JPS6138479A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To make it possible to detect only the abnormality of an actual circuit, by inputting a part of a transmission signal to a circuit for receiving the reflected wave from an object to apply processing thereto and detecting whether the signal after processing is generated. CONSTITUTION:The transmission signal A from an AND circuit 4 is attenuated by a resistance voltage dividing circuit 14 to obtain a signal E which is, in turn, inputted to a comparing circuit 16 along with the signal C, which is obtained by receiving the reflected wave from an object 5, through an amplifier 7 and both signals are respectively compared with predetermined levels to input the wave form shaping signal Pc, Pe of the signals C, E to a masking circuit 15 and a circuit abnormality discrimination circuit 30. In the circuit 30, AND logic of the signals Pc, Pe and the output M of a monostable multivibrator 11 is taken to output a pulse signal K at every input of the signal Pe and the normal and abnormal operations of the amplifier 7, the rectifier circuit 8 and the circuit 16 are judged by the presence or absence of the generation of the signal K.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ultrasonic sensor used to detect object distance, etc. using ultrasonic waves, and particularly relates to an improvement for diagnosing abnormalities in its circuit. .

(Prior art) As a conventional ultrasonic sensor, for example, Japanese Patent Laid-Open No. 57-1
There is a device as described in Japanese Patent No. 82544 which detects the ground distance r@ from the bottom of a car and is applied as a surface device to detect unevenness of the road surface such as side ditches.

Additionally, an ultrasonic sensor that can detect circuit abnormalities has been proposed (Japanese Patent Laid-Open No. 57-42866), which is the first
They form a group as shown in the figure.

One ultrasonic transmitter is driven by an oscillation signal A (shown in FIG. 2 [al]) with a pulse width W at a period supplied from the AND circuit 4, and sends an ultrasonic pulse signal Ha to the 11-dimensional object 5. Send.

Reflected wave H of ultrasonic pulse No. 18 Ha reflected by the target object
6 is received by the sound wave receiver 6 2), and this reception 12
No. 9 G (shown in FIG. 2 (b+)) is amplified by the amplifier 7 and then rectified by the rectifier circuit 8, resulting in a signal S as shown in FIG. 2 (C1).

This signal S. - is supplied to the comparison circuit 9 and compared with a predetermined threshold level D□.

A rectangular wave pulse P whose pulse width is equal to the period in which is equal to or higher than the level of Do. The signal is waveform-shaped and input to the propagation time measuring circuit 1o.

The propagation time measuring circuit 1o transmits a transmission timing signal Q (FIG. 2(e)) of the ultrasonic pulse signal Ha from the pulse generator 3.
) from the rising edge of the rectangular wave signal P generated from the received signal 0. The time difference T until the rising point of . Please check your time, this time difference is T. The information is outputted as propagation time information N from when the ultrasonic pulse signal Ha is transmitted until it is reflected by the object 5 and is not received.

Then, this propagation time↑n signal N is sent to an arithmetic circuit (as shown) such as a micro combinator, for example, and is used for object distance calculation.

In addition, the signals received by the ultrasonic receiver 6 include not only the reflected wave H0 but also the ultrasonic pulse signal Ha transmitted through the air and directly incident on the ultrasonic receiver 6 (hereinafter referred to as " The received signal B of this loop wave (2b) is also processed by the amplifier 7 and the rectifier circuit 8, and appears as a signal Sb as shown in FIG. 2+C).

However, since the level of the signal Sb generated from this loop-back wave is smaller than the threshold level D in the comparison circuit 9, it does not appear in the output of the comparison circuit 9.

In general, the output of the rectifier circuit 8 is supplied to a circuit abnormality determination circuit 20. This circuit abnormality determination circuit 20 is a circuit that performs an A N D @i 81 between the amplified output of the rectifier circuit 8 and the output M of the monostable multivibrator 11 triggered by the transmission timing signal Q.

Therefore, every time the rectified signal Sb generated from the feedback wave Hb received immediately after the ultrasonic pulse signal Ha is transmitted is input to the circuit abnormality determination circuit 20, the pulse signal K is
It is output from the D circuit 13.

In other words, if the pulse signal K is output at period T@, it can be determined that the ultrasonic signal transmission and reception system is operating normally. If the transmission is interrupted, it is determined that an abnormality has occurred in the transmission or reception system, and
8 reports etc. will be issued twice.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional example, since the ultrasonic transmitter and receiver 1.6 are included in the system targeted for abnormality diagnosis, for example, If snow clogs the ultrasonic transmitter and receivers 1 and 6 while driving during snowfall, making it impossible to transmit and receive the ultrasonic pulse signal Ha, the circuit abnormality determination circuit 20&:t determines that an abnormality has occurred. , this is a temporary anomaly that will regenerate once the snow melts.

In other words, the ρ circuit abnormality determining circuit 2o cannot discriminate whether or not there is an actual circuit abnormality.

Further, Fj11 round trip wave Hb is shown in FIG. 3, for example.

, when it overlaps with the front part of the reflected wave H8, it causes interference, and if the interfering part is in the same phase, the rectified signal of the reflected wave H6 (So,
If the level of l increases and the phase is reversed, it becomes a rectified signal.
2) The level decreases.

Therefore, the propagation time information N obtained by the propagation time measuring circuit 10 has a difference as shown by No and N2 in FIG.
This results in a decrease in detection accuracy.

Therefore, it is necessary to suppress the wraparound wave Hb to a weak level as much as possible, and the above-mentioned circuit that determines circuit abnormality based on the presence or absence of the wraparound wave Hb is not very desirable.

(Objective of the Invention) An object of the present invention is to provide an ultrasonic sensor that is capable of detecting a circuit abnormality without using a reception signal of a loop wave and has a circuit abnormality determination function that can detect only an actual circuit abnormality. It's about doing.

(Accomplishment of the invention) In order to achieve the above object, the present invention provides signal processing for amplifying, detecting, etc. an output signal of an ultrasonic receiver for a part of an oscillation signal supplied to an ultrasonic transmitter. An abnormality determination circuit that includes a wraparound circuit that inputs to the circuit, and determines whether or not there is an abnormality in the signal processing circuit based on whether or not a processed signal is generated from the signal input from the wraparound circuit to the signal processing circuit. It is characterized by having the following.

(Embodiment) The configuration of an embodiment of the present invention is shown in FIG. 4. In the figure, the same components as the conventional example shown in FIG.
The same reference numerals are given, and the explanation thereof will be omitted. The same applies to input/output signals.

In this embodiment, the oscillation signal A corresponding to the output from the AND circuit 4 is branched, and after being attenuated by the resistor voltage divider circuits 1 and 4, the output signal A is output from the ultrasonic wave receiver 6 together with Kl 1lf.
I (input to device 7.

Therefore, the signal input to the amplifier 7 is a signal that is input from the resistive voltage divider circuit 14 during the transmission period of the ultrasonic pulse signal Ha (hereinafter referred to as a "wrapping signal"), as shown in FIG. 5 (bl). The above two types of signals 0.E, which are 2flIII of the received signal C of the reflected wave S.E and then inputted from the ultrasonic receiver 6, are amplified and rectified by the amplifier 7 and the rectifier circuit 8, The signals S. and So as shown in FIG. 5 FC+ are obtained.

And these rectified signals S. ,S,G:1,ratio! The output signal is input to the output circuit 16 and compared with a predetermined threshold level D2. This threshold level D,
is set smaller than the threshold level D0 in the comparator circuit 9 in FIG.

Therefore, the comparison circuit 16 outputs a waveform shaping signal P of the received signal C as a reflected wave. At the same time, a waveform shaping signal Pe of the wraparound signal E is output, and these signals P. , Po are supplied to the masking circuit i%15 and the circuit abnormality determination circuit 30.

Masking circuit, 15G=1. Input signal P. .

This is a circuit that extracts only the component of the received signal C of one reflected wave H8 of the signal P. , P8, and an inverted signal F (shown in FIG. 5 (fl)) of the transmission timing signal Q supplied from the inverter 17.

Therefore, the masking circuit 15 outputs a rectangular wave signal P generated from the received signal C of the reflected wave. The output signal Pt is selected and supplied to the propagation time measuring circuit 1°.

The circuit abnormality determination circuit 3o receives the signal P from the comparison circuit 16.

, A between Pe and the output M of the monostable multivibrator 11
By taking the value N D JQa , pulse No. 13 "K" is output every time the signal Pe is input.

Therefore, if this pulse signal K is generated every cycle T, the amplifier 7. It can be determined that the rectifier circuit 8 and the comparison circuit 16 are operating normally.

Conversely, when the pulse signal K is interrupted, the signal processing E! consisting of 'D 71 M + '16 is performed in the above three times.
I! It was determined that an anomaly of 1:1 had occurred in the system.

Furthermore, even if it becomes impossible to transmit or receive the ultrasonic pulse signal Ha due to snow jams while driving during snowfall, the RiJ Signal Station BN! If the thread is normal, Valsui J (-) will occur, which means that only the circuit abnormality can be detected. Since this is a signal that replaces the reception signal of the wraparound wave Hb received by the sound wave receiver 6, there is no need to use the first wraparound wave Hb itself, and the reflected wave H8 described above does not need to be used.
In order to prevent any kind of interference, it is possible to adopt a configuration that suppresses the generation of wraparound waves.

This embodiment is extremely suitable as an ultrasonic sensor used in a situation where the objective alternate layer is short and interference between a one-way wraparound wave and a reflected wave is likely to occur, such as when applied to an automobile as described above.

FIG. 6 shows the U4 structure of the ultrasonic sensor of this embodiment.

The ultrasonic transmitter 1 and the ultrasonic receiver 6 are housed in a case 31 made of a synthetic resin molded body such as plastic.

At the bottom of the case 31, pawn-shaped openings are formed for transmitting and receiving the ultrasonic pulse signal Ha and the reflected wave H8.

In addition, an insulator 32.83 is interposed between the transmitter and receiver 1, 6 and the case 31 to provide a soundproofing effect. The circuit shown in FIG. 4 is incorporated into the circuit board 35, and two circuit boards 35 are mounted thereon.

(Effects of the Invention As explained in detail above, the present invention has the ability to detect an abnormality in the received signal processing circuit system without using the received signal of the wraparound wave, and also has the ability to detect Only circuit abnormalities can be discriminated and detected.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of a conventional ultrasonic sensor, Figure 2 is a timing chart showing its main outputs, and Figure A3 is a waveform where reflected waves and wraparound waves are partially overlapped. Figure 41 shows a circuit configuration of one embodiment of the present invention.
FIG. 51 is a timing chart showing the main storage input and output, and FIG. 6 is a sectional view showing the groove membrane of the same embodiment. 1... Ultrasonic transmitter 2... Oscillator 3... Pulse generator 4... AND circuit 6... Ultrasonic receiver 7... Amplifier 8... Rectifier circuit
10... Propagation time measurement circuit 11... Monostable multivibrator 18... AIJD circuit 16... Comparison circuit 1
5°...Masking circuit aO...Circuit abnormality determination circuit 31...Case 32, 33...Insulator 34...gi 85...
・Circuit board. Figure 1 Figure 5 (g) - Grass 1 Lower 9 - m Figure 6

Claims (1)

[Claims] 1. An ultrasonic transmitter that transmits an ultrasonic pulse signal toward an object; and an ultrasonic receiver that receives a reflected wave of the ultrasonic pulse signal that is reflected by the object. a signal processing circuit that performs amplification, detection, etc. of the output signal of the receiver; an oscillator that supplies an oscillation signal for generating an ultrasonic pulse signal to the ultrasonic transmitter; and a part of the oscillation signal. an ultrasonic pulse signal propagation time measuring circuit that calculates the time from the transmission of the ultrasonic pulse signal to the reception of the reflected wave based on the output signal of the signal processing circuit; , an abnormality determination circuit that determines whether or not there is an abnormality in the signal processing circuit based on whether or not a signal after processing the signal inputted by the loop circuit is generated from the signal processing circuit. sensor.