Vehicle climate control system and method for reducing ice accumulation

Abstract

The present disclosure provides "Vehicle Climate Control System and Method for Reducing Ice Accumulation". A climate control system for a vehicle is comprised of an air conditioner, a plurality of sensors, a plurality of timers, and a controller. The controller includes a timing module, a storage module, and a processor. The timing module provides the plurality of timers, and the storage module provides a plurality of calibration thresholds and timer thresholds. The processor is configured to determine and execute an anti-icing strategy to predict and prevent icing of an evaporator of the air conditioner. The processor executes the anti-icing strategy in accordance with comparisons of various inputs provided by the plurality of sensors to the plurality of calibration thresholds. Additionally, the processor executes the anti-icing strategy in accordance with comparisons of an amount of time that one or more of the plurality of timers has been activated to one or more of the plurality of timer thresholds.

Description

Technical Field

[0001] This disclosure generally relates to a vehicle climate control system, and more specifically, to preventing ice buildup on the evaporator of the air conditioner of the vehicle climate control system by implementing an anti-icing strategy. Background Technology

[0002] Vehicles may include a climate control system to provide conditioned air to vehicle occupants. The vehicle climate control system may employ an air conditioner comprising an evaporator for heat transfer with air supplied to the vehicle interior and a condenser for heat transfer with air injected to the outside of the vehicle. The evaporator and condenser are connected via a refrigerant line, through which refrigerant is pumped by a compressor connected to the refrigerant line. An expansion valve is inserted in the refrigerant line and reduces the pressure applied to the refrigerant. The depressurized refrigerant enters the evaporator and absorbs heat from the air surrounding the evaporator. The depressurized refrigerant leaves the evaporator and enters the refrigerant line, where it is subsequently repressurized by the compressor and pushed into the condenser. Inside the condenser, the pressurized refrigerant transfers heat to the surrounding air. The pressurized refrigerant then leaves the condenser, re-enters the refrigerant line, and is subsequently depressurized by the expansion valve. Thus, the refrigerant completes a heat transfer cycle, in which heat from the air supplied to the vehicle interior is transferred to the air outside the vehicle.

[0003] During air conditioning operation, the evaporator cools to temperatures below freezing, which can cause ice to accumulate on its surface. This accumulation can reduce the heat absorption efficiency provided by the reduced-pressure refrigerant within the evaporator. An enhanced system and method are desired to prevent ice accumulation on the evaporator. Summary of the Invention

[0004] According to a first aspect of this disclosure, a climate control system for a vehicle is provided, wherein the climate control system includes a compressor, an evaporator, a plurality of sensors, and a controller, the controller communicating with the plurality of sensors and including at least one timer, the controller being configured to execute an anti-icing strategy, the anti-icing strategy including the steps of: monitoring the plurality of sensors; determining the probability of ice formation on the evaporator; adjusting the climate control system based on the determined probability of ice formation; activating one or more of the at least one timer in response to the adjustment of the climate control system; monitoring the at least one timer; and controlling the climate control system based on the at least one timer.

[0005] Embodiments of the first aspect of this disclosure may include any one or a combination of the following features: - At least one of the plurality of sensors includes a duct air temperature sensor.

[0006] - At least one of the plurality of sensors includes an ambient air temperature sensor.

[0007] The controller determines the likelihood of ice formation on the evaporator by comparing the duct exhaust temperature target with the duct exhaust temperature target threshold.

[0008] The controller determines the likelihood of ice formation on the evaporator by comparing inputs provided to the controller by multiple sensors with multiple calibration thresholds.

[0009] The controller determines the likelihood of ice formation on the evaporator by comparing the duration for which at least one timer has been started with multiple timer thresholds.

[0010] The controller adjusts the climate control system by adjusting the evaporator target temperature with a calibration value based on the determined probability of ice formation.

[0011] The controller adjusts the climate control system by adjusting the evaporator target temperature with a calibration value based on a determined probability of ice formation, wherein the probability of ice formation is determined when each of the plurality of sensors detects an input that reaches a calibration threshold.

[0012] The controller adjusts the climate control system by disabling the compressor based on the determined probability of ice formation.

[0013] The controller adjusts the climate control system by disabling the compressor based on a determined probability of ice formation, wherein the controller determines the probability of ice formation when one or more of the plurality of sensors detect an input that reaches a calibration threshold, and when the at least one timer has been started for a time exceeding a timer threshold.

[0014] - The controller adjusts the climate control system by restarting the compressor based on the determined probability of ice formation, wherein when one or more of the plurality of sensors detect an input that reaches a calibration threshold, the controller determines that there is no probability of ice formation, wherein the calibration threshold is a duct air temperature outlet condition threshold.

[0015] The controller adjusts the climate control system by restarting the compressor based on a determined probability of ice formation, wherein the controller determines that there is no probability of ice formation when the at least one timer has been started for a time equal to or exceeding a timer threshold, wherein the timer threshold is a compressor restart timer threshold.

[0016] When each of the plurality of sensors detects an input that reaches a calibration threshold and the compressor is active, the controller determines that there is a possibility of ice formation.

[0017] According to a second aspect of this disclosure, a method for controlling a vehicle climate control system is provided, the method comprising the steps of: activating a compressor of the vehicle climate control system; sensing an ambient air temperature using a first temperature sensor; sensing an air duct temperature using a second temperature sensor; monitoring the sensed ambient air temperature and the air duct temperature using a controller; determining the likelihood of ice formation on the evaporator; adjusting the vehicle climate control system using the controller based on the determined likelihood of ice formation; activating at least one timer in response to the adjustment of the vehicle climate control system using the controller; and controlling the vehicle climate control system based on the at least one timer.

[0018] Embodiments of the second aspect of this disclosure may include any one or a combination of the following features: - The second temperature sensor can be composed of a duct air temperature sensor.

[0019] The controller determines the likelihood of ice formation on the evaporator by comparing the duct exhaust temperature target with the duct exhaust temperature target threshold.

[0020] The controller determines the likelihood of ice formation on the evaporator by comparing inputs provided to the controller by multiple sensors with multiple calibration thresholds.

[0021] The controller adjusts the climate control system by adjusting the evaporator target temperature of the evaporator with a calibration value based on the determined probability of ice formation.

[0022] The controller adjusts the vehicle climate control system by disabling the compressor based on a determined probability of ice formation, wherein the controller determines the probability of ice formation when one or more of the plurality of sensors detect an input that reaches a calibration threshold, and when the at least one timer has been started for a time exceeding a timer threshold.

[0023] The controller adjusts the vehicle climate control system by restarting the compressor based on the determined probability of ice formation, wherein when the second sensor detects an input greater than a calibration threshold, the controller determines that there is no probability of ice formation, wherein the calibration threshold is a duct air temperature outlet condition threshold.

[0024] These and other features, advantages and objectives of this disclosure will be further understood and appreciated by those skilled in the art upon reference to the following specification, claims and drawings. Attached Figure Description

[0025] In the attached diagram: Figure 1 This is a schematic diagram of a vehicle equipped with a climate control system.

[0026] Figure 2 This is a schematic diagram of a part of a vehicle's climate control system.

[0027] Figure 3 This is a schematic diagram of a vehicle climate control system equipped with multiple sensors.

[0028] Figure 4 This is a diagram of a control system used in vehicle climate control systems.

[0029] Figure 5 This is a diagram of the controller for a vehicle's climate control system.

[0030] Figures 6A-6B This is a flowchart illustrating the process by which the controller's processor determines and executes an anti-icing strategy according to a first embodiment.

[0031] Figures 7A-7B This is a flowchart illustrating the process by which the controller's processor determines and executes an anti-icing strategy, according to a second embodiment. Detailed Implementation

[0032] Reference will now be made in detail to the preferred embodiments of this disclosure, examples of which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. In the drawings, structural elements are depicted not to scale, and some parts are enlarged relative to others for emphasis and understanding purposes.

[0033] Detailed embodiments of this disclosure are disclosed herein as needed; however, it should be understood that the disclosed embodiments are merely examples of this disclosure and may be implemented in various and alternative forms. The accompanying drawings are not necessarily detailed designs; some schematic diagrams may be enlarged or minimized to show a functional overview. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but rather serve only as a representative basis for teaching those skilled in the art to employ this disclosure in different ways.

[0034] For descriptive purposes, the terms “up,” “down,” “right,” “left,” “back,” “front,” “vertical,” “horizontal,” and their derivatives should be used in conjunction with such terms. Figure 1The concept of orientation is not explicitly stated. However, it should be understood that the concept may present various alternative orientations unless explicitly stated otherwise. It should also be understood that the specific apparatus and processes shown in the accompanying drawings and described in the following specification are merely exemplary embodiments of the inventive concept defined in the appended claims. Therefore, unless otherwise expressly stated in the claims, the specific dimensions and other physical characteristics relating to the embodiments disclosed herein should not be considered limiting.

[0035] The embodiments shown here primarily concern combinations of method steps and equipment components related to vehicle climate control systems. Therefore, equipment components and method steps have been indicated where appropriate by conventional symbols in the accompanying drawings, with only those specific details relevant to understanding the embodiments of this disclosure shown so as not to obscure the disclosure in ways that would be obvious to those skilled in the art who would benefit from the description herein. Furthermore, the same reference numerals denote the same elements in the specification and drawings.

[0036] As used herein, the term "and / or" when used with two or more listed items means that any one of the listed items may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B, and / or C, the composition may contain: A only; B only; C only; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C.

[0037] In this document, relational terms such as first and second, top and bottom are used individually to distinguish one entity or action from another, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprising,” “including,” or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article of manufacture, or apparatus that comprises a list of elements includes not only those elements but may also include other elements not expressly listed or inherent to such process, method, article of manufacture, or apparatus. Without further constraints, an element preceded by “comprising…” does not exclude the presence of additional identical elements in the process, method, article of manufacture, or apparatus that includes said element.

[0038] As used herein, the term "about" means that a quantity, size, formulation, parameter, and other quantity and characteristic is not precise, nor is it required to be precise, but may be approximate and / or larger or smaller as needed to reflect tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art. When the term "about" is used to describe an endpoint of a value or range, this disclosure should be understood to include both the specific value and the mentioned endpoint. Whether or not the endpoints of numerical values ​​or ranges in this specification are referred to as "about," the endpoints are intended to include both embodiments: one modified by "about" and one not modified by "about." It should also be understood that each endpoint of a range is significant both in relation to and independent of another endpoint.

[0039] As used herein, the terms “substantially,” “basically,” and variations thereof are intended to indicate that the described feature is equal to or approximately equal to a value or description. For example, a “substantially planar” surface is intended to mean a planar or approximately planar surface. Furthermore, “substantially” is intended to mean that two values ​​are equal or approximately equal. In some embodiments, “substantially” may mean that the values ​​are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0040] Unless explicitly indicated otherwise, as used herein, the terms “the,” “an,” or “a” mean “at least one” and should not be limited to “only one.” Thus, for example, unless the context clearly indicates otherwise, references to “component” include embodiments having two or more such components.

[0041] refer to Figure 1 The diagram illustrates a vehicle 1. Vehicle 1 can be a manually operated vehicle, a fully autonomous vehicle, or a partially autonomous vehicle. Vehicle 1 can be powered by an internal combustion engine, a fully electric engine, or a hybrid engine utilizing both internal combustion and electricity. Vehicle 1 has an interior 2, which includes a passenger compartment 4 and a cargo compartment 5. A vehicle climate control system 10 is provided to vehicle 1 to regulate the air supplied to the vehicle's interior 2. The vehicle climate control system 10 can raise the temperature of the air supplied to the vehicle's interior 2, lower the temperature of the air supplied to the vehicle's interior 2, increase the amount of water vapor in the air supplied to the vehicle's interior 2, and decrease the amount of water vapor in the air supplied to the vehicle's interior 2.

[0042] Now for reference Figure 2A schematic diagram of a vehicle climate control system 10 is shown. The vehicle climate control system 10 may consist of an air conditioner 12, an air chamber 14, multiple air ducts 16, and multiple ventilator dampers 18. The air conditioner 12 is configured to transfer heat to air outside the vehicle 3. The air conditioner 12 may consist of a condenser 20 and an evaporator 22 interconnected by a refrigerant line 24. The condenser 20 may be positioned such that it is in thermal communication with air outside the vehicle 3. The evaporator 22 may be positioned such that it is in thermal communication with air inside the interior 2 of the vehicle 1. Both the condenser 20 and the evaporator 22 may consist of multiple channels 23, which provide surface areas to efficiently transfer heat out of the condenser 20 and into the evaporator 22. The condenser 20, the evaporator 22, and the refrigerant line 24 form a refrigerant loop through which the refrigerant circulates. The refrigerant is configured to undergo a phase change as it circulates through the refrigerant loop. Compressor 26 can be inserted into refrigerant line 24 to increase the pressure applied to the refrigerant and push the refrigerant along the refrigerant circuit. Expansion valve 28 can be inserted into refrigerant line 24 to reduce the pressure applied to the refrigerant.

[0043] When cooling the interior 2 of the vehicle, refrigerant flows through refrigerant line 24 and enters compressor 26, where it is compressed to a pressurized state, resulting in a higher temperature. The pressurized refrigerant then enters condenser 20, where it transfers heat across the surface areas of multiple channels 23 provided by condenser 20. Heat is then transferred from the pressurized refrigerant to the air surrounding condenser 20, causing the temperature of the air around condenser 20 to rise. The refrigerant then leaves condenser 20 and re-enters refrigerant line 24, continuing to expansion valve 28. Expansion valve 28 rapidly depressurizes the refrigerant, causing at least a portion of the refrigerant to undergo an evaporative phase change. Rapid depressurization and subsequent evaporation cause the refrigerant temperature to decrease. In the depressurized state, the refrigerant then enters evaporator 22, where the depressurized refrigerant absorbs heat across the surface areas of multiple channels 23 provided by evaporator 22. Heat is transferred from the air surrounding evaporator 22 to the refrigerant, causing the temperature of the air around evaporator 22 to decrease. Then, the refrigerant leaves the evaporator 22 and enters the refrigerant line 24, where it re-enters the compressor 26 to repeat the heat transfer cycle.

[0044] Still referencing Figure 2An air chamber 14, multiple air ducts 16, and multiple vent air regulators 18 are provided to supply cooled air, which has exchanged heat with the evaporator 22, to the interior 2 of the vehicle. The air chamber 14 is configured to receive air cooled by the air conditioner 12 for distribution to the remainder of the vehicle climate control system 10. Multiple air ducts 16 extend from the air chamber 14 through the interior structure 6 of the vehicle to each of the multiple vent air regulators 18. The multiple vent air regulators 18 are configured to then exhaust the cooled air into the interior 2 of the vehicle. Each of the multiple vent air regulators 18 may be equipped with a user-operable airflow control device 17 configured to allow a user within the interior 2 of the vehicle to adjust the flow rate of the cooled air exiting each of the multiple vent air regulators 18.

[0045] Now for reference Figure 3 The climate control system 10 also includes a user interface 19 that allows a user of vehicle 1 to control the climate control system 10. The user interface 19 is configured to receive input from the user of vehicle 1. Specifically, the user interface 19 may be configured to allow the user to determine, at least indirectly, the duct exhaust temperature (DAT) target of the climate control system 10. The DAT target is a calculated temperature of the air supplied to the vehicle interior 2 by the multiple vent air regulators 18, as determined by the climate control system processor 46, to achieve a user-set temperature setpoint for the vehicle interior 2. The user interface 19 may consist of a multifunction display or a human-machine interface.

[0046] Still referencing Figure 3 Multiple sensors 30 are provided to monitor multiple sensed attributes characterizing the vehicle climate control system 10. These sensed attributes may include the temperature of the air outside the vehicle 3; the temperature of the evaporator 22; the temperature of the air exhausted from one or more of the multiple vent air conditioners 18; the water vapor content of the air inside the vehicle's interior 2; and the amount of particulate matter inside the vehicle's interior 2. The multiple sensors 30 may include an ambient air temperature sensor 31; an evaporator core temperature sensor 32; a duct exhaust temperature (DAT) sensor 33; an interior humidity sensor 34; and an interior particulate matter (PM) sensor 35.

[0047] An ambient air temperature sensor 31 is configured to detect the temperature of the air outside the vehicle 3. The ambient air temperature sensor 31 may be located inside the exterior grille of the vehicle, or may be connected, for example, to one of the side mirrors of the vehicle.

[0048] An evaporator temperature sensor 32 is configured to detect the temperature of the evaporator 22. The evaporator temperature sensor 32 may be positioned near the evaporator 22 and may include a thermistor configured to change its resistance as the temperature of the thermistor is modified. Alternatively, multiple evaporator temperature sensors 32 may be present at specific locations within the evaporator 22 to monitor the temperature of different portions of the evaporator 22.

[0049] The DAT sensor 33 is configured to detect the temperature of the air supplied to the vehicle interior 2 through a plurality of air ducts 16. Multiple DAT sensors 33 may be present, each of which is located at each of a plurality of vent air regulators 18 to monitor the temperature of the air supplied by each of the plurality of vent air regulators 18. Alternatively, multiple DAT sensors 33 may be present, with more than one DAT sensor 33 located at a single vent air regulator among the plurality of vent air regulators 18 to monitor the temperature of the air supplied by that single vent air regulator among the plurality of vent air regulators 18.

[0050] An internal humidity sensor 34 is configured to detect the amount of water vapor present in the air contained within the vehicle's interior 2. Multiple internal humidity sensors 34 may be present to monitor the amount of water vapor present in the air contained within the vehicle's interior 2 at different locations within the vehicle's interior 2. The humidity sensor 34 may consist of, for example, a capacitive sensor configured to monitor changes in voltage between two electrodes.

[0051] An internal particulate matter sensor 35 is configured to detect the amount of particulate matter suspended in the air contained within the interior 2 of the vehicle. Multiple internal particulate matter sensors 35 may be present to monitor the amount of particulate matter suspended in the air contained within the interior 2 of the vehicle at different locations. The internal particulate matter sensor 35 may utilize optical sensing to detect the amount of particulate matter, or it may be configured to utilize resistance measurement to detect particulate matter deposited on the electrode structure of the internal particulate matter sensor 35.

[0052] Now for reference Figure 4The vehicle climate control system 10 may further include a controller 40 configured to control the operation of the climate control system 10. The controller 40 communicates electronically with each of a plurality of sensors 30, such that the controller 40 receives inputs from each of the plurality of sensors 30 corresponding to a plurality of sensed attributes characterizing the climate control system 10. Next, the controller 40 communicates electronically with the air conditioning unit 12 and is configured to modify the operation of the air conditioning unit 12. Additionally, the controller 40 communicates electronically with a user interface 19, such that the controller 40 receives commands generated by the user interface 19 in response to user input to the user interface 19. Specifically, the controller 40 is configured to receive the temperature setpoint of the vehicle's interior 2 from the user interface 19 and calculate the DAT target.

[0053] Still referencing Figure 4 The controller 40 includes a timing module 42, a storage module 44, and a processor 46. The controller 40 may be a dedicated controller for HVAC control or a shared controller capable of performing additional control functions. The processor 46 may include, for example, a microprocessor, or may be configured with other analog and / or digital circuitry. The storage module 44 of the controller 40 is configured to store multiple calibration thresholds 50; multiple timer thresholds 60; calibration values ​​70; and policy history 80. The timing module 42 provides multiple timers 65. The processor 46 of the controller 40 is configured to monitor multiple sensors 30 and multiple timers 65. Additionally, the processor 46 of the controller 40 is configured to monitor the operating status of the compressor 26 and the DAT target set by the user through the user interface 19. Next, the processor 46 is configured to determine and execute anti-icing strategies 98, 99 by comparing inputs provided by the multiple sensors 30 with one or more of the multiple calibration thresholds 50. Additionally, processor 46 is configured to determine and execute anti-icing strategies 98 and 99 based on a comparison of the duration for which one or more of a plurality of timers 65 have been activated with one or more of a plurality of timer thresholds 60. Furthermore, processor 46 is configured to determine and execute anti-icing strategies 98 and 99 based on the operating state of compressor 26, strategy history 80, and DAT target. Anti-icing strategies 98 and 99 are predictive methods, wherein processor 46 is configured to predict and determine whether adjustments to air conditioner 12 are needed to prevent ice formation on evaporator 22. In operation, anti-icing strategies 98 and 99 modify air conditioner 12 through multiple adjustments made by processor 46 to prevent ice formation on evaporator 22 of air conditioner 12. Specifically, the multiple adjustments include: modifying the evaporator temperature target calibration value 70 to raise the temperature of evaporator 22; disabling compressor 26; and starting compressor 26.

[0054] Still referencing Figure 4The timing module 42 provides a plurality of timers 65, including a vehicle timer 66; a compressor deactivation timer 67; a compressor restart timer 68; and an exit timer 69. The processor 46 is configured to activate at least one of the plurality of timers 65 in response to the processor 46 adjusting the climate control system 10.

[0055] Figure 5 A storage module 44 is shown, which provides a plurality of calibration thresholds 50. Each of the plurality of calibration thresholds 50 is a predictive value representing one of a plurality of attributes. Specifically, each of the plurality of calibration thresholds 50 is a value of one of a plurality of attributes at which there is a statistical probability that icing will occur on the evaporator 22 if the value of the attribute being represented reaches a value greater than or less than one of the plurality of calibration thresholds 50 over a period of time. The plurality of calibration thresholds 50 can be used to partially define the operating conditions under which the air conditioner 12 can operate before icing is likely on the evaporator 22. Each of the plurality of calibration thresholds 50 is stored in the storage module 44 of the controller 40 and can be updated via an over-the-air download system. The processor 46 is configured to access each of the plurality of calibration thresholds 50 when determining and executing anti-icing strategies 98, 99. In operation, the processor 46 can be configured to adjust the climate control system 10 in response to the processor 46 detecting that at least one of the plurality of sensors 30 has provided an input greater than or less than or equal to one of the plurality of calibration thresholds 50. Additionally, the processor 46 can be configured to adjust the climate control system 10 in response to the processor 46 detecting that each of the plurality of sensors 30 has provided an input greater than, less than, or equal to one of a plurality of calibration thresholds 50. The plurality of calibration thresholds 50 may include a DAT entry condition threshold 51; a DAT compressor function threshold 52; a DAT exit condition threshold 53; an environmental condition threshold 54; an internal humidity threshold 55; and an internal particulate matter threshold 56.

[0056] The DAT entry threshold 51 is the statistical probability that icing will occur on the evaporator 22 if the air conditioner 12 continues to operate without adjustment. The DAT entry threshold 51 can represent the DAT close to the freezing point of water.

[0057] The DAT compressor function threshold 52 is the statistical probability that ice will form on the evaporator 22 if the air conditioner 12 continues to operate without adjustment, wherein the temperature of the DAT represented by the DAT compressor function threshold 52 is higher than the temperature of the DAT represented by the DAT entry condition threshold 51.

[0058] DAT outlet condition threshold 53 is the statistical probability that ice will form on the evaporator 22 if the air conditioner 12 continues to operate without adjustment, wherein the temperature of the DAT represented by DAT outlet condition threshold 53 is higher than the temperature of the DAT represented by DAT compressor function threshold 52.

[0059] The environmental threshold 54 is the temperature of the air outside the vehicle 3, at which there is a statistical probability that the evaporator 22 will freeze if the air conditioner 12 continues to operate without adjustment.

[0060] The internal humidity threshold of 55 is the amount of water vapor inside the vehicle's interior 2. Under this level of humidity, if the air conditioning 12 continues to operate without adjustment, there is a statistical possibility that ice will form on the evaporator 22.

[0061] The internal particulate matter threshold 56 is the amount of particulate matter suspended in the air inside the vehicle 2. At this level, if the air conditioning 12 continues to operate without adjustment, there is a statistical possibility that ice will form on the evaporator 22.

[0062] Still referencing Figure 5 The storage module 44 stores a calibration value 70. Calibration value 70 is the temperature value at which the processor 46 adjusts the evaporator target temperature to raise the temperature of the evaporator 22 during the execution of the anti-icing strategy 98. The evaporator target temperature is the temperature at which the evaporator 22 supplies air at a user-set temperature to the vehicle's interior 2 via a DAT target. Calibration value 70 can represent a minimum increase in the evaporator target temperature, which will result in preventing ice formation on the evaporator 22 or removing ice that has formed on the evaporator 22. This allows the evaporator target temperature to be adjusted with calibration value 70, thereby preventing icing on the evaporator 22 while still allowing the evaporator 22 to supply air to the vehicle's interior 2 at the user-desired temperature. Calibration value 70 can be loaded into the storage module 44 before the vehicle user uses the vehicle. Alternatively, calibration value 70 can be updated via an over-the-air download system.

[0063] Figure 5Additionally, a storage module 44 is shown, which provides a plurality of timer thresholds 60. Each of the plurality of timer thresholds 60 is a predictive duration associated with at least one of a plurality of timers 65. Specifically, each of the plurality of timer thresholds 60 is a duration for which there is a statistical probability that icing will occur on the evaporator 22 if the duration for which the associated timer among the plurality of timers 65 has been activated is greater than, less than, or equal to one of the plurality of timer thresholds 60. The processor 46 is configured to adjust the climate control system 10 in response to the processor 46 detecting that the duration for which at least one of the plurality of timers 65 has been activated is greater than, less than, or equal to one of the plurality of timer thresholds 60. The plurality of timer thresholds 60 may include a vehicle timer threshold 61; a compressor deactivation timer threshold 62; a compressor activation timer threshold 63; and an exit timer threshold 64.

[0064] The vehicle timer threshold 61 is associated with the vehicle timer 66 and is the length of time during which the statistical probability of icing on the evaporator 22 increases if the vehicle timer 66 has been activated for a period of time less than the vehicle timer threshold 61.

[0065] The compressor shutdown timer threshold 62 is associated with the strategy timer 67, and is the length of time during which the statistical probability of icing on the evaporator 22 increases if the strategy timer 67 has been activated for a duration greater than or equal to the compressor shutdown timer threshold 62.

[0066] The compressor restart timer threshold 63 is associated with the compressor restart timer 68 and is the statistically significant time duration for which icing on the evaporator 22 is likely to occur if the compressor restart timer 68 has been activated for a period less than the compressor restart timer threshold 63. Additionally, the compressor restart timer threshold 63 reflects the minimum amount of time that the compressor 26 must be deactivated to prevent icing on the evaporator 22. Therefore, the compressor restart timer threshold 63 can be calibrated such that the compressor 26 will be deactivated for the minimum amount of time required to prevent and / or remedy icing on the evaporator 22.

[0067] The exit timer threshold 64 is associated with the exit timer 69, and is the length of time during which the statistical probability of icing on the evaporator 22 increases if the exit timer 69 has been started for less than the exit timer threshold 64.

[0068] Now for reference Figure 6A and Figure 6BThis illustrates a first embodiment of an anti-icing strategy 98 determined and executed by the processor 46 of the controller 40. At step 100, the processor 46 monitors the DAT sensor temperature input and compares it with a DAT entry condition threshold 51. If the processor 46 receives an input from the DAT temperature sensor 33 with a temperature less than or equal to the temperature provided by the DAT entry condition threshold 51, the processor 46 then proceeds to step 102 of the anti-icing strategy 98.

[0069] At step 102, processor 46 determines whether the DAT target has been set to a temperature less than or equal to the DAT target threshold, whether the ambient air temperature sensor 31 provides an input of a temperature greater than the ambient threshold 54, and whether compressor 26 is active. If the DAT target has been set to a temperature less than or equal to the DAT target threshold, the ambient air temperature sensor 31 provides an input of a temperature greater than the ambient threshold 54, and compressor 26 is active, then processor 46 proceeds to step 103.

[0070] At step 103, processor 46 initiates anti-icing strategy 98. Then, the processor proceeds to step 104.

[0071] At step 104, the processor starts the compressor shutdown timer 67 and begins monitoring the compressor shutdown timer 67. Then, the processor proceeds to step 105.

[0072] At step 105, processor 46 adjusts air conditioner 12 by increasing the target temperature of evaporator 22 by a calibration value 70, thereby raising the temperature of evaporator 22. Then, processor 46 proceeds to step 106.

[0073] At step 106, the processor 46 determines the length of time that the compressor deactivation timer 67 has been active and compares this length of time with the compressor deactivation timer threshold 62. If the length of time that the compressor deactivation timer 67 has been active is greater than or equal to the compressor deactivation timer threshold 62, the processor 46 proceeds to step 107 of the anti-icing strategy 98.

[0074] If, at step 106, the processor determines that the compressor stop timer 67 has been activated for a duration less than the compressor stop timer threshold 62, the processor will maintain the increased target temperature of the evaporator 22 at the calibration value 70 until the compressor stop timer 67 has been active for a duration greater than or equal to the compressor stop timer threshold 62.

[0075] At step 107, processor 46 compares the DAT sensor temperature input with the DAT compressor function threshold 52. If the DAT sensor temperature input is less than or equal to the DAT compressor function threshold 52, processor 46 then proceeds to step 108 of the anti-icing strategy 98.

[0076] If, at step 107, the processor determines that the DAT sensor temperature input is greater than the DAT compressor function threshold 52, then the processor 46 will proceed to step 112 of the anti-icing strategy 98.

[0077] At step 108, processor 46 starts compressor restart timer 68 and begins monitoring compressor restart timer 68. Then, processor 46 proceeds to step 109.

[0078] At step 109, processor 46 further adjusts air conditioner 12 by disabling compressor 26. Specifically, processor 46 sets the compressor request to the "off" state. Then, processor 46 proceeds to step 110 of anti-icing strategy 98.

[0079] At step 110, the processor 46 compares the DAT sensor temperature input with the DAT outlet condition threshold 53. If the DAT sensor temperature input is greater than or equal to the DAT outlet condition threshold 53, the processor 46 then proceeds to step 111 of the anti-icing strategy 98. Additionally, at step 110, the processor 46 determines the length of time the compressor restart timer 68 has been active and compares this length of time with the compressor restart timer threshold 63. If the length of time the compressor restart timer 68 has been active is greater than or equal to the restart timer threshold 63, the processor 46 proceeds to step 111 of the anti-icing strategy 98.

[0080] If, at step 110, the DAT sensor temperature input is less than the DAT outlet condition threshold 53, and if the compressor restart timer 68 has been inactive for a period of time greater than or equal to the compressor restart timer threshold 63, then the processor 46 will return to step 109 and keep the compressor request in the "off" state.

[0081] At step 111, processor 46 starts exit timer 69 and begins monitoring exit timer 69. Then, processor 46 proceeds to step 112 of anti-icing strategy 98.

[0082] At step 112, processor 46 adjusts compressor 26 by restarting it. Specifically, processor 46 sets the compressor request to the "on" state. Then, the processor proceeds to step 113 of the anti-icing strategy 98.

[0083] In step 113, the processor 46 determines the length of time that the exit timer 69 has been activated and compares this length with the exit timer threshold 64. Additionally, in step 113, the processor 46 compares the DAT sensor temperature input with the DAT entry condition threshold 51. If the length of time that the exit timer 69 has been activated is greater than the exit timer threshold 64 and the DAT sensor temperature input is greater than the DAT entry condition threshold 51, then the processor 46 proceeds to step 114 of the anti-icing strategy.

[0084] Alternatively, at step 113, the processor 46 determines the length of time that the exit timer 69 has been activated and compares this length of time with the exit timer threshold 64. Additionally, at step 113, the processor 46 compares the ambient air temperature sensor input with the ambient threshold 54. If the length of time that the exit timer 69 has been activated is greater than the exit timer threshold 64 and the ambient air temperature sensor input is less than or equal to the ambient threshold 54, then the processor 46 proceeds to step 114 of the anti-icing strategy.

[0085] In an alternative embodiment, at step 113, the processor 46 determines the length of time that the exit timer 69 has been activated and compares this length of time with the exit timer threshold 64. Additionally, at step 113, the processor 46 compares the DAT target with the DAT target threshold. If the length of time that the exit timer 69 has been activated is greater than the exit timer threshold 64 and the DAT target has been set to a temperature higher than the DAT target threshold, then the processor 46 proceeds to step 114 of the anti-icing strategy.

[0086] In an alternative embodiment, at step 113, processor 46 determines the length of time that exit timer 69 has been running and compares this length with exit timer threshold 64. Additionally, at step 113, processor 46 checks the compressor status. If the length of time exit timer 69 has been running is greater than exit timer threshold 64 and compressor 26 has been disabled by the user, then processor 46 proceeds to step 114 of the anti-icing strategy 98.

[0087] If, at step 113, the processor 46 determines that the time during which the exit timer 69 has not been started is greater than the exit timer threshold 64, or that the DAT sensor temperature input is not greater than the DAT entry condition threshold 51, the ambient air temperature sensor input is not less than the ambient threshold 54, the DAT target is not greater than the DAT temperature threshold, and the AC compressor request status is not "off", then the processor 46 will not proceed to step 114 and will maintain the compressor request status as "on" at step 112. The processor 46 will continue to monitor the exit timer 69 and each of the plurality of sensors 30 provided in step 113 until the prerequisites of step 113 are met.

[0088] At step 114, processor 46 is configured to provide policy history 80 to the controller's storage module 44, wherein policy history 80 indicates that processor 46 initiated anti-icing policy 98 at step 103. Storage module 44 is configured to store policy history 80 for at least one driving cycle of vehicle 1, wherein the at least one driving cycle includes vehicle 1 being deactivated, activated, and subsequently deactivated. Processor 46 then proceeds to step 116 of anti-icing policy 98.

[0089] At step 116, processor 46 exits anti-icing strategy 98. Specifically, processor 46 will stop adjusting the evaporator target temperature using the amount of calibration value 70.

[0090] Now for reference Figure 7A and Figure 7B This illustrates a second embodiment of the anti-icing strategy 99 determined and executed by the processor 46 of the controller 40. At step 101, vehicle 1 is started, and the processor 46 checks the storage module 44 to determine whether it contains a strategy history 80 provided by the processor 46 at the end of the anti-icing strategies 98 and 99 that occurred in the previous driving cycle. Additionally, the processor 46 determines the length of time that the vehicle timer 66 has been activated, where the vehicle timer 66 was activated by the processor 46 when vehicle 1 was last deactivated. If the storage module 44 contains the strategy history 80 and the length of time the vehicle timer 66 has been active is less than the vehicle timer threshold 61, then the processor 46 proceeds to step 103.

[0091] At step 103, processor 46 initiates anti-icing strategy 98. Then, the processor proceeds to step 104.

[0092] At step 104, the processor starts the compressor shutdown timer 67 and begins monitoring the compressor shutdown timer 67. Then, the processor proceeds to step 105.

[0093] At step 105, processor 46 adjusts air conditioner 12 by increasing the target temperature of evaporator 22 by a calibration value 70, thereby raising the temperature of evaporator 22. Then, processor 46 proceeds to step 106.

[0094] At step 106, the processor 46 determines the length of time that the compressor deactivation timer 67 has been active and compares this length of time with the compressor deactivation timer threshold 62. If the length of time that the compressor deactivation timer 67 has been active is greater than or equal to the compressor deactivation timer threshold 62, the processor 46 proceeds to step 107 of the anti-icing strategy 98.

[0095] If, at step 106, the processor determines that the compressor stop timer 67 has been activated for a duration less than the compressor stop timer threshold 62, then the processor maintains the increased target temperature of the evaporator 22 at the calibration value 70 at step 105 until the compressor stop timer 67 has been active for a duration greater than or equal to the compressor stop timer threshold 62.

[0096] At step 107, processor 46 compares the DAT sensor temperature input with the DAT compressor function threshold 52. If the DAT sensor temperature input is less than or equal to the DAT compressor function threshold 52, processor 46 then proceeds to step 108 of the anti-icing strategy 98.

[0097] If, at step 107, the processor determines that the DAT sensor temperature input is greater than the DAT compressor function threshold 52, then the processor 46 will proceed to step 112 of the anti-icing strategy 98.

[0098] At step 108, processor 46 starts compressor restart timer 68 and begins monitoring compressor restart timer 68. Then, processor 46 proceeds to step 109.

[0099] At step 109, processor 46 further adjusts air conditioner 12 by disabling compressor 26. Specifically, processor 46 sets the compressor request to the "off" state. Then, processor 46 proceeds to step 110 of anti-icing strategy 98.

[0100] At step 110, the processor 46 compares the DAT sensor temperature input with the DAT outlet condition threshold 53. If the DAT sensor temperature input is greater than or equal to the DAT outlet condition threshold 53, the processor 46 then proceeds to step 111 of the anti-icing strategy 98. Additionally, at step 110, the processor 46 determines the length of time the compressor restart timer 68 has been active and compares this length of time with the compressor restart timer threshold 63. If the length of time the compressor restart timer 68 has been active is greater than or equal to the restart timer threshold 63, the processor 46 proceeds to step 111 of the anti-icing strategy 98.

[0101] If, at step 110, the DAT sensor temperature input is less than the DAT outlet condition threshold 53, and if the compressor restart timer 68 has been inactive for a period of time greater than or equal to the compressor restart timer threshold 63, then the processor 46 will return to step 109 and keep the compressor request in the "off" state.

[0102] At step 111, processor 46 starts exit timer 69 and begins monitoring exit timer 69. Then, processor 46 proceeds to step 112 of anti-icing strategy 98.

[0103] At step 112, processor 46 adjusts compressor 26 by restarting it. Specifically, processor 46 sets the compressor request to the "on" state. Then, the processor proceeds to step 113 of the anti-icing strategy 98.

[0104] In step 113, the processor 46 determines the length of time that the exit timer 69 has been activated and compares this length with the exit timer threshold 64. Additionally, in step 113, the processor 46 compares the DAT sensor temperature input with the DAT entry condition threshold 51. If the length of time that the exit timer 69 has been activated is greater than the exit timer threshold 64 and the DAT sensor temperature input is greater than the DAT entry condition threshold 51, then the processor 46 proceeds to step 114 of the anti-icing strategy.

[0105] Alternatively, at step 113, the processor 46 determines the length of time that the exit timer 69 has been activated and compares this length of time with the exit timer threshold 64. Additionally, at step 113, the processor 46 compares the ambient air temperature sensor input with the ambient threshold 54. If the length of time that the exit timer 69 has been activated is greater than the exit timer threshold 64 and the ambient air temperature sensor input is less than or equal to the ambient threshold 54, then the processor 46 proceeds to step 114 of the anti-icing strategy.

[0106] In an alternative embodiment, at step 113, the processor 46 determines the length of time that the exit timer 69 has been activated and compares this length of time with the exit timer threshold 64. Additionally, at step 113, the processor 46 compares the DAT target with the DAT target threshold. If the length of time that the exit timer 69 has been activated is greater than the exit timer threshold 64 and the DAT target has been set to a temperature higher than the DAT target threshold, then the processor 46 proceeds to step 114 of the anti-icing strategy.

[0107] In an alternative embodiment, at step 113, processor 46 determines the length of time that exit timer 69 has been running and compares this length with exit timer threshold 64. Additionally, at step 113, processor 46 checks the compressor status. If the length of time exit timer 69 has been running is greater than exit timer threshold 64 and compressor 26 has been disabled by the user, then processor 46 proceeds to step 114 of the anti-icing strategy 98.

[0108] If, at step 113, the processor 46 determines that the time during which the exit timer 69 has not been started is greater than the exit timer threshold 64, or that the DAT sensor temperature input is not greater than the DAT entry condition threshold 51, the ambient air temperature sensor input is not less than the ambient threshold 54, the DAT target is not greater than the DAT temperature threshold, and the AC compressor request status is not "off", then the processor 46 will not proceed to step 114 and will maintain the compressor request status as "on" at step 112. The processor 46 will continue to monitor the exit timer 69 and each of the plurality of sensors 30 provided in step 113 until the prerequisites of step 113 are met.

[0109] At step 114, processor 46 is configured to provide policy history 80 to the controller's storage module 44, wherein policy history 80 indicates that processor 46 initiated anti-icing policy 98 at step 103. Storage module 44 is configured to store policy history 80 for at least one driving cycle of vehicle 1, wherein the at least one driving cycle includes vehicle 1 being deactivated, activated, and subsequently deactivated. Processor 46 then proceeds to step 116 of anti-icing policy 98.

[0110] At step 116, processor 46 exits anti-icing strategy 98. Specifically, processor 46 will stop adjusting the evaporator target temperature using the amount of calibration value 70.

[0111] The vehicle climate control system 10 advantageously implements an anti-icing strategy to predict and prevent icing of the evaporator 22 of the air conditioner 12 in the motor vehicle, thereby enhancing the performance of the air conditioner 12.

[0112] In an additional embodiment, anti-icing strategy 98 can be used in a vehicle climate control system 10 that includes a heat pump. Specifically, anti-icing strategy 98 can be utilized when the heat pump of the vehicle climate control system 10 is set to a cooling mode to provide cooling air to the vehicle interior 2. In this configuration, anti-icing strategy 98 will be used to prevent ice formation on the internal heat exchanger that serves as the evaporator 22.

[0113] It should be understood that changes and modifications may be made to the foregoing structures without departing from the concept of this disclosure, and it should also be understood that such concepts are intended to be covered by the following claims unless otherwise expressly stated in their language.

[0114] According to the present invention, a climate control system for a vehicle is provided, comprising: a compressor; an evaporator; a plurality of sensors; and a controller, the controller communicating with the plurality of sensors and including at least one timer, the controller being configured to execute an anti-icing strategy, the anti-icing strategy comprising the steps of: monitoring the plurality of sensors; determining the probability of ice formation on the evaporator; adjusting the climate control system based on the determined probability of ice formation; activating one or more of the at least one timer in response to the adjustment of the climate control system; and monitoring the at least one timer and controlling the climate control system based on the at least one timer.

[0115] According to an embodiment, at least one of the plurality of sensors includes a duct air temperature sensor.

[0116] According to an embodiment, at least one of the plurality of sensors includes an ambient air temperature sensor.

[0117] According to an embodiment, the controller determines the likelihood of ice formation on the evaporator by comparing a target duct exhaust temperature with a target duct exhaust temperature threshold.

[0118] According to an embodiment, the controller determines the likelihood of ice formation on the evaporator by comparing inputs provided to the controller by multiple sensors with multiple calibration thresholds.

[0119] According to an embodiment, the controller determines the likelihood of ice formation on the evaporator by comparing the duration for which at least one timer has been activated with multiple timer thresholds.

[0120] According to an embodiment, the controller adjusts the climate control system by adjusting the evaporator target temperature with a calibration value based on a determined probability of ice formation.

[0121] According to an embodiment, when each of the plurality of sensors detects an input that reaches a calibration threshold, the controller determines that there is a possibility of ice formation.

[0122] According to an embodiment, the controller adjusts the climate control system by disabling the compressor based on a determined probability of ice formation.

[0123] According to an embodiment, when one or more of the plurality of sensors detect an input that reaches a calibration threshold and when at least one timer has been activated for a time exceeding a timer threshold, the controller determines that there is a possibility of ice formation.

[0124] According to an embodiment, the controller adjusts the climate control system by restarting the compressor based on a determined probability of ice formation, wherein when one or more of the plurality of sensors detect an input that reaches a calibration threshold, the controller determines that there is no probability of ice formation, wherein the calibration threshold is a duct air temperature outlet condition threshold.

[0125] According to an embodiment, the controller adjusts the climate control system by restarting the compressor based on a determined probability of ice formation, wherein the controller determines that there is no probability of ice formation when the at least one timer has been started for a time equal to or exceeding a timer threshold, wherein the timer threshold is a compressor restart timer threshold.

[0126] According to an embodiment, when each of the plurality of sensors detects an input that reaches a calibration threshold and the compressor is active, the controller determines that there is a possibility of ice formation.

[0127] According to the present invention, a method for controlling a vehicle climate control system includes: activating a compressor of the vehicle climate control system; sensing an ambient air temperature using a first temperature sensor; sensing an air duct temperature using a second temperature sensor; monitoring the sensed ambient air temperature and the air duct temperature using a controller; determining the likelihood of ice formation on the evaporator; adjusting the vehicle climate control system using the controller based on the determined likelihood of ice formation; activating at least one timer in response to the adjustment of the vehicle climate control system using the controller; and controlling the vehicle climate control system at least in part based on the at least one timer.

[0128] In one aspect of the invention, the second temperature sensor includes a duct air temperature sensor.

[0129] In one aspect of the invention, the controller determines the likelihood of ice formation on the evaporator by comparing a target duct exhaust temperature with a target duct exhaust temperature threshold.

[0130] In one aspect of the invention, the controller determines the likelihood of ice formation on the evaporator by comparing inputs provided to the controller by multiple sensors with multiple calibration thresholds.

[0131] In one aspect of the invention, the controller adjusts the climate control system by adjusting the evaporator target temperature of the evaporator with a calibration value based on a determined probability of ice formation.

[0132] In one aspect of the invention, the controller adjusts the vehicle climate control system by disabling the compressor based on a determined probability of ice formation, wherein the controller determines the probability of ice formation when one or more of the plurality of sensors detect an input that reaches a calibration threshold, and when the at least one timer has been activated for a time exceeding a timer threshold.

[0133] In one aspect of the invention, the controller adjusts the vehicle climate control system by restarting the compressor based on a determined probability of ice formation, wherein when the second sensor detects an input greater than a calibration threshold, the controller determines that there is no probability of ice formation, wherein the calibration threshold is a duct air temperature outlet condition threshold.

Claims

1. A climate control system for a vehicle, the climate control system comprising: compressor; Evaporator; Multiple sensors; as well as A controller, which communicates with the plurality of sensors and includes at least one timer, is configured to execute an anti-icing strategy, the anti-icing strategy comprising the following steps: Monitor the multiple sensors; Determine the likelihood of ice formation on the evaporator; The climate control system is adjusted based on the determined probability of ice formation. Activating one or more of the at least one timer in response to the adjustment of the climate control system; and The climate control system is monitored based on the at least one timer and controlled based on the at least one timer.

2. The climate control system for a vehicle as claimed in claim 1, wherein at least one of the plurality of sensors includes a duct air temperature sensor.

3. The climate control system for a vehicle as claimed in claim 1, wherein at least one of the plurality of sensors includes an ambient air temperature sensor.

4. The climate control system for a vehicle as claimed in claim 1, wherein the controller determines the likelihood of ice formation on the evaporator by comparing a target duct exhaust temperature with a target duct exhaust temperature threshold.

5. The climate control system for a vehicle as claimed in claim 1, wherein the controller determines the probability of ice formation on the evaporator by comparing inputs provided to the controller by the plurality of sensors with a plurality of calibration thresholds.

6. The climate control system for a vehicle as claimed in claim 1, wherein the controller determines the likelihood of ice formation on the evaporator by comparing the duration for which the at least one timer has been activated with a plurality of timer thresholds.

7. The climate control system for a vehicle as claimed in claim 1, wherein the controller adjusts the climate control system by adjusting the evaporator target temperature with a calibration value based on the determined probability of ice formation.

8. The climate control system for a vehicle as claimed in any one of claims 1 to 7, wherein the controller determines the possibility of ice formation when each of the plurality of sensors detects an input that reaches a calibration threshold.

9. The climate control system for a vehicle as claimed in claim 1, wherein the controller adjusts the climate control system by disabling the compressor based on the determined probability of ice formation.

10. The climate control system for a vehicle as claimed in claim 9, wherein the controller determines the possibility of ice formation when one or more of the plurality of sensors detect an input reaching a calibration threshold and when the at least one timer has been activated for a time exceeding a timer threshold.

11. The climate control system of the vehicle as claimed in claim 1, wherein the controller adjusts the climate control system by restarting the compressor based on the determined probability of ice formation, wherein when one or more of the plurality of sensors detects an input reaching the calibration threshold, the controller determines that there is no probability of ice formation, wherein the calibration threshold is a duct air temperature outlet condition threshold.

12. The climate control system of the vehicle as claimed in claim 11, wherein the controller adjusts the climate control system by restarting the compressor based on the determined probability of ice formation, wherein the controller determines that there is no probability of ice formation when the at least one timer has been started for a time equal to or exceeding the timer threshold, wherein the timer threshold is a compressor restart timer threshold.

13. The climate control system for a vehicle as claimed in claim 1, wherein the controller determines the possibility of ice formation when each of the plurality of sensors detects an input that reaches a calibration threshold and the compressor is active.

14. A method for controlling a vehicle climate control system, the method comprising the following steps: Start the compressor of the vehicle's climate control system; The ambient air temperature is sensed using a first temperature sensor; The air temperature in the duct is sensed using a second temperature sensor. The controller monitors the sensed ambient air temperature and the air temperature in the air duct. Determine the likelihood of ice formation on the evaporator; The controller adjusts the vehicle climate control system based on the determined probability of ice formation. At least one timer is activated in response to the adjustment of the vehicle climate control system by the controller; as well as The vehicle climate control system is controlled at least in part based on the at least one timer.

15. The method for controlling a vehicle climate control system as claimed in claim 14, wherein the controller determines the likelihood of ice formation on the evaporator by comparing a target duct exhaust temperature with a target duct exhaust temperature threshold.

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