JPS61186880A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To stabilize the detection of an object body at the boundary of a detection area when a reflected wave is detected by providing an amplification factor varying means which makes the amplification factor of an amplifying circuit smaller as the distance to an obstacle is shorter. CONSTITUTION:Amplifying circuits 6 and 8 and a transmitter receiver 7, a tuning amplifying circuit 9, a detecting circuit 11, a level detecting circuit 12, and switching circuit 17 and an integration circuit 18, etc., are provided. When a reflected wave returns. A fine-level signal passed through the transmitter receiver 7 is amplified by the circuit 8 of a receiving circuit 2 and further selected by the circuit 9. The signal from the circuit 9 is detected by the circuit 11 and the circuit 12 operates when the signal is higher than an operation level. When the circuit 17 operates, on the other hand, the integral output of the circuit 18 is inputted to the circuit 9 to improve the amplification factor of the circuit 9 according to the distance to the object body. In this case, the output of the circuit 18 is inputted to the circuit 9 to vary the increase rate of the amplification factor according to the distance. Namely, the amplification factor is made small for short distance and made large for long distance, and the amplification factor of a reverberation component is decreased to prevent malfunction due to the reverberation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to an ultrasonic sensor for a vehicle that is attached to a vehicle to detect obstacles.

[Background technology 1] Conventionally, in reflection-type ultrasonic sensors, the reflected waves from the sensing object constantly increase and decrease due to physical conditions such as air flow, and the fluctuations are particularly noticeable at the very edge of the detection area. Because of this, the ultrasonic sensor works the moment the reflection level increases, but then decreases the next moment, and stops working because the reflection level falls below the operating level.This phenomenon repeats, so the ultrasonic sensor is constantly turned on and off. It was unstable.

Recently, in order to compensate for this drawback, once the amplifier is caught (once it is turned on), the gain of the amplifier is amplified to a constant value, and even if the reflection level decreases at the next moment, this constant value prevents it from decreasing to the off level. , a method of stabilization has been adopted. However, with this method, in order to always increase the amplification factor by a constant value, the reflected waves from a long distance, which have a lot of fluctuation, and the reflected waves from a short distance, which have relatively little fluctuation, are simultaneously multiplied by a constant value of 7. Since the reverberation component is also amplified by increasing the amplification factor, by detecting the reverberation component that was originally large and increasing the amplification factor, the reverberation component becomes large until the date time is exceeded. When detected, the reverberation component becomes large even if the detected object is removed, and since it is within the date time,
There was a problem where it wouldn't turn off. This state will be explained with reference to FIG. Figure 3 (a) shows the transmitted signal S transmitted from the ultrasonic sensor, Figure 3 (b) shows the reflected wave from an obstacle, A is the reverberation component, and the mouth is from near and far. , and C shows the reflected wave from a long distance. This third
The reflected waves a and c in the normal state shown in FIG. 3(b) fluctuate between the level shown by the broken line and the level shown by the solid line due to the influence of wind and the like. Reflection wave mouth.

Since the level indicated by the broken line exceeds the operating level vth, an operating signal is output, but no operation occurs at the level indicated by the solid line. To prevent this, the amplification factor of the amplifier is increased to a constant value, so that even if the reflected wave signal fluctuates, tpJ3 (c)
As shown in the figure, the operating level vth is always exceeded. However, when the amplification factor is increased, the reverberation component A also increases, and even if the sensing object is removed as described above, the reverberation component A remains large, and this reverberation component A increases at the date time shown in Figure 3(d). There was a problem in that the sensor entered T1 and operated even though there was no object to be detected.

[Objective of the Invention 1] The present invention has been provided in view of the above-mentioned points, and by increasing the amplification factor by detection as necessary and stabilizing the last-minute operation of the detection area, the reverberation component It is an object of the present invention to provide an ultrasonic sensor that reduces unnecessary increases in the amount of ultrasonic waves and eliminates the problem of not turning off the sensor once it has been detected.

[Disclosure of the invention 1 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an ultrasonic sensor, which is composed of a wave transmitting circuit 1, a wave transmitter/receiver 7, and a wave receiving circuit 2. The transmitter circuit 1 includes a transmitter interval control circuit 3 that determines the interval between transmitted ultrasound waves, and a monostable multivibrator 4 that is driven by the transmitter interval controller 3 and determines the width of the ultrasound transmitter signal. It is comprised of an oscillation circuit 5 driven by a monostable multivibrator 4 and an amplifier circuit 6 that amplifies the output of the oscillation circuit 5. The transducer/receiver 7 serves both to transmit 9Mi sound waves, which are often used with microphones, and to receive reflected waves. The wave receiving circuit 2 also includes an amplifier circuit 8 that amplifies the reflected wave from the transducer 7, a tuned amplifier circuit 9 that selectively amplifies the output signal of the amplifier circuit 8, and a detection circuit that detects the output of the tuned amplifier circuit 9. 11, and a level detection circuit 1 that detects whether the output of the detection circuit 11 is equal to or higher than the operating level Vth.
2, the output of the level detection circuit 12, and the output of the date circuit 14, and the logic Pl! by AND date 13! a display circuit 15 that notifies or displays the multiplied output; a switching circuit 17 that varies the amplification factor of the tuned amplifier circuit 9; and an integral circuit that inputs the integral output obtained by integrating the date signal from the date circuit 14 to the switching circuit 17. It is composed of a circuit 18 and the like. Incidentally, as will be described later, the tuned amplifier circuit 9, the switching circuit 17, and the integrating circuit 18 surrounded by the broken line in FIG. 1 constitute an amplification factor variable means.

Next, the normal operation of the ultrasonic sensor will be explained. Now, when the ultrasonic sensor is powered on, the monostable multi-pipe lake 4 is driven by the wave transmission interval control circuit 3, and the oscillation circuit 5 is driven by the output of the monostable multi-pipe lake 4. This oscillation circuit 5 generates a frequency that drives a transducer 7, and the frequency from this oscillation circuit 5 is transmitted to an amplifier circuit 6.
The ultrasonic waves are amplified and sent to the transducer 7, and the ultrasonic waves are transmitted from the transducer 10 toward the object to be detected. When the reflected wave bounces back, the weak signal that has passed through the transducer 7 is amplified by the amplifier circuit 8 of the receiver circuit 2, and is further amplified by the tuned amplifier circuit 9.
is selected. The signal from the tuned amplifier circuit 9 is transmitted to the detection circuit 1
1, and if the level is above the operating level, the level detection circuit 12 is activated. That is, so-called operation level detection is performed by this level detection circuit 12. If the detected output exceeds the operating level Vth, the signal is sent to the AND-DATE 13, and in the AND-DATE 13, the date circuit 14 is
In other words, if there is a detection output within the date time of the date circuit 14, No. 48 is output from the AND date 13 to the display circuit 15, and the display circuit 1
5 operates to perform display or notification.

Next, the gist of the present invention will be explained. Note that A-E in Fig. f52 indicates the waveform at point A-E in Fig. 1.

First, the signal shown in FIG. 2(a) is transmitted via the transducer 7, and the ultrasonic wave transmitted from the transducer 7 becomes a reflected wave as shown in FIG. 2(b). Get the waveform. A shows the reverberation component, the mouth shows the reflected wave from a short distance, and C shows the reflected wave from a long distance. At this time, the broken line to the reflected wave mouth is the MAX change, and the solid line is the MIN change. The wave reflected from a sensing object at a short distance has less fluctuation than the wave reflected from a sensing object at a long distance. Further, when this reflected wave (the state shown by the broken line) exceeds the operating level Vth set by the level detection circuit 12, an output signal is output from the AND date 13 and the switching circuit 17 is operated. At this time, the date circuit 14 outputs H as shown in FIG. 2(c).
A level date output is output, and this date output is input to the integrating circuit 18. Then, this date output is outputted by the integrating circuit 18 as an integrated signal as shown in FIG. 2(d), and is inputted to the switching circuit 17. When the switching circuit 17 is activated by the signal from the AND date 13, the integral output of the integrating circuit 18 is transmitted to the tuned amplifier circuit 9.
is input to the tuned amplifier circuit 9 according to the distance to the detected object.
Increase the amplification factor of In other words, once the reflected wave operates and exceeds the bell vth, the amplification factor of the tuned amplifier circuit 9 is increased so that even if the level of the reflected wave fluctuates due to wind etc.
In the present invention, the operation is stabilized by ensuring that the operation level Vth is exceeded even if it is the minimum.
Rather than uniformly increasing the amplification factor of the tuned amplifier circuit 9, the output of the integrating circuit 18 is input to the tuned amplifier circuit 9, and the increase rate of the amplification factor is changed according to the distance.In other words, the amplification factor is decreased at short distances. The amplification factor is increased at long distances, and the amplification factor of the reverberation component A is decreased to prevent malfunctions due to reverberation.

The details are explained below. Expressing the fluctuation range of the reflected wave opening at a short distance as a ratio, the ratio of MIN and MAX of the reflection fluctuation at a short distance is X2/
X1 becomes x2/, < b2/l+.

becomes. In addition, h2, h is the MA for reflected waves from a long distance.
It shows the width of X and MIN. Therefore, the amplification factor at a short distance may be small, that is, a sensing object located at a short distance can be made to exceed the operating level vth with a small amplification factor relative to a sensing object located at a long distance. The date signal from the date circuit 14 is processed by the integrating circuit 18 as shown in FIG.
d), and the integrated output is transmitted to the tuned amplifier circuit 9 or not by the switching circuit 17. This depends on whether the reflection level of the detection object exceeds the detection level (operation level) VLh.

Further, when an integrated voltage is applied to the tuned amplifier circuit 9, the amplification factor is changed depending on the voltage level.
Since the output voltage of the integrating circuit 18 becomes a quotient, the amplification factor of the tuned amplifier circuit 9 increases as the output voltage of the integrating circuit 18 increases.

The waveform in Fig. 2 is a state in which the output waveform of the integrating circuit 18 is input to the tuned amplifier circuit 9 and the amplification factor is increased, and once a reflected wave is detected, the operating level Vth is reached by the MIN value of the fluctuation of the reflected wave. It shows that it can be lifted. As a result, since the reverberation component A corresponds to a very close distance where the increase rate of the amplification factor is small, it is rarely amplified by detection.

In addition, for reflections from a long distance where the reflected wave level fluctuates greatly, the amplification factor by the tuned amplifier circuit 9 is increased by the amount at the time of detection, so there is no possibility of repeated unstable on/off states. be.

[Effects of the Invention 1] As described above, the present invention includes a wave transmitting circuit that transmits ultrasonic waves and a wave receiving circuit that receives waves reflected by the ultrasonic waves from obstacles, and detects the reflected waves. In an ultrasonic sensor that increases the amplification factor of the amplification circuit of the receiving circuit to increase the reflected wave level when the presence of an obstacle is detected, the amplification factor of the amplification circuit increases as the distance to the obstacle becomes shorter. Since the amplification factor variable means is provided with a small amplification factor variable means, when detecting a reflected wave, it is possible to stabilize the detection of a detection object at the edge of the detection area, and furthermore, the amplification factor can be adjusted according to the variation. This has the effect that highly reliable operation can be achieved without the need for constant on operation due to the detection of reverberant components during detection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an operational waveform diagram of the same as above, and FIG. 3 is an operational waveform diagram of a conventional example. 1 is a wave transmitting circuit, 2 is a wave receiving circuit, 9 is a tuned amplifier circuit, 18
indicates an integrating circuit. Agent Patent Attorney Stone 1) Chief 7s2 Figure 113

Claims (2)

[Claims] (1) Equipped with a wave transmitting circuit that transmits ultrasonic waves and a wave receiving circuit that receives waves reflected by the ultrasonic waves from obstacles, and when the presence of the obstacle is detected by detecting the reflected waves. In an ultrasonic sensor that increases the amplification factor of an amplification circuit of a wave circuit to increase a reflected wave level, an amplification factor variable means is provided that varies the amplification factor of the amplification circuit to a smaller value as the distance to an obstacle becomes shorter. An ultrasonic sensor characterized by: (2) The amplification factor variable means for varying the amplification factor of the amplification circuit is composed of an integrator circuit that integrates the date output signal and a tuned amplification circuit that sets the amplification factor according to the output of this integrator circuit. An ultrasonic sensor according to claim 1, characterized in: