JPS61170638A - Liquid drop detector - Google Patents

Abstract

PURPOSE:To correct the output from a photodetector generated when a raindrop, etc. oscillate by providing a filter which removes the low-frequency component occurring in the oscillation of the liquid drop sticking to a fixed position from the output of the photodetector. CONSTITUTION:An oscillation circuit 21 makes oscillation operation at 100kHz and the output thereof is applied to a driving circuit 22, by which a light emitting element 1 is driven. The light from the element 1 is detected by the photodetector 2 and the quantity of the detected light changes when the raindrop passes through an optical path 3 therebetween. The output from the photodetector 2 is applied to a BPF23 by which the noise arising from the sunlight, etc. is removed. The output from the BPF23 is applied to an amplifier circuit 24 and a detection circuit 25, by which only the component of the output fluctuation of the photodetector 2 arising when the path 3 is interrupted by the raindrop is taken out. An HPF26 shuts off the signal of the output from the photodetector 2 generated when the raindrop sticking to the fixed position in the path 3 oscillates.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a device for detecting locks or droplets, and is advantageously implemented, for example, for wiping away raindrops adhering to the front window of a car with a wiper blade. The present invention relates to a droplet detection device capable of detecting droplets.

BACKGROUND TECHNOLOGY In the prior art in which raindrops adhering to the windshield of an automobile are wiped away by a wiper blade, the raindrops pass through an optical path between a light emitting element and a light receiving element that receives light from the light emitting element. The wiper blade is configured to drive the wiper blade by detecting the varying output from the light receiving element. If a WJ droplet adheres to a fixed position near a light emitting element or a light receiving element, and the attached raindrop blocks the optical path, and the raindrop vibrates due to wind, etc., it may also be falsely detected as raining. Ru.

Problems to be Solved by the Invention It is an object of the present invention to solve the problem of reducing the output from the light receiving element caused by the vibration of droplets such as raindrops adhering to a fixed position facing the optical path between the light emitting element and the light receiving element. , an improved droplet detection device is provided.

Structure of the Invention The present invention includes a light emitting element, a light receiving element that receives light from the light emitting element, and a light receiving element that receives an output from the light receiving element and is attached to a fixed position facing an optical path between the light emitting element and the light receiving element. The droplet detection device is characterized in that it includes a filter that removes low frequency components caused by vibrations of the droplets from the output of the light receiving element.

When the droplet attached to the fixed position vibrates while facing the optical path between the light emitting element and the light receiving element, the output from the light receiving element contains a low frequency component caused by the vibration. The filter removes low frequency components from the output from the light receiving element. As a result, the output from the filter does not include the low frequency components. Therefore, it is possible to detect only droplets passing through the optical path between the light emitting element and the light receiving element.

Embodiment FIG. 1 is a block diagram showing the electrical configuration of an embodiment of the present invention.6 Light from a light emitting element 1 is received by a light receiving element 2. In FIG. As raindrops pass through the optical paths 3 of these leaps, the amount of light received by the light receiving element 2 changes. As a result, as will be described later, a wiper blade for wiping the front surface of the automobile is angularly displaced by the motor 4.

FIG. 2 is a partially cutaway perspective view showing a structure related to the light emitting element 1 and the light receiving element 2. FIG. A pair of protrusions 6 and 7 are formed on the main body 5 made of a material such as synthetic resin, spaced apart from each other in the horizontal direction. These protrusions 6 and 7 protrude upward. One of the protrusions 6 is provided with a light emitting element 1.
The light emitting element 1 may be a light emitting diode that emits infrared rays etc. 6 The light from the light emitting element 1 is transmitted to another protrusion 7
The light is received by the light receiving element 2 provided in the. In this way, the raindrop detection means 8 is constructed.

Such a raindrop detection means 8 is installed in a rearview mirror 11 attached to a door 10 of an automobile 9, as shown in FIG.
It is attached to the upper part 12 of the. When raindrops are detected by the raindrop detection means 8, the wiper blade 14 that comes into contact with the 70-nt glass 13 is automatically driven by the motor 4 with a reciprocating angular displacement.

FIG. 4 is a sectional view of the vicinity of the protrusion 6 of the raindrop detection means 8. A mounting hole 17 is formed in the casing 16 of the rearview mirror 11, through which the protrusion 6 is inserted, and the protrusion 6 protrudes upward. The other protrusion 7 also has a similar configuration. It is raining and the raindrops indicated by reference ff-18 hit the upper part 12 or the like or are directly attached to the surface within the optical path 3 of the light emitting element 1, and the raindrops indicated by reference ff-18 are
The state shown in 8a is reached. The raindrops 18a vibrate within the optical path 3 due to vibrations of the automobile 9, wind during driving, and the like. Therefore, the output from the light receiving element 2 includes a low frequency component caused by the vibration of the raindrops 18a.According to the present invention, the output from the light receiving element 2 caused by the i motion of the m droplets 18a is included. Depending on the output, the motor 4 is not driven, and the wiper blade 14 is prevented from being driven undesirably.

Generally, the falling speed v1 of a raindrop to the ground is determined by the outer diameter of the raindrop. For example, when trying to detect raindrops with an outer diameter of 1.0 m or more, the falling speed v1 is 4
m/s or more. If the outer diameter of the optical path 3 is 2 m + sφ, raindrops passing through the optical path 3 will cause the light receiving element 2 to
The frequency f1 of the electrical signal included in the output of is fjrJ
As shown in equation 1.

ri = Riichi (1) Therefore, passing through the optical path 3 of this raindrop, the frequency 1
1, Tatoe is 4000Hz/2=2kHz.

When the automatic $9 is running, refer to Figure 5 and
The frequency of the frequency component included in the output of the light receiving element 2 due to the raindrops passing through the optical path 3 can be considered as follows. Automatic $9 speed v2 is, for example, 40+*/h
Assuming that the raindrop falls on the ground at the aforementioned velocity v1, the raindrop has a velocity component indicated by reference numeral 19. This velocity component 19 is, for example, 11.8IIl/s
It is ee. Therefore, based on the first equation, the frequency WLfl is 5.9 kHz.

It is understood that when the raindrops falling on the ground pass through the optical path 3 while the automobile 9 is stopped and running in this way, a signal Q having a frequency of 2 kHz or more is derived from the light receiving probe 2. Ru.

The oscillation circuit 21 performs an oscillation operation of, for example, 100 kHz, and its output is given to the drive circuit 22 to drive the light emitting element 1. The electrical signal output from the light receiving element 2 is given to a bandpass filter 23. The bandpass filter 23 passes a frequency signal of 100 kHz±10 kHz and generates a P wave, thereby removing noise caused by sunlight and the like. The output from the bandpass filter 23 is amplified by an amplifier circuit 24 and provided to a detection circuit 25. As a result, only the component of the output fluctuation of the light-receiving element 2 that occurs when the optical path 3 between the light-emitting cable 1 and the light-receiving element 2 is blocked by raindrops is extracted. The output from the detection circuit 25 is given to a bypass filter 26. The bypass filter 26 filters raindrops 18 attached to a fixed position within the optical path 3.
Frequency 5 of the output of the light receiving element 2 that occurs when a vibrates
It blocks signals below 00 Hz and passes signals above 500 Hz as R waves. The output from this bypass filter 26 is given to a low pass filter 27. The low-pass filter 27 removes signal ripple, blocks direct current, and performs inversion amplification.

The output from line 28 is provided to two integrating circuits.

The integrating circuit 29 includes a resistor 53, a capacitor 30, and a switching transistor 31 connected in parallel to the capacitor. A resistor 32 is connected in series to the transistor 31 .

The output from integrator circuit 29 is provided on line 33 to transistor 34. The transistor 34 has a relay 3
5 relay fills 36 are connected.

The relay switch S1 of the relay 35 has a common contact 38 and individual contacts 39 and 40. When the relay coil 36 is demagnetized, the common contact 38 is electrically connected to the individual contact 40, and when the relay coil 36 is energized, the common contact 38 is switched to the individual contact 39 only during the energized period. conduction.

The individual contacts 39 are connected to a power supply via a line 41. Another individual contact 40 provides a signal via line 42 to a monostable circuit 43 .

The monostable circuit 43 receives this F signal and gives a signal having a predetermined pulse width to the transistor 31 to make the transistor 31 conductive, thereby making the capacitor 30 conductive.
is discharged and the integrating circuit 29 is reset.

Line 42 is also connected to a common contact 44 of switch S2. One individual contact 45 of switch S2 is grounded, and the other individual contact 46 is connected via line 41 to the power supply. A common contact 38 of the relay switch S1 of the relay 35 is connected to the motor 4.

FIG. 6 is a perspective view showing the motor 4 and its surrounding structure. An output shaft 47 of the motor 4 rotates a disk 48 made of an electrically insulating material in the direction of an arrow 49 . This disk 48 is formed with circumferentially extending conductors 50, 51 at radially different positions. A common @ point 44 of the switch S2 is mounted extending radially so that it can commonly contact the conductors 50,51. Individual contacts 45 can contact the conductor 50 . Individual contacts 46 can contact the conductor 51 . The wiper blade 14 is moved by the angular displacement portion 9 by power from the output shaft 47.
When the wiper blade 14 is in the rest position, the boundary between the conductors 50 and 51 of the disc 48 is at the reference position 52, and one revolution of the disc 48 causes the wiper blade 14 to be driven back and forth one time to return to its original position. can return to its rest position.

During operation, when the light from the light emitting element 1 is blocked by raindrops in the optical path 3, the bandpass filter 23
The output from is shown in FIG. 7(1). When raindrops falling on the ground pass through the optical path 3, a signal waveform p1 is obtained. When the raindrops 18a adhere to the light emitting element 1 and cause vibration, a signal waveform p2 is obtained.

Such a signal waveform p2 is similarly obtained when the light is attached within the optical path 3 of the light receiving element 2. Therefore, the output from the detection circuit 25 is as shown in FIG. 7(2) and FIG. 10(1) showing the results of the upstream experiment.

According to the inventor's experiment, when a raindrop passes through the optical path 3, the frequency spectrum of the output from the detection circuit 25 is @8.
As shown in Figure (1).

When the raindrop 18a is attached to a fixed position and faces the optical path 3, and when the raindrop 18a vibrates, the frequency spectrum of the output from the detection circuit 25 is as shown in FIG. 8(2).

Comparing the frequency spectra in FIG. 8 (1) and FIG. 8 (2), it can be seen that when the raindrop 18a adheres to a fixed position and vibrates, the low frequency component below 500 Hz is large.

The bypass filter 26 removes the vibration waveform p2a caused by the vibration of the raindrop 18a in FIG. It is applied to a low-pass filter 27. As described above, the low-pass filter 27 has the function of smoothing the signal by removing the pull caused by the 100 kHz oscillation signal output from the bypass filter 26, blocking the DC component, and performing inversion amplification. Therefore, the signal waveform derived from the low-pass filter 27 to the line 28 is as shown in Fig. 7 (3) and Fig. 10 (2) showing the experimental results, and the raindrops are continuously
When passing through the low-pass filter 27, the signal shown in FIG. 9 (
1) is obtained, and this waveform is indicated by the reference mark pi in FIG.
It corresponds to the signal component indicated by ypl a. The integral output derived from the integrating circuit 29 to the line 33 follows the trace shown in FIG. 9(2). At the time when the integrated output of the line 33 exceeds the discrimination level 1 by the transistor 34, the line 34 becomes conductive. As the transistor 34 becomes conductive, the relay coil 36 of the relay 35 is excited. Therefore, the common contact 38 of the relay switch S1 is electrically connected to the individual contact 39.

This applies power to the motor 4, driving the wiper blade 14 and rotating the disc 48. Due to this rotation, the common contact 44 of the switch S2 is switched to the individual contact 46 and remains conductive. A high-level signal is applied to the monostable circuit 43 via the switch S2 from the line 42, so that the monostable circuit 43 transfers a signal having a predetermined pulse width to the integrating circuit 43.
to make transistor 31 conductive. In this way, the capacitor 30 is discharged. Therefore, the line 33 becomes low level and the transistor 34 is cut off. Therefore, the common contact 38 of the relay switch S1 switches to the individual contact 40. Motor 4 is supplied with power from line 41 via individual contact 46 and common contact 44 of switch S2 and individual contact 40 and common contact 38 of relay switch S1, and motor 4 continues to rotate. When the output shaft 47 of the motor 4 rotates and the disc 48 reaches the reference position 1i52, the common contact 44 of the switch S2 conducts to the individual contact 45 via the conductor 50, thereby stopping the motor 4.

In this way, one reciprocating motion of the wiper blade 14 is completed. In this way, as the number of raindrops passing through the optical path 3 increases, the wiper blade 14 is frequently driven for reciprocating angular displacement.

This invention is my own! l! It is not only implemented in connection with IJ, Qt wiper blades, but can also be implemented in a wide range of other applications, and is capable of detecting not only raindrops but also other liquid droplets, etc.

Effects As described above, according to the present invention, the low frequency component contained in the output from the light receiving element caused by the vibration of a droplet attached to a fixed position is removed, so that the light emitting element and the light receiving element are It becomes possible to detect only droplets that pass through the optical path between the two.

[Brief explanation of the drawing]

Fig. ffSi is a block diagram showing the electrical configuration of an embodiment of the present invention, Fig. 2 is a perspective view with a portion of the raindrop detection hand y, 8 cut away, and Fig. f53 is a perspective view showing the rearview mirror 11 and its vicinity. 4 is a sectional view of the vicinity of the protrusion 6, FIG. 5 is a diagram for explaining the speed of raindrops while the automobile 9 is running, FIG. 6 is a perspective view showing the structure of the motor 4 and its vicinity, and FIG. 7 is a waveform diagram for explaining the operation of the detection circuit 25, FIG. 8 is a diagram showing the frequency spectrum, FIG. fJIJ9 is a waveform diagram for explaining the operation of the two integrating circuits, and FIG. FIG. 3 is a waveform diagram for explaining the operation. DESCRIPTION OF SYMBOLS 1... Light emitting element, 2... Light receiving element, 3... Light path, 8... Raindrop detection means, 9... Car, 11...
Rearview mirror, 21... Oscillation circuit, 22... Drive circuit, 23... Bandpass filter, 24... Amplification circuit, 25... Detection circuit, 26... Bypass filter, 27... Low-pass filter, 29...Integrator circuit, 35...1J Leh's agent Patent attorney Function Keibetsu 16 Figure 7 Corollary Figure 8) I wave number (KHz) Shoulder fluid softness (KHz) Line 9 Figure 10 Figure Time (msec) Kama (msecJ

Claims (1)

[Scope of Claims] A light-emitting element, a light-receiving element that receives light from the light-emitting element, and a light-receiving element that receives an output from the light-receiving element and is attached to a fixed position facing an optical path between the light-emitting element and the light-receiving element. A droplet detection device comprising: a filter that removes low frequency components caused by droplet vibration from the output of the light receiving element.