Raindrop detection device, raindrop detection method, and raindrop detection program

Abstract

To provide a raindrop detection device, a raindrop detection method, and a raindrop detection program capable of detecting raindrops precisely by restraining an influence of disturbance light.SOLUTION: A raindrop detection device 20 comprises a casing section 21, an opening 21a, a light source section 22a, a light reception section 22b, a voltage drop section 26g, and a microcomputer 25. The light reception section 22b is disposed in a position that opposes the light source section 22a in the casing section 21, receives light applied from the light source section 22a, and converts the amount of reception of light to a voltage value. The voltage drop section 26g reduces the voltage value to a predetermined voltage value or smaller when the voltage value converted by the light reception section 22b exceeds a predetermined threshold. The microcomputer 25 (raindrop detection section 25a) detects raindrops that pass between the light source section 22a and the light reception section 22b according to a change in the voltage value converted by the light reception section 22b, and detects raindrops by using the voltage value reduced by the voltage drop section 26g when the voltage value exceeds the predetermined threshold.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a raindrop detection device, a raindrop detection method, and a raindrop detection program that detect raindrops and calculate the amount of rainfall. [Background technology]

[0002] 2. Description of the Related Art In recent years, rainfall sensors that are installed outdoors and measure rainfall by detecting raindrops have come into use. For example, Patent Document 1 discloses a rain sensor that includes a light-emitting unit, a light-receiving unit, and a calculation unit, and that counts the number of times the rain sensor signal exceeds a threshold value as the amount of rain during wiper wiping control for a certain period of time, and switches the wiper between intermittent and continuous operation depending on the count value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-159580 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-described conventional rain sensor has the following problems. In other words, the rain sensor disclosed in the above publication only grasps the amount of rainfall as a count value over a certain period of time, making it difficult to grasp more accurate information about the amount of rainfall, and making it difficult to control the wiping of the wipers in accordance with changes in the actual amount of rainfall. In particular, when the light-receiving unit receives natural light such as sunlight or artificial light such as car headlights, there is a risk that the amplitude indicating the change in voltage when raindrops are detected will become smaller due to the influence of external light other than the light emitted from the light-emitting unit, making it difficult to detect the amount of rain with high accuracy.

[0005] An object of the present invention is to provide a raindrop detection device, a raindrop detection method, and a raindrop detection program that are capable of suppressing the influence of ambient light and detecting raindrops with high accuracy. [Means for solving the problem]

[0006] A raindrop detection device according to a first aspect of the present invention includes a housing, an opening, a light source, a light receiving unit, a voltage conversion unit, a voltage drop unit, and a raindrop detection unit. The housing has a cylindrical outer circumferential surface and a ceiling surface. The opening is formed on the ceiling surface of the housing. The light source is provided in the housing and emits light toward raindrops passing through the opening. The light receiving unit is disposed in a position facing the light source in the housing and receives the light emitted from the light source. The voltage conversion unit converts the amount of light received by the light receiving unit into a voltage value. The voltage drop unit reduces the voltage value when the voltage value converted by the voltage conversion unit exceeds a predetermined threshold. The raindrop detection unit detects raindrops passing between the light source and the light receiving unit in accordance with changes in the voltage value converted by the voltage conversion unit, and detects raindrops using the voltage value reduced by the voltage drop unit when the voltage value exceeds the predetermined threshold.

[0007] Here, for example, to prevent ambient light such as natural light or artificial light (car lights, flashlights, etc.) from entering the opening in the housing part of the raindrop detection device through which raindrops pass, changing the amount of light received by the light receiving part and reducing the accuracy of raindrop detection, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage value is reduced and raindrop detection is performed. Here, the light source unit is, for example, an LED (Light Emitting Diode), and irradiates light in a predetermined direction onto the light receiving units that are arranged opposite each other with a predetermined distance therebetween.

[0008] The light receiving section is, for example, a photodiode, which receives light emitted from the light source section and outputs it as a voltage value. Detecting raindrops includes detecting, for example, the diameter of the raindrop, the volume of one raindrop, the amount of rainfall per unit time, and the speed of the raindrop. Examples of ambient light that can reduce raindrop detection accuracy include natural light such as sunlight, and artificial light such as automobile headlights, flashlights, and outdoor electric lights.

[0009] The voltage drop unit is, for example, an electric circuit including a transistor that reduces the voltage when a high voltage exceeding a predetermined voltage value is applied, and by discharging the voltage exceeding a predetermined threshold, the voltage value sent to the raindrop detection unit is reduced. As a result, even if the amount of light received by the light receiving unit fluctuates significantly due to the influence of ambient light, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the increase in voltage due to the ambient light can be reduced to a range that does not affect raindrop detection, and raindrops can then be detected. As a result, the influence of ambient light can be suppressed and raindrops can be detected with high accuracy.

[0010] A raindrop detection device according to a second aspect of the present invention is the raindrop detection device according to the first aspect of the present invention, wherein the voltage drop unit increases the voltage value that is reduced as the voltage value that exceeds the threshold increases. As a result, for example, in an electric circuit (voltage drop unit) including a transistor, the larger the voltage value exceeding the threshold, the larger the voltage value to be dropped. This increases the voltage value to be dropped, thereby minimizing the impact on raindrop detection accuracy.

[0011] The raindrop detection device according to the third aspect of the present invention is the raindrop detection device according to the first or second aspect of the present invention, further comprising an abnormality determination unit that determines that an abnormality has occurred if the voltage value in the voltage drop unit does not drop to or below the predetermined voltage value when the voltage value exceeds a predetermined threshold. As a result, if the voltage value does not drop to the predetermined value even after the voltage drop unit performs a process to drop the voltage value above a predetermined threshold, it can be assumed that strong light, such as artificial light, has been detected by the light receiving unit, and it can be determined that an abnormality has occurred. As a result, the result of the abnormality determination can be notified to a server connected for communication, or a light indicating an abnormality can be turned on in the raindrop detection device.

[0012] A raindrop detection device according to a fourth aspect of the present invention is the raindrop detection device according to the first or second aspect of the present invention, further comprising a first disturbance factor processing unit that cuts out changes in light intensity due to disturbance factors corresponding to the second frequency band, out of a first frequency band corresponding to changes in light intensity due to raindrop detection and a second frequency band corresponding to changes in light intensity due to disturbance factors. This allows the falling speed of raindrops, which have different frequency bands, to be separated from changes in light intensity due to disturbance factors, and processing is performed to cut out changes in light intensity due to changes in light intensity caused by disturbance factors. This allows only changes in light intensity due to raindrop detection to be detected with high accuracy.

[0013] The raindrop detection device according to the fifth aspect of the present invention is the raindrop detection device according to the fourth aspect of the present invention, further comprising a second disturbance factor processing unit that performs processing to cut out changes in light quantity due to disturbance factors that were not completely cut out by lowering the voltage value in the voltage drop unit. This allows for more accurate raindrop detection by cutting out unnecessary changes in light intensity in the voltage drop section and then further cutting out changes in light intensity due to external disturbances that could not be completely cut out.

[0014] The raindrop detection device according to a sixth aspect of the present invention is the raindrop detection device according to the first or second aspect of the present invention, further comprising a shielding structure that blocks sunlight entering through the opening from entering the light receiving section. This allows, for example, taking into account the angle and time of day at which natural light such as sunlight enters the opening, to prevent natural light from being detected by the light receiving unit. By adopting a shielding structure that makes it difficult for light other than light from the light source unit to enter by arranging the light receiving unit and the depth of the opening, it is possible to eliminate the effects of external light other than the natural light described above, and perform highly accurate raindrop detection.

[0015] A seventh aspect of the present invention provides a raindrop detection method for a raindrop detection device including a housing having a cylindrical outer circumferential surface and a ceiling surface, an opening formed in the ceiling surface of the housing, a light source provided in the housing for irradiating light toward raindrops passing through the opening, and a light receiving unit disposed opposite the light source in the housing for receiving the light irradiated from the light source and converting the amount of received light into a voltage value. The raindrop detection method includes a voltage drop step and a raindrop detection step. In the voltage drop step, the voltage value is lowered when the voltage value converted by the light receiving unit exceeds a predetermined threshold. In the raindrop detection step, raindrops passing between the light source and the light receiving unit are detected in accordance with changes in the voltage value converted by the light receiving unit, and when the voltage value exceeds the predetermined threshold, raindrops are detected using the voltage value lowered in the voltage drop step.

[0016] Here, for example, to prevent ambient light such as natural light or artificial light (car lights, flashlights, etc.) from entering the opening in the housing part of the raindrop detection device through which raindrops pass, changing the amount of light received by the light receiving part and reducing the accuracy of raindrop detection, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage value is reduced and raindrop detection is performed. Here, the light source unit is, for example, an LED (Light Emitting Diode), and irradiates light in a predetermined direction onto the light receiving units that are arranged opposite each other with a predetermined distance therebetween.

[0017] The light receiving section is, for example, a photodiode, which receives light emitted from the light source section and outputs it as a voltage value. Detecting raindrops includes detecting, for example, the diameter of the raindrop, the volume of one raindrop, the amount of rainfall per unit time, and the speed of the raindrop. Examples of ambient light that can reduce raindrop detection accuracy include natural light such as sunlight, and artificial light such as automobile headlights, flashlights, and outdoor electric lights.

[0018] In the voltage drop step, for example, an electric circuit including a transistor that drops the voltage when a high voltage exceeding a predetermined voltage value is applied is used to release the voltage that exceeds a predetermined threshold. The voltage value sent to the raindrop detection unit is dropped. As a result, even if the amount of light received by the light receiving unit fluctuates significantly due to the influence of ambient light, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the increase in voltage due to the ambient light can be reduced to a range that does not affect raindrop detection, and raindrops can then be detected. As a result, the influence of ambient light can be suppressed and raindrops can be detected with high accuracy.

[0019] A raindrop detection program according to an eighth aspect of the present invention causes a computer to execute a raindrop detection method for a raindrop detection device including a housing having a cylindrical outer circumferential surface and a ceiling surface, an opening formed in the ceiling surface of the housing, a light source provided in the housing for irradiating light toward raindrops passing through the opening, and a light receiving unit disposed opposite the light source in the housing for receiving the light irradiated from the light source and converting the amount of received light into a voltage value. The raindrop detection program includes a voltage drop step and a raindrop detection step. In the voltage drop step, the voltage value is lowered when the voltage value converted by the light receiving unit exceeds a predetermined threshold. In the raindrop detection step, raindrops passing between the light source and the light receiving unit are detected in accordance with changes in the voltage value converted by the light receiving unit, and when the voltage value exceeds the predetermined threshold, raindrops are detected using the voltage value lowered in the voltage drop step.

[0020] Here, for example, to prevent ambient light such as natural light or artificial light (car lights, flashlights, etc.) from entering the opening in the housing part of the raindrop detection device through which raindrops pass, changing the amount of light received by the light receiving part and reducing the accuracy of raindrop detection, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage value is reduced and raindrop detection is performed. Here, the light source unit is, for example, an LED (Light Emitting Diode), and irradiates light in a predetermined direction onto the light receiving units that are arranged opposite each other with a predetermined distance therebetween.

[0021] The light receiving section is, for example, a photodiode, which receives light emitted from the light source section and outputs it as a voltage value. Detecting raindrops includes detecting, for example, the diameter of the raindrop, the volume of one raindrop, the amount of rainfall per unit time, and the speed of the raindrop. Examples of ambient light that can reduce raindrop detection accuracy include natural light such as sunlight, and artificial light such as automobile headlights, flashlights, and outdoor electric lights.

[0022] In the voltage drop step, for example, an electric circuit including a transistor that drops the voltage when a high voltage exceeding a predetermined voltage value is applied is used to release the voltage that exceeds a predetermined threshold. The voltage value sent to the raindrop detection unit is dropped. As a result, even if the amount of light received by the light receiving unit fluctuates significantly due to the influence of ambient light, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the increase in voltage due to the ambient light can be reduced to a range that does not affect raindrop detection, and raindrops can then be detected.

[0023] As a result, the influence of ambient light can be suppressed and raindrops can be detected with high accuracy. [Effects of the Invention]

[0024] The raindrop detection device according to the present invention can suppress the influence of ambient light and perform highly accurate raindrop detection. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is an overall perspective view showing the configuration of a raindrop detection device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a side view of the raindrop detection device of FIG. 1. [Figure 3] FIG. 2 is a top view of the raindrop detection device of FIG. 1. [Figure 4] 4 is a cross-sectional view showing the configuration of the raindrop detection device taken along the line AA in FIG. 3. [Figure 5] 5A is a perspective view showing a substrate on which the main components of the raindrop detection device shown in FIG. 4 are arranged, and FIG. 5B is a top view thereof. [Figure 6] FIG. 5 is a control block diagram of the raindrop detection device of FIG. 4. [Figure 7] FIG. 7 is a diagram showing functional blocks generated inside the microcontroller of FIG. 6. [Figure 8] 7 is a graph showing the relationship between the change in voltage indicating raindrops detected by the raindrop detection device of FIG. 6 and the elapsed time. [Figure 9] 3 is a flowchart showing the basic flow of processing of a raindrop detection method performed by the raindrop detection device of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] A raindrop detection device according to one embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. Furthermore, the applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present invention, and they are not intended to limit the subject matter described in the claims.

[0027] (1) Configuration of the raindrop detection device 20 As shown in Figures 1 to 3, the raindrop detection device 20 of this embodiment detects raindrops that have passed through a predetermined opening 21a provided on the top surface of the housing unit 21, and calculates the amount of rainfall by detecting the size of the detected raindrops and the amount per unit time.

[0028] As shown in FIG. 4, the raindrop detection device 20 includes a housing 21, a light source 22a and a light receiving unit 22b provided inside the housing 21, legs 23, a base 24, and a microcomputer 25. As shown in FIG. 4, the housing 21 is a substantially cylindrical member, and has an opening 21a, an inner wall surface 21b, a ceiling surface 21c, and an outer peripheral surface 21d.

[0029] The opening 21a is provided at approximately the center of the ceiling surface 21c, and is formed to penetrate the inside of the housing 21. The inner wall surface 21b forms the inner wall of the housing part 21 at the through portion formed by the opening part 21a. The light source part 22a and the light receiving part 22b are arranged at positions facing each other on the inner wall surface 21b.

[0030] The ceiling surface 21c is a substantially disk-shaped portion that forms the ceiling portion of the substantially cylindrical housing portion 21, and has an opening 21a in its central portion. The outer peripheral surface 21d is a surface that forms the outer peripheral portion of the substantially cylindrical housing portion 21, and a gap of a predetermined size is provided between the lower end of the outer peripheral surface 21d and the base 24. The light source unit 22a and the light receiving unit 22b are arranged at positions facing each other on the inner wall surface 21b of the opening 21a, as shown in Fig. 4. Furthermore, the light source unit 22a and the light receiving unit 22b are arranged at positions facing each other on a substantially circular substrate 22c so as to sandwich the raindrop detection area A1 therebetween, as shown in Fig. 5(a) and Fig. 5(b).

[0031] The light source unit 22a is, for example, an LED (Light Emitting Diode), and as shown in FIGS. 5(a) and 5(b), irradiates infrared light toward the light receiving unit 22b via a lens 22d that collimates the light. The light receiving unit 22b is, for example, a photodiode, and is arranged opposite the light source unit 22a as shown in Figures 5(a) and 5(b). It receives light condensed through a lens 22e that condenses the light irradiated from the light source unit 22a, converts it into a voltage value corresponding to the amount of received light, and outputs it.

[0032] Light is then irradiated from the light source unit 22a onto a raindrop detection area A1 (see Figure 4) formed between the light source unit 22a and the light receiving unit 22b, and part of the light detected by the light receiving unit 22b is blocked by raindrops, reducing the amount of light received by the light receiving unit 22b, thereby detecting the presence or absence of raindrops. 4, in the raindrop detection device 20 of this embodiment, the light source unit 22a and the light receiving unit 22b are each disposed at a position recessed from the opening 21a. That is, the light source unit 22a and the light receiving unit 22b are disposed not near the inner wall surface 21b that forms the opening 21a but at a position spaced apart from the inner wall surface 21b (shielding structure). Furthermore, the opening 21a is set to a sufficient height so that sunlight with a shallow angle of incidence, such as morning sun or evening sun, does not enter the light receiving unit 22b (shielding structure).

[0033] This makes it possible to prevent sunlight from being received by the light receiving portion 22b, for example, by taking into consideration the angle at which sunlight enters the opening 21a. As shown in Figures 5(a) and 5(b), the substrate 22c is an approximately circular member with an opening formed in the center, and the light source unit 22a, the light receiving unit 22b, and the lenses 22d and 22e are arranged on its upper surface.

[0034] An opening formed in the center of the substrate 22c corresponds to the raindrop sensing area A1 and the opening 21a formed in the housing 21. Lens 22d is disposed above light source unit 22a such as an LED, and is disposed so that its multiple fan-shaped portions face light-receiving unit 22b. Lens 22d reflects the infrared light emitted from light source unit 22a by 90 degrees to convert it into parallel light, which is then emitted toward light-receiving unit 22b.

[0035] Lens 22e is disposed above light receiving unit 22b such as a photodiode, and is disposed so that its multiple fan-shaped portions face the light source unit 22a. Lens 22e collects the infrared light emitted from light source unit 22a, reflects it at an angle of 90 degrees, and directs it to light receiving unit 22b disposed directly below. The plurality of legs 23 are erected on the upper surface of the base 24 .

[0036] The base 24 is a substantially disk-shaped member, and supports the housing 21 of the raindrop detection device 20 and the like via a plurality of legs 23 erected on an upper surface 24a thereof. The microcomputer 25 is connected to the light source unit 22a and the light receiving unit 22b, and detects raindrops that have passed between the light source unit 22a and the light receiving unit 22b in accordance with changes in the amount of light received by the light receiving unit 22b.

[0037] More specifically, in addition to the light source unit 22a and the light receiving unit 22b, the raindrop detection device 20 includes a microcomputer 25, a DC (direct current) cut unit 26a, an amplifier unit 26b, an AC (alternating current) / DC (direct current) light quantity conversion unit 26c, an amplifier unit 26d, an AC (alternating current) environmental component cancellation unit (first disturbance factor processing unit) 26e, an AC modulation drive unit 26f, a voltage drop unit 26g, an abnormality determination unit 26h, a disturbance light cut unit (second disturbance factor processing unit) 26i, and a memory (storage unit) 27, as shown in FIG. 6.

[0038] As shown in FIG. 6, the microcomputer 25 is connected to the memory 27, and reads various programs and data stored in the memory 27 to control each part of the raindrop detection device 20 and to implement a correction method for the raindrop detection device 20, which will be described later. Here, the infrared light emitted from the light source unit 22a is received by the light receiving unit 22b and converted into a voltage value, and then the DC cutting unit 26a removes DC environmental components such as ambient light from the detection result detected by the light receiving unit 22b.

[0039] The detection result from which the DC environmental component has been removed is amplified in amplifier 26b, converted into a DC component in AC / DC light quantity converter 26c, and the amplified signal in amplifier 26d is input to microcomputer 25. In the raindrop detection device 20 of this embodiment, the infrared light emitted from the light source unit 22a is received by the light receiving unit 22b, converted into a voltage value, and then sent to the voltage drop unit 26g.

[0040] The voltage drop unit 26g is an electric circuit including a transistor that drops the voltage when a voltage value equal to or greater than a predetermined voltage is applied. When the voltage value converted from the amount of light received by the light receiving unit 22b exceeds a predetermined threshold, the voltage drop unit 26g determines that the increase in the amount of received light is due to the reception of artificial light such as an automobile headlight or a flashlight, and drops the voltage value to a range that does not affect raindrop detection.

[0041] The magnitude of the voltage dropped by voltage drop unit 26g depends on whether a current flows through the base (input) of the transistor and turns it on. For example, when the ambient light is strong, the base current increases, and when the current exceeds a certain value, the transistor turns on and the photocurrent caused by the ambient light flows to GND. Specifically, when the voltage drop unit 26g receives a voltage value that exceeds a predetermined voltage value from the light receiving unit 22b, the voltage drop unit 26g drops the voltage value such that the larger the voltage value that exceeds the threshold, the larger the voltage value that is dropped.

[0042] As a result, in a configuration in which the above-mentioned shielding structure (arrangement of the light receiving section 22b) is used to prevent an increase in the amount of light received due to natural light such as sunlight, a significant increase in the amount of light received by the light receiving section 22b due to the influence of ambient light other than natural light can be detected, and the voltage value can be reduced so as to reduce the increase. Therefore, even if light from an artificial light or the like enters through the opening 21a and is received by the light receiving unit 22b, the increased amount of received light can be cut off, and only the change in the amount of received light associated with raindrop detection can be extracted, allowing subsequent raindrop detection processing to be performed.

[0043] The DC cut unit 26a transmits the data (ADRAW) of the detection result at the light receiving unit 22b before removing the disturbance light component to the microcomputer 25 via the abnormality determination unit 26h. The abnormality determination unit 26h receives an electrical signal from which DC environmental components have been removed from the voltage value that has been reduced by the voltage reduction unit 26g, and if the reduced voltage value does not decrease to a predetermined voltage value or below that does not affect raindrop detection, it determines that an abnormality has occurred.

[0044] As a result, if the voltage value does not drop below the predetermined value even after the voltage drop unit 26g performs a process to drop the voltage value above a predetermined threshold, it can be assumed that strong artificial light, such as from a light, has been detected by the light receiving unit, and it can be determined that an abnormality has occurred. As a result, the result of the abnormality determination can be notified to a server connected for communication, or a light indicating an abnormality can be turned on in the raindrop detection device 20.

[0045] The microcontroller 25 receives the detection results (excluding detection results determined to be abnormal) from the light receiving unit 22b, and controls the AC / DC light intensity conversion unit 26c to perform AC / DC conversion processing using PWM (Pulse Width Modulation) control, and controls the AC modulation drive unit 26f to switch the light intensity of the light source unit 22a. Furthermore, the signal indicating the light intensity level converted into an AC component in the AC / DC light intensity conversion unit 26c is sent to an AC environmental component cancellation unit 26e, which removes the AC voltage component that drives the light source unit 22a, such as an LED, and then sent to an AC modulation drive unit 26f, where it is used to adjust the output of the light source unit 22a.

[0046] Furthermore, the AC environmental component cancellation unit (first disturbance factor processing unit) 26e, which receives a signal indicating the light quantity level from the AC / DC light quantity conversion unit 26c, cuts out the change in light quantity due to the disturbance factor corresponding to the second frequency band out of the first frequency band corresponding to the change in light quantity due to the detection of raindrops and the second frequency band corresponding to the change in light quantity due to the disturbance factor. Specifically, the first frequency band corresponding to the falling speed of raindrops is, for example, about 500 to 3000 Hz, and the second frequency band corresponding to changes in light intensity due to disturbance factors is, for example, several Hz to 100 Hz.

[0047] This allows the system to detect only the change in light intensity due to raindrop detection by cutting out changes in light intensity that are presumed to be caused by external disturbances depending on the frequency band, thereby enabling highly accurate raindrop detection. Furthermore, the disturbance light cut unit (second disturbance factor processing unit) 26i, which receives a DC signal indicating the light quantity level from the AC / DC light quantity conversion unit 26c, performs processing to cut out the change in light quantity that was not completely cut out among the changes in light quantity caused by disturbance factors that were cut out by lowering the voltage value in the voltage drop unit 26g.

[0048] That is, the voltage input to the ambient light cutter 26i is “raindrop voltage component + ambient light component.” Only the ambient light component (close to DC) is extracted by the low-pass filter, and the ambient light cutter 26i can extract only the raindrop voltage component by taking the difference between the “raindrop voltage component + ambient light component” and the “ambient light component.” This allows for more accurate raindrop detection by cutting out unnecessary changes in light intensity at the voltage drop section 26g and then further cutting out changes in light intensity due to disturbance factors that could not be completely cut out.

[0049] Here, the microcomputer 25 reads various programs stored in the memory 27 and generates the functional blocks shown in FIG. That is, as shown in FIG. 7, the microcomputer 25 has a raindrop detection unit 25a, a diameter calculation unit 25b, and a rainfall calculation unit 25c. The raindrop detector 25a detects raindrops that have passed between the light source 22a and the light receiver 22b (raindrop detection area A1) in accordance with changes in the amount of light received by the light receiver 22b.

[0050] More specifically, when a raindrop passes through the raindrop detection area A1, part of the infrared light emitted from the light source unit 22a is blocked, and the light detection result at the light receiving unit 22b changes. As shown in Fig. 8, the raindrop detection unit 25a regards the change in voltage value (peak value) obtained by amplifying the detection result at the light receiving unit 22b as a raindrop candidate, and detects the raindrop candidate as a raindrop when the peak value of the voltage corresponding to each raindrop candidate exceeds a predetermined threshold.

[0051] The detection results shown in Figure 8 show an example in which three raindrop candidates were detected within the measurement time, and all of the raindrop candidates had peak values ​​exceeding the threshold, so they were detected as raindrops. The differences between the three peak values ​​in the graph shown in FIG. 8 mainly appear as differences in the diameter, transmittance, etc. of the detected raindrops. The diameter calculation unit 25b calculates the diameter of the raindrop detected by the raindrop detection unit 25a. Specifically, the diameter calculation unit 25b calculates the diameter of the voltage value having a peak value corresponding to the raindrop detected by the raindrop detection unit 25a using a table or the like showing the relationship between the voltage value and the diameter.

[0052] Here, assuming that the transmittance of raindrops is approximately constant, the larger the diameter of the raindrops, the greater the amount of infrared light blocked by the light source unit 22a, and therefore the larger the diameter of the raindrops. The rainfall calculation unit 25c calculates the amount of rainfall per unit time using the diameter of the raindrops calculated by the diameter calculation unit 25b. Specifically, the rainfall calculation unit 25c calculates the volume V (= 4 / 3 × π × r) of each raindrop from the diameter R of the raindrops that have passed through the raindrop detection area A1. 3 ) and then integrate the volume of raindrops detected per unit time to calculate the amount of rainfall. Note that π is the circumference constant and r is the radius (= diameter R / 2).

[0053] <Raindrop detection method> In the raindrop detection method of this embodiment, the raindrop detection device 20 detects raindrops (rainfall sensing) according to the flowchart shown in FIG. That is, in step S11, the microcomputer 25 repeatedly determines whether the sampling interval has elapsed, for example, using a timer, and proceeds to step S12 each time the sampling interval has elapsed.

[0054] Next, in step S12, the microcomputer 25 acquires data (AD values ​​(converted into A / D converted light receiving voltage values)) indicating the measurement results of the light receiving section 22b. Next, in step S13, voltage drop unit 26g determines whether the voltage value changed in light receiving unit 22b is greater than a predetermined threshold value. If it is greater than the threshold value, the process proceeds to step S14. If it is equal to or less than the threshold value, the process skips steps S14 and S15 and proceeds to step S16.

[0055] Next, in step S14, since it was determined in step S13 that the voltage value converted by the light receiving unit 22b is greater than a predetermined threshold value, the voltage drop unit 26g performs a process of lowering the voltage value received from the light receiving unit 22b in order to cut off the increase in the amount of light received due to external disturbance factors. Next, in step S15, abnormality determination unit 26h determines whether the voltage value reduced by voltage drop unit 26g has decreased to a predetermined voltage value. If the voltage value has decreased to the predetermined voltage value, the process proceeds to step S15. If the voltage value has not decreased to the predetermined voltage value, the process proceeds to step S20, where abnormality determination unit 26h determines that an abnormal amount of light has been detected that cannot be reduced by the processing in voltage drop unit 26g, determines that an abnormality has occurred, and ends the process.

[0056] Next, in step S16, since it was determined in steps S13 and S15 that the voltage value is below a predetermined threshold or has dropped to a predetermined voltage value, the diameter calculation unit 25b calculates the diameter of the raindrop based on the voltage value. Next, in step S17, the rainfall calculation unit 25c calculates the volume of the raindrop from the diameter of the raindrop calculated in step S16.

[0057] Next, in step S18, the microcomputer 25 determines whether or not the specified number of items have been retained. If it is determined that the specified number of items have been retained, the measurement is terminated. If it is determined that the specified number of items have not been retained, the processing from step S11 onwards is repeated. Next, in step S19, the rainfall calculation unit 25c calculates the amount of rainfall per unit time using the raindrop volume calculated in step S17, and then ends the process.

[0058] As a result, if the amount of light received by the light receiving unit 22b increases significantly due to the influence of external light, when the voltage value converted from the amount of light received by the light receiving unit 22b exceeds a predetermined threshold, the voltage corresponding to the increase in the amount of light received due to the disturbance factor is reduced to a range that does not affect raindrop detection, and raindrops can be detected by detecting only the change in the amount of light received due to the detection of raindrops. As a result, the influence of ambient light can be suppressed and raindrops can be detected with high accuracy.

[0059] <Major features> The raindrop detection device 20 of this embodiment includes a housing 21, an opening 21a, a light source 22a, a light receiving unit 22b, a voltage drop unit 26g, and a microcomputer 25 (raindrop detection unit 25a). The housing 21 has a cylindrical outer circumferential surface and a ceiling surface. The opening 21a is formed on the ceiling surface of the housing 21. The light source 22a is provided in the housing 21 and emits light toward raindrops passing through the opening 21a. The light receiving unit 22b is disposed opposite the light source 22a in the housing 21. The light receiving unit 22b receives light emitted from the light source 22a and converts the amount of received light into a voltage value. The voltage drop unit 26g reduces the voltage value when the voltage value converted by the light receiving unit 22b exceeds a predetermined threshold. The microcomputer 25 (raindrop detection unit 25a) detects raindrops that have passed between the light source unit 22a and the light receiving unit 22b in accordance with changes in the voltage value converted by the light receiving unit 22b, and when the voltage value exceeds a predetermined threshold, detects raindrops using the voltage value reduced by the voltage drop unit 26g.

[0060] As a result, even if the amount of light received by the light receiving unit 22b fluctuates significantly due to the influence of external light (e.g., weak artificial light), when the voltage value converted from the amount of received light exceeds a predetermined threshold, raindrops can be detected by reducing the voltage equivalent to the increase in the amount of received light caused by the external disturbance factor to a range that does not affect raindrop detection. As a result, the influence of ambient light can be suppressed and raindrops can be detected with high accuracy.

[0061] In addition, in the raindrop detection device 20 of this embodiment, the light source unit 22a and the light receiving unit 22b are each positioned at a recessed position from the opening 21a (shielding structure) while ensuring a sufficient height (depth) of the opening 21a so that natural light such as sunlight is not received by the light receiving unit 22b, as shown in FIG. 4. This makes it possible to prevent strong sunlight from entering through the opening 21a and being received by the light receiving portion 22b, for example, by taking into consideration the angle at which sunlight enters the opening 21a. As a result, the above-mentioned shielding structure eliminates the effects of natural light such as strong sunlight, and by performing voltage reduction processing to suppress an abnormal increase in the amount of light received by the voltage drop section 26g, it is possible to reduce the effects of artificial light being received by the light receiving section 22b, or to perform abnormality determination processing.

[0062] [Other embodiments] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0063] (A) In the above embodiment, the raindrop detection device and the raindrop detection method are described as examples of realizing the present invention, but the present invention is not limited to this. For example, the present invention may be realized as a raindrop detection program that causes a computer to execute the raindrop detection method described above.

[0064] This raindrop detection program is stored in a memory (storage unit) installed in the raindrop detection device, and the CPU loads the raindrop detection program stored in the memory and causes the hardware to execute each step. More specifically, the CPU loads the raindrop detection program and executes the above-mentioned steps, thereby achieving the same effects as those described above. The present invention may also be realized as a recording medium storing a raindrop detection program.

[0065] (B) In the above embodiment, an example has been described in which, when a significant increase in the amount of received light is detected, the voltage drop unit 26g reduces the voltage value to cut off the amount of received light caused by disturbance factors, and the AC environmental component cancellation unit 26e and the disturbance light cutting unit 26i perform processing to further cut off the increase in the amount of received light caused by disturbance factors. However, the present invention is not limited to this.

[0066] For example, the voltage drop unit 26g may be configured to reduce the voltage value and only cut off the amount of received light caused by disturbance factors. In other words, it is not essential to further cut off the amount of received light caused by disturbance factors downstream of the voltage drop unit 26g. Furthermore, in addition to the voltage drop in the voltage drop section 26g, only one of the AC environmental component cancel section 26e and the ambient light cut section 26i may be used.

[0067] (C) In the above embodiment, an example has been described in which it is determined that an abnormality has occurred when the voltage value reduced by the voltage drop unit 26g has not reduced to a predetermined voltage value. However, the present invention is not limited to this. For example, as long as the voltage drop unit can sufficiently reduce the voltage, the voltage drop unit may have a configuration that does not have a function for determining abnormality.

[0068] (D) In the above embodiment, an example was described in which a shielding structure was adopted in which the light receiving unit 22b was located at a position separated from the opening 21a (at a position recessed from the inner wall surface 21b) in order to prevent natural light such as sunlight from entering the opening 21a and causing an abnormal amount of received light to be detected by the light receiving unit 22b. However, the present invention is not limited to this. For example, a configuration may be adopted in which a shielding member is disposed near the light receiving section to prevent natural light such as sunlight from being received by the light receiving section, or a shielding structure may be adopted in which the size of the opening is reduced to suppress the influence of sunlight or the like on the light receiving section.

[0069] <Additional Notes> The raindrop detection device according to the first invention is a housing portion having a cylindrical outer circumferential surface and a ceiling surface; an opening formed in the ceiling surface of the housing; A light source unit provided in the housing unit and irradiating light toward raindrops passing through the opening; a light receiving unit disposed in a position facing the light source unit in the housing unit, receiving light emitted from the light source unit and converting an amount of the received light into a voltage value; a voltage drop unit that drops the voltage value converted by the light receiving unit when the voltage value exceeds a predetermined threshold; A raindrop detection unit that detects raindrops that have passed between the light source unit and the light receiving unit according to changes in the voltage value converted in the light receiving unit, and detects raindrops using the voltage value reduced in the voltage drop unit when the voltage value exceeds a predetermined threshold. It is equipped with:

[0070] A raindrop detection device according to a second aspect of the present invention is the raindrop detection device according to the first aspect of the present invention, The voltage drop unit increases the voltage value that is reduced as the voltage value that exceeds the threshold increases. A raindrop detection device according to a third aspect of the present invention is the raindrop detection device according to the first or second aspect of the present invention, The power supply further includes an abnormality determination unit that determines that an abnormality has occurred if the voltage value does not drop to a predetermined voltage value or less in the voltage drop unit when the voltage value exceeds a predetermined threshold value.

[0071] A raindrop detection device according to a fourth aspect of the present invention is the raindrop detection device according to any one of the first to third aspects of the present invention, The sensor further includes a first disturbance factor processing unit that cuts out the change in light quantity due to a disturbance factor corresponding to the second frequency band, out of a first frequency band corresponding to the change in light quantity due to the detection of raindrops and a second frequency band corresponding to the change in light quantity due to a disturbance factor.

[0072] A raindrop detection device according to a fifth aspect of the present invention is the raindrop detection device according to the fourth aspect of the present invention, The light source further includes a second disturbance factor processing unit that performs processing to cut out the change in light quantity caused by the disturbance factor that was not completely cut out by lowering the voltage value in the voltage drop unit. A raindrop detection device according to a sixth aspect of the present invention is the raindrop detection device according to any one of the first to fifth aspects of the present invention, The light receiving device further includes a shielding structure that blocks sunlight incident through the opening from entering the light receiving portion. [Industrial Applicability]

[0073] The raindrop detection device of the present invention has the effect of suppressing the influence of external light and enabling highly accurate detection of raindrops, and is therefore widely applicable to sensors that measure rainfall, weather sensors that include such sensors, and the like. [Explanation of symbols]

[0074] 20 Raindrop detector 21 Housing 21a opening 21b Inner wall 21c Ceiling surface 21d Outer surface 22a Light source section 22b Light receiving part 22c board 22d, 22e lenses 23 Legs 24 base 24a Top side 25 Microcomputer 25a Raindrop detection part 25b Diameter calculation section 25c Rainfall calculation part 26a DC cut section 26b Amplification section 26c AC / DC light intensity conversion unit 26d Amplifier 26e AC environmental component cancellation unit (first disturbance factor processing unit) 26f AC modulation driver 26g Voltage drop section 26h Abnormality judgment section 26i Ambient light cut section (second disturbance factor processing section) 27 Memory (storage section) A1 Raindrop detection area

Claims

1. a housing portion having a cylindrical outer circumferential surface and a ceiling surface; an opening formed in the ceiling surface of the housing; A light source unit provided in the housing unit and irradiating light toward raindrops passing through the opening; a light receiving unit disposed in a position facing the light source unit in the housing unit, receiving light emitted from the light source unit and converting an amount of the received light into a voltage value; a voltage drop unit that drops the voltage value converted by the light receiving unit when the voltage value exceeds a predetermined threshold; A raindrop detection unit that detects raindrops that have passed between the light source unit and the light receiving unit according to changes in the voltage value converted in the light receiving unit, and detects raindrops using the voltage value reduced in the voltage drop unit when the voltage value exceeds a predetermined threshold. A raindrop detection device comprising:

2. the voltage drop unit increases the voltage value to be dropped as the voltage value exceeding the threshold increases, The raindrop detection device of claim 1 .

3. and an abnormality determination unit that determines that an abnormality has occurred if the voltage value does not drop to a predetermined voltage value or less in the voltage drop unit when the voltage value exceeds a predetermined threshold.

3. The raindrop detection device according to claim 1 or 2.

4. A first disturbance factor processing unit that cuts the change in light amount due to a disturbance factor corresponding to the second frequency band among a first frequency band corresponding to a change in light amount due to the detection of raindrops and a second frequency band corresponding to a change in light amount due to a disturbance factor. Further provided is 3. The raindrop detection device according to claim 1 or 2.

5. The light source further includes a second disturbance factor processing unit that performs processing to cut a change in the light amount caused by the disturbance factor that has not been completely cut out, among the changes in the light amount caused by the disturbance factor that have been cut out by lowering the voltage value in the voltage drop unit.

5. The raindrop detection device of claim 4.

6. The light receiving unit may further include a shielding structure that blocks sunlight incident through the opening from entering the light receiving unit.

3. The raindrop detection device according to claim 1 or 2.

7. a housing portion having a cylindrical outer circumferential surface and a ceiling surface; an opening formed in the ceiling surface of the housing; A light source unit provided in the housing unit and irradiating light toward raindrops passing through the opening; a light receiving unit disposed in a position facing the light source unit in the housing unit, receiving light emitted from the light source unit and converting an amount of the received light into a voltage value; A raindrop detection method for a raindrop detection device comprising: a voltage drop step of, when the voltage value converted by the light receiving unit exceeds a predetermined threshold, dropping the voltage value until the voltage value is equal to or less than a predetermined voltage value; A raindrop detection step in which raindrops that have passed between the light source unit and the light receiving unit are detected according to a change in the voltage value converted in the light receiving unit, and when the voltage value exceeds a predetermined threshold, raindrops are detected using the voltage value reduced in the voltage reduction step; A raindrop detection method comprising:

8. a housing portion having a cylindrical outer circumferential surface and a ceiling surface; an opening formed in the ceiling surface of the housing; A light source unit provided in the housing unit and irradiating light toward raindrops passing through the opening; a light receiving unit disposed in a position facing the light source unit in the housing unit, receiving light emitted from the light source unit and converting an amount of the received light into a voltage value; A raindrop detection program for a raindrop detection device comprising: a voltage drop step of, when the voltage value converted by the light receiving unit exceeds a predetermined threshold, dropping the voltage value until the voltage value is equal to or less than a predetermined voltage value; A raindrop detection step in which raindrops that have passed between the light source unit and the light receiving unit are detected according to a change in the voltage value converted in the light receiving unit, and when the voltage value exceeds a predetermined threshold, raindrops are detected using the voltage value reduced in the voltage reduction step; A raindrop detection program that causes a computer to execute a raindrop detection method comprising:

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