Control system of air handling system of vehicle, and control method of air handling system of vehicle

Abstract

In this control system of an air handling system of a vehicle, the air handling system controls the supply of fresh air and recirculation air to a cabin of the vehicle. The control system is provided with one or more controllers. The one or more controllers receive a signal indicating the number of occupants in the cabin, determine a maximum period for operating the air handling system in an air recirculation mode, on the basis of the number of occupants, and output one or more control signals for terminating the air recirculation mode to the air handling system, when the maximum period has elapsed from the start of the air recirculation mode.

Description

Control system for a vehicle air handling system and control method for a vehicle air handling system

[0001] The present invention relates to a control system for a vehicle air handling system and a control method for a vehicle air handling system.

[0002] Air handling systems have been developed to control the supply of fresh and recirculated air to a vehicle cabin. Such systems can operate in an air recirculation mode, which may shut off or reduce the supply of fresh air and recirculate air from the vehicle cabin. The recirculated air heats or cools the vehicle cabin while minimizing the energy consumption of the air handling system.

[0003] However, when the fresh air supply is reduced or cut off, oxygen levels in the cabin decrease, and as occupants breathe, the oxygen is replaced with carbon dioxide. As a result, high levels of carbon dioxide can accumulate in the vehicle cabin, which can induce drowsiness and reduce responsiveness among vehicle occupants. To mitigate the risk of carbon dioxide accumulation in the vehicle cabin, air handling systems have been proposed that provide real-time air quality control using complex arrangements of air quality sensors located both inside and outside the vehicle cabin. However, such air handling systems are expensive, add complexity to the vehicle, and require additional sensors, complex control modules, harnesses, etc. for the system to function.

[0004] SUMMARY OF THE INVENTION It is an object of the present invention to provide a simpler and less expensive control system for a vehicle air handling system.

[0005] In one aspect of the present invention, there is provided a control system for a vehicle air handling system, the air handling system controlling the supply of fresh air and recirculated air to a cabin of the vehicle, the control system including one or more controllers configured to receive a signal indicative of a number of occupants in the cabin, determine a maximum time period for operating the air handling system in an air recirculation mode based on the number of occupants, and output one or more control signals to the air handling system to terminate the air recirculation mode after the maximum time period has elapsed since initiation of the air recirculation mode.

[0006] According to the above configuration, it is possible to provide a simpler and less expensive control system for a vehicle air handling system.

[0007] Figure 1 is a schematic diagram of a plan view of a vehicle with an overlay of an exemplary system according to an embodiment. Figure 2A is a schematic diagram of the air handling system of the exemplary vehicle according to Figure 1 operating in fresh air mode. Figure 2B is a schematic diagram of the air handling system shown in Figure 2A operating in air recirculation mode. Figure 3 is a schematic diagram of the controller and control system of the exemplary system according to Figure 1. Figure 4 is an exemplary graph having first and second curves plotting the increase in carbon dioxide (CO2) concentration in the cabin of the vehicle shown in Figure 1 for each number of occupants from the start of air recirculation mode. Figure 5 schematically illustrates an exemplary method of operating a system according to an embodiment.

[0008] SUMMARY OF THE INVENTION Embodiments of the present invention relate to control systems and methods for controlling the supply of fresh and recirculated air to a vehicle cabin, such as the cabin of an automobile.

[0009] The supply of fresh air and recirculated air to the cabin may include one or more flaps, valves, or other airflow control elements operable to control the supply of each of the fresh air and recirculated air to the vehicle cabin, which are controlled by an air handling system. For example, the air handling system may include an air duct arrangement, such as first and second air ducts, for supplying each of the fresh air and recirculated air to the vehicle cabin, and one or more flaps may be controllable to open and close outlets from such air ducts to the vehicle cabin.

[0010] Thus, fresh air may be supplied to the cabin by directing an airflow from an inlet in an air duct that communicates with the outside air, and then the air within the cabin may be sucked in from another inlet that communicates with the cabin and recirculated through the air handling system.

[0011] In embodiments, the air handling system is operable in at least two operating modes, including a fresh air operating mode and an air recirculation mode. In the fresh air mode, the proportion of fresh air supplied to the cabin is greater than the proportion of recirculated air supplied to the vehicle cabin, such that the recirculated air is not detrimental to the air quality within the cabin. In some embodiments, the supply of recirculated air to the vehicle cabin may be completely or substantially shut off or stopped in the fresh air mode. In contrast, in the air recirculation mode, the proportion of recirculated air supplied to the cabin is greater than the proportion of fresh air supplied to the cabin, and therefore, the air quality within the cabin may deteriorate over time. For example, in the air recirculation mode, the supply of fresh air may be completely or substantially shut off or stopped, which may increase carbon dioxide (CO2) concentrations within the cabin. In either case, the air handling system may be controlled to supply fresh air and recirculated air to the cabin in respective proportions in each of the fresh air and recirculated air operating modes.

[0012] Preferably, to maximize utilization of recycled air while maintaining air quality standards, the control system is configured to determine a maximum period of time for operating the air handling system in air recirculation mode based on an indicated number of occupants in the vehicle cabin. The maximum period is estimated as the time it takes for one or more air quality parameters to reach a predetermined threshold, and the control system outputs one or more control signals to terminate the air recirculation mode once the maximum period has elapsed from its initiation. In this regard, the inventors have found through testing that one or more air quality parameters (e.g., carbon dioxide levels) in the vehicle cabin can be accurately estimated based on the number of occupants in the cabin and the time spent in air recirculation mode during operation.

[0013] Thus, the control system is configured to receive a signal indicative of the number of occupants in the cabin, for example, from the vehicle's occupant detection system or by input via the vehicle's human-machine interface, and the control system is configured to determine a maximum time period for operating the air handling system in air recirculation mode based on the indicated number of occupants. Once the maximum time period has elapsed, the control system outputs a control signal to the air handling system to terminate the air recirculation mode, for example, by switching to a fresh air operating mode.

[0014] Thus, it is contemplated that the methods and systems of the present invention provide energy-efficient air handling and cabin heating and cooling without the deleterious effects, such as occupant drowsiness, typically associated with air recirculation modes.

[0015] The embodiment will now be described in more detail with reference to FIGS.

[0016] 1 shows a plan view of a vehicle 100 with a schematic overlay of a system 102 according to an embodiment. In this embodiment, the vehicle 100 takes the form of a passenger car having a cabin 106 configured for five passengers. Accordingly, the cabin 106 includes first, second, third, fourth, and fifth seats 105a-e provided for each occupant.

[0017] This embodiment is not intended to limit the scope of the present invention, and in other embodiments, vehicle 100 may take various other forms, such as a bus, truck, or train, among other passenger vehicles. Accordingly, the passenger capacity of cabin 106 may vary in other examples. Accordingly, the five-seat cabin configuration shown in FIG. 1 is not intended to limit the scope of the present invention. For example, while exemplary vehicle 100 in FIG. 1 is shown with a five-seat cabin configuration, in other embodiments, vehicle 100 may take the form of a larger passenger vehicle, such as a bus, having a twenty-seat cabin configuration. In the following description, cabin is intended to mean the passenger compartment of a vehicle, and in each case, occupants may be provided with respective seats or designated areas within the cabin.

[0018] The equipment of system 102 includes an air handling system 108 , an occupant detection system 110 , and a control system 112 configured to control air handling system 108 based on the number of occupants in cabin 106 .

[0019] The air handling system 108 is configured to control the airflow into the cabin 106. In particular, the air handling system 108 is configured to control the respective supply of fresh air and recirculated air to the cabin 106. To this end, the air handling system may include one or more airflow control elements for controlling or setting the proportion of fresh air and recirculated air for supplying the cabin 106. As will be appreciated by those skilled in the art, such airflow control elements may include, for example, one or more controllable flaps, fans, blowers, or valves.

[0020] This type of air handling system is well known in the art. By way of example, Figures 2A and 2B show simplified schematic diagrams of an exemplary air handling system 108 according to an embodiment of the present invention.

[0021] 2A and 2B , the air handling system 108 includes a first air duct 126 for supplying fresh air 120 and a second air duct 128 for supplying recirculated air 122 to the cabin 106. The first and second air ducts 126, 128 meet at a junction 130 in this embodiment, and the air handling system 108 includes an airflow control element 124 in the form of a controllable flap. The controllable flap 124 is operable to control the proportion of fresh air 120 and recirculated air 122 supplied to a downstream third air duct 132 that extends from the junction 130 to supply air to the cabin 106. Thus, in use, the flap 124 may be operated to block or close the supply of either the fresh air 120 or the recirculated air 122 from the first and second air ducts 126, 128. In other embodiments, the supply of fresh air 120 and recirculated air 122 to the cabin 106 may be controlled by one or more additional airflow control elements 124 of the air handling system 108. However, for simplicity, in the following embodiments, the flaps 124 are operated to control the supply of fresh air 120 and recirculated air 122 to the cabin 106.

[0022] 2A and 2B, the first air duct 126 extends from one or more inlets that communicate with air outside the cabin 106 and supply air to the junction 130. The second air duct 128 extends from one or more inlets (not shown) that communicate with air inside the cabin 106 and return cabin air to the junction 130. For example, the second air duct 128 may include a set of inlets distributed around the periphery of the cabin 106, from which air is drawn into the second air duct 128, for example, by a fan.

[0023] The third air duct 132 extends from the junction 130 and may include a series of pipes or channels through which air may flow to different outlets located around the cabin 106 to achieve a distributed supply of the output air 134 around the cabin 106.

[0024] Accordingly, third air duct 132 may include one or more air handling devices 136 (shown schematically in FIGS. 2A and 2B ) for preparing output air 134 for supplying cabin 106. For example, such air handling device(s) may include one or more filters, heat exchangers, or fans disposed within third air duct 132 or within each connected air handling unit. For example, fresh air 120 may be passed through filters to prevent particulates, such as dust, soot, or pollen, from entering cabin 106 from outside, while recirculated air 122 may be passed through one or more filters to capture dust or particulates already present in cabin 106. The filtered air may then be heated or cooled by a heat exchanger in air handling system 108 to provide the desired air supply temperature, or may be pressurized by a fan or blower for supplying air to cabin 106. In other embodiments, the air handling system 108 may additionally or alternatively include one or more filters, heat exchangers, or fans disposed in the first and second air ducts 126, 128 to treat the respective air supplies upstream of the junction 130.

[0025] Additionally, air handling system 108 may have a different layout from vehicle to vehicle, and FIG. 2 depicts only a simplified, schematic version of air handling system 108. Thus, in either case, in addition to controlling the respective supplies of fresh air 120 and recirculated air 122 to cabin 106, air handling system 108 may vary the airflow into cabin 106, selectively distribute air within cabin 106, and / or modify the temperature of supplied output air 134 by either heating or cooling. As noted above, to this end, air handling system 108 may include one or more fans or blowers for controlling the volume fraction of air delivered to cabin 106, heat exchangers for adding or removing thermal energy from the air before it enters cabin 106, ducts for distributing air to selected locations within cabin 106, and flaps and / or valves for selectively distributing air through the ducts.

[0026] The air handling system 108 is operable in at least two operating modes, including a fresh air operating mode and a recirculated air operating mode. In the fresh air mode, the proportion of fresh air 120 supplied to the cabin 106 is greater than the proportion of recirculated air 122 supplied to the cabin 106. For example, the flap 124 may be operated in the fresh air operating mode to close the second air duct 128, thereby blocking or stopping the supply of recirculated air 122 to the cabin 106.

[0027] In particular, FIG. 2A shows air handling system 108 operating in a fresh air operating mode with flap 124 moved to a first position to close second air duct 128 and provide fresh air 120 to cabin 106 via third air duct 132.

[0028] In contrast, in the air recirculation mode, the proportion of recirculated air 122 supplied to the cabin 106 is greater than the proportion of fresh air 120 supplied to the cabin 106. For example, the supply of fresh air 120 may be stopped or shut off in the air recirculation mode by operating the flap 124 to close the first air duct 126 and open the second air duct 128.

[0029] 2B is shown operating in an air recirculation mode by moving the flap 124 to a second position to open the second air duct 128 and close the first air duct 126. Thus, air within the cabin 106 is drawn into one or more air inlets of the second air duct 128 and passes through the second and third air ducts 128, 132 for re-airing the cabin 106. The recirculated air 122 may be reheated or cooled within the third air duct 132 to control the air temperature within the cabin 106 in an energy-efficient manner.

[0030] This embodiment is not intended to limit the scope of the invention, and in other embodiments, air handling system 108 may not generate a binary output, i.e., providing either a fresh air or recirculated air supply. Instead, one or more airflow control elements 124, such as flaps, may be controlled to provide a greater ratio of fresh air to recirculated air in a fresh air operating mode, and a greater ratio of recirculated air to fresh air in an air recirculation mode, each having a mixture of recycled air and fresh air.

[0031] Returning to FIG. 1, system 102 further includes an occupant detection system 110 for determining the number of occupants in cabin 106, which may be used, among other things, to control air handling system 108 in air recirculation mode.

[0032] The occupant detection system 110 may take various suitable forms known in the art for this purpose. In an embodiment, the occupant detection system 110 may include a set of seat pressure sensors 140a-e. Each seat pressure sensor 140a-e may be disposed in a respective seat 105a-e in the cabin 106 and configured to generate a signal indicative of occupancy of that seat 105a-e. Additionally or alternatively, the occupant detection system 110 may include one or more seat belt sensors, such as a seat belt engagement sensor, configured to generate a signal indicative of the use of each seat belt. The use of seat belts in a vehicle is very often a legal requirement and, therefore, may be used to determine the number of occupants in the cabin 106.

[0033] However, occupant detection system 110 is not intended to be limited to the use of sensors to determine the number of occupants in cabin 106. In other embodiments, the number of occupants may additionally or alternatively be determined via user input. For example, occupant detection system 110 may additionally or alternatively include a human-machine interface including one or more buttons, dials, a touchscreen, or an interactive display through which a user may manually input, select, or adjust the number of occupants in cabin 106.

[0034] In each case, control system 112 is configured to receive a signal from occupant detection system 110 indicative of the number of occupants in cabin 106. Based on this information, control system 112 is configured to determine a maximum period of time for operating air handling system 108 in air recirculation mode, as will be further described in detail below with reference to FIG.

[0035] FIG. 3 illustrates a schematic diagram of an exemplary control system 112 according to an embodiment.

[0036] As shown in FIG. 3, control system 112 includes one or more controllers or modules for controlling air handling system 108 based on the indicated number of occupants.

[0037] In this embodiment, control system 112 is shown to include an input module 202, a processor module 204, a memory module 206, and an output module 208. That is, in the illustrated embodiment, four functional elements, units, or modules are shown. Each of these units or modules may be provided, at least in part, by suitable software executing on any suitable computing board using conventional or custom processors and memory. Some or all of the units or modules may use a common computing board (e.g., may run on the same server) or separate boards, or different combinations of modules may be distributed among multiple computing devices. The exemplary architecture of control system 112 is not intended to limit the scope of the invention, and in other embodiments, the architecture may take other suitable forms.

[0038] The input module 202 is electrically connected to the occupant detection system 110 and is configured to receive signals from the occupant detection system 110 indicative of the number of occupants within the cabin 106 .

[0039] The processor module 204 is configured to determine a maximum time period for operating the air handling system 108 in air recirculation mode based on the indicated number of occupants. In this context, the maximum time period is determined as the maximum length of time during which one or more air quality parameters can be maintained within a desired operating range while operating the air handling system 108 in air recirculation mode, i.e., the time it takes for the air quality parameters to reach a threshold level. For example, the maximum time period may be determined as the maximum length of time that a CO2 concentration level remains below a respective CO2 concentration threshold. The CO2 concentration threshold may be set at a respective level to avoid inducing one or more adverse effects, such as drowsiness, in the occupants.

[0040] To this end, the processor module 204 may access one or more look-up tables containing data indicating the time it takes from the start of the air recirculation mode for an air quality parameter within the cabin 106 to reach a threshold value according to the number of vehicle occupants.

[0041] In an embodiment, the maximum duration may be a predetermined value in a look-up table for each vehicle occupancy.

[0042] In other embodiments, one or more lookup tables may include values ​​of an air quality parameter, such as a CO2 concentration level, as a function of time for each number of occupants in the cabin 106. For example, the lookup table may include or be derived from one or more curves or graphical plots, each curve representing the change in CO2 concentration level for each number of occupants in the cabin 106 from the start of the air recirculation mode.

[0043] The data in the one or more lookup tables may be preprogrammed into the processor module 204, for example, as predetermined by experimentation or predictive modeling. In this regard, the experimentation may take the form of physical testing, and thus the one or more lookup tables may store test data associated with the vehicle 100 for indicated vehicle occupancy counts. The test data may include actual measurements obtained from test versions of the vehicle 100 while monitoring air quality parameters during air recirculation mode with different vehicle occupancy counts. One example of such test data may be obtained from a test version of the vehicle 100 equipped with a sensing device configured to measure CO2 concentrations in the cabin 106 for each occupancy count while the air recirculation mode is enabled. Once the test data is obtained from a test vehicle, which may be substantially identical to the vehicle 100, the data may be more generally applicable to inform control of the air handling system 108 based solely on the number of occupants in the vehicle 100. Additionally or alternatively, predictive modeling may be used in computational studies, etc., conducted using known inputs, such as average CO2 emissions for an adult and a model of the cabin 106, including cabin 106 volumetric measurements. Because cabin volume is proportional to the amount of air available within the cabin 106, cabin volume is an important factor to consider when modeling air quality parameters, such as CO2 concentration.

[0044] An exemplary graph 300, which may be stored, reflected, or otherwise used to derive data in one or more lookup tables, is shown in FIG. 4. Graph 300 includes a first curve 302 and a second curve 304, each showing the increase in carbon dioxide (CO) concentration levels over time within cabin 106 for various numbers of occupants during air recirculation mode. In particular, in this embodiment, first curve 302 shows the increase in CO concentration levels over time when two occupants are present within cabin 106, and second curve 304 shows the increase in CO concentration levels over time when three occupants are present within cabin 106.

[0045] During breathing, or exhalation, oxygen (O2) is taken in by the body and CO2 is released. When a person is in a confined space where oxygen is not easily replenished by fresh air, the amount of available oxygen can decrease significantly and the amount of carbon dioxide present in the air of the space can increase. The same is true for the cabin of a vehicle with one or more occupants.

[0046] As can be seen from graph 300, the number of occupants present in cabin 106 has a significant effect on the rate of carbon dioxide increase. By way of example, graph 300 also illustrates different thresholds for carbon dioxide concentration, indicated on graph 300 by first region 306, second region 308, third region 310, and fourth region 312.

[0047] In this embodiment, the thresholds shown correspond to levels of carbon dioxide concentration that may affect the human body, as follows:

[0048] Zone 1 306: <400 ppm - normal concentration of carbon dioxide present in the fresh air 120; Zone 2 308: 1,000-2,000 ppm - concentrations associated with complaints of drowsiness; Zone 3 310: 2,000-5,000 ppm - concentrations associated with headaches, drowsiness, stale / stuffy / stuffy air; and Zone 4 312: >= 5,000 ppm or greater - concentrations considered by the Occupational Safety and Health Administration (OSHA) to be the Permissible Exposure Limit (PEL) for CO2 over an 8-hour period.

[0049] The processor module 204 may be configured to use the thresholds in such regions to determine a maximum duration for the air recirculation mode. For example, if the control system 112 is configured to maintain the CO2 concentration below one of the CO2 concentration thresholds described above, the processor module 204 may use that threshold to read or otherwise determine a respective maximum duration for operating in the air recirculation mode based on the indicated number of occupants.

[0050] Thus, the processor module 204 may be configured to use one or more look-up tables to determine the maximum duration of the air recirculation mode based on the indicated number of occupants.

[0051] Such a look-up table may be stored in the memory module 206 of the control system 112 and may be accessed by the processor module 204 to determine the maximum period of operation in the air recirculation mode.

[0052] In an embodiment, the processor module 204 may be configured to calculate the maximum duration using lookup table data. To this end, the processor module 204 may use a baseline reference level of the air quality parameter when the air recirculation mode is initiated, and the processor module 204 may include one or more data processing algorithms known in the art for determining the time required for the air quality parameter to reach a threshold value based on the indicated number of occupants and the data in the lookup table. In particular, the processor module 204 may include one or more algorithms for calculating the time required for the air quality parameter level to change from the baseline reference level to the threshold level. By way of example, the processor module 204 may be configured to determine the maximum duration of the air recirculation mode by assuming that the CO2 concentration level is equal to a baseline concentration of CO2 present in fresh air (e.g., equal to a predetermined normal CO2 concentration present in fresh air) when the air recirculation mode is initiated, and calculate the time required for the CO2 concentration level to increase to the threshold level based on the lookup table data. To maintain this assumption, control system 112 may be further configured to operate air handling system 108 in fresh air mode for a minimum period of time before initiating air recirculation mode. By way of example, the minimum period of time may be less than or equal to a determined maximum period of time for air recirculation mode.

[0053] Output module 208 of control system 112 is configured to output one or more control signals to air handling system 108 to terminate the air recirculation mode once a maximum period of time has elapsed since the initiation of the air recirculation mode.

[0054] As one example, input module 202 may receive a signal indicating the start time of the air recirculation mode, and output module 208 may output one or more control signals to air handling system 108 once a maximum time period has elapsed to terminate the air recirculation mode. Alternatively, control system 112 may be limited to setting the duration of the air recirculation mode, and thus control system 112 may be configured to output one or more control signals to a controller of air handling system 108 to set the maximum time period. The controller may record the start time when the air recirculation mode is initiated, and may then control air handling system 108 to terminate the air recirculation mode once the determined time period has elapsed.

[0055] In this manner, system 102 is configured to automatically shut off air recirculation mode after a maximum period of time to ensure that one or more air quality parameters, such as CO2 concentration, do not exceed acceptable limits or thresholds. Because most road-legal vehicles have existing occupant detection systems 110 in place to detect seat belt engagement, information captured by these existing sensors can be used for additional purposes to control air handling system 108 in embodiments of the present invention.

[0056] FIG. 5 illustrates an exemplary method 400 of operating system 102 to control the air recirculation mode of air handling system 108, according to an embodiment.

[0057] In an embodiment, the air recirculation mode may be initiated manually, for example, in response to a user command provided via interaction with the vehicle's human-machine interface. Alternatively or additionally, air handling system 108 may be configured to automatically initiate the air recirculation mode, for example, after vehicle start-up or after a period of time, such as a threshold period of operation in the fresh air operating mode.

[0058] In either case, the method 400 begins in step 402 with the occupant detection system 110 determining the number of occupants in the cabin 106 and transmitting a signal indicative of the number of occupants to the control system 112 .

[0059] As an example, the occupant detection system 110 may include a seat pressure sensor 140a-e for each of the first, second, third, fourth, and fifth seats 105a-e, respectively, shown in Figure 1. In step 402, the occupant detection system 110 may receive signals from the seat pressure sensors 140a-e indicating that the first, second, and third seats 105a-c are occupied and send corresponding signals to the control system 112 indicating the presence of three occupants in the cabin 106.

[0060] While it is important to know how many occupants are in the cabin 106 when the air recirculation mode is initiated, the occupant count may be determined in response to initiating the air recirculation mode or at any time before initiating the air recirculation mode. For example, the occupant detection system 110 may be triggered to determine the vehicle occupant count upon starting the vehicle 100, upon opening or closing a vehicle door, or upon detecting a seat belt engagement / release (or other change in vehicle occupancy). Thus, the determined occupant count may be stored in step 402, for example, in the memory module 206, and may be recalled when the recirculation mode is initiated.

[0061] In step 404, control system 112 receives a signal from occupant detection system 110 and determines a maximum period of time to operate air handling system 108 in air recirculation mode based on the indicated number of occupants.

[0062] Thus, control system 112 may process the signals received at input module 202 and use one or more look-up tables to determine the maximum duration of air recirculation mode based on the indicated number of occupants.

[0063] Continuing with the previous example, the processor module 204 may determine that there are three occupants in the cabin 106. Based on such information, the processor module 204 may be configured to apply one or more data processing algorithms to a second curve 304 (associated with the three occupants in the cabin 106) stored in one or more lookup tables. The data processing algorithms may be configured to retrieve or otherwise determine a maximum time to ensure that the CO2 concentration remains below a threshold level, which may be set at, for example, 1,000 ppm.

[0064] Thus, the processor module 204 may determine the time it takes for the CO2 concentration level to increase from the baseline level when the air recirculation mode is initiated to the threshold level according to the second curve 304. Thus, the processor module 204 may determine a maximum duration of the air recirculation mode of approximately 275 seconds or four and a half minutes using the second curve 304 shown in FIG.

[0065] Once the maximum time period has been determined, control system 112 outputs one or more control signals to air handling system 108 in step 404 to terminate the air recirculation mode once the maximum time period has elapsed.

[0066] In an embodiment, control system 112 may output the determined maximum time period to the respective controller of air handling system 108, which in turn monitors the duration of the air recirculation mode and terminates the air recirculation mode when the maximum time period has elapsed. Alternatively, control system 112 may be configured to perform step 402 and / or step 404 in response to initiation of the air recirculation mode, and thus, control system 112 may output one or more control signals in step 406 upon determining that the maximum time period has elapsed.

[0067] In this manner, control system 112 may use the determined maximum duration while operating air handling system 108 in air recirculation mode, or may determine a maximum duration prior to operating air handling system 108 in air recirculation mode for use following initiation of air recirculation mode.

[0068] To terminate the air recirculation mode, air handling system 108 may be configured to operate one or more airflow control elements 124 of air handling system 108 to switch to a fresh air operating mode. For example, air handling system 108 may operate flap 124 between the positions shown in Figures 2B and 2A to close second air duct 128, thereby cutting off the supply of recirculated air 122 while restoring the supply of fresh air 120 to cabin 106.

[0069] In this manner, the supply of fresh air 120 to the cabin 106 is increased so that a greater proportion of fresh air is supplied to the cabin 106 relative to recirculated air. In this manner, the fresh air replaces the recirculated air 122, improving cabin air quality so that, for example, CO2 concentration levels within the cabin 106 do not exceed respective thresholds. As a result, the control system 112 maximizes the energy-saving effects of the reused recirculated air 122 while avoiding inducing harmful effects of air recirculation, such as drowsiness.

[0070] Various modifications and improvements can be made to the above-described embodiments without departing from the scope of the present invention.

[0071] For example, the system 102 may be further configured to warn the user, e.g., via a human-machine interface of the vehicle 100, after the maximum period has elapsed and the air recirculation mode has ended, that there is a risk of elevated CO2 in the cabin 106 associated with further use of the air recirculation mode.

[0072] Furthermore, in the above-described embodiments, the maximum duration of the air recirculation mode is determined based on the assumption that the CO2 concentration level is equal to the baseline concentration of CO2 present in the fresh air when the air recirculation mode is initiated (e.g., equal to a predetermined normal CO2 concentration present in the fresh air).

[0073] In an embodiment, the system 102 may be configured to operate the air handling system 108 in a fresh air operating mode for a minimum period of time before or after the air recirculation mode to ensure that the air quality in the cabin 106 has been restored to a baseline level. When the recycle air supply is shut off in the fresh air mode, the baseline level is reached within a few seconds. However, the time required to reach the baseline level will depend on the ratio of fresh air to recirculated air provided in the fresh air operating mode, as well as, to some extent, the number of occupants in the cabin 106.

[0074] In an embodiment, control system 112 may be configured to determine a minimum period between operation of air handling system 108 in air recirculation mode in substantially the same manner, using respective test data regarding changes in air quality parameters over time during fresh air operation mode. Such test data may likewise be incorporated into one or more look-up tables stored in control system 112 and used to output one or more control signals to activate or enable the air recirculation mode.

[0075] In other embodiments, control system 112 may be configured to continuously or repeatedly model air quality parameters while operating based on the indicated number of occupants and the time spent in each operating mode using corresponding test data applicable to fresh air and air recirculation modes. Thus, control system 112 may be configured to model an increase in CO2 concentration within cabin 106 while operating in air recirculation mode and a subsequent decrease in CO2 concentration within cabin 106 while operating in fresh air operating mode. In this case, when determining the maximum duration of air recirculation mode, the baseline level may be updated based on the current estimate of the air quality parameter obtained from the model at the start of air recirculation mode.

[0076] In other embodiments, the control system 112 may receive a reference baseline CO2 concentration level within the cabin 106 when the air recirculation mode is initiated, and the control system 112 may determine the maximum period of time based on a calculation of the time it takes for the CO2 concentration level to increase from the reference baseline level to a threshold level using one or more lookup tables.

[0077] Additionally, although not specifically described, the maximum duration of the air recirculation mode is reset if the air recirculation mode is canceled or overridden in some other way, such as by opening a window to allow fresh air into the vehicle cabin.

[0078] (1) In a control system for an air handling system of a vehicle according to an embodiment, an air handling system 108 controls the supply of fresh air 120 and recirculated air 122 to a cabin 106 of a vehicle 100. A control system 112 includes one or more controllers that receive a signal indicating the number of occupants in the cabin 106, determine a maximum period for operating the air handling system 108 in an air recirculation mode based on the number of occupants, and output one or more control signals to the air handling system 108 to terminate the air recirculation mode when the maximum period has elapsed since the start of the air recirculation mode.

[0079] This configuration allows the air handling system 108 to indirectly control the air quality within the cabin 106 based on the occupancy level of the cabin 106. The control system 112 eliminates the need for complex and expensive air quality sensors and instead uses a correlation between cabin occupancy and changes in air quality over time to derive a maximum period for operating in air recirculation mode. This configuration therefore provides a simpler and less expensive control system 112 for the air handling system 108 of the vehicle 100. This maximum period is adjustable so that the control system intervenes as carbon dioxide levels increase and terminates recirculation mode when the air quality level is expected to reach a threshold level.

[0080] (2) Also, in embodiments, the one or more control signals may include a control signal for controlling air handling system 108 to switch air handling system 108 from an air recirculation mode to a fresh air operating mode, thereby improving the air quality within cabin 106 by introducing fresh air 120 into cabin 106 to dilute the recirculated air 122 within cabin 106 and exhausting the poorer quality air from cabin 106 to the atmosphere.

[0081] (3) Additionally, in embodiments, the air handling system 108 may shut off the supply of fresh air 120 to the cabin 106 during the air recirculation mode. Shutting off the supply of fresh air 120 to the cabin 106 during the air recirculation mode is beneficial when the temperature of the air outside the cabin 106 is significantly different from the air inside the cabin 106. This can improve the comfort of the occupants in the cabin 106 and minimize the energy requirements for conditioning the cabin 106. Additionally, if the fresh air 120 or outside air itself is polluted to the point that its entry into the cabin 106 adversely affects the air quality in the cabin 106, the air recirculation mode can help mitigate this problem.

[0082] (4) In embodiments, the one or more controllers may be configured to determine the maximum duration of the air recirculation mode using a lookup table containing data indicating the time it takes for an air quality parameter in the cabin 106 to reach a threshold value for each number of vehicle occupants after initiating the air recirculation mode. The lookup table may then be used to determine the maximum duration of the air recirculation mode based on cabin occupancy, thereby conveniently providing data necessary for operation of the control system 112. Empirical data may also be used to generate or derive each time threshold value for each number of occupants in the cabin 106 stored in the lookup table.

[0083] (5) Furthermore, in an embodiment, the air quality parameter may be the carbon dioxide level in the cabin 106 or the carbon dioxide concentration level in the cabin 106. The increase in the carbon dioxide concentration of the air in the cabin 106 over time is due to the breathing of the occupants and is therefore strongly correlated with the number of occupants in the cabin 106. Inhaling air containing excessive levels of carbon dioxide can cause headaches, drowsiness, decreased concentration, and the like. The above configuration can suppress and alleviate these symptoms.

[0084] (6) In embodiments, the data in the lookup table may also include test data associated with test versions of the vehicle 100, such as survey data regarding cabin air quality over time for a given cabin 106 based on its occupancy. The air quality within the cabin 106 based on cabin occupancy depends on the total amount of air contained within the cabin 106 and any passive air exchange that may occur. Therefore, results may vary from model to model, and it may be desirable to tailor the data in the lookup table for a given cabin 106.

[0085] (7) Additionally, in embodiments, the test data may include actual measurements obtained from a test version of the vehicle 100 while monitoring air quality parameters during air recirculation mode. Bench tests or simulations may produce inaccurate results due to idealized or oversimplified test conditions. Corroborating the test data with actual measurements ensures the accuracy of the data and enables the control system 112 to provide the desired results.

[0086] (8) In embodiments, the lookup table data may also include one or more graphs 300 plotting the change in air quality parameters over time for each vehicle occupancy count since the start of the air recirculation mode. Providing plots of air quality information over time for a given cabin occupancy to the control system 112 may enable enhanced control of the air recirculation system, such as blending fresh air 120 with recirculated air 122, as the air quality parameters approach selected thresholds.

[0087] (9) Additionally, in an embodiment, the air handling system 108 may have one or more airflow control elements 124 that are controlled to set the respective proportions of fresh air 120 and recirculated air 122 supplied to the cabin 106 when operating in an air recirculation mode.

[0088] (10) The one or more airflow control elements 124 may include a flap 124 disposed at the outlet of a first air duct 126 for supplying fresh air 120, and the flap 124 may be disposed at a junction 130 between the first air duct 126 and a second air duct 128 for supplying recirculated air 122. This configuration allows mixing of the recirculated air 122 with fresh air 120 from outside the cabin 106, providing the benefit, in part, of extending the effective recirculation of cabin air.

[0089] (11) Also, in embodiments, the control system 112 may be connected to an occupant detection system 110 of the vehicle 100, and the control system 112 may be configured to receive signals from the occupant detection system 110 indicative of the number of occupants in the vehicle 100. The occupant detection system 110 is widely adopted in modern vehicles 100 and may provide additional functionality to other control systems 112 of the vehicle 100. For example, the occupant detection system 110 may be used by a seat belt warning light system. Thus, the control system 112 may advantageously utilize existing vehicle sensors and may be operable without requiring additional sensors in the vehicle 100. This may enhance the value of the existing occupant detection system 110 and reduce the cost of the air handling system 108.

[0090] (12) Additionally, in embodiments, occupant detection system 110 may include one or more seat pressure sensors 140a-e or seat belt engagement sensors. Utilizing existing seat pressure sensors 140a-e, seat belt engagement sensors, or a combination of the two, provides a means for automatically detecting cabin occupancy in vehicle 100.

[0091] (13) In another embodiment, a vehicle system may include an air handling system 108 that controls the supply of fresh air 120 and recirculated air 122 to the cabin 106, and an occupant detection system 110 that detects the number of vehicle occupants inside the vehicle.

[0092] (14) Additionally, in another embodiment, the vehicle 100 may include any of the control systems 112 and vehicle systems described in the previous aspects of the present invention.

[0093] (15) In a control method for an air handling system of a vehicle according to an embodiment, the air handling system 108 controls the supply of fresh air 120 and recirculated air 122 to the cabin 106 of the vehicle 100. The control method receives a signal indicating the number of occupants in the cabin 106, determines a maximum period for operating the air handling system 108 in an air recirculation mode based on the number of occupants, and controls the air handling system 108 to terminate the air recirculation mode when the maximum period has elapsed since the start of the air recirculation mode. This method allows for simpler and less expensive control of the air handling system 108 of the vehicle 100.

[0094] The above-described embodiments are merely examples described to facilitate understanding of the invention. The technical scope of the invention is not limited to the specific technical matters disclosed in the above-described embodiments, but also includes various modifications, changes, alternative technologies, etc. that can be easily derived therefrom.

[0095] 100 Vehicle 106 Cabin 108 Air handling system 110 Occupant detection system 112 Control system 120 Fresh air 122 Recirculated air 124 Flap (airflow control element) 126 First air duct 128 Second air duct 130 Junction 140a-e Seat pressure sensor 300 Graph

Claims

1. A control system for an air handling system of a vehicle, said air handling system controlling the supply of fresh air and recirculated air to a cabin of the vehicle, said control system having one or more controllers, said one or more controllers receiving a signal indicative of a number of occupants in the cabin, determining a maximum time period for operating the air handling system in an air recirculation mode based on the number of occupants, and outputting one or more control signals to the air handling system to terminate the air recirculation mode after the maximum time period has elapsed since initiation of the air recirculation mode.

2. The control system of claim 1, wherein the one or more control signals include a control signal for controlling the air handling system to switch the air handling system from the air recirculation mode to a fresh air operating mode.

3. The control system of claim 1 or 2, wherein the air handling system blocks fresh air supply to the cabin during the air recirculation mode.

4. A control system as claimed in any one of claims 1 to 3, wherein the one or more controllers are configured to determine the maximum duration of the air recirculation mode using a look-up table containing data indicative of the time it takes from initiating the air recirculation mode until an air quality parameter within the cabin reaches a threshold value for each number of vehicle occupants.

5. A control system as claimed in claim 4, wherein the air quality parameter is a carbon dioxide level within the cabin or a carbon dioxide concentration level within the cabin.

6. A control system as claimed in claim 4 or 5, wherein the data in the look-up table includes test data relating to a test version of the vehicle.

7. The control system of claim 6, wherein said test data includes actual measurements obtained from said test version of said vehicle while monitoring said air quality parameters during said air recirculation mode.

8. A control system as claimed in any one of claims 4 to 7, wherein the look-up table data includes one or more graphs plotting the change in the air quality parameter over time for each number of vehicle occupants from the start of the air recirculation mode.

9. A control system as claimed in any one of claims 1 to 8, wherein the air handling system has one or more airflow control elements controlled to set the respective proportions of fresh air and recirculated air supplied to the cabin when operated in the air recirculation mode.

10. The control system of claim 9, wherein the one or more airflow control elements include a flap disposed at an outlet of a first air duct for supplying fresh air, the flap being disposed at a junction between the first air duct and a second air duct for supplying recirculated air.

11. A control system as claimed in any one of claims 1 to 10, wherein the control system is connectable to an occupant detection system of the vehicle, and the control system is configured to receive the signal indicative of the number of occupants in the vehicle from the occupant detection system.

12. The control system of claim 11, wherein the occupant detection system includes one or more of a seat pressure sensor or a seat belt engagement sensor.

13. A vehicle system having a control system according to any one of claims 1 to 12, comprising: an air handling system for controlling the supply of fresh air and recirculated air to the cabin; and an occupant detection system for detecting the number of vehicle occupants inside the vehicle.

14. A vehicle comprising a control system according to any one of claims 1 to 12 or a vehicle system according to claim 13.

15. A method of controlling an air handling system of a vehicle, wherein the air handling system controls the supply of fresh air and recirculated air to a cabin of the vehicle, the method comprising: obtaining a signal indicative of a number of occupants in the cabin; determining a maximum time period for operating the air handling system in an air recirculation mode based on the number of occupants; and controlling the air handling system to terminate the air recirculation mode once the maximum time period has elapsed since initiation of the air recirculation mode.

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