Patent Publication Number: US-2018029442-A1

Title: Air conditioning control system

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2016-147767 filed on Jul. 27, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an air conditioning control system. 
     2. Description of Related Art 
     A technique which, in an on state of a start switch (for example, an ignition switch) of a vehicle, separately calculates both of an increase amount and a decrease amount of vehicle inside absolute humidity as absolute humidity (weight absolute humidity) in the vehicle interior in real time, calculates (updates) vehicle inside absolute humidity based on the increase amount and the decrease amount, and controls an air conditioning device based on the calculated vehicle inside absolute humidity is known (for example, see Japanese Patent Application Publication No. 2015-54688 (JP 2015-54688 A)). In the related art, there is a case where the vehicle inside absolute humidity (initial value) when the start switch is turned on is calculated on an assumption that relative humidity (hereinafter, referred to as “vehicle inside relative humidity”) in the vehicle interior is 100%, or a case where a variable value varying based on weather information or the like at a vehicle position is used as another value. According to the related art, even in a case where a humidity sensor which detects the vehicle inside relative humidity is not used, the vehicle inside relative humidity is calculated based on the vehicle inside absolute humidity calculated as described above and an inside air temperature, whereby it is possible to perform air conditioning control, such as determination of an inlet mode (inside air circulation mode or outside air introduction mode) according to the vehicle inside relative humidity. 
     SUMMARY 
     However, in the related art described above, outside air introduction into the vehicle interior in the off state of the start switch of the vehicle is not taken into consideration, making it difficult to increase the calculation accuracy of the vehicle inside absolute humidity. For example, in a case where an outside air introduction ratio of the air conditioning device is greater than 0% in the off state of the start switch, an inside-outside air humidity difference in the off state of the start switch is apt to become small. In a case where the inside-outside air humidity difference is comparatively small, the calculation accuracy of the vehicle inside absolute humidity can be increased using information representing humidity of outside air. 
     The disclosure provides an air conditioning control system which increases a possibility of obtaining vehicle inside absolute humidity with high calculation accuracy using information representing humidity of outside air. 
     An air conditioning control system according to a first aspect of the disclosure is an air conditioning control system which is mounted in a vehicle, and includes an air conditioning device and a controller. The controller is configured to acquire vehicle outside humidity information representing humidity when a start switch of the vehicle is turned on, execute outside air introduction processing for making an outside air introduction ratio of the air conditioning device greater than 0% in an off state of the start switch, and in a case where a first condition that the outside air introduction processing is executed is satisfied, calculate vehicle inside absolute humidity of the vehicle in an on state of the start switch with absolute humidity based on the acquired vehicle outside humidity information as an initial value. The vehicle outside humidity information is information representing humidity of outside air at a position of the vehicle. 
     According to the first aspect, the outside air introduction processing for making the outside air introduction ratio of the air conditioning device greater than 0% is executed in the off state of the start switch. If the outside air introduction ratio of the air conditioning device becomes greater than 0 in the off state of the start switch, since the amount of outside air introduced into the vehicle interior increases compared to a case where the outside air introduction ratio is 0, an inside-outside air humidity difference (the difference between vehicle inside relative humidity and vehicle outside relative humidity or the difference between vehicle inside absolute humidity and vehicle outside absolute humidity) is apt to become small in the off state of the start switch. Accordingly, in a case where the first condition is satisfied, there is a high possibility that the absolute humidity (absolute humidity of outside air) based on the vehicle outside humidity information coincides with the vehicle inside absolute humidity when the start switch is turned on. For this reason, the absolute humidity based on the vehicle outside humidity information can be effectively used as the vehicle inside absolute humidity (initial value) when the start switch is turned on. Therefore, according to the first aspect, in a case where the first condition is satisfied, it is possible to increase a possibility of obtaining the vehicle inside absolute humidity with high calculation accuracy using the vehicle outside humidity information. 
     In the above-described aspect, the controller may be further configured to detect a parking state in which the length of an off period of the start switch exceeds a predetermined time. The controller may be configured to, in a case where a second condition that the parking state is detected is further satisfied, calculate the vehicle inside absolute humidity with the absolute humidity based on the vehicle outside humidity information as an initial value. 
     When the off period of the start switch is longer, the inside-outside air humidity difference is apt to become smaller. Therefore, in the above-described configuration, in a case where the second condition is further satisfied, it is possible to further increase a possibility of obtaining the vehicle inside absolute humidity with high calculation accuracy. 
     In the above-described aspect, the controller may be further configured to determine whether or not the difference between an inside air temperature and an outside air temperature or the difference between a saturated water vapor amount according to the inside air temperature and a saturated water vapor amount according to the outside air temperature is equal to or less than a predetermined value in the off state of the start switch or when the start switch is turned on. The controller may be configured to, in a case where a third condition that it is determined that the difference is equal to or less than the predetermined value is further satisfied, calculate the vehicle inside absolute humidity with the absolute humidity based on the vehicle outside humidity information as an initial value. 
     If outside air is introduced into the vehicle interior in the off state of the start switch, like the inside-outside air humidity difference, an inside-outside air temperature difference (the difference between the inside air temperature and the outside air temperature) is apt to become small. Therefore, in the above-described configuration, in a case where the third condition is further satisfied, it is possible to further increase a possibility of obtaining the vehicle inside absolute humidity with high calculation accuracy. The difference (that is, the difference in the saturated water vapor amount between inside air and outside air) between the saturated water vapor amount according to the inside air temperature and the saturated water vapor amount according to the outside air temperature has a high correlation with the inside-outside air temperature difference, and can be used like the inside-outside air temperature difference. 
     In the above-described aspect, the controller may be further configured to execute blower operation processing for operating a blower motor of the air conditioning device in a state in which the outside air introduction ratio is greater than 0% in the off state of the start switch. The controller may be configured to, in a case where a fourth condition that the blower operation processing is executed is further satisfied, calculate the vehicle inside absolute humidity with the absolute humidity based on the vehicle outside humidity information as an initial value. 
     If the blower motor is operated in a state in which the outside air introduction ratio of the air conditioning device is greater than 0%, the amount of outside air introduced into the vehicle interior increases compared to a case where the blower motor is not operated in the same state. When the amount of outside air introduced into the vehicle interior is larger, the inside-outside air humidity difference is apt to become smaller. Therefore, in the above-described configuration, in a case where the fourth condition is further satisfied, it is possible to further increase a possibility of obtaining the vehicle inside absolute humidity with high calculation accuracy. 
     In the above-described aspect, the controller may be further configured to determine whether or not the difference between an inside air temperature and an outside air temperature or the difference between a saturated water vapor amount according to the inside air temperature and a saturated water vapor amount according to the outside air temperature is equal to or less than a predetermined value in the off state of the start switch. The controller may be configured to, in a case where it is determined that the difference is not equal to or less than the predetermined value, start the blower operation processing. 
     According to the above-described configuration, in a case where it is determined, by the controller, that the difference is not equal to or less than the predetermined value, since the blower operation processing is started, it is possible to reduce the difference comparatively rapidly. 
     In the above-described first aspect, the humidity represented by the vehicle outside humidity information may be relative humidity, and the controller may be configured to calculate the initial value based on temperature information representing an outside air temperature or an inside air temperature when the start switch is turned on and the vehicle outside humidity information. 
     According to the above-described configuration, it is possible to increase a possibility of obtaining the vehicle inside absolute humidity with high calculation accuracy using the vehicle outside humidity information representing relative humidity of outside air. As described above, if outside air is introduced into the vehicle interior, like the inside-outside air humidity difference, the inside-outside air temperature difference is apt to become small. Therefore, in a case where there is a high possibility that the inside-outside air humidity difference is small, the inside air temperature and the outside air temperature can be used equivalently. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a diagram showing the basic configuration of an air conditioning control system according to an example; 
         FIG. 2  is a diagram showing an example of an air conditioning device; 
         FIG. 3  is a diagram showing an example of the air conditioning device; 
         FIG. 4  is a diagram showing an example of the hardware configuration of a controller; 
         FIG. 5A  is a diagram showing an example of a vehicle outside humidity derivation map; 
         FIG. 5B  is an explanatory view of the relationship of relative humidity, absolute humidity, and temperature; 
         FIG. 6  is an explanatory view of a ventilation loss reduction effect; 
         FIG. 7  is a schematic flowchart showing an example of processing which is executed by the controller; 
         FIG. 8A  is a schematic flowchart showing another example of processing which is executed by the controller; 
         FIG. 8B  is a schematic flowchart showing another example of processing which is executed by the controller; and 
         FIG. 9  is an explanatory view of processing of  FIG. 8A  and  FIG. 8B . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, respective examples will be described in detail referring to the accompanying drawings. 
       FIG. 1  is a diagram showing the basic configuration of an air conditioning control system  1  according to an example. 
     An air conditioning control system  1  is mounted in a vehicle. Hereinafter, the vehicle in which the air conditioning control system  1  is mounted is referred to as a “host vehicle”. The air conditioning control system  1  includes an air conditioning device  10  and a controller  40 . 
     The air conditioning device  10  has an ability to vary the amount of outside air (for example, the amount of outside air per unit time) introduced into the vehicle interior of the host vehicle. The amount of outside air introduced into the vehicle interior of the host vehicle can be changed by changing the openings of outside/inside air doors (for example, outside/inside air doors  119  shown in  FIG. 3 ). The amount of outside air introduced into the vehicle interior of the host vehicle can be changed by changing the rotation speed of the blower motor (for example, a blower motor  122  shown in  FIG. 3 ) when an outside air introduction ratio is greater than 0%. 
       FIGS. 2 and 3  are diagrams showing an example of the air conditioning device  10 . In the examples shown in  FIGS. 2 and 3 , the air conditioning device  10  includes a compressor  112  which compresses a refrigerant. The refrigerant compressed by the compressor  112  circulates through a refrigerant passage  118  including a condenser  114  or an evaporator  116 . The condenser  114  functions to cool a gasified refrigerant to change the gasified refrigerant to a liquid refrigerant to be supplied to the evaporator  116 . In front of the condenser  114 , a suction type electric fan  115  which cools the condenser  114  is disposed. The evaporator  116  is provided in the vehicle interior. In front of the evaporator  116 , as shown in  FIGS. 2 and 3 , a blower motor (blower fan)  122  whose rotation speed is regulatable is disposed. The blower motor  122  communicates with the outside of the vehicle or the vehicle interior through the outside/inside air doors  119 . The blower motor  122  has a function of pumping air (that is, outside air, inside air, or mixed air thereof) outside the vehicle or in the vehicle interior into the vehicle interior through the evaporator  116 . A flow rate (that is, blower air volume) of air pumped into the vehicle interior is regulated by controlling the rotation speed of the blower motor  122 . If the blower motor  122  rotates, air (that is, outside air, inside air, or mixed air thereof) flowing through the outside/inside air doors  119  passes through the evaporator  116 . The evaporator  116  gasifies the refrigerant compressed by the compressor  112  to cool air passing through the evaporator  116 . On a backstream side of the evaporator  116 , a heater core  120  is disposed. In the heater core  120 , air mix doors  124  whose openings are regulatable (for example, are driven by servo motors) are set. The heater core  120  has a function (reheat function) of mixing warm air with air cooled by the evaporator  116  in cooperation with the air mix doors  124 . A temperature of air pumped into the vehicle interior is regulated by controlling the openings (that is, a mixture ratio of cold air and warm air) of the air mix doors  124 . On a backstream side of the heater core  120 , respective ducts which guide mixed air to respective outlets (foot outlets  131 , rear heater ducts  132 , center register  133 , center defrosters  134 , side defrosters  135 , side registers  136 ) are provided at predetermined locations in the vehicle interior. On the backstream side of the heater core  120 , mode doors  128  which selectively guide mixed air to a predetermined outlet are set. 
     The controller  40  is formed of a computer. For example, the controller  40  is an air conditioner electronic control unit (ECU).  FIG. 4  is a diagram showing an example of the hardware configuration of the controller  40 . In  FIG. 4 , in association with the hardware configuration of the controller  40 , examples of elements including an in-vehicle electronic apparatus group  8  and air conditioning device  10  are schematically shown. 
     The controller  40  includes a central processing unit (CPU)  11 , a random access memory (RAM)  12 , a read only memory (ROM)  13 , an auxiliary storage device  14 , and a communication interface  17  connected to one another through a bus  19 , and a wired transmission-reception unit  25  connected to the communication interface  17 . 
     The wired transmission-reception unit  25  includes a transmission-reception unit which can perform communication using a vehicle network, such as a controller area network (CAN) or a local interconnect network (LIN). The controller  40  may include a wireless transmission-reception unit (not shown) connected to the communication interface  17 , in addition to the wired transmission-reception unit  25 . In this case, the wireless transmission-reception unit may include a near field communication (NFC) unit, a Bluetooth (Registered Trademark) communication unit, a Wireless-Fidelity (Wi-Fi) transmission-reception unit, an infrared transmission-reception unit, or the like. 
     The in-vehicle electronic apparatus group  8  includes a global positioning system (GPS) receiver  81 , a communication module  82 , a display  83 , an operation switch group  84 , and an air conditioner related sensor  86 . 
     The GPS receiver  81  measures a position of the host vehicle based on electric waves from GPS satellites. 
     The communication module  82  is, for example, a transmission-reception unit which can perform wireless communication using a wireless communication network in a mobile phone. The communication module  82  is fixed into the host vehicle. However, in a modification example, the communication module  82  may be implemented by a portable terminal (for example, a smartphone, a tablet, or the like) which can be carried into the host vehicle. In this case, the controller  40  can perform communication with the outside through the wireless transmission-reception unit (for example, a Bluetooth communication unit) and the communication module  82 . 
     The display  83  is, for example, a touch panel type liquid crystal display. The display  83  is disposed at a position where a user (occupant) of the host vehicle can visually observe. The display  83  is a display which is fixed into the host vehicle, but may be a display of a portable terminal which can be carried into the host vehicle. In this case, communication between the portable terminal and the controller  40  can be implemented through the wireless transmission-reception unit (for example, a Bluetooth communication unit). 
     The operation switch group  84  is provided in a control panel (not shown) on which the user performs an operation on the air conditioning device  10 . The control panel is disposed in, for example, an instrument panel. The operation switch group  84  includes an A/C switch for turning on/off the operation of the compressor  112 , a switch for switching an operation mode (auto mode or manual mode) of the air conditioning device  10 , a switch for switching an inlet mode (inside air circulation mode or outside air introduction mode), a switch (blower dial) for regulating the blower air volume, a defroster switch for switching on/off of a foot/defroster mode or a defroster mode, a switch (temperature setting dial) for performing temperature setting, and the like. A part or the whole of the operation switch group  84  may be set in the portable terminal which can be carried into the host vehicle. 
     The air conditioner related sensor  86  includes an inside air temperature sensor  861  which detects an inside air temperature as a temperature in the vehicle interior, and an outside air temperature sensor  862  which detects an outside air temperature as a temperature outside the vehicle. In addition, the air conditioner related sensor  86  may include a solar radiation sensor which detects the amount of solar radiation, a rain sensor which detects raindrops, a temperature sensor which detects a temperature of cold air immediately after passing through the evaporator  116 , and the like. 
     As shown in  FIG. 1 , the controller  40  includes a start on/off event detection unit  41 , a parking state detection unit  42 , a vehicle outside humidity information acquisition unit  44 , an inside-outside air temperature difference determination unit  45  (an example of a difference determination unit), an outside air introduction processing unit  46 , a blower operation processing unit  47 , a humidity calculation unit  48 , and a control unit  49 . The start on/off event detection unit  41 , the vehicle outside humidity information acquisition unit  44 , the parking state detection unit  42 , the inside-outside air temperature difference determination unit  45 , the outside air introduction processing unit  46 , the blower operation processing unit  47 , the humidity calculation unit  48 , and the control unit  49  can be respectively implemented by the CPU  11  shown in  FIG. 4  executing one or more programs stored in the ROM  13 . 
     The start on/off event detection unit  41  detects an on/off event of a start switch  5  of the host vehicle. The start switch  5  is a switch which is turned on by the user when starting the host vehicle in a travelable state, and is turned off by the user when releasing the travelable state. The start switch  5  is generally an ignition switch, but in a case of an electric vehicle, the start switch  5  is a power switch which is provided in an electric power supply path from a high voltage battery (not shown) to an electric motor for traveling (not shown). For example, in a case of the ignition switch, the user presses an engine start switch (not shown) in the vehicle interior while operating a brake pedal (not shown), thereby transiting the ignition switch to an on state. If the start switch  5  is brought into the on state, a power supply voltage (hereinafter, referred to as a “microcomputer power supply voltage”) for the operation of the controller  40  is generated based on a power supply Ba by a power supply generation circuit (not shown) in the controller  40 . The on/off event of the start switch  5  of the host vehicle can be detected based on the state of the microcomputer power supply voltage which changes according to the on/off state of the start switch  5 . In the off state of the start switch  5 , the controller  40  can operate based on a power supply voltage (+B) from the power supply Ba without passing through the start switch  5 . Hereinafter, a period which starts when the start switch  5  is turned off and ends when the start switch  5  is next turned on is referred to as “an off period of the start switch  5 ”. 
     The parking state detection unit  42  detects a parking state in which the length of the off period of the start switch  5  exceeds a first predetermined time T 1 . The first predetermined time T 1  is a time until the inside-outside air humidity difference becomes sufficiently small, and depends on an execution form of outside air introduction processing described below, the volume of the vehicle interior, or the like. The first predetermined time T 1  is, for example, one hour. Hereinafter, the parking state in which the length of the off period of the start switch  5  exceeds the first predetermined time T 1  is referred to as a “predetermined parking state”. 
     In an example, based on a timer TM (not shown), which times out when an elapsed time after the start switch  5  is turned off becomes the first predetermined time T 1 , the parking state detection unit  42  detects the predetermined parking state in a case where the timer TM times out until the start switch  5  is turned on. 
     In another example, the parking state detection unit  42  determines whether or not an elapsed time after the start switch  5  is turned off previously exceeds the first predetermined time T 1  when the start switch  5  is turned on, and in a case where the elapsed time exceeds the first predetermined time T 1 , detects the predetermined parking state. 
     The vehicle outside humidity information acquisition unit  44  acquires vehicle outside humidity information representing humidity of the outside (outside air) of the host vehicle in the position of the host vehicle. Hereinafter, humidity of outside air is referred to as “vehicle outside humidity”. The term “vehicle outside humidity” is a concept representing both of relative humidity and absolute humidity of the outside of the host vehicle. Hereinafter, relative humidity of outside air is referred to as “vehicle outside relative humidity”, and absolute humidity of outside air is referred to as “vehicle outside absolute humidity”. 
     In an example, the vehicle outside humidity information acquisition unit  44  acquires vehicle outside humidity information representing the vehicle outside relative humidity at the position of the host vehicle. In an example, the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  is information indicating the vehicle outside relative humidity itself. The vehicle outside humidity information can be acquired from, for example, a server (not shown) which provides weather information. In this case, the vehicle outside humidity information acquisition unit  44  acquires the vehicle outside humidity information at the position of the host vehicle from the server through the communication module  82 . The vehicle outside humidity information may be acquired in the form of being included in the weather information, or may be acquired alone. In a case where there is vehicle outside humidity information, which can be provided from the server, for each area, the vehicle outside humidity information at the position of the host vehicle is vehicle outside humidity information related to an area to which the position of the host vehicle belongs. The position of the host vehicle can be determined based on positioning information from the GPS receiver  81 . 
     In another example, the vehicle outside humidity information acquisition unit  44  acquires vehicle outside humidity information representing the vehicle outside absolute humidity at the position of the host vehicle. The vehicle outside humidity information representing the vehicle outside absolute humidity can also be acquired from, for example, a server (not shown) which provides weather data. In such a server, the vehicle outside absolute humidity is calculated from the vehicle outside relative humidity and the outside air temperature. In this case, the vehicle outside humidity information acquisition unit  44  acquires the vehicle outside humidity information at the position of the host vehicle from the server through the communication module  82 . 
     In a further example, the vehicle outside humidity information acquisition unit  44  first acquires weather information representing the type of weather, such as rain, fine, or snow, and a rainfall amount or a snowfall amount. In this case, the vehicle outside humidity information acquisition unit  44  predicts vehicle outside humidity at the position of the host vehicle based on the weather information, for example, using a vehicle outside humidity derivation map (see  FIG. 5A ), thereby acquiring vehicle outside humidity information. In the vehicle outside humidity derivation map shown in  FIG. 5A , corresponding vehicle outside relative humidity is specified for each season and each weather. In  FIG. 5A , “**” means that there is any corresponding information. The weather information can be acquired from, for example, a server (not shown) which provides weather data. Such a server is, for example, a server which derives and provides weather information with a high real-time property based on raw information received from many observers all over the country, observation data from observation devices provided all over the country, and prediction from movement of clouds by a radar. In a case where there is weather information, which can be provided from the server, for each area, the weather information at the position of the host vehicle is weather information related to an area to which the position of the host vehicle belongs. Alternatively, in a case where a rain sensor is mounted in the host vehicle as one element of the air conditioner related sensor  86 , weather information can be acquired from the rain sensor. For example, detection information of raindrops by the rain sensor represents that the type of weather is “rain”. 
     The vehicle outside humidity information acquisition unit  44  acquires vehicle outside humidity information representing vehicle outside humidity when the start switch  5  is turned on. 
     In an example, the vehicle outside humidity information acquisition unit  44  acquires vehicle outside humidity information when the start switch  5  is turned on. In another example, the vehicle outside humidity information acquisition unit  44  acquires vehicle outside humidity information (for example, vehicle outside humidity information at every given time) over the off period of the start switch  5 . In this case, an average value or a maximum value of the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  can be used as information representing vehicle outside humidity when the start switch  5  is turned on. In a further example, the vehicle outside humidity information acquisition unit  44  acquires the vehicle outside humidity information at an arbitrary time during the last off period of the start switch  5  (however, before the start switch  5  is turned on). In a case where change in vehicle outside humidity during the off period of the start switch  5  is small, although accuracy is slightly reduced, the vehicle outside humidity information before the start switch  5  is turned on can also be used as information representing the vehicle outside humidity when the start switch  5  is turned on. 
     The inside-outside air temperature difference determination unit  45  determines whether or not the difference (hereinafter, referred to as an “inside-outside air temperature difference”) between the outside air temperature and the inside air temperature is equal to or less than a predetermined value Dth in the off state of the start switch  5  or when the start switch  5  is turned on. The predetermined value Dth is an inside-outside air temperature difference at which it can be estimated that the inside-outside air humidity difference becomes sufficiently small, and is, for example, 5° C. In a case of further increasing accuracy, the predetermined value Dth is, for example, 1° C. Outside air temperature information can be acquired from the outside air temperature sensor  862 . Inside air temperature information can be acquired from the inside air temperature sensor  861 . The same acquisition methods apply to outside air temperature information and the like described in the following description. 
     In an example, when a second predetermined time T 2  has elapsed from the off event of the start switch  5 , the inside-outside air temperature difference determination unit  45  determines whether or not the inside-outside air temperature difference is equal to or less than the predetermined value Dth based on the outside air temperature information and the inside air temperature information at this time. The second predetermined time T 2  is equal to, for example, the first predetermined time T 1 . In this case, the inside-outside air temperature difference determination unit  45  can start using the timer TM common to the parking state detection unit  42 . However, the second predetermined time T 2  may be longer or shorter than the first predetermined time T 1 . 
     In another example, when the start switch  5  is turned on, the inside-outside air temperature difference determination unit  45  determines whether or not the inside-outside air temperature difference is equal to or less than the predetermined value Dth based on the outside air temperature information and the inside air temperature information at this time. 
     The outside air introduction processing unit  46  executes outside air introduction processing for making the outside air introduction ratio of the air conditioning device  10  greater than 0% in the off state of the start switch  5 . The outside air introduction ratio can be changed by regulating the openings of the outside/inside air doors  119 . For example, when the start switch  5  is turned off, the outside air introduction processing unit  46  sets the outside air introduction ratio of the air conditioning device  10  to a predetermined ratio α (&gt;0). Alternatively, when a predetermined short time (for example, a time within one minute) has elapsed after the start switch  5  is turned off, the outside air introduction processing unit  46  sets the outside air introduction ratio of the air conditioning device  10  to the predetermined ratio α. In the off state of the start switch  5 , when the outside air introduction ratio is higher, the inside-outside air humidity difference is apt to become smaller. Accordingly, the predetermined ratio α is preferably equal to or greater than 50%, and is, for example, 100%. 
     In an example, if the outside air introduction ratio of the air conditioning device  10  is set to the predetermined ratio α, the outside air introduction processing unit  46  maintains the outside air introduction ratio of the air conditioning device  10  to be equal to or greater than the predetermined ratio α in the subsequent off state of the start switch  5 . This is because, when the time for which the outside air introduction ratio is great is longer, the inside-outside air humidity difference is apt to become smaller. 
     In another example, the outside air introduction processing unit  46  sets the outside air introduction ratio of the air conditioning device  10  to the predetermined ratio α, and then, in a case where a fourth predetermined time T 4  has elapsed in the off state of the start switch  5 , returns the outside air introduction ratio to 0% (that is, ends a state in which the outside air introduction ratio is greater than 0%). This is because, even in a case where the outside air introduction ratio returns to 0%, there is a high possibility that a state in which the inside-outside air humidity difference is sufficiently small is maintained until the start switch  5  is turned on. The fourth predetermined time T 4  is a time required for making the inside-outside air humidity difference sufficiently small in a state in which the outside air introduction ratio is the predetermined ratio α, and is, for example, one hour. 
     The blower operation processing unit  47  executes blower operation processing in the off state of the start switch  5 . The blower operation processing is processing for operating the blower motor  122  in a state in which the outside air introduction ratio of the air conditioning device  10  is greater than 0%. In this example, as an example, the blower operation processing unit  47  starts the blower operation processing in a case where it is determined by the inside-outside air temperature difference determination unit  45  that the inside-outside air temperature difference is not equal to or less than the predetermined value Dth in the off state of the start switch  5 . If the blower operation processing starts, the blower operation processing unit  47  continues the blower operation processing until a predetermined end condition (hereinafter, simply referred to as a “blower operation end condition”) is satisfied in the off state of the start switch  5 . 
     The blower operation end condition is set such that the blower operation processing ends at the timing at which it can be estimated that the inside-outside air humidity difference becomes sufficiently small. In an example, the blower operation end condition is formed of a first end condition that the inside-outside air temperature difference based on current outside air temperature information and inside air temperature information is equal to or less than the predetermined value Dth. In a case of using the first end condition, the blower operation processing unit  47  determines whether or not the first end condition is established in cooperation with the inside-outside air temperature difference determination unit  45 . In another example, the blower operation end condition is formed of a second end condition that an operation time of the blower motor  122  exceeds a third predetermined time T 3 . The third predetermined time T 3  depends on the predetermined value Dth or the like, and is, for example, ten minutes. In a further example, the blower operation end condition includes both of the first end condition and the second end condition in an OR manner, and may be satisfied in a case where either of the first end condition or the second end condition is satisfied. 
     In a case where a predetermined condition (hereinafter, referred to as a “vehicle outside humidity use condition”) is satisfied, the humidity calculation unit  48  calculates vehicle inside absolute humidity (absolute humidity inside the host vehicle) of the host vehicle in the on state of the start switch  5  with absolute humidity based on the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  as an initial value. The expression “absolute humidity based on the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44 ” is a conversion value (for example, a first initial value described below) to absolute humidity based on the vehicle outside relative humidity in a case where the vehicle outside humidity information represents the vehicle outside relative humidity, and is the vehicle outside absolute humidity in a case where the vehicle outside humidity information represents the vehicle outside absolute humidity. The initial value is a value representing the vehicle inside absolute humidity when the start switch  5  is turned on. 
     The vehicle outside humidity use condition is a condition which is specified so as to be satisfied under a situation in which the inside-outside air humidity difference is sufficiently small, and includes a first condition among the following four conditions: (First Condition) the outside air introduction processing is executed by the outside air introduction processing unit  46 ; (Second Condition) the predetermined parking state is detected by the parking state detection unit  42 ; (Third Condition) the inside-outside air temperature difference determination unit  45  determines that the inside-outside air temperature difference is equal to or less than the predetermined value Dth; and (Fourth Condition) the blower operation processing is executed by the blower operation processing unit  47 . 
     In a first example, the vehicle outside humidity use condition is satisfied simply in a case where the first condition is established. Alternatively, the vehicle outside humidity use condition is satisfied in a case where the first condition and the second condition are established simultaneously. Alternatively, the vehicle outside humidity use condition is satisfied in a case where the first condition and the third condition are established simultaneously. Alternatively, the vehicle outside humidity use condition is satisfied in a case where the first condition and the fourth condition are established simultaneously. Alternatively, the vehicle outside humidity use condition is satisfied in a case where the first condition to the third condition are established simultaneously. Alternatively, the vehicle outside humidity use condition is satisfied in a case where the first condition, the second condition, and the fourth condition are established simultaneously. 
     In a second example, the vehicle outside humidity use condition is satisfied in a case where either of a first predetermined condition or a second predetermined condition is satisfied. 
     In the second example, in an example, the first predetermined condition is satisfied in a case where the first condition and the third condition are established simultaneously. The second predetermined condition is satisfied in a case where the first condition and the fourth condition are established simultaneously. As described above, since the blower operation processing is executed in a state in which the outside air introduction ratio is greater than 0%, when the fourth condition is satisfied, the first condition is necessarily satisfied. 
     In the second example, in another example, the first predetermined condition is satisfied in a case where the first condition to the third condition are established simultaneously. The second predetermined condition is satisfied in a case where the first condition, the second condition, and the fourth condition are established simultaneously. 
     The fourth condition may be substituted with the following 4A-th condition: (4A-th Condition) the blower operation processing is executed by the blower operation processing unit  47  and the blower operation processing ends when the blower operation end condition is satisfied. In a case where the blower operation end condition is formed of the above-described first end condition, if the 4A-th condition is satisfied, the above-described third condition is necessarily satisfied. In a configuration in which the blower operation end condition is satisfied in a case where either of the first end condition or the second end condition is satisfied, the 4A-th condition may be substituted with, for example, the following 4B-th condition: (4B-th Condition) the blower operation processing is executed by the blower operation processing unit  47 , and the blower operation processing ends when the first end condition is satisfied. In this case, if the 4B-th condition is satisfied, the above-described third condition is necessarily satisfied. Both of the 4A-th condition and the 4B-th condition require the fourth condition. That is, when the 4A-th condition is satisfied, the fourth condition is necessarily satisfied, and when the 4B-th condition is satisfied, the fourth condition is necessarily satisfied. In a case where the 4A-th condition or the 4B-th condition is used instead of the fourth condition, a possibility that the vehicle outside humidity use condition is satisfied only under a situation in which the inside-outside air humidity difference is sufficiently small further increases. 
     In this example, as an example, the humidity calculation unit  48  includes a first humidity initial value calculation unit  481 , a second humidity initial value calculation unit  482 , and a humidity update unit  483 . 
     In this example, in a case where the above-described vehicle outside humidity use condition is satisfied, the humidity update unit  483  of the humidity calculation unit  48  calculates the vehicle inside absolute humidity in the on state of the start switch  5  with vehicle inside absolute humidity (a first initial value described below) calculated by the first humidity initial value calculation unit  481  based on the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  as an initial value. In a case where the vehicle outside humidity use condition is not satisfied, the humidity update unit  483  of the humidity calculation unit  48  calculates the vehicle inside absolute humidity in the on state of the start switch  5  with vehicle inside absolute humidity (a second initial value described below) calculated by the second humidity initial value calculation unit  482  as an initial value. 
     However, in a modification example, the humidity calculation unit  48  does not include the first humidity initial value calculation unit  481 . In this case, the vehicle outside humidity information acquisition unit  44  acquires the vehicle outside humidity information representing the vehicle outside absolute humidity. In a case where the vehicle outside humidity use condition is satisfied, the humidity calculation unit  48  sets the vehicle outside absolute humidity represented by the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  as the initial value of the vehicle inside absolute humidity. Thereafter, the humidity calculation unit  48  calculates (updates) the vehicle inside absolute humidity based on the initial value in real time. Accordingly, in a case of such a modification example, as in a case of this example described below, in a case where the vehicle outside humidity use condition is satisfied, the humidity calculation unit  48  calculates the vehicle inside absolute humidity in the on state of the start switch  5  with the absolute humidity based on the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  as an initial value. 
     Hereinafter, unless specifically described, it is assumed that the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  represents the vehicle outside relative humidity. The vehicle outside humidity information included in easily available weather information generally represents the vehicle outside relative humidity. 
     The first humidity initial value calculation unit  481  calculates the vehicle inside absolute humidity based on temperature information representing the outside air temperature or the inside air temperature when the start switch  5  is turned on and the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44 . In a case where the vehicle outside humidity use condition is satisfied, the vehicle inside absolute humidity calculated by the first humidity initial value calculation unit  481  is used as the initial value of the vehicle inside absolute humidity. Hereinafter, the vehicle inside absolute humidity calculated by the first humidity initial value calculation unit  481  is referred to as “the first initial value of the vehicle inside absolute humidity”. 
     As the temperature information representing the outside air temperature when the start switch  5  is turned on, the outside air temperature information obtained from the outside air temperature sensor  862  when the start switch  5  is turned on can be used. However, in another example, the outside air temperature information from the outside air temperature sensor  862  obtained at an arbitrary time (however, before the start switch  5  is turned on) during the last off period of the start switch  5  may be used. In a case where change in the outside air temperature is small, although accuracy is slightly reduced, such outside air temperature information can also be used as information representing the outside air temperature when the start switch  5  is turned on. Similarly, as the temperature information representing the inside air temperature when the start switch  5  is turned on, the inside air temperature information obtained from the inside air temperature sensor  861  when the start switch  5  is turned on can be used. However, similarly, in another example, the inside air temperature information from the inside air temperature sensor  861  obtained at an arbitrary time (however, before the start switch  5  is turned on) during the last off period of the start switch  5  may be used. 
     A calculation method of the first initial value of the vehicle inside absolute humidity is as follows, for example. 
     In an example, the first humidity initial value calculation unit  481  calculates the vehicle outside absolute humidity from the outside air temperature and the vehicle outside relative humidity, and sets the calculated vehicle outside absolute humidity as the first initial value of the vehicle inside absolute humidity. This is because, as described above, in a case where the vehicle outside humidity use condition is satisfied, there is a high possibility that the inside-outside air humidity difference is small. A calculation method of the vehicle outside absolute humidity based on the outside air temperature and the vehicle outside relative humidity is as follows, for example. 
       (vehicle outside absolute humidity)=(saturated water vapor amount with respect to outside air temperature)×(vehicle outside relative humidity)/100
 
     The saturated water vapor amount with respect to the outside air temperature can be found from a characteristic (the relationship between temperature and absolute humidity) C 1  (see  FIG. 5B ) of relative humidity 100%. 
     In another example, the first humidity initial value calculation unit  481  calculates the vehicle outside absolute humidity from the vehicle outside relative humidity using the inside air temperature as the outside air temperature, and sets the calculated vehicle outside absolute humidity as the first initial value of the vehicle inside absolute humidity. This is because, as described above, in a case where the vehicle outside humidity use condition is satisfied, there is a high possibility that both of the inside-outside air humidity difference and the inside-outside air temperature difference are small. 
     The second humidity initial value calculation unit  482  calculates the vehicle inside absolute humidity based on the inside air temperature information representing the inside air temperature when the start switch  5  is turned on. In a case where the vehicle outside humidity use condition is not satisfied, the vehicle inside absolute humidity calculated by the second humidity initial value calculation unit  482  is used as the initial value of the vehicle inside absolute humidity. Hereinafter, the vehicle inside absolute humidity calculated by the second humidity initial value calculation unit  482  is referred to as “the second initial value of the vehicle inside absolute humidity”. 
     In an example, the second humidity initial value calculation unit  482  sets the saturated water vapor amount corresponding to the inside air temperature as the second initial value of the vehicle inside absolute humidity. That is, the second humidity initial value calculation unit  482  sets the saturated water vapor amount corresponding to the inside air temperature as the second initial value of the vehicle inside absolute humidity on an assumption that the vehicle inside relative humidity is 100%. The saturated water vapor amount corresponding to the inside air temperature can be found from the characteristic (the relationship between temperature and absolute humidity) C 1  (see  FIG. 5B ) of relative humidity 100%. 
     The humidity update unit  483  calculates (updates) the subsequent vehicle inside absolute humidity (that is, vehicle inside absolute humidity after the start switch  5  is turned on) using the first initial value of the vehicle inside absolute humidity calculated by the first humidity initial value calculation unit  481  or the second initial value of the vehicle inside absolute humidity calculated by the second humidity initial value calculation unit  482 . The update method can be implemented by, for example, a method disclosed in JP 2015-54688 A. That is, the humidity update unit  483  separately calculates both of an increase amount of the vehicle inside absolute humidity and a decrease amount of the vehicle inside absolute humidity during traveling of the host vehicle in real time, and calculates (updates) the vehicle inside absolute humidity based on the increase amount and the decrease amount. The increase amount of the vehicle inside absolute humidity includes an increase amount due to a water vapor generation amount (evaporated moisture amount accompanied by breathing and sweating) from an occupant, for example. The decrease amount of the vehicle inside absolute humidity includes a decrease amount due to ventilation of inside-outside air, a decrease amount due to condensation in a low temperature region in the vehicle interior, and a decrease amount due to moisture absorption into an interior member in the vehicle interior. 
     The control unit  49  controls the inlet mode of the air conditioning device  10  after the start switch  5  is turned on. In a case where an operation mode of the air conditioning device  10  is a manual mode, the control unit  49  sets the inlet mode according to the state of the switch for switching the inlet mode (inside air circulation mode or outside air introduction mode). In a case where the operation mode of the air conditioning device  10  is an auto mode, the control unit  49  determines the inlet mode based on the vehicle inside absolute humidity calculated by the humidity update unit  483 . For example, the control unit  49  calculates the vehicle inside relative humidity corresponding to the inside air temperature and the vehicle inside absolute humidity based on the inside air temperature and the vehicle inside absolute humidity from the characteristic shown in  FIG. 5B . Then, in a case where the calculated vehicle inside relative humidity is equal to or lower than inside air conversion start humidity, the control unit  49  sets the outside air introduction ratio to 0% (inside air circulation mode). In a case where the calculated vehicle inside relative humidity exceeds the inside air conversion start humidity, the control unit  49  sets the outside air introduction ratio to 100% (outside air introduction mode). In this way, control of the inlet mode according to the vehicle inside relative humidity is implemented without using a humidity sensor. Hereinafter, transition from the outside air introduction mode to the inside air circulation mode after the start switch  5  is turned on is referred to as “inside air conversion”. 
     According to the air conditioning control system  1 , as described above, in a case where the vehicle outside humidity use condition is satisfied, the first humidity initial value calculation unit  481  calculates the first initial value of the vehicle inside absolute humidity using the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44 . In a case where the vehicle outside humidity use condition is satisfied, there is a high possibility that the inside-outside air humidity difference is sufficiently small. Accordingly, with the use of the vehicle outside humidity information, a possibility that the first initial value of the vehicle inside absolute humidity can be calculated with high accuracy increases. If the first initial value with high calculation accuracy is obtained, the calculation accuracy of the subsequent vehicle inside absolute humidity calculated by the humidity update unit  483  based on the first initial value of the vehicle inside absolute humidity increases. In this way, according to the air conditioning control system  1 , in a case where the vehicle outside humidity use condition is satisfied, it is possible to increase a possibility that the vehicle inside absolute humidity with high calculation accuracy is obtained using the vehicle outside humidity information. 
     According to the air conditioning control system  1 , as described above, in a case where the vehicle outside humidity use condition is not satisfied, the second humidity initial value calculation unit  482  calculates the second initial value of the vehicle inside absolute humidity without using the vehicle outside humidity information. In a case where the inside-outside air humidity difference is comparatively large, if the initial value of the vehicle inside absolute humidity is found using the vehicle outside humidity information, there is a concern that the accuracy of the initial value is deteriorated. In this respect, according to the air conditioning control system  1 , in a case where there is a possibility that the inside-outside air humidity difference is comparatively large, the second initial value of the vehicle inside absolute humidity is calculated. With this, it is possible to reduce inconvenience (for example, inconvenience that fogging of a front windshield occurs due to acceleration of the inside air conversion more than necessary) which may be caused in a case where the initial value of the vehicle inside absolute humidity is found using the vehicle outside humidity information under a situation in which, actually, the relative humidity of outside air is significantly lower than that of inside air. 
       FIG. 6  is an explanatory view of effects of this example. In  FIG. 6 , transition (time-series) of the vehicle inside relative humidity (the calculation value by the humidity update unit  483 ) after the start switch  5  is turned on in a case of using the first initial value is indicated by a curve L 1 , and transition (time-series) of the vehicle inside relative humidity in a case of using the second initial value is indicated by a curve L 2 . In regards to the curve L 1  and the curve L 2 , the condition of the inside air temperature is identical. When the inside air temperature is identical, the second initial value is greater than the first initial value. In  FIG. 6 , it is assumed that the vehicle outside relative humidity at the position of the host vehicle indicated by the vehicle outside humidity information is significantly lower than 100% (for example, 80%). 
     In a case where the vehicle inside relative humidity is calculated using the second initial value, the calculation value of the vehicle inside relative humidity becomes the transition of the curve L 2 , and at a time t 2 , the inside air conversion (transition from the outside air introduction mode to the inside air circulation mode) is implemented. In contrast, in a case where the vehicle inside relative humidity is calculated using the first initial value, the calculation value of the vehicle inside relative humidity becomes the transition of the curve L 1  lower than the curve L 2  by an amount in which the first initial value is smaller than the second initial value, and at a time t 1  before the time t 2 , the inside air conversion is implemented. In this way, in a case where the vehicle inside relative humidity is calculated using the first initial value, the inside air conversion of the air conditioning device  10  is accelerated by the time difference between the time t 2  and the time t 1  compared to a case where the vehicle inside relative humidity is calculated using the second initial value. 
     In recent years, exhaust heat tends to decrease with improvement of the efficiency of the internal combustion engine, additional energy is used in order to obtain necessary heating ability, and there is a problem in that vehicle fuel efficiency is deteriorated. In a hybrid vehicle or an electric vehicle in which exhaust heat cannot be used, a heating load significantly affects fuel efficiency or a cruising distance. In order to reduce the heating load, it is useful to increase an inside air circulation rate or to reduce a ventilation loss. In a case where the host vehicle includes an internal combustion engine, it is useful to reduce a ventilation loss for early warming-up of the internal combustion engine. 
     In this respect, according to the air conditioning control system  1 , as described above, in a case where the vehicle outside humidity use condition is satisfied, since the humidity update unit  483  calculates the vehicle inside absolute humidity using the first initial value, compared to a configuration in which the humidity update unit  483  calculates the vehicle inside absolute humidity using the second initial value in such a case, the inside air conversion is accelerated, and the ventilation loss can be reduced. According to the air conditioning control system  1 , as described above, in a case where the vehicle outside humidity use condition is satisfied, since there is a high possibility that the first initial value of the vehicle inside absolute humidity has high accuracy, it is possible to reduce inconvenience (for example, inconvenience that fogging of the front windshield occurs due to acceleration of the inside air conversion more than necessary) in a case where the initial value has poor accuracy and is significantly lower than an actual value. In this way, according to the above-described air conditioning control system  1 , it is possible to reduce a ventilation loss while reducing fogging of a window. 
     Next, several operation examples by the controller  40  will be described referring to  FIGS. 7 to 9 . 
       FIG. 7  is a schematic flowchart showing an example of processing which is executed by the controller  40 . The processing shown in  FIG. 7  is executed in each predetermined cycle. 
     In Step S 700 , the start on/off event detection unit  41  determines whether or not the start switch  5  is in the on state. In a case where the determination result is “YES”, the process progresses to Step S 724 , and otherwise (that is, in a case where the start switch  5  is in the off state), the process progresses to Step S 702 . 
     In Step S 702 , the start on/off event detection unit  41  determines whether or not the off event of the start switch  5  is detected. In a case where the start switch  5  is changed from the on state to the off state in the present cycle, the start on/off event detection unit  41  detects the off event of the start switch  5 . In a case where the determination result is “YES”, the process progresses to Step S 704 , and otherwise (that is, in a case where the start switch  5  is in the off state after the off event), the processing in the present cycle ends. 
     In Step S 704 , the start on/off event detection unit  41  resets a first condition establishment flag to “0”. The first condition establishment flag is a flag representing whether or not the outside air introduction processing is executed by the outside air introduction processing unit  46 . When the first condition establishment flag is “1”, this represents that the outside air introduction processing is executed. 
     In Step S 706 , the outside air introduction processing unit  46  sets the outside air introduction ratio of the air conditioning device  10  to the predetermined ratio α. In  FIG. 7 , it is assumed that the predetermined ratio α is 100%. When the outside air introduction ratio of the air conditioning device  10  at the present time is already 100%, the outside air introduction processing unit  46  maintains this state. When the outside air introduction ratio of the air conditioning device  10  at the present time is less than 100%, the outside air introduction processing unit  46  changes the outside air introduction ratio of the air conditioning device  10  to 100%. 
     In Step S 708 , the outside air introduction processing unit  46  sets the first condition establishment flag to “1”. 
     In Step S 724 , the humidity calculation unit  48  acquires current values of respective sensor information (inside air temperature information and the like) from the air conditioner related sensor  86 . 
     In Step S 726 , the start on/off event detection unit  41  determines whether or not the on event of the start switch  5  is detected. In a case where the start switch  5  is changed from the off state to the on state in the present cycle, the start on/off event detection unit  41  detects the on event of the start switch  5 . In a case where the determination result is “YES”, the process progresses to Step S 732 , and otherwise (that is, in a case where the start switch  5  is in the on state after the on event), the process progresses to Step S 740 . 
     In Step S 732 , the humidity calculation unit  48  determines whether or not the first condition establishment flag is “1”. In a case where the determination result is “YES”, the process progresses to Step S 734 , and otherwise (that is, in a case where the first condition establishment flag is “0”), the process progresses to Step S 738 . 
     In Step S 734 , the vehicle outside humidity information acquisition unit  44  acquires the vehicle outside humidity information. In  FIG. 7 , the vehicle outside humidity information acquisition unit  44  acquires the vehicle outside humidity information at the present time. 
     In Step S 736 , the first humidity initial value calculation unit  481  calculates the first initial value of the vehicle inside absolute humidity based on the vehicle outside relative humidity represented by the vehicle outside humidity information acquired by the vehicle outside humidity information acquisition unit  44  in Step S 734  and the inside air temperature information obtained in Step S 724 . The calculation method of the first initial value of the vehicle inside absolute humidity is as described above. 
     In Step S 738 , the second humidity initial value calculation unit  482  calculates the second initial value of the vehicle inside absolute humidity based on the inside air temperature information obtained in Step S 724 . The calculation method of the second initial value of the vehicle inside absolute humidity is as described above. 
     In Step S 740 , the humidity update unit  483  calculates (updates) a current value of the vehicle inside absolute humidity. The update method is as described above. For example, when the initial value (first initial value or the second initial value) calculated in Step S 736  or Step S 738  is referred to as Hr(t 0 ), and the increase amount and the decrease amount of the vehicle inside absolute humidity from the present on event of the start switch  5  until the present time are respectively referred to as ΔHr 1 ( t ) and ΔHr 2 ( t ), the current value Hr(t) of the vehicle inside absolute humidity is calculated as follows. Hr(t)=Hr(t 0 )+ΔHr 1 ( t )−ΔHr 2 ( t ). In Step S 742 , the control unit  49  calculates a current value of the vehicle inside relative humidity based on the current value of the vehicle inside absolute humidity calculated by the humidity update unit  483  in Step S 740 , and determines the inlet mode based on the calculated current value of the vehicle inside relative humidity. The determination method of the inlet mode is as described above. 
     According to the processing shown in  FIG. 7 , if the start on/off event detection unit  41  detects the off event of the start switch  5 , the outside air introduction processing unit  46  sets the outside air introduction ratio of the air conditioning device  10  to 100%. With this, it is possible to promote outside air introduction into the vehicle interior in the off state of the start switch  5  compared to a case where the outside air introduction ratio of the air conditioning device  10  is set to, for example, 0%. Accordingly, compared to a case where the outside air introduction ratio of the air conditioning device  10  is set to, for example, 0% in the off state of the start switch  5 , a possibility that the inside-outside air humidity difference becomes sufficiently small in the off state of the start switch  5  increases, and as a result, a possibility that the first initial value with high accuracy is calculated increases. If the first initial value with high accuracy is calculated, as described above, it is possible to increase the calculation accuracy of the subsequent vehicle inside absolute humidity which is calculated by the humidity update unit  483 . 
     In  FIG. 7 , although the vehicle outside humidity use condition is formed of the first condition, in a modification example, the vehicle outside humidity use condition further includes the second condition. In this modification example, though not shown, prior to the determination in Step S 732 , the parking state detection unit  42  determines whether or not the length of the period from the previous off event of the start switch  5  until the present on event of the start switch  5  exceeds the first predetermined time T 1 . In a case where the determination result is “YES” (that is, in a case where the predetermined parking state is detected), the process progresses to Step S 732 , and otherwise, the process progresses to Step S 738 . According to such a modification example, the second condition is added, whereby a possibility that the first initial value with high accuracy is calculated further increases. 
     In a case where the operation example shown in  FIG. 7  is employed, in the controller  40  of the air conditioning control system  1 , the parking state detection unit  42 , the inside-outside air temperature difference determination unit  45 , and the blower operation processing unit  47  are not required, and a controller which does not include the parking state detection unit  42 , the inside-outside air temperature difference determination unit  45 , and the blower operation processing unit  47  may be used. 
       FIG. 8A  and  FIG. 8B  are schematic flowcharts showing another example (a substitutive example of  FIG. 7 ) of processing which is executed by the controller  40 . The processing shown in  FIG. 8A  and  FIG. 8B  is executed, for example, in each predetermined cycle. The processing shown in  FIG. 8A  and  FIG. 8B  is different from the processing shown in  FIG. 7  in that Step S 704  is substituted with Step S 704 ′, Step S 802  is added after Step S 708 , in a case where the determination result in Step S 702  is “NO”, Step S 804  to Step S 822  are additionally executed, and Step S 830  and Step S 832  are executed instead of Step S 732 . Hereinafter, different portions will be described. In  FIG. 8A  and  FIG. 8B , as described below, the vehicle outside humidity use condition is satisfied in a case where either of the first predetermined condition or the second predetermined condition is satisfied. 
     In Step S 704 ′, the start on/off event detection unit  41  resets all of a first condition establishment flag, a second condition establishment flag, a third condition establishment flag, and a fourth condition establishment flag to “0”. The first condition establishment flag is as described above. The second condition establishment flag is a flag representing whether or not the predetermined parking state is detected by the parking state detection unit  42 . When the second condition establishment flag is “1”, this represents that the predetermined parking state is detected by the parking state detection unit  42 . The third condition establishment flag is a flag representing whether or not it is determined by the inside-outside air temperature difference determination unit  45  that the inside-outside air temperature difference is equal to or less than the predetermined value Dth. When the third condition establishment flag is “1”, this represents that it is determined by the inside-outside air temperature difference determination unit  45  that the inside-outside air temperature difference is equal to or less than the predetermined value Dth. The fourth condition establishment flag is a flag representing whether or not the blower operation processing is executed by the blower operation processing unit  47  and the blower operation processing ends when the blower operation end condition is satisfied (that is, a flag representing whether or not the above-described 4A-th condition is satisfied). When the fourth condition establishment flag is “1”, this represents that “the blower operation processing is executed by the blower operation processing unit  47  and the blower operation processing ends when the blower operation end condition is satisfied”. 
     In Step S 802 , the start on/off event detection unit  41  starts the timer TM which times out after the first predetermined time T 1 . The timer TM stops at the time of time-out or when the start switch  5  is turned on. 
     In Step S 804 , the start on/off event detection unit  41  determines whether or not the timer TM times out. In a case where the determination result is “YES”, the process progresses to Step S 806 , and otherwise, the processing in the present cycle ends. 
     In Step S 806 , the parking state detection unit  42  sets the second condition establishment flag to “1”. 
     In Step S 810 , the inside-outside air temperature difference determination unit  45  acquires the inside air temperature information at the present time from the inside air temperature sensor  861  and acquires the outside air temperature information at the present time from the outside air temperature sensor  862 . 
     In Step S 811 , the inside-outside air temperature difference determination unit  45  determines whether or not the inside-outside air temperature difference is equal to or less than the predetermined value Dth based on the inside air temperature information and the outside air temperature information obtained in Step S 810 . In a case where the determination result is “YES”, the process progresses to Step S 812 , and otherwise, the process progresses to Step S 814 . 
     In Step S 812 , the inside-outside air temperature difference determination unit  45  sets the third condition establishment flag to “1”. 
     In Step S 814 , the blower operation processing unit  47  operates the blower motor  122  to start the blower operation processing. In  FIG. 8A  and  FIG. 8B , the blower operation processing unit  47  sets the rotation speed of the blower motor  122  to a maximum value and starts the blower operation processing. 
     In Step S 816 , the blower operation processing unit  47  determines whether or not the blower operation end condition is established. In  FIG. 8A  and  FIG. 8B , the blower operation end condition is formed of the above-described second end condition (“the operation time of the blower motor  122  exceeds the third predetermined time T 3 ”). In a case where the determination result is “YES”, the process progresses to Step S 817 , and otherwise, the process progresses to Step S 820 . 
     In Step S 817 , the blower operation processing unit  47  ends the blower operation processing. 
     In Step S 818 , the blower operation processing unit  47  sets the fourth condition establishment flag to “1”. 
     In Step S 820 , the blower operation processing unit  47  determines whether or not the on event of the start switch  5  is detected by the start on/off event detection unit  41 . In a case where the determination result is “YES”, the process progresses to Step S 738 , and otherwise, the process progresses to Step S 822 . In Step S 738  which progresses in a case where the determination result in Step S 820  is “YES”, the second humidity initial value calculation unit  482  acquires the current value of the inside air temperature from the inside air temperature sensor  861  of the air conditioner related sensor  86 , and then, calculates the second initial value of the vehicle inside absolute humidity. A case where the determination result in Step S 820  is “YES” refers to a case where the blower operation processing has not been continued due to the on event of the start switch  5  until the blower operation end condition is established. In a case where the blower operation processing has not been continued until the blower operation end condition is established, there is a possibility that the inside-outside air humidity difference does not become sufficiently small. For this reason, in  FIG. 8A  and  FIG. 8B , in a case where the determination result in Step S 820  is “YES”, the process progresses to Step S 738 . 
     In Step S 822 , the blower operation processing unit  47  stands by for a time of one predetermined cycle. That is, the blower operation processing unit  47  performs the determination in Step S 816  in the next processing cycle again. 
     In Step S 830 , the humidity calculation unit  48  determines whether or not the first predetermined condition is satisfied. That is, the humidity calculation unit  48  determines whether or not all of the first condition establishment flag, the second condition establishment flag, and the third condition establishment flag are “1”. In a case where the determination result is “YES”, the process progresses to Step S 734 , and otherwise (that is, in a case where at least one of the first condition establishment flag, the second condition establishment flag, or the third condition establishment flag is “0”), the process progresses to Step S 832 . 
     In Step S 832 , the humidity calculation unit  48  determines whether or not the second predetermined condition is satisfied. That is, the humidity calculation unit  48  determines whether or not all of the first condition establishment flag, the second condition establishment flag, and the fourth condition establishment flag are “1”. In a case where the determination result is “YES”, the process progresses to Step S 734 , and otherwise (that is, in a case where at least one of the first condition establishment flag, the second condition establishment flag, or the fourth condition establishment flag is “0”), the process progresses to Step S 738 . 
     According to the processing shown in  FIG. 8A  and  FIG. 8B , like the processing shown in  FIG. 7 , since the outside air introduction processing unit  46  sets the outside air introduction ratio of the air conditioning device  10  to 100%, it is possible to promote outside air introduction in the off state of the start switch  5  compared to a case where the outside air introduction ratio of the air conditioning device  10  is set to, for example, 50%. Accordingly, compared to a case where the outside air introduction ratio of the air conditioning device  10  is set to, for example, 50%, it is possible to shorten the first predetermined time T 1  which is a threshold for detecting the predetermined parking state, and a possibility that, even in a case where the off period of the start switch  5  is comparatively short, first initial value with high accuracy is calculated increases. If the first initial value with high accuracy is calculated, as described above, it is possible to increase the calculation accuracy of the subsequent vehicle inside absolute humidity which is calculated by the humidity update unit  483 . 
     On the other hand, even in a case where the outside air introduction ratio is set to the predetermined ratio α (for example, 100%) and the state (predetermined parking state) in which the off period of the start switch  5  exceeds the first predetermined time T 1  is detected, the inside-outside air humidity difference may not become sufficiently small due to the predetermined ratio α, the setting form of the first predetermined time T 1 , or other factors. For example, in a case where the inside-outside air humidity difference when the start switch  5  is turned off is excessively large, even when the off period of the start switch  5  exceeds the first predetermined time T 1  in a state in which the outside air introduction ratio is set to the predetermined ratio α, the inside-outside air humidity difference may not become sufficiently small. 
     In this respect, according to the processing shown in  FIG. 8A  and  FIG. 8B , in a case where the first predetermined condition or the second predetermined condition is satisfied as the vehicle outside humidity use condition, it is determined that the inside-outside air humidity difference is sufficiently small, and the first initial value is used. In  FIG. 8A  and  FIG. 8B , the first predetermined condition is a condition in which the condition that it is determined by the inside-outside air temperature difference determination unit  45  that the inside-outside air temperature difference is equal to or less than the predetermined value Dth (third condition) is added to the first condition and the second condition in an AND manner. The inside-outside air temperature difference can be used as an index value regarding whether or not outside air is sufficiently introduced into the vehicle interior. This is because the larger outside air introduced into the vehicle interior, the smaller the inside-outside air temperature difference. Therefore, according to the processing shown in  FIG. 8A  and  FIG. 8B , it is possible to further increase a possibility that the first initial value is used when the inside-outside air humidity difference is comparatively small. 
     In  FIG. 8A  and  FIG. 8B , as described above, the second predetermined condition is a condition in which the 4A-th condition is added to the first condition and the second condition in an AND manner. The blower operation processing can promote introduction of outside air into the vehicle interior at the same outside air introduction ratio (&gt;0) compared to natural ventilation. The blower operation processing can reduce the inside-outside air humidity difference rapidly compared to natural ventilation. Therefore, according to the processing shown in  FIG. 8A  and  FIG. 8B , it is possible to further increase a possibility that the first initial value is used when the inside-outside air humidity difference is comparatively small. Since the blower operation processing is not executed in a case where it is determined by the inside-outside air temperature difference determination unit  45  that the inside-outside air temperature difference is equal to or less than the predetermined value Dth, it is possible to reduce an opportunity of execution of the blower operation processing in the off state of the start switch  5 , and to achieve power saving. 
     In the processing shown in  FIG. 8A  and  FIG. 8B , in a case where the determination result in Step S 811  is “NO”, the process progresses to Step S 814  and the blower operation processing is executed, but the disclosure is not limited thereto. For example, in a first modification example, in  FIG. 8A  and  FIG. 8B , Step S 814  to Step S 822 , and Step S 832  may be omitted. In this case, in a case where the determination result in Step S 811  is “NO”, the processing in the present cycle may end, and in a case where the determination result in Step S 830  is “NO”, the process may progress to Step S 738 . In the first modification example, the blower operation processing unit  47  can be eliminated. 
     In a further modification example (hereinafter, referred to as a “second modification example”) to the first modification example, Step S 810  is omitted, and Step S 811  and Step S 812  are executed when the start switch  5  is turned on. In a case of the second modification example, in  FIG. 8A  and  FIG. 8B , the inside-outside air temperature difference determination unit  45  determines whether or not the inside-outside air temperature difference is equal to or less than the predetermined value Dth based on the outside air temperature information and the inside air temperature information obtained in Step S 724  prior to the determination in Step S 830  by the humidity calculation unit  48 . Then, in a case where the inside-outside air temperature difference is equal to or less than the predetermined value Dth, the inside-outside air temperature difference determination unit  45  sets the third condition establishment flag to “1”. 
     In a further modification example (hereinafter, referred to as a “third modification example”) to the second modification example, Steps S 802  to  806  are omitted. In the third modification example, in a case where the determination result in Step S 702  is “NO”, the processing in the present cycle ends. In a case of the third modification example, the parking state detection unit  42  determines whether or not the length of a period from the previous off event of the start switch  5  to the present on event exceeds the first predetermined time T 1  prior to the determination in Step S 830  by the humidity calculation unit  48 . Then, in a case where the determination result is “YES”, the parking state detection unit  42  determines that the predetermined parking state is detected, and sets the second condition establishment flag to “1”. 
     In the processing shown in  FIG. 8A  and  FIG. 8B , the parking state detection unit  42  is used, but the disclosure is not limited thereto. For example, in a fourth modification example, the timer TM is substituted with another timer TM 2  which times out after a second predetermined time T 2  from the start, and the second predetermined time T 2  is shorter than the first predetermined time T 1 . In the fourth modification example, Step S 806  is omitted, and the condition that the second condition establishment flag is “1” is excluded from the respective determination conditions in Step S 830  and Step S 832 . 
       FIG. 9  is an explanatory view of the processing of  FIG. 8A  and  FIG. 8B , and is a timing chart schematically showing various states over a period from any off event of the start switch  5  to the next on event. In  FIG. 9 , in order from the above, the on/off state of the start switch  5 , an inside air temperature Tr and an outside air temperature Ta, vehicle inside relative humidity H 1  and vehicle outside relative humidity H 2 , the state of the outside air introduction ratio, and the operation state of the blower motor  122  are shown in time series. 
     In  FIG. 9 , at a time t 1 , the off event of the start switch  5  is generated, and at this time, the inside air temperature Tr is significantly higher than the outside air temperature Ta and the vehicle inside relative humidity H 1  is significantly higher than the vehicle outside relative humidity H 2 . However, at the time t 1 , since the outside air introduction ratio is set to 100%, the difference between the inside air temperature Tr and the outside air temperature Ta and the difference between the vehicle inside relative humidity H 1  and the vehicle outside relative humidity H 2  decrease over time. In  FIG. 9 , at a time t 2  after the first predetermined time T 1  from the time t 1 , the difference between the inside air temperature Tr and the outside air temperature Ta does not become equal to or less than the predetermined value Dth, and the blower operation processing is executed. With this, the difference between the inside air temperature Tr and the outside air temperature Ta and the difference between the vehicle inside relative humidity H 1  and the vehicle outside relative humidity H 2  become small comparatively rapidly. At a time t 3  at which the blower operation processing ends, the difference between the inside air temperature Tr and the outside air temperature Ta and the difference between the vehicle inside relative humidity H 1  and the vehicle outside relative humidity H 2  become excessively small. Thereafter, the on event of the start switch  5  is generated at a time t 4 . At the time t 4 , the difference between the vehicle inside relative humidity H 1  and the vehicle outside relative humidity H 2  becomes substantially zero. Accordingly, in such a case, it is understood that the calculation accuracy of the vehicle inside absolute humidity (and the vehicle inside relative humidity based thereon) calculated by the humidity calculation unit  48  based on the vehicle outside humidity information increases. 
     Although the example has been described in detail, the disclosure is not limited to a specific example, and various modifications and alterations may be made without departing from the scope of the appended claims. In addition, all or a plurality of constituent elements of the example described above may be combined with one another. 
     For example, in the above-described example, instead of the inside-outside air temperature difference determination unit  45 , a determination unit (hereinafter, referred to as a “saturated water vapor amount difference determination unit”, another example of a difference determination unit) (not shown) which determines whether or not the difference between a saturated water vapor amount of outside air and a saturated water vapor amount of inside air is equal to or less than a predetermined value Dw may be provided. This is because the difference between the saturated water vapor amount of outside air and the saturated water vapor amount of inside air has a high correlation with the inside-outside air temperature difference. The saturated water vapor amount of outside air is a water vapor amount when the relative humidity is 100%, and changes depending on the outside air temperature (see  FIG. 5B ). The saturated water vapor amount of inside air is a water vapor amount when the relative humidity is 100%, and changes depending on the inside air temperature (see  FIG. 5B ). In this case, the above-described third condition is substituted with the following 3A-th condition: (3A-th condition) it is determined by the saturated water vapor amount difference determination unit that the saturated water vapor amount difference is equal to or less than the predetermined value Dw. 
     In the above-described example, the outside air introduction processing unit  46  may end a state in which the outside air introduction ratio is greater than 0% in a case where the above-described third condition is satisfied or in a case where the fourth condition is satisfied. This is because, even in this case, there is a possibility that a state in which the inside-outside air humidity difference is small is maintained until the start switch  5  is turned on thereafter. 
     In the above-described example, in a case where it is determined by the inside-outside air temperature difference determination unit  45  that the inside-outside air temperature difference is not equal to or less than the predetermined value Dth in the off state of the start switch  5 , the blower operation processing unit  47  starts the blower operation processing, but the disclosure is not limited thereto. In a modification example, the blower operation processing unit  47  may start the blower operation processing under a situation in which it is not determined by the inside-outside air temperature difference determination unit  45  whether or not the inside-outside air temperature difference is equal to or less than the predetermined value Dth in the off state of the start switch  5 . For example, the blower operation processing unit  47  may execute the blower operation processing prior to the determination by the inside-outside air temperature difference determination unit  45 . In this case, the blower operation processing unit  47  may continue the blower operation processing in cooperation with the inside-outside air temperature difference determination unit  45  in the off state of the start switch  5  until the above-described first end condition is established. Alternatively, in a configuration in which the inside-outside air temperature difference determination unit  45  is not provided, blower operation processing unit  47  starts the blower operation processing, for example, a fifth predetermined time T 5  has elapsed from the off event of the start switch  5 . Thereafter, the blower operation processing unit  47  continues the blower operation processing in the off state of the start switch  5  until the second end condition is established. In this case, even in a configuration in which the inside-outside air temperature difference determination unit  45  is not provided, the blower operation processing unit  47  can function.