Display device, snow accretion preventing method for display device, and snow accretion preventing program for display device

Abstract

To improve detection accuracy of snowfall in a snowfall sensor in which the trend of detection values may change with the passage of time.SOLUTION: A display device includes: a display plate; a heater for heating the display surface of the display plate; a snowfall sensor provided with a snow detection part for detecting the passage of snow based on a threshold value; and a control part for controlling the amount of heat generated by the heater based on the detection result of snow in the snowfall sensor, where the control part acquires the detection values of the snowfall sensor a plurality of times in a first period and updates the threshold value based on the statistical values of the detection values.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a display device, a method for preventing snow from accumulating on a display device, and a program for preventing snow from accumulating on a display device. [Background technology]

[0002] 2. Description of the Related Art Display devices equipped with a snowfall sensor are known in the art (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6712531 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of an optical snowfall sensor, if the snow detection section of the snowfall sensor becomes dirty over time, the received light value decreases, making it difficult to detect whether or not snow is falling. The present invention has been made in consideration of the above-mentioned problems, and has an object to improve the accuracy of detecting snowfall in a snowfall sensor in which the trend of the detection value can change over time. [Means for solving the problem]

[0005] In order to achieve the above-mentioned objective, the display device comprises a display panel, a heater for heating the display surface of the display panel, a snowfall sensor having a snow detection unit for detecting the passage of snow based on a threshold value, and a control unit for controlling the amount of heat generated by the heater based on the snow detection result of the snowfall sensor, the control unit obtaining the detection value of the snowfall sensor multiple times during a first period, and updating the threshold value based on a statistical value of the detection value.

[0006] That is, the display device obtains the detection value of the snowfall sensor multiple times during the first period and updates the threshold value based on the statistical value of the detection value.The display device then detects the passage of snow using the threshold value updated in this manner.As a result, it is possible to set a threshold value that follows the change over time in the detection value due to dirt on the snow detection unit, etc., and to improve the detection accuracy of snowfall in a snowfall sensor that may change over time. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1A is a front view of the display device, and FIG. 1B is an enlarged side view of the display device. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a block diagram of a display device. [Figure 4] 13 is a flowchart of a snow accretion prevention process. [Diagram 5] 13 is a flowchart of a threshold correction process. [Figure 6] 13 is a flowchart of a threshold correction process. [Figure 7] 4 is a diagram illustrating an example of the relationship between a detection value, a standard value, a threshold value, and a first range of a snowfall sensor. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Here, the embodiments of the present invention will be described in the following order. (1) First embodiment: (2) Other embodiments:

[0009] (1) First embodiment: 1A is a front view of a display device 1 according to one embodiment of the present invention. The display device 1 of this embodiment is a display device for passengers of a vehicle traveling on a road to visually recognize various information. However, the display device 1 may be installed outdoors and is not necessarily a display device for use on roads.

[0010] The display device 1 comprises a support pillar V, a cross beam Y, a display board B, and a snowfall sensor S. The support pillar V is a columnar member whose lower end is fixed to the ground (hatched) so that its length is vertical. The cross beam Y is a horizontal beam that connects the support pillar V and the display board B. The display board B is cantilevered by the support pillar V above the road. The display board B has a rectangular plate-shaped housing, and a display surface M is formed on one surface of the housing.

[0011] The direction in which the display surface M is formed is the forward direction, and the display surface M is visually recognized by passengers of a vehicle approaching from the front. On the display surface M, light-emitting elements such as LEDs are arranged in a dot matrix, and by individually controlling the lighting of the light-emitting elements, an image can be formed on the display surface M and various information can be displayed.

[0012] FIG. 1B is an enlarged side view of the vicinity where the snow sensor S is provided. Note that the support column V is omitted in FIG. 1B. As shown in FIG. 1B, by tilting the direction of the display surface M from the vertical direction by an inclination angle α (for example, 3 degrees), the display surface M can be easily viewed by passengers of a vehicle traveling in front of and below the display surface M. The inclination angle α can be set according to the height and size of the display surface M, the gradient of the road, and the like. In this embodiment, the height H of the display board B is 2200 mm, the width W is 3200 mm, and the depth D is 300 mm. Of course, the size of the display board B is not limited to the illustrated size. As shown in FIG. 1A and FIG. 1B, the snow sensor S is fixed to the right side surface of the display board B via a connecting member C. The connecting member C includes a fixing portion fixed to the side surface by a bolt and an arm portion connecting the fixing portion and the snow sensor S. The arm portion is formed so that the display surface M of the display board B and the front surface of the snow sensor S are aligned on the same plane. That is, the connecting member C fixes the snow sensor S so that the front surface of the snow sensor S is inclined at an inclination angle α from the vertical direction.

[0013] A roof R is provided above the snow sensor S. When the roof R is viewed vertically from above, the snow sensor S and its snow detection unit A are entirely obscured by the roof R and cannot be seen. The snow sensor S is disposed forward of the bisector X that bisects the roof R into a front-to-rear direction. The roof R is composed of two planes inclined at an angle of more than 45 degrees with respect to the horizontal plane. In addition, the height of the rear end of the roof R is lower than the height of the front end of the roof R.

[0014] As shown in Figure 1B, the snow trajectory KB (dash-dotted line) that descends diagonally from the rear and can pass through the light beam L of the snow detection unit A without being blocked by the roof R is at an angle closer to horizontal than the snow trajectory KF (dash-dotted line) that descends diagonally from the front and can pass through the light beam L of the snow detection unit A. Therefore, snow blowing from the front can be more easily detected by the snowfall sensor S than snow blowing from behind. By lowering the height of the rear end of the roof R, snow blowing from behind can be reliably blocked.

[0015] FIG. 2 is a perspective view of the snowfall sensor S. The snowfall sensor S has an almost rectangular parallelepiped outer shape with a rectangular parallelepiped recess (snow detection section A) formed at the bottom. A light emitting section S1 is provided on one side of the snow detection section A in the width direction, and a light receiving section S2 is provided on the other side of the snow detection section A in the width direction. A light ray L (thick arrow) emitted from the light emitting section S1 penetrates the snow detection section A in the width direction and is received by the light receiving section S2. When snow passes on the optical path of the light ray L, the received light value at the light receiving section S2 is smaller than when snow does not pass. That is, in the snowfall sensor S, when snow passes through the snow detection section A, a detection value (received light value) that is smaller than when snow does not pass is acquired. A threshold value is provided to distinguish between a state in which the light ray L can be received because snow does not pass through the snow detection section A and a state in which the amount of received light is reduced because snow passes through. The snowfall sensor S constantly emits light from the light-emitting unit S1, and can detect the amount of snow by detecting the number of times per hour that the detection value of the light-receiving unit S2 falls below a threshold value. Any method can be used to detect the amount of snow, and for example, the total length of the period during which light cannot be received can be detected as the amount of snow. The wavelength of the light beam L is not particularly limited, and the light beam L may be infrared light or visible light. The light beam L may also be laser light. Furthermore, instead of the light beam L, sound waves or radio waves other than electromagnetic waves that can penetrate the snow detection unit A may be used.

[0016] The snowfall sensor S outputs the amount of snow as a detection result, and the control unit 20 controls the heater 12 according to the amount of snow, as described later. Since the snowfall sensor S is installed outdoors, it gradually becomes dirty over time due to various substances in the atmosphere. When dirt gradually accumulates on the light-emitting unit S1 and the light-receiving unit S2, the detection value (received light value) in a state where nothing passes through the snow detection unit A gradually decreases. If the detection value in a state where nothing passes through the snow detection unit A decreases to a threshold value or less, it will be determined that snow has passed through the snow detection unit A even though snow has not passed through it. This reduces the reliability of the snowfall sensor S. To prevent this from happening, in this embodiment, the threshold value is updated based on a statistical value of the detection value of the snowfall sensor S (details will be described later). For this reason, the snowfall sensor S is configured to output the detection value (received light value) itself to the control unit 20.

[0017] In this embodiment, the height h of the snow sensor S is 100 mm, the width w is 200 mm, and the depth d is 20 mm. The height h1 of the snow detection unit A is 40 mm, and the width w4 is 140 mm. The widths w2 and w3 of the left and right parts of the snow detection unit A in the snow sensor S are each 30 mm.

[0018] FIG. 3 is a block diagram of the display device 1. The display device 1 includes a display board B, a snowfall sensor S, a control unit 20, a temperature sensor 30, a power supply unit 40, a power supply circuit 50, a communication unit 60, and a UI unit 70. The control unit 20, the power supply unit 40, and the power supply circuit 50 may be provided inside the display board B, or may be provided in a control box separate from the display board B. The display board B includes a display unit 11 and a heater 12. The display unit 11 includes a plurality of light-emitting elements such as LEDs arranged in a dot matrix, and a driver circuit that generates a drive current for the plurality of light-emitting elements. The heater 12 is a heating wire that is stretched so as to weave between the plurality of light-emitting elements arranged in a dot matrix on the display surface M. By supplying power to the heater 12, the heater 12 generates Joule heat in an amount corresponding to the magnitude of the power, and heats the display surface M. The heater 12 may be any element that generates heat, and does not necessarily have to be a heating wire.

[0019] The temperature sensor 30 is a sensor that measures the outside air temperature. The power supply unit 40 is a power supply circuit that generates power to be supplied to each unit of the display device 1 from an external power source (commercial power source). The power supply unit 40 includes, for example, a DC circuit and a transformer circuit. The power supply circuit 50 is a circuit that generates a current to be supplied to the heater 12 based on a control signal from the control unit 20. The power supply circuit 50 generates a square wave having high and low current values ​​as the current to be supplied to the heater 12, and adjusts the duty ratio, which is the ratio of the period during which the current value is high, based on the control signal from the control unit 20. The high current value is constant, and the low current value is 0. Since the resistance value of the heater 12 is constant, the power supplied to the heater 12 can be adjusted by adjusting the duty ratio of the current supplied to the heater 12.

[0020] The communication unit 60 includes a communication circuit for wireless or wired communication with an external device. In this embodiment, when it is determined that cleaning of the snowfall sensor S is necessary, the display device 1 can communicate with a management center (not shown) through the communication unit 60 and output a message to that effect to the management center.

[0021] The UI unit 70 includes an input unit for a user to input instructions to the display device 1, and more specifically, includes a switch for resetting a standard value, which will be described later, after cleaning the snowfall sensor S. The UI unit 70 may also include an output unit for notifying the user of various statuses of the display device 1.

[0022] The control unit 20 is a computer including a CPU, a ROM, a RAM, etc., and a control program 21 recorded in the ROM is executed by the CPU. The control program 21 includes a display control module 21a and a heater control module 21b. The control unit 20 controls the lighting of a plurality of light-emitting elements provided in the display unit 11 by the function of the display control module 21a. Specifically, the control unit 20 generates a control signal to be output to a driver circuit of the display unit 11 based on the display image data recorded in the ROM by the function of the display control module 21a. The display image data may be acquired from an external device via a communication unit (not shown). Note that the control unit 20 does not necessarily have to realize the functions of the present invention using software, and may be an ASIC (application specific integrated circuit) or the like.

[0023] Using the function of the heater control module 21b, the control unit 20 executes a snow accretion prevention process (FIG. 4) for controlling the heater 12 to prevent snow from accumulating on the display surface M, and a threshold correction process (FIGS. 5 and 6) for correcting a threshold for determining whether or not snow has passed through. The snow accretion prevention process and the threshold correction process are repeatedly executed during the season when snow may fall (e.g., winter).

[0024] First, the snow accretion prevention process of Fig. 4 will be described. When the snow accretion prevention process is started, the control unit 20 detects the temperature (step S100). That is, the control unit 20 acquires the outside air temperature detected by the temperature sensor 30. Next, the control unit 20 determines whether the temperature is equal to or lower than a temperature threshold value (step S105). The temperature threshold value may be, for example, the upper limit temperature (e.g., 2 degrees Celsius) at which snow accretion on the display surface M can occur.

[0025] If it is not determined that the temperature is equal to or lower than the temperature threshold value (step S105: N), the control unit 20 turns off the heater 12 (step S110). That is, the control unit 20 outputs a control signal to the power supply circuit 50 to supply a current to the heater 12 such that the duty ratio becomes 0. Note that the method of turning off the heater 12 is not limited to setting the duty ratio to 0, and for example, a switch may be switched to cut off the electrical connection between the heater 12 and the power supply circuit 50.

[0026] On the other hand, if it is determined that the temperature is equal to or lower than the temperature threshold (step S105: Y), the control unit 20 acquires the amount of snow detected by the snowfall sensor S (step S115). Specifically, the control unit 20 acquires the amount of snow from the snowfall sensor S (side snow sensor Z) that is arranged so as to be able to detect the amount of snow blowing mainly from the front. In other words, the control unit 20 acquires the amount of snow blowing mainly from the front.

[0027] Next, the control unit 20 judges whether the amount of snow is equal to or greater than a first judgment value T1 (step S120). That is, the control unit 20 judges whether the amount of snow blowing mainly from the front is equal to or greater than a first judgment value T1. The first judgment value T1 (e.g., 0) is a predetermined value, and is a minute amount of snow that will not adhere to the display surface M even if the temperature is equal to or less than the temperature threshold.

[0028] If it is not determined that the amount of snow is equal to or greater than the first determination value T1 (step S120: N), the control unit 20 turns off the heater 12 (step S110). That is, the control unit 20 determines that snow cannot accumulate on the display surface M, and turns off the heater 12, in the same way as when the temperature is equal to or greater than the temperature threshold.

[0029] On the other hand, if it is determined that the amount of snow is equal to or greater than the first determination value T1 (step S120: Y), the control unit 20 determines whether the amount of snow is equal to or greater than a second determination value T2 (step S125). Here, the second determination value T2 is a predetermined value that is greater than the first determination value T1.

[0030] If it is not determined that the amount of snow is equal to or greater than the second judgment value T2 (step S125: N), the control unit 20 sets the power supply to the heater 12 to G1×P (step S130). That is, when the amount of snow blowing mainly from the front is equal to or greater than the first judgment value T1 but less than the second judgment value T2, the control unit 20 turns on the heater 12 and sets the power supply to G1×P. Here, P is the maximum power that can be supplied to the heater 12, and is the power when the duty ratio of the current supplied to the heater 12 is 100%. G1 (for example, 0.5) is a coefficient that takes a value between 0 and 1. The duty ratio of the current to be supplied to the heater 12 can be derived based on the supplied power, the resistance value of the heater 12, and the High current value.

[0031] On the other hand, if it is determined that the amount of snow is equal to or greater than the second determination value T2 (step S125: Y), the control unit 20 determines whether the amount of snow is equal to or greater than a third determination value T3 (step S135). Here, the third determination value T3 is a predetermined value that is greater than the first determination value T1 and the second determination value T2.

[0032] If it is not determined that the amount of snow is equal to or greater than the third judgment value T3 (step S135: N), the control unit 20 sets the supply power of the heater 12 to G2×P (step S140). That is, when the amount of snow blowing mainly from the front is equal to or greater than the second judgment value T2 but less than the third judgment value T3, the control unit 20 turns on the heater 12 and sets the supply power to G2×P. Here, G2 (for example, 0.75) is a coefficient that takes a value between 0 and 1 and is a coefficient larger than G1. The amount of heat generated by the heater 12 when the supply power is set to G2×P (step S140) is larger than the amount of heat generated by the heater 12 when the supply power is set to G1×P (step S130).

[0033] On the other hand, if it is determined that the amount of snow is equal to or greater than the third judgment value T3 (step S135: Y), the control unit 20 sets the supply power of the heater 12 to G3×P (step S145). That is, when the amount of snow blowing mainly from the front is equal to or greater than the third judgment value T3, the control unit 20 turns on the heater 12 and sets the supply power to G3×P. Here, G3 (for example, 1) is a coefficient that takes a value between 0 and 1 and is a coefficient larger than G2. The amount of heat generated by the heater 12 when the supply power is set to G3×P (step S145) is larger than the amount of heat generated by the heater 12 when the supply power is set to G2×P (step S140). When the above process is completed, the control unit 20 waits for a certain period of time and then returns to step S100.

[0034] Next, the threshold correction process will be described with reference to Figures 5 and 6. The threshold correction process is a process for making the above-mentioned threshold for detecting the amount of snow acquired in step S115 of the snow accumulation prevention process in Figure 4 follow statistical changes in the detection value caused by various factors such as accumulation of dirt on the snowfall sensor S and cleaning.

[0035] When the threshold correction process is started, the control unit 20 sets a set value (step S200). That is, the control unit 20 sets a variable V A ,V B ,V C ,V D ,V E ,V F Set the value of the variable V A ,V B ,V C ,V D ,V E ,V F The value set in can be changed as appropriate depending on the specifications of the snowfall sensor S, other specifications, the installation environment, etc. A is a sampling period for acquiring the detection value of the snowfall sensor S, and may be, for example, "1 second", "100 ms", "10 ms", etc. A For example, "1 second" is used.

[0036] V B is a value for defining a range for determining whether a detection value is valid or invalid. More specifically, it is a value for defining a first range including a standard value, and can assume a value of about ±20% to ±5% based on the standard value, for example. In this embodiment, V B For example, "15%" is used for the detection value. In this case, the range of ±15% based on the standard value (i.e., the range of 85% to 115% of the standard value) corresponds to the first range. FIG. 7 is a diagram for explaining an example of the relationship between the range of the detection value of the snowfall sensor S and the standard value, the first range, and the threshold value. The standard value is a value that is used as a reference in the current state for detection values ​​whose tendency may change. The initial value of the standard value is the detection value detected when the snowfall sensor S is shipped in a state where there is no rain or snow. The standard value is updated with a statistical value (average value in this embodiment) of detection values ​​acquired multiple times during the first period. The threshold value of the snowfall sensor S is set based on the standard value. In this embodiment, the threshold value is set to the standard value (100-V B )% (i.e., the lower limit of the first range in this embodiment). When using a snowfall sensor S that detects a smaller detection value when snow has passed than when no snow has passed, the threshold value may be set to a value smaller than the standard value, and does not necessarily have to match the lower limit of the first range.

[0037] V C is a value that specifies the period for acquiring the detection value in order to update the threshold value or standard value of the snowfall sensor S when the detection value changes little by little, and can be assumed to be, for example, about 1 to 24 hours. C For example, "3 hours" is used.

[0038] V D is a threshold value used to change the processing content according to the proportion of valid values ​​(detection values ​​that are within the first range) among the detection values ​​acquired in the first period, and may be assumed to be, for example, about 100% to 80%. In this embodiment, V D For example, "90%" is used. D In this embodiment, V corresponds to the first reference value. Eis the lower limit of the standard value at which the snow sensor S can be used without cleaning, and is set appropriately according to the range of the output value of the snow sensor S. E corresponds to the second reference value in this embodiment.

[0039] V F is a value that specifies the period (second period) for acquiring the detection value in order to update the threshold value or standard value of the snowfall sensor S when the detection value changes suddenly, and can be assumed to be, for example, about 1 to 24 hours. F For example, "3 hours" is used.

[0040] The control unit 20 is A The detection value is obtained every V seconds for a first period. In this embodiment, the first period is two minutes. Steps S205 to S235 are performed by A This is a processing step group for continuing to obtain a detection value every second for two minutes. Note that the first period does not have to be limited to "two minutes", but may be included as one of the set values ​​set in step S200 and may be variably set according to the specifications. In step S205, the control unit 20 sets the sampling period V A In other words, the control unit 20 acquires a detection value every V seconds since the previous acquisition of a detection value, which is a light reception value, from the snowfall sensor S. A Wait for seconds to elapse and then press V A After seconds have passed, the detection value (received light value) of the snowfall sensor S is obtained.

[0041] Next, the control unit 20 determines whether an update signal has been received, and if so, updates the standard value and threshold value based on the current detection value (received light value) (step S220). In this embodiment, it is assumed that after the light-emitting unit S1 and light-receiving unit S2 of the snowfall sensor S are cleaned, a switch for resetting the standard value is operated, and when the switch is operated, the control unit 20 considers that an update signal has been received. The control unit 20 updates the standard value with the detection value of the snowfall sensor S when the update signal is received. Furthermore, the control unit 20 updates the standard value (100-V B)% is set as the threshold value. It is assumed that the user will operate the switch after cleaning the snowfall sensor S and confirming that there is no rain or snow.

[0042] If it is not determined in step S210 that an update signal has been received, or after step S220 is executed, the control unit 20 saves the detection value in the save buffer (step S215). The detection value saved in the save buffer can be used in S285, which will be described later. That is, the control unit 20 A The detection values ​​acquired every second are stored separately from the valid value buffer of S230, which will be described later, in preparation for the execution of S285. The detection values ​​are stored in the save buffer regardless of whether they are valid or invalid.

[0043] The control unit 20 detects the detected value ±V B % (step S225). B In this embodiment, the range within ±V B %, the control unit 20 stores the detected value in a valid value buffer (step S230). B % (first range), the detected value is regarded as a valid value and the detected value is stored in a valid value buffer. Detected values ​​outside the first range (called invalid values) are not stored in the valid value buffer.

[0044] Next, the control unit 20 determines whether or not two minutes have passed (step S235), and if two minutes have not passed, the process returns to step S205, and if two minutes have passed, the process from step S140 onwards is carried out. That is, the processes from S205 to S230 are repeated for two minutes, and the processes from step S240 onwards are carried out every time two minutes pass.

[0045] Next, the control unit 20 calculates the ratio of valid values ​​(step S240). That is, the control unit 20 subtracts the number of invalid values ​​(the number of times that N was judged in S225) from the number of samples for two minutes, and divides the number after subtraction by the number of samples to calculate the ratio of valid values. Next, the control unit 20 calculates whether the ratio of valid values ​​is V D % or more (step S245). D % or more, the process of steps S250 to S280 is performed to make the standard value and the threshold value follow the detected value when the detected value gradually decreases due to the gradual accumulation of dirt over time. D %, the process of steps S285 to S315 is performed to update the standard value and the threshold value when the detection value rises or falls suddenly due to some factor.

[0046] In step S245, the ratio of valid values ​​is V D % or more, the control unit 20 calculates and stores the average value of the detection values ​​that are valid values ​​(step S250). That is, the control unit 20 divides the total of the detection values ​​stored in the valid value buffer in step S230 by the number of detection values ​​stored in the valid value buffer to calculate and store the average value. The stored average value is held until the threshold correction process is completed. Note that if the valid value is V D % or more, the detection value of the snowfall sensor S when it detects the passage of snow is the standard value of -V B % (i.e., an invalid value). In step S250, even in a situation where snowfall is estimated, the detection value when the passage of snow is detected (the standard value of -V B % (i.e., invalid values) are excluded, and the average is calculated using the valid values ​​that are assumed to be the detection values ​​when nothing is passing through.

[0047] Next, the control unit 20 deletes the stored detection value (step S255). That is, the control unit 20 clears the valid value buffer and the save buffer. Next, the control unit 20 CIt is determined whether the time has elapsed (step S260), and if the time has not elapsed, the process returns to step S205. C If it is determined that the time has elapsed, the control unit 20 determines that the ratio of the valid values ​​is V D % or more (step S265). C In step S245, which is executed every two minutes within the time, the ratio of valid values ​​is V D % or more (V C The value divided by (time ÷ 2 minutes) is V D % or more.

[0048] In step S265, the ratio of valid values ​​is V D % or more, the control unit 20 calculates a standard value (step S270). That is, the control unit 20 multiplies the sum of the average values ​​calculated every two minutes (calculated in step S250) by the ratio of the valid value every two minutes to V D % (the number of times the judgment was Y in step S245) to obtain V C The average value of the effective values ​​over the time period is calculated, and the calculated average value is used as the standard value.

[0049] Next, the control unit 20 calculates the threshold value (step S275). B )% to calculate the threshold value. Next, the control unit 20 updates the threshold value of the snowfall sensor S (step S280). That is, the threshold value of the snowfall sensor S is updated so that the snowfall sensor S determines whether or not snow has passed by using the threshold value calculated in step S275. As mentioned above, the ratio of valid values ​​is V D % or higher, the trend of changes in the detection values ​​can be obtained using only valid values ​​(detection values ​​that assume that nothing has passed through the snow detection section A), and new standard values ​​and threshold values ​​can be set to reflect this trend.

[0050] On the other hand, in step S245, the effective value is V D% or more, the control unit 20 calculates and stores the average value of the detection values ​​stored in the save buffer (step S285). A The total number of detection values ​​acquired every 2 minutes and stored in the evacuation buffer is calculated by dividing the total number of detection values ​​stored in the evacuation buffer by the number of detection values ​​(2 minutes ÷ V A The average value is calculated by dividing the time by the number of seconds (seconds) and saved. The saved average value is held until the threshold correction process is completed. Thus, the percentage of invalid values ​​is (100-V D )%, the overall trend of the detected values ​​can be estimated by calculating statistics for all detected values, including valid and invalid values.

[0051] Next, the control unit 20 checks whether the average value calculated in step S285 is within ±V B % (step S290). The standard dirt value of the snow sensor S gradually decreases, and when it decreases to the point where cleaning is necessary, the user cleans the snow sensor S by wiping it with a cloth, for example. As a result, the average detection value (received light value) immediately after cleaning may suddenly rise above the preset amount. Also, if flying objects adhere to the snow sensor S or the snow sensor S malfunctions, the average detection value may suddenly fall below the preset amount. In step S290, it is determined whether such a situation has occurred. In this embodiment, the preset amount is the standard value V B %. Therefore, in step S290, it is determined whether the average value calculated in step S285 exceeds the upper limit of the first range or falls below the lower limit of the first range.

[0052] In step S290, the average value is ±V B % is not exceeded, the control unit 20 proceeds to step S255. B % outside the range, the control unit 20 F ±V of standard value for a continuous period (second period) B % or not (step S295). That is, the control unit 20 refers to the average value stored in step S285 and FThe time stored in step S285 (V F Time ÷ 2 minutes) average values ​​are all +V B % or the average value of the number of pieces is all below the standard value -V B % or less.

[0053] In step S295, V F ±V of standard value over time B If it is not determined that the range is within the range 0 to 100%, the control unit 20 proceeds to step S255. F ±V of standard value over time B %, the control unit 20 sets the average value for two minutes to the standard value (step S300). F The standard value is the average of the average values ​​of the samples (time ÷ 2 minutes).

[0054] Next, the control unit 20 determines whether the standard value is V E It is determined whether the standard value is equal to or greater than V (step S305). E If it is equal to or greater than the standard value, the control unit 20 calculates the threshold value (step S310). B )% to calculate the threshold value. Next, the control unit 20 updates the threshold value of the snowfall sensor S (step S310). That is, the threshold value of the snowfall sensor S is updated so that the snowfall sensor S determines whether or not snow has passed by using the threshold value calculated in step S310.

[0055] According to the above steps S285 to S310, the standard value should be reset by operating the switch after cleaning the snow sensor S. However, even if the switch is not operated after cleaning, the standard value is reset to approximately V F After a certain time, the standard value and threshold value can be updated to reflect the current situation. Also, even if the detection value drops suddenly, the standard value and threshold value can be updated to reflect the current situation. FAfter a certain time, the standard value and the threshold value can be updated to reflect the current situation. If the detected value drops suddenly, the control unit 20 may transmit a notification to the management center via the communication unit 60 to prompt the management center to perform an inspection.

[0056] After step S280 or step S315 is executed, or if the determination is N in step S265, or if the determination is N in step S305, the control unit 20 sets the standard value to V E In step S320, it is determined whether the standard value is V E If it is determined that the amount is equal to or less than the amount of dirt, the control unit 20 outputs a message indicating that dirt has been detected (step S325). That is, the control unit 20 communicates with a management center (not shown) via the communication unit 60, and outputs information indicating that dirt has been detected to the management center. In this manner, the control unit 20 can prompt the cleaning of the snowfall sensor S. Note that the display device 1 may be configured to store information such as the time when dirt was detected as a log in a predetermined storage medium.

[0057] In step S320, the standard value is V E %, or after executing step S325, the control unit 20 ends the threshold correction process. The threshold correction process is periodically and repeatedly executed.

[0058] As described above, according to this embodiment, the threshold value can be made to follow the change in the trend of the detection value of the snowfall sensor S. Therefore, even if the trend of the detection value changes over time, it is possible to increase the possibility of accurately detecting whether snow has passed. As a result, it is possible to increase the possibility of accurately detecting the amount of snow. Furthermore, compared to when the threshold value is fixed, it is possible to reduce the frequency of cleaning and inspection work on the snowfall sensor S, which is expected to reduce costs. Furthermore, it is also possible to suggest the timing of cleaning and inspection work.

[0059] (2) Other embodiments: The control unit may update the threshold value of the snow sensor based on a statistical value of the detection value of the snow sensor. The statistical value may be an average value of the detection values ​​acquired in the first period, a mode value, or a value calculated by other statistical methods.

[0060] The first range may be set so long as it includes the standard value. The standard value may be the median value of the first range, or may be, for example, the upper limit or lower limit of the first range.

[0061] The control unit may be configured to update the standard value with the statistical value when the statistical value calculated when the ratio of the valid values ​​is less than the first reference value continues to increase by a predetermined amount or decrease by a predetermined amount from the current standard value for a second period or more. In the above embodiment, the predetermined amount is V of the standard value. B %, but the standard value of V B % may be smaller than the standard value of V B It may be a value greater than %.

[0062] Also, the amount of heat generated by the heater 12 does not necessarily have to be controlled in multiple stages, and the heater 12 may simply be switched ON / OFF according to the amount of snow detected by the snowfall sensor S. Furthermore, in the present invention, the temperature sensor 30 is not essential, and the temperature sensor 30 and steps S100 to S105 in Fig. 4 may be omitted.

[0063] The snowfall sensor S may be provided below the display board B. Since the snowfall sensor S evaluates the possibility of snow accumulating on the display board B, the location of the snowfall sensor S is not particularly limited as long as it is close to the display board B. Therefore, for example, a space may be secured between the display board B and the support column V, and the snowfall sensor S may be disposed in that space.

[0064] Furthermore, the technique of the present invention can also be applied as a program or method. The above-mentioned system, program, and method may be realized as a single device or may be realized by using parts shared with each part provided in the vehicle, and include various aspects. In addition, they can be modified as appropriate, such as being partly software and partly hardware. Furthermore, the invention can also be realized as a recording medium of a program that controls the system. Of course, the recording medium of the program may be a magnetic recording medium or a semiconductor memory, and any recording medium developed in the future can be considered in the same way. [Explanation of symbols]

[0065] 1...display device, 11...display unit, 12...heater, 20...control unit, 21...control program, 21a...display control module, 21b...heater control module, 30...temperature sensor, 40...power supply unit, 50...power supply circuit, 60...communication unit, 70...UI unit, A...snow detection unit, B...display board, B1...bottom surface, C...connecting member, KB, KF...snow trail, L...ray of light, M...display surface, R...roof, S...snowfall sensor, Y...horizontal beam, S1...light-emitting unit, S2...light-receiving unit, T1...first judgment value, T2...second judgment value, T3...third judgment value, V...support, X...bisector, Z...horizontal snow sensor

Claims

1. A display board, a heater for heating a display surface of the display plate; A snowfall sensor including a snow detection unit that detects the passage of snow based on a threshold value; a control unit that controls the amount of heat generated by the heater based on a result of snow detection by the snowfall sensor, the control unit acquiring a detection value of the snowfall sensor multiple times during a first period, and updating the threshold value based on a statistical value of the detection value; A display device comprising:

2. The control unit is calculating the statistical value for the detection values ​​that are within a first range including a standard value among the detection values ​​that are acquired a plurality of times; updating the standard value with the statistical value; updating the threshold value based on the updated standard value; The display device according to claim 1 .

3. when a ratio of the detection values ​​within the first range acquired in the first time period to all the detection values ​​acquired in the first time period is less than a first reference value, the control unit calculates the statistical value based on all the detection values ​​acquired in the first time period. The display device according to claim 2 .

4. In the snowfall sensor, the detection value obtained when snow has passed is smaller than the detection value obtained when snow has not passed, The control unit is When the ratio is less than the first reference value, if the state in which the calculated statistical value is increased by a predetermined amount or more from the current standard value or decreased by a predetermined amount or less continues for a second period or more, the standard value is updated with the statistical value; updating the threshold value based on the updated standard value; The display device according to claim 3 .

5. When the standard value is equal to or smaller than a second reference value, the control unit outputs information indicating that dirt on the snow sensor has been detected. The display device according to claim 2 .

6. A method for preventing snow from accumulating on a display device including a display surface and a heater for heating the display surface, comprising the steps of: a snowfall sensor that includes a snow detection unit that detects the passage of snow based on a threshold value and controls the amount of heat generated by the heater based on the result of the detection of snow; obtaining a detection value of the snowfall sensor a plurality of times during a first period, and updating the threshold value based on a statistical value of the detection value; A method for preventing snow from accumulating on a display device, comprising:

7. Computer, a control unit that controls the amount of heat generated by a heater that heats a display surface of the display device based on a snow detection result of a snowfall sensor having a snow detection unit that detects the passage of snow based on a threshold value, the control unit acquiring the detection value of the snowfall sensor multiple times during a first period and updating the threshold value based on a statistical value of the detection value; A snow accretion prevention program for a display device that functions as a

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