JPS62179637A - Rain drop detector - Google Patents

Abstract

PURPOSE:To increase noise resistance when rain fall is detected, by integrating values corresponding to an extended pulse width. CONSTITUTION:A rain drop detection circuit 81 outputs a rain drop detection pulse with a level corresponding to the size of rain drops passing through a detection area while a pulse extension circuit 1 outputs a pulse signal obtained by extending the pulse width of the rain drop detection pulse according to the level thereof. A comparator 2 compares an output from the circuit 1 with a threshold V1 and give comparison output '1' while the output of the circuit 1 is larger to be supplied to a wiper action timing circuit 3 through a line 88. The circuit 3 integrates the input signal through an LPF to form a wiper driving signal. Thus, rain fall can be detected by removing noise even when the noise overlaps the line 88.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a raindrop detection device for detecting raindrops.

[Conventional technology]

2. Description of the Related Art Techniques for detecting raindrops and automatically controlling the operating timing of automobile wipers based on the detection results have been proposed.

FIG. 8 is a block diagram showing an example of a conventional device of this type, in which 81 is a raindrop detection circuit, 82 is a pulse drive circuit, and 8 is a block diagram showing an example of a conventional device of this type.
3 is a light emitting element such as a light emitting diode, 84 is a light receiving element such as a photodiode, 85 is a tuning circuit, 86 is an amplifier, 8
7 is a detection circuit, 88 is a signal line, 89 is a wiper operation timing circuit, 90 is a peak value integrator, 91 is a comparator,
92 is a wiper drive circuit, and 93 is a wiper motor. Moreover, FIG. 9 is a block diagram showing a configuration example of the peak value integrator 90, and 0PI1.0P12 is an operational amplifier, Dll
is a diode, C1l is a capacitor, Qll is a transistor, and R11 is a resistor. Further, FIG. 10 is an explanatory diagram of the operation of FIG. 8.

A raindrop detection circuit 81 is arranged near a raindrop detection area, and a wiper operation timing circuit 89 is connected to this raindrop detection circuit 81 via a signal line 88.

The pulse drive circuit 82 in the raindrop detection circuit 81 pulse-drives the light emitting element 83 with a pulse signal of a predetermined frequency, and the light receiving element 84 converts the light emitted from the light emitting element 83 and passing through the raindrop detection area into an electrical signal. In addition to the tuning circuit 85, an amplifier 86 amplifies the output signal of the tuning circuit 85 and applies it to a detection circuit 87, and the detection circuit 87 detects and outputs the output signal of the amplifier 86. Therefore, when a raindrop passes through the detection area between the light emitting element 83 and the light receiving element 84, a raindrop detection pulse having a level (peak value) corresponding to the size of the raindrop is sent from the raindrop detection circuit 81 via the signal line 88. It is then added to the wiper operation timing circuit 89.

Peak value integrator 90 in wiper operation timing circuit 89
integrates the peak value of the raindrop detection pulse applied via the signal line 88, and the output signal of the wiper drive circuit 92 becomes '
1'', the integrated value becomes zero. For example, if the raindrop detection pulse shown by the solid line in FIG. 10(A) is detected from the raindrop detection circuit 81, the output of the peak value integrator 90 As shown by the solid line in the same figure (B), the signal is
Each time a raindrop detection pulse is applied, the value increases by a value corresponding to its peak value. Then, when the output signal of the peak value integrator 90 exceeds the threshold value VS of the comparator 91 shown by the dotted line in FIG. The output signal is “1”
'', the wiper morph 93 is operated, and the peak value product 'M and the integrated value of the device 90 are set to zero.Then, the same operation as described above is performed, and the output signal of the peak value integrator 90 is applied to the comparator 91. The wiper will operate every time the threshold value Vs is exceeded.

That is, in the conventional example shown in FIG. 8, the peak value of the raindrop detection pulse having a level corresponding to the size of the raindrop passing through the detection area is integrated, and the wiper is operated every time the integrated value reaches a predetermined amount. Because of this, the wipers operate at intervals depending on the amount of rainfall.

[Problem that the invention seeks to solve]

In the conventional example shown in Fig. 8, the wipers can be operated every time the amount of rainfall reaches a predetermined amount, as described above.
There were the following problems. That is, the raindrop detection circuit 81 and the wiper operation timing circuit 89 are connected by the signal line 8, but in the case of a vehicle, since there is a high possibility that noise will be superimposed on the signal line 8, For example, the raindrop detection pulse output from the raindrop detection circuit 81 has noises (a) and (b) shown by dotted lines in FIG. 10(A).
If noise is superimposed, the output signal of the peak value integrator 90 will be as shown in FIG. Note that in order to remove noises (a) and (b), it is possible to provide a low-pass filter on the input side of the peak value product X unit 90, but the frequency component of the raindrop detection pulse is
00 Hz to several tens of KHz, and since the noise is several KHz or more, it is impossible to remove only the noise with a low-pass filter.

The present invention solves the above-mentioned problems, and its purpose is to improve noise resistance.

[Failure to solve the problem]

In order to solve the above-mentioned problems, the present invention includes a raindrop detection circuit that outputs a raindrop detection pulse of a level corresponding to the size of a raindrop passing through a detection area, and a raindrop detection circuit that outputs a raindrop detection pulse of a level corresponding to the size of a raindrop passing through a detection area. The pulse expansion circuit is provided with a pulse expansion circuit that expands, a low-pass filter to which the output of the pulse expansion circuit is input, and an integration means that integrates a value corresponding to the pulse width of the output pulse of the low-pass filter.

[Effect]

The pulse width of the output pulse of the pulse expansion circuit corresponds to the size of the raindrop that has passed through the detection area. Therefore,
The amount of rainfall can be detected by integrating values corresponding to the pulse width of the output pulse of the pulse expansion circuit using the integrating means. Furthermore, since the pulse width of the raindrop detection pulse is expanded by the pulse expansion circuit, even if noise is superimposed on the output signal of the pulse expansion circuit, only the noise can be removed by the low-pass filter.

〔Example〕

FIG. 1 is a block diagram of an embodiment of the present invention, in which 1 is a pulse expansion circuit, 2 is a comparator, 3 is a wiper operation timing circuit, 4 is a low-pass filter, 5 is an integrator, 6 is a comparator, 7 8 is a wiper drive circuit, and the same reference numerals as in other parts of FIG. 8 represent the same parts.

2 and 3 are block diagrams showing configuration examples of the pulse expansion circuit 1 and the integrator 5, respectively, where Di and D2 are diodes, C1 and C2 are capacitors, OPI is an operational amplifier, and R1 and R2 are The resistor Ql is a transistor.

Further, FIG. 4 is an explanatory diagram of the operation of FIG. 1.

The raindrop detection circuit 81 outputs a raindrop detection pulse with a level corresponding to the size of the raindrop passing through the detection area, as described above, and the pulse expansion circuit 1 adjusts the pulse width of the raindrop detection pulse from the raindrop detection circuit 81 to that level. Outputs a pulse signal expanded according to the level.

That is, the capacitor C1 in the pulse expansion circuit 1 is charged via the diode DI, and its charge! Since the charge is discharged through the resistor R1, by appropriately setting the capacitance of the capacitor C1 and the resistance value of the resistor R1, and making the discharging time constant longer than the charging time constant, the pulse stretching circuit 1 output voltage may be as described above. Therefore, for example, from the raindrop detection circuit 81 to FIG.
If the raindrop detection pulse shown in A) is output, the output of the pulse expansion circuit 1 will be as shown by the solid line in FIG. 2B. In this case, it is necessary to make the frequency component of the output signal of the pulse expansion circuit l lower than the frequency component of the noise.

Further, the comparator 2 compares the output pulse of the pulse expansion circuit 1 with a threshold value v1 shown by a dotted line in FIG. (C
) is set to "1" as shown by the solid line. Here, since the pulse width of the output pulse of the pulse expansion circuit 1 corresponds to the level of the raindrop detection pulse, and the level of the raindrop detection pulse corresponds to the size of the raindrop passing through the detection area, the comparator 2 The pulse width of the output pulse corresponds to the size of the raindrop passing through the detection area. Note that the pulse width Tc of the comparator 2 is expressed by the following equation (1).

Tc = -r 1n(V+ /Vr) -
(1) However, vl is the dark value of the comparator 2, Vp is the peak value of the output signal of the pulse stretching circuit l, and τ is the discharge time constant Cl-R1 of the pulse stretching circuit l.

The output pulses of comparator 2 are applied to integrator 5 via signal line 88 and low pass filter 4 in wiper actuation timing circuit 3. The integrator 5 outputs a signal with a level corresponding to the value obtained by integrating the pulse width of the pulse applied from the comparator 2 via the low-pass filter 4, and when the signal applied from the wiper drive circuit 7 becomes "L", , the integral value (output signal) is set to zero. That is, integrator 5
The voltage appearing across the capacitor C2 in the transistor Q1 gradually increases while the output signal I of the comparator 2 is "1", and the output signal of the wiper drive circuit 7 becomes "1".
Since it becomes zero when it turns on, the output signal of the integrator 5 becomes as described above. Therefore, by adding the signal shown by the solid line in FIG. 4(C) from the comparator 2, the output signal of the integrator 5 becomes the one shown by the solid line in FIG. 4(D). That is, the output signal of the integrator 5 corresponds to the amount of rainfall.

Further, the comparator 6 compares the output signal of the integrator 5 with a threshold value v2 shown by a dotted line in FIG. ”. In addition, the wiper drive circuit 7 sets the output signal to 11'' as shown in FIG. It shall be zero.

Therefore, the wiper motor 93 is driven every time the integral value of the integrator 5 reaches a predetermined value, that is, every time the amount of rainfall reaches a predetermined amount.

In this way, in this embodiment, the pulse width of the raindrop detection pulse is expanded by the pulse expansion circuit 1, so even if noise is superimposed on the output signal of the comparator 2 in the signal line 88, the pulse width of the raindrop detection pulse is expanded by the low-pass filter 4. Noise can be removed, and therefore rainfall can be detected without being affected by noise. In this embodiment, the comparator 2 is provided at the front stage of the signal line 88 where noise is likely to be superimposed, but it is of course possible to provide it at the rear stage of the signal line 88. However, the pulse expansion circuit 1 must be placed before the signal line 88.

FIG. 5 is a block diagram of another embodiment of the present invention, 50
51 is a wiper operation timing circuit, 51 is a low-pass filter, 52 is a microprocessor, and 53 is a wiper drive circuit, and the same reference numerals as in FIG. 1 represent the same parts.

6 is a flowchart showing the processing contents of the microprocessor 52, and FIG. 7 is an explanatory diagram of the operation of FIG. 5. The operation of FIG. 5 will be explained below with reference to FIGS. 6 and 7. .

The microprocessor 52 performs the process shown in the flowchart of FIG. 6 at predetermined time intervals, and includes step S1.
Then, the count value CT of the counter provided internally by software is set to zero, and in step S2, it is determined whether the output signal a of the low-pass filter 51 is "1". If the judgment result is YES, set the flag F to rl
If the determination result is No, the flag F is set to "0" (Step S4). After this, when the time Δt has elapsed (step S5), it is determined whether the flag F is "1" or not (step S6), and if the determination result is YES, the signal a is "l" again. It is determined whether or not (step S7).

If the determination result in step S7 is YES, the count value CT of the counter described above is increased by +1 in step S7.
8), and then the time Δ after the processing of step S7 is completed.
When it is determined that t has elapsed (step S9), it is determined whether the count value CT exceeds a predetermined reference value CT (step S10). If the determination result in step 510 is YES, the wiper drive circuit 53
A wiper drive command is applied to the wiper motor 93 to operate the wiper motor 93 (step 5ll), and if the determination result is No, the process returns to step S2. Further, if the determination result in step S6 is No, the process in step 310 is performed, and if the determination result in step S7 is No, the process in step S9 is performed. That is, the microprocessor 53 determines whether the signal a is "1" at predetermined time intervals, and only when it determines that the signal a is "1" twice in a row, it increments the count value CT by 1 and starts counting. When the value CT exceeds CTa, the wiper motor 93 is operated.

Therefore, the output signal a of the low-pass filter 51 is as shown in FIG.
Assuming that the count value CT is as shown in A), the count value CT will be as shown in FIG.

Note that (B) in the same figure shows the timing at which the microprocessor 52 reads the signal a. In this way, according to this embodiment, the noise (A) as shown in FIG.
Even if the noise (a) is superimposed, the count value CT is not incremented by the noise (a), so that the noise resistance can be further improved compared to the embodiment shown in FIG. Further, although this embodiment uses the microprocessor 52 that performs digital processing, the AD
Since no converter is required, the device can be constructed economically.

〔Effect of the invention〕

As explained above, the present invention extends the pulse width of the raindrop detection pulse, applies the signal to a low-pass filter, and detects the amount of rainfall based on the integral value of the value corresponding to the pulse width of the output pulse of the low-pass filter. Therefore, there is an advantage that noise resistance can be improved compared to the conventional example.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of the configuration of a pulse expansion circuit, FIG. 3 is a circuit diagram showing an example of the configuration of an integrator, and FIG. 5 is a block diagram of another embodiment of the present invention, FIG. 6 is a flowchart showing the processing contents of the microprocessor 52, FIG. 7 is an explanatory diagram of the operation of FIG. 5, and FIG. 8 is a block diagram of another embodiment of the present invention. FIG. 9 is a block diagram of a conventional example; FIG. 9 is a circuit diagram showing a configuration example of a peak value integrator; and FIG. 10 is an explanatory diagram of the operation of FIG. In the figure, 1 is a pulse expansion circuit, 2.6.91 is a comparator, 3.50.89 is a wiper operation timing circuit, and 4.
51 is a low-pass filter, 5 is an integrator, 7° 53, 92
is a wiper drive circuit, 81 is a raindrop detection circuit, 82 is a pulse drive circuit, 83 is a light emitting element, 84 is a light receiving element, 85 is a tuning circuit, 86 is an amplifier, 87 is a detection circuit, 88 is a signal line, 90 is a peak value The integrator 93 is a wiper motor.

Claims (1)

[Claims] A raindrop detection circuit that outputs a raindrop detection pulse at a level corresponding to the size of a raindrop passing through a detection area, and a pulse width of the raindrop detection pulse output from the raindrop detection circuit according to the level. The pulse extension circuit is characterized by comprising: a pulse extension circuit that extends the pulses by the pulse extension circuit; a low-pass filter into which the output pulse of the pulse extension circuit is input; and integration means that integrates a value corresponding to the pulse width of the output pulse of the low-pass filter. Raindrop detection device.