller12, an external ambient temperature sensor component14, a sun load sensor component16, an internal temperature sensor component18, a blower component20, a mass airflow determination component22, an outlet air temperature sensor24and a refrigerant circuit26as well as other conventional parts such including a heater core and a blend door system (air blending component), ductwork, valves and the like. The controller12, the ambient temperature sensor component14, the sun load sensor component16, the internal temperature sensor component18, the blower component20, the mass airflow determination component22, the outlet temperature sensor24, and the refrigerant circuit26are basically conventional, except that the controller12utilizes the data provided from the various sensors and a control logic in accordance with the present invention in order to optimize performance of the climate control system10in a variety of operating conditions, as mentioned above. In particular, the blower component20and the refrigerant circuit26form parts of a cabin air regulating structure that is controlled by the controller12in accordance with the present invention to optimize performance. Accordingly, the controller12, the ambient temperature sensor component14, the sun load sensor component16, the internal temperature sensor component18, the blower component20, the mass airflow determination component22, the outlet temperature sensor24and the refrigerant circuit26will not be discussed and/or illustrated in detail herein, except as needed to make and use the present invention.

The external ambient temperature sensor component14provides external ambient temperature (Ta) data for the controller12, preferably at predetermined intervals (e.g. every 15 seconds). The sun load sensor component16provides the measured sun load ASL (qsunfor a single zone system or driver and passenger side sun loads qsun(d)and qsun(p)for a dual zone system) data, preferably at predetermined intervals (e.g. every 15 seconds). The sun load ASL is a measured or detected sun load that is measured by the sun load sensor component16. If the sun load sensor component16includes multiple sensor elements (such as with a dual zone climate control system), the measured sun load ASL is the average sun load measured by the different sensor elements (e.g. 0.5 (qsun(d)and qsun(p))). If the sun load sensor component16includes a single sensor, ASL simply equals (qsun).

The internal temperature sensor component18provides internal cabin temperature (Tr) data, preferably at predetermined intervals (e.g. every 15 seconds). The mass airflow determination component22provides mass airflow (GA) data, preferably at predetermined intervals (e.g. every 15 seconds). The outlet temperature sensor24provides outlet temperature (To) data, preferably at predetermined intervals (e.g. every 15 seconds). The controller12uses the data obtained from the various other components of the system10as well as stored control algorithms containing prescribed virtual heat load data (based on thermodynamic principles, thermodynamic relationships between the variables and/or empirical data) in order to control the output blower speed (i.e. the mass airflow GA) of the blower component20and to regulate the refrigerant circuit26in order to control the climate within the passenger compartment11in accordance with the present invention.

The mass airflow determination component22provides mass airflow (GA) data, as mentioned above. In particular, the mass airflow determination component22senses voltage across the blower component20, which can be converted to mass airflow (GA) based on empirical data stored in the controller12. Similarly, when it is desired to set the blower component20to a certain mass airflow (GA) rate, the controller12uses the empirical data to set the blower voltage corresponding to the desired mass airflow rate (GA). This is a relatively conventional way to determine mass airflow (GA) and to control the blower component20of the climate control system10.

The climate control system10can be a single zone climate control system as illustrated inFIG. 2, or a dual zone climate control system as illustrated inFIG. 11in accordance with the present invention. For the sake of simplicity, the single zone climate control system will initially be explained. In either case, the present invention operates in a very similar manner to U.S. Pat. No. 5,995,889. However, the present invention utilizes the ambient external temperature component14and the sun load sensor component16, which are omitted from the system of the '889 patent, in the control logic illustrated inFIG. 3to optimize performance of the climate control system10of the present invention. The control logic illustrated inFIG. 3is used in conjunction with the control logic of the '889 patent, as explained below.

The controller12of the climate control system10is basically conventional, except that the controller (control unit)12utilizes the control logic illustrated inFIG. 3. Thus, the controller12preferably includes a microcomputer or central processing unit (CPU), input/output circuits (I/O interface), and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. The microcomputer of the controller12is programmed to control the climate control system10. Specifically, the memory devices store the programming (control logic) as well store control algorithms containing the prescribed heat load data and the processing results (sensor data). The controller12is operatively (e.g. electrically) coupled to the ambient temperature sensor component14, the sun load sensor component16, the internal temperature sensor component18, the blower component20, the mass airflow determination component22, the outlet temperature sensor24and the parts of the refrigerant circuit26in a conventional manner. The controller12is capable of selectively controlling any of the components of the climate control system10in accordance with the control logic. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the controller12can be any combination of hardware and software that will carry out the functions of the present invention. In other words, it will be apparent to those skilled in the art from this disclosure that these components can be any type of structure and/or programming that can be used to carry out the present invention.

The refrigerant circuit26basically includes an evaporator26ev, a compressor26cpwith an electromagnetic clutch, a condenser26cdand an expansion valve or orifice26vas well as other conventional parts including a heater core26hcand a blend door system26bd(air blending component). Typically, the condenser26cdis located in front of a radiator (not shown) that cools the engine coolant of the engine (not shown), while the blower component20is located to pull air across the evaporator26evto cool/warm the air entering the passenger compartment11via the blower component20. As mentioned above, the controller12controls the output blower speed (i.e. the mass airflow GA) of the blower component20and regulates the refrigerant circuit26in order to control the climate within the passenger compartment11in accordance with the present invention. In regulating the temperature of the passenger compartment11, the blend door system26bdthat diverts air around the heater core26hcis controlled by the controller12to manage the outlet temperature Toof the air expelled into the passenger compartment11in a conventional manner. These components26ev,26cp,26cd,26v,26hcand26bdare conventional components that are well known in the art. Accordingly, these components will not be discussed or illustrated in detail herein, except as related to the present invention.

Referring still toFIGS. 1-3, the control logic (i.e. ofFIG. 3) of the present invention will now be explained in more detail. The control logic ofFIG. 3basically includes a start, ten action blocks or steps S1, S2, S3, S4, S5, S6, S7, S8, S9and S10, and an end. At the end of the logic, the logic will be restarted (repeated).

In action block S1, the external ambient temperature sensor component14provides external ambient temperature (Ta) data, the sun load sensor component provides sun load ASL (qsunfor a single zone system or driver and passenger side sun loads qsun(d)and qsun(p)for a dual zone system) data indicated by the sensor(s), the internal temperature sensor component18provides internal cabin temperature (Tr) data, the mass airflow determination component22provides mass airflow (GA) data, and the outlet temperature sensor24provides outlet temperature (To) data. The data is sent to the controller, preferably at the same time, in predetermined intervals (e.g. every 15 seconds). Of course, if multiple sun sensor elements are used, the measured sun load ASL will need to be calculated, as explained below.

In action block S2, an Extvirt (estimated external load) is determined. The value of ExtVirt is determined using the control logic ofFIG. 4in accordance with the '889 patent, as described below in more detail. The control logic ofFIG. 4further utilizes the initialization logic and the filter logic ofFIGS. 6 and 7, respectively, in accordance with the '889 patent, as also described below in more detail.

In action block S3, the virtual sun load VSL is determined. The virtual sun load VSL is computed using the formula
VSL=(ExtVirt−Ta)/(GL/K)
The virtual sun load is ≧0. GL/K comes from an empirical test of a thoroughly soaked vehicle in an empirical measured sun load (Qsun) with the system off. The equation for a vehicle in this condition is disclosed in SAE Paper 960684 and is as follows:
0=K·(Ta−Tr)+GL·Qsun
Accordingly,
GL/K=(Tr−Ta)/Qsun
Ta=the ambient (external) temperature and Tr=the room or cabin temperature. GL is the effective glass area for solar load transmission. K is a conduction/convection heat transfer coefficient between the vehicle passenger compartment and ambient.

In action block S4, the (measured) sun load ASL is determined. For a single zone climate control system, the measured sun load ASL is simply the measured actual sun load qsunobtained from the sun load sensor component16. In a dual zone system, the measured sun load ASL=0.5 (qsun(d)+qsun(p)) or the average measured sun load indicated by the sensors as explained below.

In action block S5, it is determined whether the vehicle V is in a daylight condition or a night time (substantial dark) condition. When the sun load sensor component16indicates an ASL (qsun) less than 50 W/m2the sky is considered to be dark (i.e. no daylight is considered to be received). 50 W/m2is a predetermined threshold value to which the ASL (qsun) is compared in action block S5. In the case of modest sun sensor shading such as in overcast conditions or clear sky conditions but shaded by the vehicle (e.g. A-pillar, the roof or wiper) or an outside obstruction such as a building or a mountain, the sun load sensor component16generally indicates well over 100 W/m2(sometimes 1000 W/m2) during the daylight hours due to diffuse sunlight or reflected sunlight. The sun load sensor component16is most sensitive to infrared light (released by the sun). Thus, it does not react to common artificial light sources such as street lights or car headlights. If the measured sun load ASL is ≧50 W/m2indicating that daylight is being received (i.e. a daylight condition), the control logic proceeds to action block S6. If not, the control logic proceeds to action block S7.

If the measured sun load ASL is not ≧50 W/m2(i.e. it is night time or substantially dark) then the control logic proceeds to action block S7. In action block S7, an optimized thermal sun load TSL value is set to be the measured sun load ASL (qsunfor a single zone system or an average of driver and passenger side sun loads qsun(d)and qsun(p)for a dual zone system). The optimized thermal sun load TSL is used in controlling the climate control system10, as explained below. The virtual sun load VSL is preferably not used (i.e. ignored) in this situation because the value of the virtual sun load VSL is an estimate, which may be erroneously high due to residual heat that dissipates just after nightfall that is being indicated by the thermal estimate.

If the measured sun load ASL is ≧50 W/m2(i.e. it is day time), the control logic has proceeded to action block S6. In action block S6, the measured sun load ASL determined in action block S4is compared to the virtual sun load VSL determined in action block S3. If the measured sun load ASL is ≧ the virtual sun load VSL, the control logic will proceed to action block S7. If not, the control logic will proceed to action block S8.

If the measured sun load ASL is ≧50 W/m2(action block S5) indicating daylight and if the measured sun load ASL is ≧ the virtual sun load VSL, the control logic has proceeded to action block S7. In action block S7, the optimized thermal sun load TSL value is set to be the measured sun load ASL as mentioned above. The optimized thermal sun load TSL is used in controlling the climate control system10, as mentioned above and explained below. In this situation, because the sun load sensor component16provides actual (qsunfor a single zone system or driver and passenger side sun loads qsun(d)and qsun(p)for a dual zone system) data rather than an estimate, the measured sun load ASL is preferably used because it can be more accurate in indicating direct sun impingement on the passenger(s). This situation may arise when direct sunlight is shining on the passenger(s) and the sun load sensor component16. In such a situation, because the virtual sun load VSL only keeps the target room temperature, the virtual sun load VSL may be subjectively insufficient to deal with the sun's warming of the passengers.

If the measured sun load ASL is ≧50 W/m2(action block S5) indicating daylight and if the virtual sun load VSL is > the measured sun load ASL indicated by the sensor(s), the control logic has proceeded to action block S8. In action block S8, a value for the optimized thermal sun load TSL is computed using the formula
TSL=μ·ASL+(1−μ)·VSL
In this formula, μ is a weighting factor that is obtained from the table illustrated inFIG. 8. Thus, in this situation, weighted values of the virtual sun load VSL and the measured sun load ASL are components of the optimized thermal sun load TSL. As can be understood fromFIG. 8, if the room temperature Tris more than 10° C. warmer than the desired cabin temperature, TSL=VSL such that the optimized thermal sun load TSL will not be reduced by including any weighted factor of the measured sun load ASL (VSL>ASL in this situation). On the other hand, if the desired cabin temperature is more than 10° C. warmer than room temperature Tr, TSL=ASL such that the TSL will not be increased by including any weighted factor of the virtual sun load VSL (VSL>ASL in this situation). However, as the difference between the room temperature Trand the desired temperature get closer to zero, different weighted values of the virtual sun load VSL and the measured sun load ASL will be used to compute the optimized thermal sun load TSL. The values for μ inFIG. 8can be interpolated by the controller12in the ranges between −10° C., −5° C., 0° C., 5° C. and 10° C. The table inFIG. 8is merely one example of weighting factors μ for climate control system10. Of course, it will be apparent to those skilled in the art from this disclosure that the values for the weighting factor μ can be modified to increase/decrease the influence of the measured sun load ASL and/or virtual sun load VSL in action block S8, based on empirical testing and/or depending on the type of vehicle and the typical driving conditions for that vehicle. For example, the weighting factors μ (ofFIG. 8used in action block S8) could be set such that the climate control system10effectively uses TSL=ASL in heating applications and effectively uses TSL=VSL in cooling applications for a simplified control logic. However, at least some weighted factor of the virtual sun load VSL is preferably utilized in action block S8in order to improve performance in situations where the virtual sun load VSL is higher than the measured sun load ASL in daylight conditions, possibly due to shading or the like. The optimized thermal sun load TSL is used in controlling the climate control system10, as mentioned above and explained below.

Action block S7or S8is used to determine the optimized thermal sun load TSL, as explained above. In either case, once the optimized thermal sun load TSL is determined, the control logic proceeds to action block S9. In action block S9, the sun load heat flux values or factors (Qs for a single zone system or Qsd and Qsp for a dual zone system) are determined. In a single zone system, the sun load heat flux Qs is simply set to be equal to the optimized thermal sun load TSL. However, in a dual zone system, the driver and passenger Qsd and Qsp need to be calculated. In order to calculate these values, weighting factors SunD and SunP are first determined where SunD=qsun(d)−ASL and SunP=qsun(p)−ASL. Here, the measured sun load ASL is the average of the driver and passenger side sun loads qsun(d)and qsun(p). These weighting factors SunD and SunP are then applied (added) to the optimized thermal sun load TSL to obtain the driver and passenger sun load factors Qsd and Qsp, respectively. Thus, Qsd=SunD+TSL and Qsp=SunP+TSL. The driver and passenger sun load factors Qsd and Qsp are corrected (adjusted) inputs that replace the sensor inputs and functionally replace the conventional sun sensor inputs to the control logic.

Then, in action block S10, the sun load heat flux values or factors (Qs for a single zone system or Qsd and Qsp for a dual zone system) are used as the sun load inputs to enable the appropriate blower voltage (i.e. blower speed, and thus, GA) to be set using any conventional technique that is well known in the art as well as regulate the outlet temperature by management of the compressor26cpand/or the blend door system26bd(air blending component).

Referring now toFIGS. 4-7, the virtual logic from U.S. Pat. No. 5,995,889 used in action block S2ofFIG. 3will now be explained. Since this virtual logic is now well known, it will not be discussed and/or illustrated in great detail herein. Rather, the virtual logic will only be discussed as needed to make and use the present invention. The symbols used in the discussion below are identified as follows: GL is the effective glass area for solar load transmission. K is a conduction/convection heat transfer coefficient between the vehicle passenger compartment and ambient. Q is the sun load heat flux. Tais the ambient external temperature. MCris the heat capacitance in the vehicle passenger compartment11. GA is the mass airflow rate (enthalpy rate per degree).GAis the average mass airflow. Finally, Tois the outlet temperature of the air delivered to the passenger compartment11by the blower component20after passing through the heat exchangers of the climate control system10.

For the purpose of explaining the thermodynamic principles of ambient temperature and solar load estimation, the start-up condition for the climate control system10first will be discussed. During start-up, the energy balance of a soaked vehicle can be estimated in accordance with the following relationship:
K·(Tr−Ta)=Q·GL
During an energy balanced state, the external estimated conditions (EXTVIRT) equals

EXTVIRT=Ta+Q·G⁢⁢LK=Tr
The interior airflow must be established to provide information regarding bulk heat transfer to the interior. For this reason, during the first few minutes of operation of the blower component20, the control system relies on this calculated value of EXTVIRT without adjustment.

Following start-up, the estimate of the external conditions during normal driving can be calculated. This requires a determination of the average outlet temperature, To, the steady state interior temperature, Trss, and the average airflow,GA. Each of these affects the determination of the external conditions. For stabilized operation during normal driving, the following equation applies:

EXTVIRT=(1+G⁢⁢A_K)·Trrs-(G⁢⁢A_K)·To
If this value for the external condition is substituted in the preceding energy balance equation, the following equation is derived:

G⁢⁢A_·(Trss-To)=K·(Ta+Q·G⁢⁢LK-Trss)
In order to solve this equation, the average airflow and outlet temperature must be known for a given time interval. This will be explained subsequently with respect toFIG. 4.

The term Trssin the foregoing equations represents the average temperature in the vehicle passenger compartment during steady state operation of the interior temperature control system. The airflow represented by the symbol GA can be determined by converting the voltage across the blower component20into GA. The voltage value and/or GA can be obtained using an empirical relationship between voltage and blower speed that may be stored in the memory of the microprocessor. In the case of a control system of the kind shown in the '990 patent identified above, the airflow would be determined as part of the heat flux calculation carried out by the processor using the interior temperature control algorithm disclosed in that patent. The determination of the steady state temperature (Trss) in the interior of the vehicle passenger compartment11of the vehicle V is done by taking periodic samplings of room temperature (Tr). This information is used in the estimate of Trssduring a given time interval.

This process involves the use of a first order differential equation solution as follows:
T2=Tss·(1−e−t/τ)+T1·e−t/τ
where T2=the end of the interval temperature;Tss=the steady state temperature;T1=the start of interval temperature;τ=the time constant;t=the time of the interval; ande=the natural logarithm base.
The derivative of this solution yields:
dT1=└Tss·(1/τ·e−t/τ)+T1·(−1/τ·e−t/τ)┘·dt
For a finite interval (duration of Δt):
T2−T1=[Tss1−T1]·(1/τ·e−(1/τ)Δt)·Δt
If all Δt values are equal for “n” small intervals:
Tn−T1=[ΣTssi−ΣTi−1]·(1/τ·e−(1/τ)Δt)·Δt
Tn−T1=n·[T(ss)avg−Ti−1)avg]·(1/τ·e−(1/τ)Δt)·Δt
Let, n·Δt=Δt1−nThus,
(Tn−T1)/Δt1−n=[T(ss)avg−T(i−1)avg]·(1/τ·e−(1/τ)Δt)
If “Δt/τ” is small, e−(1/τ)Δtis ≅1 (Note: The smallness of Δt is arbitrary) then:
(Tn−T1)/Δtt−n=└T(ss)avg−T(i−1)avg┘·1/τ
Thus,
T(ss)avg=T(i−1)avg+τ·(Tn−T1)/Δt1−n
This equation uses simple measurements and a time constant to estimate the steady state condition for a given time interval.

In the above equation, T(ss)avgequals the average temperature under steady state conditions in the interior of the vehicle passenger compartment11. The term T(i−1)avgis the average of the first four temperature values that are stored in memory and stacked as shown inFIG. 5. These are table values that are recorded during calculations at each 15 second interval over a period of one minute. The quantity (Tn−T1) is the change in room temperature over a one minute period. The earliest value for Trin the example illustrated inFIG. 5is 19° C. and the recent value for Tris 26° C. The difference in these values represents an average temperature history over the preceding one minute interval, which is Δt1−n. The one minute time interval and the 15 second time interval are arbitrary values that are chosen based on engineering judgment and empirical test data. As new data is entered into the top of the stack shown inFIG. 5, the existing data is shifted down as the oldest entry is dropped.

The following equation results from the calculation of the steady state passenger compartment temperature.

Trss=Triavg+Δ⁢⁢Tr·[M⁢⁢CrK+G⁢⁢A_]/Δ⁢⁢t
In the foregoing equation, MCris the effective interior heat capacitance, ΔTris the change in room temperature for a given time interval. Triavgis the average of all but the last room temperature measurement during the time interval. Sampling of the temperature during the time interval (i.e., Δt) is necessary. A sample rate of one sample for each 15 seconds is used to help determine the value of Trssduring the preceding minute (Δt).

Under unusual conditions where there are unwanted fluctuations in the response to the external conditions, a filtering logic is used periodically to limit the fluctuations. These fluctuations might occur, for example, when a vehicle passenger compartment door is opened and closed or when a window is opened and closed. When an unusual change in heat flux occurs during such transient conditions, the interior temperature sensor component18may not correlate correctly with the actual passenger compartment temperature. The following filtering logic is applied periodically to limit the incorrect fluctuations of the response to external conditions.
EXTVIRT(old)=EXTVIRT(old)+M·[EXTVIRT(new)−EXTVIRT(old)]
or
EXTVIRT=EXTVIRT+VIRFIL2·(NewEXT−EXTVIRT)
where: 1>M>0, EXTVIRT(old)=computed EXTVIRT in the previous control loop during steady state operation, and EXTVIRT (old)=computed EXTVIRT at the end of the current control loop during steady state operation.

This filtering logic will be explained with reference toFIG. 7. Under unusual start-up conditions, a special logic is used in the determination of the response to external conditions. If the soak time is very short, the room temperature may not be stabilized (i.e., Trdoes not equal Ta+Q·GL/K). The EXTVIRT value under these circumstances can be represented by the value stored in memory during the last driving mission. If the vehicle V is cooling to the ambient temperature after a driving mission, stabilization may take a long time. Thus, a temperature offset is taken away from the room temperature and used in the estimate of EXTVIRT. This will be explained with reference toFIG. 6. This effect has an advantage during warm-up performance, even for a completely soaked vehicle. If the vehicle is soaking to a hot condition, the interior temperature sensor component18used to measure interior passenger compartment temperature Trprovides the best estimate of temperature of the interior passenger compartment11. In previously cold conditions without a long soak, the logic assumes that the remembered value for EXTVIRT is the best estimate.

Referring now to the flow chart ofFIG. 4, the virtual external load logic now will be described. The control logic (routine) of the processor begins with initialization logic at30. This will be described with reference toFIG. 6. The processor then enters a filter logic routine at32, which will be described with reference toFIG. 7. The next step at34involves an inquiry as to whether the 15-second interval described previously is over. If it is not over, the routine will inquire at36whether the engine is turned off. If the engine is running, the routine then will proceed at the beginning step of the logic where initialization occurs at30and a filtering logic is carried out at32. If the fifteen second interval has terminated, a calculation of airflow takes place at action block38. This involves a calculation of airflow GA based on voltage, as explained previously. In certain temperature control systems, this can be done, as explained previously, by referring to a functional relationship between blower voltage determined by the driver's selection of blower motor speed and airflow based on empirical test data.

The outlet temperature Toand the airflow GA data are computed at action block40in accordance with the equations described previously. This information then is transferred to a memory stack as shown inFIG. 5. This is done at each 15-second interval. The newest data stacked in the memory, as indicated inFIG. 5, is entered at the top of the stack. The average temperature then is the average of the four most recently stored readings. In an example shown inFIG. 5, the average of initial room temperatures (AvgInit) is the average of 19° C., 21° C., 23° C. and 24° C. The average outlet temperature (Avg Outlet) would be the average of the four most recently stored values 45° C., 45° C., 48° C. and 54° C. The corresponding average airflowGAis calculated similarly in cubic meters per minute using the values 3.0, 3.9, 4.0 and 4.1.

The routine then proceeds to action block42, where the interior heat capacitance is calculated in accordance with the equations described previously. A determination then is made at step44to determine whether the engine is running and whether it has been running for at least two minutes, which is an arbitrary time established by test data. If it has not been running for at least two minutes, the routine will proceed to action block46where the next 15-second interval is set so that the previously described steps of the routine can be repeated. If the engine still is running as determined at step36, the routine then will proceed to the beginning, where initialization logic will be confirmed to have been completed. If the engine is off, the external conditions (EXTVIRT) will be stored in memory where it will be made available for the next operating cycle, as shown at48.

If the inquiry at step44is positive, the engine will have been running for at least two minutes. The routine then will proceed directly to action block50where the steady state room temperature is calculated. This is done as previously described in accordance with the equation indicated above for Trss. The routine then will calculate a new external load at action block52in accordance with the relationship
NewEXT=(1+GA/K)·Steady−Average Outlet·GA/K
The filtering calculation then is carried out at action block54, as will be explained with reference toFIG. 7. This is done in accordance with the equation:
EXTVIRT=EXTVIRT+VIRFIL2·(NewEXT−EXTVIRT)
The value for the filtered virtual load then is stored in memory as shown at action block48after the engine is turned off, as confirmed at block36, and after the next 15-second interval is set as shown at46. This EXTVIRT value is stored in RAM where it can be used during the next driving mission.

The initialization logic that is carried out at step30in the flow chart atFIG. 4is illustrated in flow chart form inFIG. 6. Before the virtual external load logic can be carried out, the initialization routine proceeds to determine at step56whether the engine coolant is less than 50° C. If it is less than 50° C., which would indicate that the vehicle has been sitting for a long time after the engine was shut down following the previous mission. If the vehicle engine has indeed cooled down to a value less than 50° C., a determination at step58is made to determine whether the room temperature is less than 30° C. If it is less than 30° C., that would indicate that the vehicle, on initial start-up, has not been soaking in the sun. The routine then will proceed to action block60where the value for EXTVIRT stored in memory is equal to room temperature minus an offset of a predetermined value such as 5°. Thus, a lower passenger compartment temperature is used in the load calculation to provide a more gentle response. If the temperature on initial start-up is over 30° Centigrade, that indicates that the vehicle has been soaking in the sun and has accumulated a sun load. Under those conditions, the stored value for EXTVIRT is chosen as shown at action block62. Thus, this portion of the routine is a long soak indicator.

If the engine coolant is greater than 50° Centigrade, that indicates that the engine has not been shut down for a long time. In that event, the routine will proceed to step64where the memory is accessed to obtain the stored value for temperature. If the memory value stored at the end of the execution of the preceding logic is greater than 15° C., a test is then made at step66to determine whether the coolant temperature is less than 77° C. If the coolant temperature is less than 77° C., the routine then will proceed to step58. If the engine coolant temperature is higher than 77° C., the routine will use the value for EXTVIRT stored in memory in the load logic. This is indicated at70.

If the room temperature is higher than 30° Centigrade, the value for EXTVIRT is the same as the measured interior temperature Tr, that value then is used in the previous external load logic routine as shown inFIG. 4. As indicated in the foregoing description ofFIG. 6, it is determined at the outset of the routine ofFIG. 6whether the vehicle has been soaking for a long time or a short time. This information affects the sequence of the method steps illustrated inFIG. 6.

The filter constant logic for EXTVIRT is shown inFIG. 7. This logic is used at the beginning of the routine shown inFIG. 4. A test is made at step76to determine whether the engine has been running for at least two minutes. As in the case of the other time intervals, a period of two minutes is an arbitrary value established by engineering judgment and empirical data obtained by test. This time period gives the system sufficient time to gather data to carry out the load logic calculations. It takes one minute, for example, to obtain the average interior temperature, outlet temperature and airflow value stacked in the memory registers indicated inFIG. 5. It also provides the engine sufficient time to develop warm water for use by the climate control system10.

If the engine has not been running for two minutes, a test is made to determine whether the blower component20is on or off as shown at78. If the blower component20is off, the routine at action block80will set the filter constant Filter1=0 in the computation at action block54in the external load logic computation routine ofFIG. 4. A test is made then at step82to compare filter constant Filter1with the virtual filter constant VIRFIL2. Since Filter1is zero, a positive response at step82will require that the comparison between the two filter constants at action block84will be the same. Thus, both the filter constants would be zero and the external load logic then will proceed as indicated inFIG. 6. If Filter1is greater than VIRFIL2, the routine will proceed to action block86where a calculation is made to make sure that VIRFIL2 increases in value so that it will match Filter1. This is done using the equation
VIRFIL2=M·(Filter1−VIRFIL2)+VIRFIL2
where M is a multiplier between 0 and 1.

The filter constants are obtained at action block88inFIG. 7and compared at action block82. These values for filter constants, which are obtained from a look-up table stored in ROM, are based on interior temperature Tr. Such look-up tables are well known in the art. An example of such a look-up table is shown in U.S. Pat. No. 5,995,889 (FIG. 7). If the duration of the filter constant response is short, the value for VIRFIL2 will rise until it matches Filter1. The gradual increase in VIRFIL2 is due to multiplier M. The same is true if the response time is long. If the filter constant from the look-up table (Filter1) should decrease below VIRFIL2, VIRFIL2 will immediately decrease without a gradual response.

Of course, it will be apparent to those skilled in the art from this disclosure that certain action blocks and/or logic fromFIGS. 4-7could be omitted in view of the improvements provided by the present invention as illustrated in the control logic ofFIG. 3, if needed and/or desired.

Referring now toFIG. 11, the vehicle V equipped with a dual zone automatic climate control system10′ in accordance with the present invention will now be explained. The dual zone climate control system10′ basically includes a controller12, an external temperature sensor14, a sun load sensor component16′, an internal temperature sensor component18′, a blower component20′, a mass airflow determination component22′, an outlet temperature sensor component24′ and the refrigerant circuit26. The sun load sensor component16′ includes driver and passenger side sun load sensor elements17dand17p. The internal temperature sensor component18′ includes driver and passenger side internal temperature sensor elements19dand19p. The blower component20′ includes driver and passenger side blower elements21dand21p. The mass airflow determination component22′ includes driver and passenger side mass airflow determination elements23dand23pand an outlet temperature sensor component24′ includes driver and passenger side outlet temperature sensor elements25dand25p.

In this system, the sun load sensor elements17dand17pobtain readings for the measured driver and passenger side sun loads qsun(d)and qsun(p),respectively. These readings are averaged to obtain a measured sun load ASL that is an average of the measured sun loads qsun(d)and qsun(p),as mentioned above. Similarly, the driver and passenger side internal temperature sensor elements19dand19pprovide driver and passenger room temperatures Trdand Trp, respectively, the driver and passenger side blower elements21dand21pexpel driver and passenger air into the passenger compartment11, respectively, the driver and passenger side mass airflow determination elements23dand23pmeasure the driver and passenger airflow GAdand GAp, respectively, and the driver and passenger side outlet temperature sensor elements25dand25pprovide driver and passenger side outlet temperatures Todand Top, respectively.

Then the control logic ofFIG. 3is applied to each side of the passenger compartment11using the controller12and the data obtained from respective driver and passenger side internal temperature sensor elements19dand19p, and driver and passenger side mass airflow determination elements23dand23pto control the driver and passenger side blower elements21dand21p. Preferably, rather than using the measured sun load ASL (i.e. the average of the driver and passenger side sun loads qsun(d)and qsun(p)) or the sun loads qsun(d)and qsun(p)themselves in the computations, these values are be weighted based on their variance from the measured sun load ASL to obtain driver and passenger sun load (factors) heat flux values Qsd and Qsp that emphasize/deemphasize the variance therebetween as mentioned above. However, it will be apparent to those skilled in the art from this disclosure that the driver and passenger side sun loads qsun(d)and qsun(p)themselves can be used or the measured sun load ASL can be used in the computations to control the blower elements21dand21pand the refrigerant circuit26, if needed and/or desired.

In order to obtain driver and passenger sun load (factors) heat flux values Qsd and Qsp that emphasize/deemphasize the variance therebetween, weighting factors SunD and SunP are first determined where SunD=qsun(d)−ASL and SunP=qsun(p)−ASL. Here ASL is the average of the driver and passenger side sun loads qsun(d)and qsun(p). In this case, these weighting factors SunD and SunP are then applied (added) to the optimized thermal sun load TSL to obtain driver and passenger sun load factors Qsd and Qsp, respectively. Thus, Qsd=SunD+TSL and Qsp=SunP+TSL. The driver and passenger sun load factors Qsd and Qsp are corrected (adjusted) inputs that replace the sensor inputs and functionally replace the conventional sun sensor inputs to the control logic.

In any case, each of the blower elements21dand21pis controlled in a manner identical to the blower component20of the single zone climate control system10, discussed above. The refrigerant circuit26is also regulated in order to regulate (control the outlet air temperature of the climate control system10′. Since a single refrigerant circuit26is used for both zones of the climate control system10′ optimized cycling of the compressor26cpis preferably determined using an average of the various computed values for the two zones. In other words, the dual zone system is basically a duplication (or splitting) of the single zone system, where each side has a one-half of the GL. Thus, the controller12basically has a pair of control logics as illustrated inFIG. 3running simultaneously to control the climate on both sides of the passenger compartment11. Other simple modifications (i.e. utilizing the principles of a single zone climate control system in a dual zone climate control system) are well known to those skilled in the art. Thus, the dual zone climate control system10′ will not be explained and/or illustrated in detail herein.

As used herein to describe the above embodiment(s), the following directional terms “forward, rearward, above, downward, vertical, horizontal, below and transverse” as well as any other similar directional terms refer to those directions of a vehicle equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a vehicle equipped with the present invention. The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function. The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.