JPH01296182A - Ultrasonic distance sensor - Google Patents

Abstract

PURPOSE:To exclude the effect of a reverberation signal in the measurement of a proximity distance, by suppressing a reverberation signal component by the integration/differentiation signal outputted in synchronous relation to the transmission timing of the reverberation signal suppressing circuit connected to an output signal. CONSTITUTION:A reverberation signal suppressing circuit 18 consists of transistors 181-184, a condenser 185 and a diode 186 and, when the output of a timer circuit 11 is reversed to high and low potentials, the condenser 185 of the circuit 18 performs charge and discharge actions and, corresponding to the charge and discharge potentials thereof, a signal current having an integrating waveform is supplied to the collector of the transistor 181. Therefore, an output signal E is attenuated corresponding to the collector current of the transistor 181 to become an output signal G. Next, the signal G is detected by a detection circuit 16 to become an output signal H. When the signal H is equal to or more than the value of the threshold voltage inputted to the non-reversal input part of a differential amplifier 171, low voltage is outputted to an output signal I part and, when said signal H is the threshold voltage value or less, high voltage is outputted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an ultrasonic distance sensor that detects proximity by transmitting and receiving ultrasonic waves using a single ultrasonic transmitter and receiver and measuring the arrival time of reflected waves. Regarding improvements.

[Conventional technology]

Recently, various ultrasonic distance sensors have been developed that are mounted on a vehicle to measure vehicle height distance, distance between the vehicle and surrounding obstacles, etc.

The ultrasonic distance sensor (hereinafter simply referred to as "road surface sensor") that measures the vehicle height distance is a sensor that is installed under the floor of a vehicle and has been developed to measure the distance between the vehicle floor and the road surface. .

This sensor measures the distance between the road surface and the vehicle body over time while the vehicle is running. The output signal of the road surface sensor is then connected to a suspension control device that controls the stiffness of the suspension and the vehicle height. For example, if the distance between the road surface and the vehicle body changes greatly due to unevenness of the road surface, the suspension may be stiffened or the vehicle height may be increased. On the other hand, when the distance remains relatively unchanged due to a flat road surface, it is used to soften the suspension or lower the vehicle height.

There is also an ultrasonic distance sensor (hereinafter simply referred to as "obstacle sensor") that measures the distance between the vehicle and surrounding objects or pedestrians, etc.
is installed near the bumper of the vehicle or on the side of the vehicle to detect obstacles and pedestrians that approach the vehicle relatively when parking the vehicle or turning left or right. It is used as a so-called alarm sensor in a means for displaying distance on a display or in a device that generates an alarm or voice warning sound to prevent contact.

These ultrasonic distance sensors are generally configured as a pair of a transmitting part (sender) and a receiving part (receiver). It can be said that configuring with one ultrasonic transmitter/receiver is more advantageous in terms of cost, size and weight, and reduction in the number of parts.

[Problem that the invention seeks to solve]

However, when a single ultrasonic transmitter/receiver is mounted on a vehicle and used as an ultrasonic distance sensor, the following problems need to be solved.

For example, the road surface sensor needs to measure a vehicle height distance of about 20 to 30 am. When transmitting and receiving ultrasonic waves over the close distance, the time required from the timing of transmitting the ultrasonic waves to the timing of receiving reflected waves on the road surface is about 1.2 to 1.8 (mSee) at room temperature. However, the ultrasonic transmitter/receiver emits reverberant sound for a while after transmitting the ultrasonic wave, for example, from the time shown in FIG. Therefore, it was difficult to detect the arrival time of one reflected wave. This problem also applies to obstacle sensors.

[Means for solving problems]

This invention was devised to deal with the problem caused by the generation of reverberant sound mentioned above, and it transmits and receives ultrasonic waves using a single ultrasonic transmitter/receiver and measures the arrival time of the reflected waves. An ultrasonic distance sensor for detecting ultrasonic waves, characterized in that a reverberation signal suppression circuit that outputs a differential signal in synchronization with the transmission timing of ultrasonic waves is connected to the output stage of the ultrasonic transmitter/receiver. I will provide a. Also, as an embodiment thereof.

The present invention provides an ultrasonic distance sensor characterized in that the reverberation signal suppression circuit includes a charging/discharging circuit including a capacitor and a resistor.

[For production]

The single ultrasonic transmitter/receiver transmits ultrasonic waves in time series according to a timing signal from a control circuit, and receives the reflected waves. The reverberation signal suppression circuit outputs a differential and integral signal in synchronization with the timing signal, and suppresses the reverberation signal component in the signal output from the ultrasound transmitter/receiver.

In this ultrasonic distance sensor, the reverberant signal component mixed in the received signal can be eliminated by the action of the reverberant signal suppression circuit, and the received signal of the reflected wave can be accurately detected.

〔Example〕

Figures 1 to 5 are drawings showing preferred embodiments of the present invention. Figure 1 is a sectional view of the ultrasonic transceiver attached to the case, and Figure 2 is a cross-sectional view of the ultrasonic transceiver shown in Figure 1. Disassembled three-dimensional diagram,
Fig. 3 is an exploded top view of the device shown in Fig. 1. Fig. 4 is an electrical circuit diagram showing an example of the circuit including the ultrasonic transceiver shown in Fig. 1. It is an electrical characteristic diagram.

In the drawing, 1 is an ultrasonic transmitter/receiver, 2 is a first elastic member, 3 is a second elastic member, and 4 is a case.

5 is a cover, 6 is a tapping screw, and 7 is a lead wire.

The ultrasonic transmitting/receiving body 1 is a vibrating body having a piezoelectric element (not shown) therein, and generates approximately 30 (K) by external excitation, for example.
Generates ultrasonic waves (Hz).

The first elastic member 2 is formed of rubber or the like into a cylindrical shape, and has a first bead 21 at a location located at the opening 41 of the case 4, and a second bead 22 at the opposite location. .

The second elastic member 3 is made of the same material as the first elastic member 2 and formed into a disc shape, and has a first bead 31 on the inner peripheral edge.
It has a second bead 32 on its outer periphery.

The case 4 and the cover 5 are molded products such as plastic or die-casting, and the case 4 has a housing portion 42 having an inner diameter d2 that is slightly smaller than the outer diameter d1 of the first elastic member 2.

Here, the order of assembling each of the above components will be explained. First, the first elastic member 2 is attached to the ultrasonic transmitting/receiving body 1, and then this assembled product is fitted into the case 4.

At this time, the outer diameter dimension d1 of the first elastic member 2 is
The outer diameter dimension is larger than the inner diameter dimension d2 of the case 4 by an overhang dimension of 2.

Therefore, the above-mentioned combination product is press-fitted into the case 4.

Next, the second elastic member 3 is placed on the ultrasonic transmitting/receiving body 1, and the cover 5 is placed on top of the ultrasonic transmitting/receiving body 1.
Tighten and secure it to case 4. By tightening this tapping screw 6, the first bead 21 of the first elastic member is tightened to the case 4.
is pressed against.

As described above, the ultrasonic transmitter/receiver 1 is press-fitted into the case 4 by the first elastic member 2 and the second elastic member 3, and the reverberation sound is attenuated.

Next, the configuration and operation of the circuit diagram shown in FIG. 4 will be explained.

In FIG. 4, 10 is a control circuit, 11 is a protection circuit, 1
2 is an oscillation circuit, 13 is an output circuit, I4 is a bypass filter, 15 is an amplifier circuit, 16 is a detection circuit, 17 is a waveform shaping circuit, and 18 is a reverberation signal suppression circuit.

The control circuit 10 includes transistors 101. Resistance 102゜1
03 and an inverter 104, and the base of the transistor 101 is connected to a circuit such as a microcomputer (not shown). The control circuit 1
0 is a time width tl (msec), for example, t, as shown in FIG. 5A, according to a microcomputer program, etc.
1 =0.3 (m5ec) timing pulse signal at t2 (m5ec) For example, t2==20 (m5e
c) This circuit outputs the output to the protection circuit 11 at the subsequent stage.

The protection circuit 11 includes a timer circuit Ill and an AND circuit 112.
One input section 112a of the AND circuit 112 is connected to the control circuit 10, and the other input section 112b is connected to the control circuit 10 via the timer circuit 111.

The timer circuit 111 is, for example, a circuit composed of a one-shot multivibrator.

As shown in the characteristics of FIG.
ec) For example, t 3 = l (This is a circuit that outputs the one-shot pulse signal of m5ecl to the AND circuit 112 at the subsequent stage.

The AND circuit 112 outputs a “1” level signal when both inputs are “1” level signals.
When the D circuit 112 receives the signals shown in FIGS. 5A and 5B, it selects the signal with the shorter time width and outputs the signal as shown in FIG. 5C.

Therefore, even if the signal shown in FIG. 5A remains at the "1" level due to a failure in the internal wiring of the control circuit 10, the signal shown in FIG. The regulated time width t3 (msec
), the output circuit 13 is prevented from continuing to be in the on state, and the output transistor 133 and the like are prevented from being burnt out.

The oscillation circuit 12 is a gate circuit composed of an oscillation section 121 and an AND circuit 122. One input section 122a of the AND circuit 122 is connected to the protection circuit 11, and the other input section 122b is connected to the oscillation section 121. It is connected. As shown in Figure 5, the AND circuit 122 outputs, for example, an oscillation signal of 30 (02) to the output circuit 13 in the subsequent stage while the timing pulse signal is inputted through the protection circuit 11 in the previous stage.

The output circuit 13 is composed of resistors 131 and 132, an output transistor 133, and an output transistor 134. Specifically, the output transistor 133 is composed of a Darlington-connected transistor, and the output transistor 134 is connected to the primary side, that is, the output transistor 133. The turns ratio between the primary side and the secondary side is set so that the applied voltage on the opposite side is boosted and output to the secondary side.

The bypass filter 14 is a circuit composed of capacitors 141 and 142 and diodes 143 and 144,
It is connected between the ultrasonic transmitter/receiver 1 and the amplifier circuit 15.

The amplifier circuit 15 includes a differential amplifier 151. Resistance 152°15
3.154, 155 and a capacitor 156, and the output section of the differential amplifier 151 is connected to the reverberation signal suppression circuit 18 at the subsequent stage.

The resistors 154, 155 and the capacitor 156 are a circuit configuration for inputting a predetermined bias voltage to the non-inverting input section of the differential amplifier 151, and the bias voltage is further applied to the subsequent detection circuit 16 and waveform shaping circuit 17. Commonly assigned to.

The detection circuit 16 includes a differential amplifier 161 and a transistor 16
2. This circuit is composed of a diode 163, resistors 164 and 165, and a capacitor 166, and the collector of the transistor 162 is connected to the waveform shaping circuit 17 at the subsequent stage.

The waveform shaping circuit 17 includes a differential amplifier 171, a transistor 172 . This circuit is composed of resistors 173 to 177.

The reverberation signal suppression circuit 18 includes a transistor 181 and a resistor 1.
82, 183, 184, a capacitor 185, and a diode 186.

A resistor 182 is interposed in a signal line connecting the amplifier circuit 15 and the detection circuit 16, and the collector of the transistor 181 is connected to the output side of the resistor 182.

The emitter of the transistor 181 is grounded, and the base of the transistor 181 is connected to the resistor 184 and the diode 18.
A resistor 183 and a capacitor 185 are connected in parallel between the base and emitter of the transistor 181.

Note that the emitter of the transistor 181 may be grounded via a resistor.

Further, the time constant obtained by the resistors 183, 184 and the capacitor 185 is set in advance in accordance with the duration of reverberant vibrations that the ultrasonic transmitter/receiver 1 has.

Next, the operation of this embodiment consisting of each of the above circuit configurations will be explained in the fifth section.
This will be explained with reference to the characteristic diagram shown in the figure.

In FIG. 5, FIG. 5A to FIG. 5E and FIG. 5G to FIG. FIG. 5F shows the collector current [V] waveform of the transistor 181 of the reverberation signal suppression circuit 18 of FIG.

Also, ■b1 [v] in Fig. 5G is the differential amplification 13151 (
i') The potential of the non-inverting input section, that is, the voltage level approximately corresponds to the divided voltage of the resistors 154 and 155 of the amplifier circuit 15.

In addition, Fig. 5 H (7) Vb2 (Vl is the differential amplifier 93171
It is the potential of the non-inverting input part of the resistor 154 of the amplifier circuit 15.
and resistor 155 and resistors 173 to 17 of waveform shaping circuit 17
This is the threshold voltage level corresponding to the divided voltage obtained by the combined resistance with 5.

First, at time T I (+5 Sec) shown in FIG. 5, when section A in FIG. 4 is inverted to a high potential, the timer circuit 111 is activated and outputs a high potential to section B.

As a result, a high potential is output to the C section until time T2 (■5 ecl), and an oscillation signal of approximately 30 (K) 12, for example, is output to the D section, and the ultrasonic transceiver 1 is excited by the output circuit 13. .

The ultrasonic transmitting/receiving body l emits ultrasonic waves by the excitation,
Receive reflected waves from the object to be detected. The received signal is inputted to the inverting input section of the differential amplifier 151 of the amplifier circuit 15 via the bypass filter 14, so that the time T l (msec) appears in the E section of FIG. 4.
The transmitted signal S is transmitted at time T4 (msecl), and the received signal R is transmitted at time T4 (msecl).
is output.

On the other hand, the reverberation signal suppression circuit 18 is operated according to the output potential of the timer circuit 111.

That is, time T I (+wSec) and T3 (msa
In c), when the output of the timer circuit 111 is inverted to a high potential and a low potential, the capacitor 185 of the reverberation signal suppression circuit 18 acts to charge and discharge, and the collector of the transistor 181 is charged and discharged according to the charging and discharging potential. A signal current having an integral waveform is applied as shown in FIG. 5F.

Therefore, it is attenuated as shown in FIG. 5G in accordance with the mother cloud flow output to section E in FIG. 4, and is output to section G in FIG.

The signal outputted to section G in FIG. 4 is detected by the detection circuit 16 as shown in section H in FIG. 5 and output to section H in FIG. 4.

The signal output to the H section in FIG. 4 above is the waveform shaping circuit 17.
The waveform is shaped as shown in Figure 5 ■ by 1 in Figure 4.
output to the section. That is, if the signal potential of the H section in FIG.
A low voltage is output to one part of the figure, and a high voltage is output if the value is below the threshold voltage Vb2 (V).

Then, as shown in I in FIG. 5, the time t4 (msec) from the first falling edge dl to the second falling edge dl output in the first part of FIG. 4 is measured. Accordingly, the distance from the ultrasonic transmitter/receiver 1 to an object to be detected such as a road surface can be measured.

The invention is a technology suitable for mounting on a vehicle to measure close distances such as the vehicle height distance or the distance between the vehicle and surrounding obstacles, but its application range is wide, for example, in automatic doors and factories. It can also be used in automated lines, robots, etc.

It can also be used for liquid level gauges, etc.

〔Effect of the invention〕

As described above, the present invention connects a reverberation signal suppression circuit to the output stage of the ultrasonic transmitter/receiver.

The reverberation signal suppression circuit is characterized in that it is configured to attenuate the signal output by the ultrasonic transceiver using a differential signal output in synchronization with the transmission timing of the ultrasonic wave, thereby suppressing the reverberation signal component.

Therefore, when measuring the proximity distance, the influence of reverberant signals can be reliably eliminated.

Further, the ultrasonic distance sensor according to the present invention is suitable for measuring close distances in vehicles, and has excellent effects in that it has a wide range of applications.

[Brief explanation of the drawing]

1 to 5 are drawings showing a preferred embodiment of the present invention, and FIG. 1 is a sectional view of an ultrasonic transmitter/receiver attached to a case. FIG. 2 is an exploded three-dimensional view of what is shown in FIG. FIG. 3 is an exploded top view of what is shown in FIG. FIG. 4 is an electrical circuit diagram including the ultrasonic transmitter/receiver shown in FIG. 1. FIG. 5 is an electrical characteristic diagram of each part of FIG. 4. FIG. 6 and FIG. 7 are electrical characteristic diagrams in the conventional technology. 1... Ultrasonic transmitter/receiver, 2... First elastic member, 3... Second elastic member, 4...
Case, 5...Cover, 21...1st
First bead of the elastic member, 22... Second bead of the first elastic member 531... First bead of the second elastic member, 32... of the second elastic member 2nd bead, 1
0...control circuit, 11...protection circuit,
12...Oscillation circuit. 13...Output circuit, 14...Bypass filter, 15...Amplification circuit, 16...
・Detection circuit, 17...Waveform shaping circuit, 18...
...Reverberant signal suppression circuit, tat... Transistor, 182, 183, 184... Resistor, 185... Capacitor, 186...
diode. Above Figure 1 Figure 2 Figure 4 41 Figure 3

Claims (2)

[Claims] (1) In an ultrasonic distance sensor that detects close distance by transmitting and receiving ultrasonic waves using a single ultrasonic transceiver and measuring the arrival time of reflected waves, a differential and integral signal is generated in synchronization with the ultrasonic transmission timing. An ultrasonic distance sensor characterized in that a reverberation signal suppression circuit that outputs a reverberation signal is connected to an output stage of the ultrasonic transmitter/receiver. (2) The ultrasonic distance sensor according to claim 1, wherein the reverberation signal suppression circuit includes a charging/discharging circuit consisting of a capacitor and a resistor.