Anti-fog system

Abstract

To provide a defroster system capable of allowing output from a heater and also properly controlling the output of the heater so as to suppress windows from getting frosted.SOLUTION: The present invention relates to a defroster system X for a photographic device 10 for photographing the vehicle outside SP2 through a predetermined visual field region R set on a window 6 of a vehicle 1, and the defroster system has a heater 31 which heats the visual field region, and a controller 26 which applies voltage pulses of a supply voltage at a predetermined duty ratio to the heater to generate heat by the heater to prevent the visual field region from getting frosted, wherein the controller acquires a voltage value of the supply voltage and then sets the duty ratio of voltage pulses.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an anti-fog system for reducing fogging on vehicle windows. [Background technology]

[0002] Conventionally, vehicles equipped with an imaging device that captures an image of an exterior space of the vehicle through a window from inside the vehicle are known. Such vehicles are sometimes provided with a defogging system for suppressing fogging of the window to prevent fogging of the window from interfering with imaging by the imaging device. The defogging system includes a defogging device (e.g., a heating device for heating the window) that suppresses fogging of the window and a control device that controls the defogging device.

[0003] For example, Patent Document 1 discloses a mobile body equipped with a monitoring device capable of monitoring the surrounding environment of the mobile body through a translucent window member, a heating device for heating a portion of the window member within the monitoring area of ​​the monitoring device, and a control device for controlling the operation of the heating device.

[0004] The heating device includes an electric heating wire, and a driver supplies an electric current based on the power of the battery to the electric heating wire of the heating device, thereby heating a portion of the window member within the monitoring area of ​​the monitoring device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-152324 Summary of the Invention [Problem to be solved by the invention]

[0006] The voltage supplied from the battery to the heating wire (heater) can change depending on the operating state of other devices (e.g., wipers, headlights, etc.) that are powered by the battery. Therefore, depending on the operating state of other devices, the power supplied to the heating wire may be too much or too little, which could result in an insufficient defogging effect or an excessive amount of power being supplied to the heating wire, which could cause heat damage.

[0007] In view of the above background, an object of the present invention is to provide an anti-fogging system that outputs power from a heater and can appropriately control the heater output to suppress window fogging. By suppressing window fogging, situations in which vehicle driving control based on the image capture results from the image capture device cannot be performed will be reduced, and ultimately, traffic safety will be further improved, contributing to the development of a sustainable transportation system. [Means for solving the problem]

[0008] In order to solve the above problem, one aspect of the present invention is an anti-fogging system (X) for an imaging device (10) that images the outside of a vehicle (SP2) through a predetermined viewing area (R) set on a window (6) of a vehicle (1), the anti-fogging system having a heater (31) that heats the viewing area, and a control device (26) that applies a voltage pulse of a supply voltage to the heater at a predetermined duty ratio to heat the heater and prevent the viewing area from fogging up, the control device obtaining a voltage value of the supply voltage and setting the duty ratio of the voltage pulse based on the voltage value of the supply voltage.

[0009] According to this aspect, the duty ratio of the voltage pulse is set based on the voltage value of the supply voltage, so that the heater output can be set to an appropriate value.

[0010] In the above aspect, preferably, the control device sets the duty ratio of the voltage pulse to increase as the voltage value of the supply voltage decreases.

[0011] According to this aspect, it is possible to prevent the heat output from the heater from becoming insufficient or excessive.

[0012] In the above aspect, preferably, the control device obtains a target output to be output from the heater to prevent fogging in the viewing area, and sets the duty ratio of the voltage pulse based on the target output and the voltage value of the supply voltage.

[0013] According to this aspect, the duty ratio can be set to match the target output to be output from the heater.

[0014] In the above aspect, preferably, the control device acquires weather information while the vehicle is traveling and the vehicle's own speed, and acquires the target output based on the acquired weather information and the vehicle's own speed.

[0015] According to this aspect, the target output is set based on weather conditions that make the windows more likely to condense and the degree to which the windows are cooled by the wind while driving, so the heater output can be set to an appropriate value compared to when it is not based on weather conditions or vehicle speed.

[0016] In the above aspect, preferably, a solar radiation sensor (44) is provided to detect the amount of solar radiation on the vehicle, and the control device acquires the amount of solar radiation from the solar radiation sensor as the weather information while the vehicle is traveling.

[0017] The lower the amount of solar radiation, the smaller the temperature rise of the window due to solar radiation, making the window more likely to become cold and prone to condensation. Therefore, the lower the amount of solar radiation, the more desirable it is to increase the heater output. According to this aspect, the control device acquires the amount of solar radiation as weather information and sets the target heater output based on the acquired weather information, so the duty ratio can be set to an appropriate value depending on the likelihood of the window fogging up.

[0018] In the above aspect, preferably, the control device sets the duty ratio lower when the amount of solar radiation is equal to or greater than a predetermined solar radiation threshold value than when the amount of solar radiation is less than the solar radiation threshold value.

[0019] The lower the amount of solar radiation, the smaller the temperature rise of the window due to solar radiation, making it easier for the window to become cold and for condensation to form on the window. Therefore, it is desirable to increase the heater output the lower the amount of solar radiation. According to this aspect, when the amount of solar radiation is below the solar radiation threshold and condensation is likely to form on the window, the duty ratio is set high, thereby preventing condensation on the window. Furthermore, when the amount of solar radiation is equal to or greater than the solar radiation threshold and condensation is unlikely to form on the window, the duty ratio is set low, thereby preventing excessive output from the heater.

[0020] In the above aspect, preferably, the control device sets the duty ratio higher when the host vehicle speed is equal to or higher than a predetermined vehicle speed threshold compared to when the host vehicle speed is lower than the vehicle speed threshold.

[0021] The higher the vehicle speed, the more the window is cooled by the wind while the vehicle is traveling. As a result, water vapor inside the vehicle cabin is more likely to condense near the window, making the window more likely to fog up. Therefore, according to this aspect, when the vehicle speed is equal to or greater than the vehicle speed threshold, and the window is more likely to fog up, the duty ratio is increased compared to when the vehicle speed is less than the vehicle speed threshold, making it possible to set the duty ratio to an appropriate value.

[0022] In the above aspect, preferably, the control device acquires the weather information via a network (N).

[0023] According to this aspect, even if it is difficult to provide a sensor for acquiring the environmental conditions around the vehicle in the vehicle, the target output of the heater can be set.

[0024] In the above aspect, the weather information acquired by the control device via the network preferably includes a predicted wind speed along the travel route of the vehicle.

[0025] When the vehicle travels along a travel route, the wind blowing against the vehicle also cools the windows. According to this aspect, the control device can set the duty ratio by taking into account the influence of the wind blowing against the vehicle by acquiring the wind speed predicted along the travel route, and therefore can set the duty ratio to an appropriate value. [Effects of the Invention]

[0026] According to the above aspects, it is possible to provide an anti-fogging system that outputs power from a heater and can appropriately control the heater output in order to suppress fogging of a window. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a perspective view showing a vehicle according to an embodiment of the present invention; [Figure 2] FIG. 1 is a perspective view showing a front camera and its peripheral portion according to an embodiment of the present invention; [Figure 3] FIG. 1 is a functional block diagram illustrating an anti-fogging system according to an embodiment of the present invention. [Figure 4] Control device block diagram [Figure 5] Target output map according to an embodiment of the present invention [Figure 6] 10 is a flowchart showing an output setting process according to an embodiment of the present invention; [Figure 7] Graphs showing (A) an example of heater temperature change over time and pulse voltage when PWM control set in the output setting process is performed, and (B) an example of heater temperature change over time and pulse voltage when the supply voltage is lower than that of (A). DETAILED DESCRIPTION OF THE INVENTION

[0028] <Vehicle> First, a vehicle 1 equipped with an anti-fogging system X according to one embodiment of the present invention will be described with reference to the drawings. An arrow Fr in Figs. 1 and 2 indicates the front of the vehicle 1.

[0029] 1, vehicle 1 is a four-wheeled vehicle, or what is known as an automobile. Vehicle 1 may be an electric vehicle using only an electric motor as a drive source, or may be a hybrid vehicle equipped with an electric motor and an engine as drive sources.

[0030] Vehicle 1 has a vehicle body 2 that forms its exterior shape. Vehicle body 2 has a shape that is long in the front-to-rear direction of the vehicle. An interior space SP1 is formed inside vehicle body 2, and a passenger compartment 3 that accommodates occupants is provided in the center of interior space SP1 in the front-to-rear direction. The passenger compartment 3 is provided with, for example, a plurality of front seats 4 (driver's seat, passenger seat) and a plurality of rear seats 5 arranged behind the front seats 4. Note that in this embodiment, two rows of seats are provided in the front and rear, but in other embodiments, there may be only one row of seats in the front and rear, or three or more rows of seats in the front and rear.

[0031] A front windshield 6 (an example of a window) is provided in the front part of the vehicle body 2, in front of the front seats 4. The front windshield 6 is made of glass. In other embodiments, the front windshield 6 may be made of a transparent material other than glass (for example, a transparent resin). A rear window 7 is provided in the rear part of the vehicle body 2, behind the rear seats 5. A plurality of side doors 8 are provided on both sides of the vehicle body 2, beside the front seats 4 and rear seats 5, and a side window 9 is provided above each side door 8.

[0032] As shown in FIGS. 1 and 2, a front camera 10 (an example of an imaging device) is provided at the upper rear of the windshield 6. The front camera 10 is an imaging device that images (photographs) an exterior space SP2 (in this embodiment, the space in front of the vehicle 1) from an interior space SP1 through the windshield 6. The front camera 10 is, for example, a digital camera that uses a solid-state imaging element such as a CCD or CMOS. The front camera 10 includes a lens 10A that converges light incident from the front through the windshield 6, and a sensor (not shown) that converts the light converged by the lens 10A into an electrical signal.

[0033] 2, the front camera 10 is attached to the inner surface of the windshield 6 via a bracket 11. The bracket 11 has a fixing frame 12 fixed to the inner surface of the windshield 6 and a hood 13 protruding from the fixing frame 12 toward the rear lower side (inside the vehicle). When viewed from the front of the vehicle 1, the fixing frame 12 overlaps with black ceramic 6A printed on the surface of the windshield 6 facing inside the vehicle.

[0034] The hood 13 is provided behind the windshield 6 (inside the vehicle). The hood 13 is installed to prevent, for example, light reflected by an object in the vehicle interior space SP1 from being reflected by the windshield 6 and thereby capturing an object in the vehicle interior space SP1 in an image captured by the front camera 10. The hood 13 may be provided with a stray light shield (SLS) to prevent light reflected by the hood 13 from entering the front camera 10. The hood 13 defines the lower edge of a space (hereinafter referred to as a visual field space S) through which light entering the front camera 10 from the vehicle exterior space SP2 passes. The front camera 10 captures an image of the vehicle exterior space SP2 through a portion of the windshield 6 located within the visual field space S of the front camera 10 (hereinafter referred to as a visual field region R).

[0035] 3, the vehicle 1 includes a propulsion device 14, a braking device 15, a steering device 16, an HMI (Human Machine Interface) 17, a navigation device 18, a heating device 19, an external sensor 22, a vehicle sensor 23, and a control device 26. The navigation device 18, the heating device 19, the vehicle sensor 23, and the control device 26 constitute an anti-fogging system X for the vehicle 1.

[0036] The propulsion device 14 is a device that applies driving force to the vehicle 1. The propulsion device 14 includes, for example, an internal combustion engine such as a gasoline engine or a diesel engine and / or an electric motor.

[0037] The braking device 15 is a device that applies braking force to the vehicle 1. The braking device 15 includes, for example, a brake caliper that presses a pad against a brake rotor, and an electric cylinder that supplies hydraulic pressure to the brake caliper.

[0038] The steering device 16 is a device that changes the steering angle of the wheels. The steering device 16 includes, for example, a rack and pinion mechanism that steers the wheels, and an electric motor that drives the rack and pinion mechanism.

[0039] The HMI 17 is a device that notifies the occupant of various information and receives input operations from the occupant. The HMI 17 includes, for example, a power switch for switching the power state of the vehicle 1, a touch panel, a sound generating device (speaker), a sound acquiring device (microphone), and the like.

[0040] The navigation device 18 is a device that provides route guidance to the destination of the vehicle 1. The navigation device 18 includes an input device that accepts input operations from the occupant. This input device may be configured as a part of the HMI 17, or may be provided separately from the HMI 17.

[0041] The navigation device 18 stores map information of the area in which the vehicle 1 travels. The navigation device 18 identifies the current position (latitude and longitude) of the vehicle 1 based on GNSS signals (e.g., GPS signals) received from artificial satellites. The navigation device 18 sets a driving route from the departure point (e.g., current position) of the vehicle 1 to the destination based on the map information, the current position of the vehicle 1, and the destination of the vehicle 1 input by the occupant to the input device.

[0042] The navigation device 18 is connected to various servers 30 via a network N such as the Internet. Each server 30 is a computer equipped with a CPU, memories such as ROM and RAM, and storage devices such as HDD and SSD. Each server 30 provides corresponding information in response to a request from the navigation device 18. The server 30 to which the navigation device 18 is connected may include a weather server 30A that provides weather forecast information for the driving route in response to a request from the navigation device 18. The weather forecast information includes the weather, temperature, and wind speed predicted for each point on the driving route. Furthermore, the weather forecast information may also include the amount of solar radiation, temperature, humidity, etc. predicted for each point on the driving route.

[0043] The heating device 19 is a device that heats the windshield 6 to suppress fogging of the windshield 6, and includes a heater 31 for performing the heating. In this embodiment, the heater 31 heats the viewing area R of the windshield 6 to suppress fogging of the viewing area R. In this way, suppressing fogging of the viewing area R (i.e., the portion of the windshield 6 required for the front camera 10 to capture an image of the vehicle exterior space SP2) prevents the front camera 10 from being unable to capture an image of the vehicle exterior space SP2.

[0044] The heater 31 is composed of a heating wire 33. As shown in Fig. 2, the heating wire 33 is fixed to the inner surface of the windshield 6 and is arranged along the outer periphery of the visual field space S of the front camera 10, specifically, along the outer edge of the visual field area R. Note that in other embodiments, the heating wire 33 may be built into the windshield 6 or may be fixed to the bracket 11.

[0045] The external sensor 22 is a sensor that detects objects (such as obstacles on the road on which the vehicle 1 is traveling, lane markings, and vehicles ahead) present in the vehicle exterior space SP2. As shown in FIG. 3 , the external sensor 22 includes the front camera 10 described above, a sonar 38, and an exterior camera 39 that captures images of the left and right sides and rear of the vehicle 1 through the window.

[0046] The vehicle sensor 23 is a sensor that detects the state of the interior space SP1 and the exterior space SP2, the traveling state of the vehicle 1, etc. The vehicle sensor 23 includes an exterior temperature sensor 41 that detects the temperature of the exterior space SP2 (an example of the state of the exterior space SP2; hereinafter referred to as the "exterior temperature"), an interior temperature sensor 42 that detects the temperature of the interior space SP1 (an example of the state of the interior space SP1; hereinafter referred to as the "interior temperature"), a vehicle speed sensor 43 that detects the speed of the vehicle 1 (i.e., the host vehicle), a solar radiation sensor 44 that detects the amount of solar radiation on the windshield 6 (hereinafter referred to as the "solar radiation"), and an exterior humidity sensor 45 that detects the humidity in the exterior space SP2 (hereinafter referred to as the "exterior humidity"). Note that in other embodiments, the solar radiation sensor 44 may detect the amount of solar radiation on a portion of the vehicle 1 other than the windshield 6.

[0047] As shown in Fig. 4, the control device 26 is an electronic control unit (ECU) configured by a computer including a processor 26A such as a CPU (Central Processing Unit) or an MPU (Microprocessor Unit), a memory 26B such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and a storage device 26C such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The control device 26 can execute various processes by having the processor 26A read necessary data and application software from the memory 26B or the storage device 26C and execute predetermined arithmetic processing in accordance with the software. The control device 26 may be configured as a single piece of hardware, or may be configured as a unit consisting of multiple pieces of hardware.

[0048] 3, the control device 26 is connected to each component of the vehicle 1 via a communication network 21 such as a CAN (Controller Area Network), and controls each component of the vehicle 1. The communication network 21 may be made up of multiple networks, and may include, for example, a B-CAN and an F-CAN, which has a faster communication speed than the B-CAN.

[0049] The vehicle 1 is equipped with a battery 46. The battery 46 may be charged by regeneration using an electric motor, or may be charged by electric power from an ACG (alternator) provided in a gasoline engine.

[0050] The battery 46 functions as a voltage source that supplies power to various devices installed on the vehicle 1, including the propulsion device 14, the braking device 15, the HMI 17, the navigation device 18, the heating device 19, the external sensor 22, the vehicle sensor 23, and the control device 26.

[0051] The battery 46 supplies a predetermined supply voltage (e.g., 13.5 V, also referred to as the reference voltage) to various devices mounted on the vehicle 1 via a known reference voltage circuit (not shown) or the like. However, if an electric motor or the like is driven when the battery 46 or the engine is cold, the supply voltage may drop. Also, if a break occurs in the wiring from the battery 46 while the alternator is generating power, the supply voltage may rise. Also, depending on the usage status of various devices mounted on the vehicle 1, for example, when the wipers or headlights are in use, the supply voltage may be controlled to compensate for the voltage drop caused by those devices. However, the reference voltage circuit is not essential, and the supply voltage may be supplied to the various devices directly from the battery 46, or may be supplied to the various devices from the battery 46 via other electrical circuits.

[0052] The control device 26 includes, as functional units, an external environment recognition unit 52, a driving control unit 53, an anti-fogging control unit 54, and a memory unit 55. At least a portion of the functional units of the control device 26 may be realized by hardware such as an LSI, an ASIC, or an FPGA, or may be realized by a combination of software and hardware.

[0053] The external environment recognition unit 52 of the control device 26 recognizes the positions of targets (obstacles on the road on which the vehicle 1 is traveling, lane markings, vehicles ahead, etc.) present in the vehicle exterior space SP2 based on the detection results of the external environment sensor 22. For example, the external environment recognition unit 52 recognizes the positions of targets present ahead of the vehicle 1 by analyzing changes in density values ​​on the image captured by the front camera 10.

[0054] The driving control unit 53 of the control device 26 performs driving control of the vehicle 1 based on the positions of targets (obstacles on the roadway of the vehicle 1, lane markings, vehicles ahead, etc.) recognized by the external environment recognition unit 52. The driving control performed by the driving control unit 53 includes various driving controls (driving control equivalent to SAE autonomous driving levels 1 to 2) for configuring an Advanced Driver Assistance System (ADAS). In other embodiments, the driving control performed by the driving control unit 53 may include various driving controls (driving control equivalent to SAE autonomous driving levels 3 or higher) for achieving autonomous driving (AD).

[0055] Various types of driving controls that realize ADAS include, for example, lane keeping control and vehicle-in-front following control. In lane keeping control, the driving control unit 53 controls the steering device 16 so that the vehicle 1 travels at a reference position (for example, the center of the lane in the width direction) within a lane defined by dividing lines. In vehicle-in-front following control, the driving control unit 53 controls the propulsion device 14 and the braking device 15 so that the distance between the vehicle 1 and the vehicle in front is maintained within a predetermined range.

[0056] The defogging control unit 54 of the control device 26 controls the heater 31 of the heating device 19 to suppress fogging of the windshield 6. The defogging control unit 54 may control the heater 31 based on, for example, detection results from the vehicle sensors 23. In this embodiment, the control device 26 (defogging control unit 54) is connected to the navigation device 18 to acquire weather forecast information for each point on the travel route and the position of the vehicle 1, and performs PWM (Pulse Width Modulation) control of the heater 31 based on the acquired weather forecast information and detection results from the vehicle sensors 23. In this embodiment, the defogging control unit 54 repeatedly switches on and off in PWM control to generate a voltage pulse train with a constant period that becomes a supply voltage when on (High) and becomes 0 V when off, and applies the generated voltage pulse train to the heater 31. In PWM control, the anti-fogging control unit 54 controls the output from the heater 31 (more specifically, the amount of heat generated per unit time from the heater 31) by changing the proportion of time that the voltage pulse remains on per cycle, i.e., the duty ratio.

[0057] The storage unit 55 of the control device 26 is configured with the memory 26B and / or the storage device 26C. The storage unit 55 stores various information required for controlling the vehicle 1 and for controlling the heater 31 performed by the defogging control unit 54.

[0058] The information stored in the memory unit 55 includes, for example, dynamic map data. The dynamic map data includes static information, quasi-static information, quasi-dynamic information, and dynamic information. The static information includes three-dimensional map information with higher accuracy than the map information stored in the navigation device 18. The quasi-static information includes traffic regulation information, road construction information, and wide-area weather information. The quasi-dynamic information includes accident information, congestion information, and narrow-area weather information. The dynamic information includes traffic signal information, nearby vehicle information, and pedestrian information. The control device 26 may connect to the high-accuracy map server 30B via the network N as appropriate and update the dynamic map data stored in the memory device 26C.

[0059] The information stored in the storage unit 55 includes various types of information required for the defogging control unit 54 to control the heater 31 (hereinafter referred to as heater control information).

[0060] The heater control information includes a heater resistance value and a target output map 56. The heater resistance value is the resistance value of the heater 31. The target output map 56 is a map showing the relationship between the amount of solar radiation and the vehicle speed, and the output value to be output from the heater 31 (hereinafter referred to as target output). The target output map 56 in this embodiment is schematically shown in FIG. 5. However, instead of the target output map 56, the storage unit 55 may store, as heater control information, the relationship between weather conditions such as the amount of solar radiation and the vehicle speed, and the target output, in the form of a table, a formula, or the like.

[0061] The target output map 56 is recorded so that when the host vehicle speed is equal to or greater than a predetermined vehicle speed threshold and the amount of solar radiation is equal to or less than a predetermined solar radiation threshold, the target output is set to a first output value. When the host vehicle speed is less than the vehicle speed threshold and the amount of solar radiation is less than the solar radiation threshold, the target output is set to a second output value. When the host vehicle speed is equal to or greater than the vehicle speed threshold and the amount of solar radiation is equal to or greater than the solar radiation threshold, the target output is set to a second output value. When the host vehicle speed is less than the vehicle speed threshold and the amount of solar radiation is equal to or greater than the solar radiation threshold, the target output is set to a third output value. The first output value is greater than the second output value, and the second output value is greater than the third output value.

[0062] <Output setting process> After the vehicle 1 starts, until the vehicle 1 stops, the defogging control unit 54 of the control device 26 executes an output setting process at predetermined time intervals to determine a duty ratio for PWM control of the heater 31. The output setting process will be described in detail below with reference to Fig. 6. However, although the following description will be given assuming that the defogging control unit 54, which is a functional unit, executes various processes, this means that the processor 26A of the control device 26 executes predetermined processes in accordance with software, thereby executing various processes as the defogging control unit 54.

[0063] At the beginning of the output setting process, in step ST1, the defogging control unit 54 acquires the voltage value of the supply voltage. After acquiring the supply voltage, the defogging control unit 54 executes step ST2.

[0064] In step ST2, the defogging control unit 54 acquires the host vehicle speed from the vehicle speed sensor 43. After acquiring the host vehicle speed, the defogging control unit 54 executes step ST3.

[0065] In step ST3, the defogging control unit 54 acquires the amount of solar radiation from the solar radiation sensor 44. After acquiring the amount of solar radiation, the defogging control unit 54 executes step ST4.

[0066] In step ST4, the defogging control unit 54 acquires the target output power based on the vehicle speed acquired in step ST2 and the amount of solar radiation acquired in step ST4, by referring to the target output power map 56. After acquiring the target output power, the defogging control unit 54 executes step ST5.

[0067] In step ST5, the defogging control unit 54 acquires the heater resistance value from the storage unit 55. Thereafter, the defogging control unit 54 calculates the product of the heater resistance value and the supply voltage acquired in step ST1 to calculate the maximum output. After the calculation of the maximum output is completed, the defogging control unit 54 executes step ST6.

[0068] In step ST6, the defogging control unit 54 determines the duty ratio by dividing the target output obtained in step ST4 by the maximum output obtained in step ST5. However, if the target output is greater than the maximum output, the defogging control unit 54 may set the duty ratio to 1 or a value sufficiently close to 1. Once the duty ratio has been obtained, the defogging control unit 54 ends the output setting process.

[0069] The defogging control unit 54 performs PWM control by applying a pulse voltage to the heater 31 based on the duty ratio acquired in the output setting process. After completing the output setting process, when a predetermined time has elapsed, the defogging control unit 54 may perform the output setting process again to update the duty ratio for PWM control.

[0070] <Effects> Next, we will explain the effects of the defogging system X configured in this way. Figures 7(A) and (B) respectively show the temperature change of the heater 31 and the pulse voltage applied by the defogging control unit 54 when the resistance value and target output of the heater 31 are equal and the supply voltage is different.

[0071] FIG. 7(A) shows a case where the supply voltage is higher than that of FIG. 7(B). Because the target output is the same in FIGS. 7(A) and 7(B), in step ST6, the duty ratio (proportion of time the device is ON) in the case of FIG. 7(A) is set to be smaller than that in FIG. 7(B). In this way, by setting the duty ratio based on the supply voltage, it is possible to set the duty ratio to an appropriate value. Furthermore, because the duty ratio is set to decrease as the supply voltage increases, it is possible to prevent the heat output from the heater 31 from being insufficient or excessive, even when the supply voltage fluctuates.

[0072] In this embodiment, the duty ratio is determined by dividing the target output by the maximum output based on the supply voltage, and is set so that the heat per unit time output from the heater 31 in one cycle is equal to the target output. Therefore, even if the supply voltage fluctuates, the duty ratio is set to match the target output to be output from the heater 31, so that insufficient or excessive heat output from the heater 31 can be more reliably prevented.

[0073] The lower the amount of solar radiation, the smaller the temperature rise due to solar radiation on windows, including the windshield 6, and therefore the glass installed in the window is more likely to become cold and condensation is more likely to form on the window. Therefore, the lower the amount of solar radiation, the more desirable it is to increase the heater output. In this embodiment, as shown in FIG. 5 , when the amount of solar radiation is less than the solar radiation threshold, the target output is set to be higher than when the amount of solar radiation is equal to or greater than the solar radiation threshold. In this way, the defogging control unit 54 acquires the amount of solar radiation as weather information and sets the target output of the heater 31 based on the acquired amount of solar radiation, so that the duty ratio can be set to an appropriate value depending on how easily the windshield 6 fogs up.

[0074] Furthermore, the defogging control unit 54 sets the duty ratio high when the amount of solar radiation is below the solar radiation threshold and condensation is likely to occur on the windshield 6. This effectively prevents condensation on the windshield 6. On the other hand, when the amount of solar radiation is equal to or greater than the solar radiation threshold and condensation is unlikely to occur on the windshield 6, the defogging control unit 54 sets the duty ratio low. This ensures the performance of the heater 31 while preventing excessive output from the heater 31 and preventing heat damage.

[0075] The higher the vehicle speed, the more the wind cools the windshield. This makes it easier for water vapor inside the vehicle cabin to condense near the window, making the window more likely to fog up. In this embodiment, as shown in FIG. 5, when the vehicle speed is equal to or greater than the vehicle speed threshold, the target output is set to be higher than when the vehicle speed is less than the vehicle speed threshold. In this way, the defogging control unit 54 sets the target output of the heater 31 based on the acquired vehicle speed, and therefore can set the duty ratio to an appropriate value depending on how easily the windshield 6 fogs up.

[0076] Furthermore, when the vehicle speed is equal to or greater than the vehicle speed threshold, the defogging control unit 54 sets a higher duty ratio than when the vehicle speed is less than the vehicle speed threshold. Therefore, when the window is prone to fogging, the duty ratio is increased, so that condensation on the windshield 6 can be effectively prevented while ensuring the performance of the heater 31, and heat damage can be prevented.

[0077] In this way, by suppressing fogging of the front windshield 6, it is possible to reduce situations in which driving control of the vehicle 1 cannot be performed based on the image capture results of the front camera 10. Therefore, the present invention further improves traffic safety and contributes to the development of sustainable transportation systems.

[0078] <Other variations> In the above embodiment, the defogging control unit 54 acquires the target output by referring to a two-dimensional target output map 56 based on the vehicle speed and the amount of solar radiation, but the target output map 56 is not limited to this. The defogging control unit 54 may acquire the target output by referring to a three-dimensional target output map 56 based on parameters other than the vehicle speed and the amount of solar radiation. The parameters other than the vehicle speed and the amount of solar radiation may be, for example, wind speed.

[0079] The defogging control unit 54 may acquire environmental information about the surroundings of the vehicle 1 at its current location and along its travel route from the weather server 30A via the network N, and calculate the target output based on the environmental information. The defogging control unit 54 may acquire environmental information provided by the weather server 30A via the navigation device 18, or may directly connect to the weather server 30A via the network N and acquire environmental information provided by the weather server 30A. The environmental information may include meteorological information such as wind speed and weather. For example, the defogging control unit 54 acquires the wind speed along the travel route of the vehicle 1 as meteorological information when the vehicle 1 starts traveling. Thereafter, when the vehicle 1 starts traveling, the defogging control unit 54 may acquire the current location of the vehicle 1 from the navigation device 18 and predict the wind speed at the current location of the vehicle 1 by referring to the weather information acquired at the start of traveling. Alternatively, the defogging control unit 54 may constantly acquire meteorological information from the weather server 30A and predict the wind speed at the current location of the vehicle 1. The defogging control unit 54 may obtain the target output using the target output map 56 based on the predicted wind speed at the current location of the vehicle 1. This allows the duty ratio to be set taking into consideration that the wind blowing against the vehicle 1 will cool the windshield 6 while the vehicle is traveling, and therefore the duty ratio can be set to an appropriate value.

[0080] Alternatively, the defogging control unit 54 may acquire weather information, such as the weather, solar radiation, temperature, and humidity at the current location and along the travel route of the vehicle 1, from the weather server 30A, and set the target output using the target output map 56. In this way, by acquiring the environmental conditions around the vehicle from the weather server 30A and using the environmental conditions to acquire the target output, it is possible to set the target output of the heater 31 even when it is difficult to provide the vehicle 1 with a sensor for acquiring the environmental conditions.

[0081] In the above embodiment, the anti-fogging system X prevents fogging of the front window 6, but in other embodiments, the anti-fogging system X may also prevent fogging of the rear window 7 or the side window 9. In other words, in the above embodiment, the front camera 10 is an example of the image capturing device, but in other embodiments, a rear camera or a side camera (neither of which is shown) may be an example of the image capturing device.

[0082] In the above embodiment, the defogging control unit 54 is configured to perform PWM control, which changes the duty ratio (ratio of ON to OFF per cycle) by changing the pulse width while keeping the cycle (frequency) constant, but is not limited to this. The defogging control unit 54 may also be configured to perform PFM (Pulse Frequency Modulation) control, which changes the duty ratio by changing the frequency (cycle) while keeping the pulse width at which the defogging control unit is ON (or OFF) constant.

[0083] In the above embodiment, the defogging control unit 54 is configured to obtain the voltage value of the supply voltage and set the duty ratio by dividing the target output by the maximum output, but this is not limiting. The defogging control unit 54 may be configured to select one from a plurality of pulse patterns with different duty ratios based on the voltage value of the supply voltage and output a voltage pulse based on the selected pulse pattern.

[0084] For example, the defogging control unit 54 may be configured to select one of two pulse patterns with different duty ratios and output a voltage pulse based on the selected pulse pattern to the heater 31. In this case, the defogging control unit 54 may be configured to compare the supply voltage with a predetermined threshold, and when the supply voltage is lower than the threshold, select a pulse pattern with a lower duty ratio than the pulse pattern selected when the supply voltage is equal to or higher than the threshold.

[0085] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and its modifications, and can be modified in a wide range of ways.

[0086] In the above embodiment, an example has been described in which the driving control unit 53 of the vehicle 1 performs driving control related to ADAS and AD, but it is not essential for the present invention that the driving control unit 53 performs driving control. The anti-fogging system X may have any configuration as long as it includes a control device 26 provided with an anti-fogging control unit 54, and the control device 26 controls the output of the heater 31 to prevent fogging of windows such as the front windshield 6. [Explanation of symbols]

[0087] 1: Vehicle 6: Front window (example of a window) 10: Front camera (an example of an imaging device) 26: Control device 31: Heater 43: Vehicle speed sensor 44: Solar radiation sensor 54: Anti-fog control unit R:Visual field SP2: Space outside the vehicle (outside the vehicle) N: Network X: Anti-fog system

Claims

1. An anti-fogging system for an imaging device that captures an image of the outside of a vehicle through a predetermined field of view set on a vehicle window, comprising: a heater for heating the viewing area; a solar radiation sensor that detects the amount of solar radiation on the vehicle; a control device that applies a voltage pulse to the heater with a predetermined duty ratio, the voltage pulse being a supply voltage value when the heater is on and being 0 V when the heater is off, thereby heating the heater and preventing fogging of the viewing area; The control device obtaining the supply voltage value; acquiring the amount of solar radiation acquired from the solar radiation sensor and the vehicle speed of the vehicle, and setting a target output; An anti-fogging system that uses the supply voltage value and the target output to set the duty ratio of the voltage pulse so that the output of the heater becomes the target output.

2. The anti-fogging system according to claim 1 , wherein the control device sets the target output lower when the amount of solar radiation is equal to or greater than a predetermined solar radiation threshold value than when the amount of solar radiation is less than the solar radiation threshold value.

3. 3. The anti-fogging system according to claim 1, wherein the control device sets the target output higher when the vehicle speed is equal to or greater than a predetermined vehicle speed threshold than when the vehicle speed is less than the vehicle speed threshold.

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