JPH0320789Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an ultrasonic object detection device, and more particularly, to an ultrasonic object detection device that can easily determine the distance to an object.

Prior Art A conventional ultrasonic object detection device transmits an ultrasonic pulse, receives the reflected pulse, and determines the distance to the object based on the time interval from the time of transmission to the time of reception. In other words, the time from transmitting an ultrasonic pulse to receiving an ultrasonic pulse is
This method focuses on the point that is proportional to the distance from the transmission position to the object.

An example of such a conventional ultrasonic object detection device is the device disclosed in Japanese Patent Application Laid-Open No. 57-84377.

Problems with the conventional technology The time from when an ultrasonic pulse is emitted to when a reflected pulse is received is limited to a distance of several centimeters to an object.
It is several milliseconds to several tens of milliseconds for several meters.

Therefore, with conventional devices that determine distance by detecting the time between transmitting an ultrasonic pulse and receiving a reflected pulse, it is necessary to measure a very short time, and the circuit configuration for this purpose is complicated. There is a problem.

Additionally, when attempting to notify the distance to an object by changing the tone of the alarm sound, the conventional device described above converts the change in the length of time from the time the ultrasonic pulse is transmitted to the time the reflected pulse is received into a change in tone. There is a problem in that a relatively complicated circuit is required for this purpose.

Purpose of the invention The purpose of the invention is to be able to determine the distance to an object with a simple configuration, and to convert the results of this determination into a change in the tone of an alarm sound with a relatively simple configuration. The object of the present invention is to provide a new type of ultrasonic object detection device that can detect objects.

Structure of the invention The ultrasonic object detection device of the invention includes a transmitter that sequentially outputs ultrasonic pulses with different transmission output levels toward an object in a predetermined order and at predetermined intervals, and a transmitter that receives reflected pulses and receives the reflected pulses. The configuration is characterized in that it includes a receiving section that detects the period of a reflected pulse whose input is at a predetermined level or higher and determines the distance to an object based on the period.

Effect Ultrasonic pulses are sound waves, so they are considerably attenuated in the air. In other words, when the output power of the ultrasonic pulse is small, the received input of the reflected pulse will be large enough only when the object is close, and if the object is far away, the reflected pulse will hardly be received due to attenuation. . Furthermore, when the transmission output of the ultrasonic pulse is large, the reception input of the reflected pulse will be sufficiently large no matter where the object is located, from a short distance to a long distance.

Therefore, in conventional ultrasonic object detection systems, the transmission output of ultrasonic pulses is increased.

However, in the ultrasonic object detection device of the present invention, the output power of the ultrasonic pulse is changed in at least two stages from small to large.

Then, when the object is at a short distance, reflected pulses of a predetermined level or higher are received regardless of whether the transmitted output is small or large, and the period of intermittent transmission of ultrasonic pulses matches the period of the received reflected pulses.

On the other hand, if the object is far away, the reflected pulses will not be received when the transmitted output of the ultrasonic pulse is small, and the reflected pulses of a predetermined level or higher will be received only when the transmitted output is large. Therefore, the period of the received reflected pulses is longer than the period of intermittent transmission of ultrasonic pulses.

In other words, the frequency of the reflected pulse received at a predetermined level or higher will be a high frequency if the object is close, and a low frequency if the object is far away.

Such frequency changes can be easily detected using an f-converter or the like, so distance determination can be performed with a simple configuration.

Moreover, since this frequency change can be made from several tens of Hz to several hundred Hz, it can be used as is to change the tone of the alarm sound, and the configuration for changing the tone of the alarm sound can be simplified.

Embodiments Hereinafter, the present invention will be explained in more detail based on embodiments shown in the drawings. Here, Fig. 1 is a block diagram of the configuration of an ultrasonic object detection device according to an embodiment of the present invention, Fig. 2 is a signal waveform diagram when the object is close, and Fig. 3 is a diagram showing the signal waveform when the object is far away. FIG. Note that the present invention is not limited to the embodiments shown in the figures.

As shown in FIG. 1, an ultrasonic object detection device 1
consists of a transmitting section 2 and a receiving section 8.

The transmitter 2 includes an oscillator 3 that generates ultrasonic vibrations of 40 kHz, a gate circuit 4 that passes the oscillation signal of the oscillator 3 for a time width of τ ₁ , and as a result, ultrasonic waves are generated in the form of a pulse with a width of τ ₁ . A transducer 5 that transmits a signal, a power control circuit 6 that adjusts the transmission output of the transducer 5, and a timing control circuit that controls the timing of operation of the gate circuit 4 and the timing of switching the transmission output of the power control circuit 6. 7.

On the other hand, the receiving section 8 includes a transducer 9 that detects reflected pulses, an amplification/detection/shaping circuit 10 that amplifies, detects, and shapes the detected reflected pulses, and an oscillator 11 that oscillates at 1 kHz as a basic alarm sound.
and a modulation method that modulates the 1kHz oscillation signal with the output of the amplification/detection/shaping circuit 10 to output audio.
It has an output circuit 12 and a speaker 13.

Next, the operation of the ultrasonic object detection device 1 will be explained with reference to FIGS. 2 and 3.

As shown in FIG. 2a, the ultrasonic pulse having a width of τ ₁ is sequentially switched in three stages of transmission outputs P ₁ , P ₂ , and P ₃ and is repeatedly and intermittently output at a period T ₁ .

Here, the transmission output _P1 is such a power that a reflected pulse is received at a predetermined level or higher when an object is present in the short distance region L shown in FIG. Furthermore, the transmission output P ₂ has such power that a reflected pulse of a predetermined level or higher can be received when the object is in the intermediate range region M. Also, the outgoing output P ₃ is
The power is such that even if the object is in the far distance region D, the reflected pulse can be received at a predetermined level or higher.

The value of τ ₁ is for example 300μs and T ₁ is for example 10ms
, L is, for example, within 0.5 m, M is, for example, within 0.5 m to 1.0 m, and D is, for example, within 1.0 m to
Within 1.5m.

If the object is in the short distance region L, then Fig. 2b
As shown in , the magnitude of the received reflected pulse is at a predetermined level or higher for any transmitted output of the ultrasonic pulse. In FIG. 2b, the predetermined level is represented by a broken line, and the waveform of the reflected pulse is represented by the waveform after detection. The reflected pulse signal shown in FIG. 2b is shaped by, for example, a monostable multivibrator circuit, and converted into a shaped wave as shown in FIG. 2c. This shaped wave has a pulse width τ ₂ ,
It is a rectangular wave signal with a period T ₂ . where the pulse width τ ₂
can be set arbitrarily, and the period T ₂ matches the period T ₁ of intermittent transmission of ultrasonic pulses.

The alarm sound modulated by the shaped wave shown in Fig. 2c is a 1kHz sound wave f ₁ (=
The alarm sound is modulated at a frequency of 1/T ₂ ).

FIG. 3 shows a case where the object is in the far distance area D.

Figure 3a shows the ultrasonic pulse, which is the second
This is exactly the same signal as in Figure a.

However, as shown in FIG. 3b, the reflected pulses are different. That is, when the transmitted outputs P ₁ and P ₂ because the object is far away,
The reflected pulse is attenuated and the received level is below a predetermined level. The transmission output P ₃ can receive reflected pulses of a predetermined level or higher.
Only when.

The shaped wave is therefore a rectangular wave with a period T ₃ for the ultrasonic pulse of the transmitted output P ₃ as shown in FIG. 3c. Note that T ₃ =3T ₁ .

Then, the alarm sound is as shown in Figure 3d.
1kHz sound wave f ₂ (=1/T ₃ = 1/3T ₁ = f ₁ /3)
It becomes a sound wave modulated by

Furthermore, it will be understood that when there is an object in the intermediate distance region M, the period of the reflected pulses received at a predetermined level or higher changes similarly, and the timbre of the alarm sound changes accordingly.

Therefore, the difference in distance to the object is output in a distinguishable manner as a difference in the tone of the alarm sound.

As can be understood from the above description, this ultrasonic object detection device 1 can determine the distance to an object with a simple configuration, and can also determine the distance by emitting an alarm sound with a relatively simple configuration. It can be expressed as a change in tone.

In addition, the power method of the ultrasonic object detection device of the present invention and the time method of the conventional device can be used at the same time, and in that case, the reliability of discrimination can be further improved by comparing the results of the two methods. can do.

Effects of the invention According to the invention, there is provided a transmitter that sequentially outputs ultrasonic pulses with different transmission output levels toward an object in a predetermined order and at predetermined intervals, and a transmitter that receives reflected pulses and whose input is at a predetermined level or higher. An ultrasonic object detection device is provided, characterized in that it is equipped with a receiving section that detects the period of a certain reflected pulse and determines the distance to the object based on the period. You will be able to determine the distance. Furthermore, the detected distance can be expressed as a change in the tone of the alarm sound with a relatively simple configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the configuration of an ultrasonic object detection device according to an embodiment of the present invention, Fig. 2 is a signal waveform diagram when the object is at a short distance, and Fig. 3 is a diagram of the signal waveform when the object is at a long distance. It is a signal waveform diagram. Explanation of symbols, 1... Ultrasonic object detection device, 2
... Transmission section, 4 ... Gate circuit, 6 ... Power control circuit, 7 ... Timing control circuit, 8 ... Receiving section, 10 ... Amplification/detection/shaping circuit, 12 ... Modulation/output circuit, 13 ...Speaker, L...Near range, M...Medium range, D...Long range.

Claims (1)

[Claims for Utility Model Registration] A transmitter that sequentially outputs ultrasonic pulses with different output output levels toward an object in a predetermined order and at predetermined intervals; and a transmitter that receives reflected pulses whose input is at a predetermined level or higher. An ultrasonic object detection device characterized by comprising a receiving section that detects a period of a reflected pulse and determines a distance to an object based on the period.