JPH0961523A - Ultrasonic distance-measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic distance-measuring circuit, which eliminates a booster circuit used in a conventional ultrasonic distance-measuring circuit, and can be simplified and compact in circuit structure. SOLUTION: Terminals P1, P2 are set at a microcomputer 10 to output driving signals S1, S2 to a transmission ultrasonic vibrator 11. The signals S1 and S2 are inverted in phase and have amplitudes determined by a high level voltage and a low level voltage of the microcomputer 10. When the signals S1, S2 are connected to both terminals of the transmission ultrasonic vibrator 11, the vibrator 11 can be driven with a signal of an amplitude approximately twice the high level voltage of the microcomputer 10. When an amplification rate of an amplifier 14 is increased, driving voltage for the transmission ultrasonic vibrator 11 is not required to be raised. A booster circuit is consequently eliminated and a circuit for generation of a driving signal is not necessary to be added. Accordingly, the whole circuit can be simplified and compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic distance measuring device using an ultrasonic transducer.

[0002]

2. Description of the Related Art An ultrasonic distance measuring device is installed in the rear part of an automobile and is used for various purposes such as a back sonar for measuring the distance between the rear part of the vehicle and an obstacle, and corner clearance sonars installed in the four corners of the automobile. in use.

Since the back sonar, the corner clearance sonar and the like are mounted on a vehicle, it is preferable that they are as small as possible. FIG. 5 is a configuration diagram of a conventional ultrasonic distance measuring device.

This ultrasonic distance measuring apparatus is mainly controlled by a microcomputer 50. The microcomputer 50 outputs a signal S11 for operating the transmitting ultrasonic transducer 52 from the terminal P1. The signal output from the terminal P1 is a rectangular wave signal composed of a low level voltage (for example, 0 volt) of the microcomputer when the level is low and a high level voltage V _H volt of the microcomputer when the level is high.

This signal S11 is input to the booster circuit 51, boosted to a signal S21 having a higher voltage, and applied to the transmitting ultrasonic oscillator 52 to oscillate ultrasonic waves. In this case, it is general that one terminal of the transmitting ultrasonic transducer 52 is connected to the booster circuit 51 and the other terminal is grounded.

The ultrasonic wave 61 emitted from the transmitting ultrasonic vibrator 52 is reflected by the measuring object 63 and is received by the receiving ultrasonic vibrator 53 as a reflected wave 62. Measurement target 63
For example, in the case of a back sonar or a corner clearance sonar installed in a car, it is a part of the car or the wall that is close to your car. Is effective in improving.

The received ultrasonic wave is converted into an electric signal by the receiving ultrasonic vibrator 53 and sent to the amplifier 54. Since the reflected wave 62 is generally weak, the electric signal generated thereby is also weak. Amplifier 54 amplifies this weak electrical signal for easy detection.

The electric signal amplified by the amplifier 54 is sent to a bandpass filter 55 having a predetermined frequency characteristic to filter only a necessary frequency band, and then sent to a detection circuit 56. In the detection circuit 56, the electric signal filtered by the bandpass filter 55 is waveform-shaped and supplied to the gate circuit 57.

The gate circuit 57 is controlled by a signal output from the terminal P3 of the microcomputer, and the gate is opened / closed so that only the electric signal by the reflected wave 62 can be surely detected. That is, since the circuit configuration shown in the figure is formed on one substrate, an electric sneak signal is generated on the receiving side with the generation of ultrasonic waves for transmission, and this sneak signal is mistaken as a reflected wave. The wraparound signal is masked by the gate circuit so that it will not be detected.

The electric signal that has passed through the gate circuit 57 is sent to the comparator 58. The comparator 58 converts the electric signal sent from the gate circuit 57 into a signal that can be processed by the microcomputer, and inputs this into the terminal P4 of the microcomputer 50 as a received signal of the reflected wave 62.

The microcomputer 50 calculates the distance to the measurement object 63 based on the time difference between the time when the transmission signal S11 is transmitted and the time when the reception signal is received, and displays it on the distance display 59. Such an ultrasonic distance measuring device is described in detail, for example, in JP-A-6-201824.

[0012]

As described above, since the conventional ultrasonic distance measuring device requires the booster device 51, the number of parts constituting the device is increased and the circuit tends to be complicated. It was That is, the high level voltage V _H of the transmission signal S11 output from the microcomputer becomes the high level output voltage of the microcomputer, which is generally as small as several volts.
Therefore, it is necessary to provide a booster circuit between the output P1 of the microcomputer and the transmitting ultrasonic transducer in order to drive the ultrasonic transducer.

Therefore, an object of the present invention is to provide an ultrasonic distance measuring device which can simplify the circuit configuration by changing the output configuration of the microcomputer without using a booster circuit. It is to be.

[0014]

According to the present invention, a microcomputer is provided with two output terminals for driving an ultrasonic oscillator, and a signal output from one terminal is phased with a signal output from the other terminal. Is inverted. Then, the signals output from both output terminals of the microcomputer are input to both terminals of the ultrasonic transducer for transmission to drive them directly.

[0015]

[Operation] By preparing the outputs of the microcomputers whose phases are mutually inverted and applying them to both terminals of the ultrasonic transducer for transmission, it is possible to transmit a voltage having an amplitude twice the output voltage of the microcomputer without a booster circuit. It can be applied to an ultrasonic transducer.

As a result, the ultrasonic transducer for transmission can be driven without the need for a booster circuit and without separately providing a special circuit, and the number of parts of the ultrasonic distance measuring device can be reduced to simplify the circuit. Can be achieved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of the ultrasonic distance measuring apparatus of the present invention. Further, FIG. 2 is a diagram showing a state of a signal at each point in the embodiment of FIG. Hereinafter, this embodiment will be described with reference to FIGS. 1 and 2.

The structure shown in FIG. 1 is composed of almost the same components as the conventional ultrasonic distance measuring device. That is, the microcomputer 1 that outputs a signal for driving the transmitting ultrasonic transducer 11
0, transmission and reception ultrasonic transducers 11 and 12, an amplifier 14 for amplifying signals from the reception ultrasonic transducer 12, a bandpass filter 15, a detection circuit 16, a gate circuit 17, a comparator 18, and a distance indicator 19. Consists of.

The difference from the conventional configuration is that a booster circuit is not provided between the output terminal of the microcomputer 10 and the transmitting ultrasonic transducer 11, and that the transmitting ultrasonic transducer 11 of the microcomputer 10 is driven. This is the point that two signal output terminals P1 and P2 are provided.

FIG. 2 shows the state of signals on each circuit line in FIG. Signal S1 from the terminal P1 of the microcomputer 10
However, the signal S2 is output from the terminal P2. The signals S1 and S2 are opposite in phase to each other, as shown in FIG. The low level voltage of each signal is the low level voltage of the microcomputer 10 (0 volt in FIG. 2), the high level voltage is the high level voltage of the microcomputer 10, and this high level voltage is about several volts. Yes,
In FIG. 2, it is shown as V _OH . Also, microcomputer 1
Signal S1 output from terminals P1 and P2 of 0
The frequencies of S2 and S2 are, for example, 40 kHz.

Conventionally, only the signal for driving the transmitting ultrasonic transducer 11 was S1, but in the present embodiment, in particular, a new terminal P2 is provided in the microcomputer 10 and a signal whose phase is inverted with respect to S1 is transmitted. Configure to send.

The terminals P1 and P2 are respectively connected to both terminals of the transmitting ultrasonic vibrator 11, and the vibrator is vibrated by using the energy supplied by the signals S1 and S2.
Generate ultrasonic waves. The signal applied to both ends of the transmitting ultrasonic transducer 11 is indicated by S3 in FIG. As shown in the figure, the signal S3 applied to both ends of the transmitting ultrasonic transducer 11 has an amplitude of + V _OH to −V _OH .

As in the prior art, one terminal of the transmitting ultrasonic transducer 11 is grounded and the signal S1 is applied to the other terminal.
It is considered that the terminal on the grounded side is always 0 volt when only is input, so that a signal having an amplitude of the high level voltage V _{OH of the} microcomputer 10 to 0 volt at the maximum can only be applied.

As described above, as the signals output from the microcomputer 10, two signals whose phases are opposite to each other are output, and these signals are applied to both terminals of the ultrasonic transducer 11 for transmission, whereby the microcomputer 10 Since it is possible to drive the transmitting ultrasonic transducer 11 with a signal having an amplitude twice as high as the high level voltage of, it is not necessary to provide a booster circuit on the way and the signal generation source is the microcomputer 10 itself. An extra circuit for signal generation is not required, and a very simple circuit configuration can be achieved.

The ultrasonic wave emitted from the ultrasonic transducer 11 for transmission is reflected by the object 13 to be measured, and the ultrasonic transducer 1 for reception is used.
2 is received. The signal received by the receiving ultrasonic transducer 12 is composed of a signal with a large waveform and a signal with a small waveform, as indicated by S4 in FIG. A signal having a large waveform is generated by the microcomputer 10 to drive the transmitting ultrasonic transducer 11.
The influence of the signal generated by is detected by backflowing the electric circuit as noise, and is due to the electric sneak. The small waveform signal is the ultrasonic wave reflected by the measurement target 13, and this small signal must be detected in order to measure the distance.

First, the signal of S4 is amplified by the amplifier 14, and then passes through the bandpass filter 15 for extracting only the band corresponding to the frequency of the reflected signal for extracting the reflected signal from the noise. The detection circuit 16 shapes the waveform of the signal that has passed through the bandpass filter 15 and sends the signal to the gate circuit 17.

The gate circuit 17 is a terminal P of the microcomputer 10.
3 receives a signal for controlling so as not to detect a signal due to electrical sneak. The signal output from the terminal P3 is a control signal for closing the gate of the gate circuit 17 for a predetermined time from the output of the driving signals S1 and S2 of the transmitting ultrasonic transducer 11. Therefore, the signal sent to the comparator 18 is a signal obtained by eliminating the electric sneak signal, and only the signal by the reflected wave is extracted.

In the comparator 18, the signal sent from the gate circuit 17 is shaped into a waveform that can be processed by the microcomputer, and is input to the terminal P4 of the microcomputer 10 as a reflected wave detection signal as shown in S5 of FIG.

The comparator 18 may also be configured to compare the magnitude of the detection signal of the reflected wave with a predetermined threshold value and input only the signal larger than the threshold value to the terminal P4 of the microcomputer 10. . The reason why the threshold value is compared with the signal strength in this way is that the signal due to noise caused by various factors is not erroneously recognized. However, when the measurement target 13 is relatively far away, the signal itself due to the reflected wave also becomes small. Therefore, if the threshold value is made too large, the measurable distance becomes very small. Therefore, this threshold should be appropriately set according to the application.

The microcomputer 10 starts measuring time simultaneously with the output of the signals S1 and S2, and in response to the input of the signal from the terminal P4, specifies the time indicated by T ₃ in FIG. In response to the specification of the time until the ultrasonic wave is reflected back to the measurement target 13 and returned, the microcomputer 10 performs the calculation by the following formula and specifies the distance to the measurement target 13.

[0031] _{L = C · T 3/2} ···· (1) where, C is the distance of the ultrasonic wave sound velocity, L is to the measurement target. The distance to the measurement target 13 calculated using the above equation (1) is sent as data to the distance indicator 19 to inform the user of the distance to the measurement target 13.

As described above, in this embodiment, the transmitting ultrasonic transducer 11 is driven by using the signals output from the microcomputer 10 and having opposite phases, without using the booster circuit. However, even with such a configuration, it is not possible to apply a large voltage as in the booster circuit, so the output of the transmitting ultrasonic transducer 11 is slightly reduced, but this is sufficient by increasing the amplification factor of the amplifier 14. Can be used. Further, the output of the ultrasonic transducer has a property that it is leveled off when the applied voltage increases, and even if the voltage is increased too much in the booster circuit, the output does not rise to any extent, so the configuration of this embodiment is sufficient. Is. In particular, in a back sonar, a corner clearance sonar, and the like mounted on an automobile or the like, there is a great advantage due to simplification of the circuit.

FIG. 3 is a block diagram of another embodiment of the ultrasonic distance measuring apparatus of the present invention. Further, FIG. 4 is a diagram showing the state of signals at each point of the configuration of this embodiment. This embodiment will be described below with reference to FIGS. 3 and 4.

In this embodiment, the ultrasonic transducer 32 for both transmission and reception is used as the ultrasonic transducer. In this way, by using the ultrasonic transducer for both transmission and reception, the overall configuration of the ultrasonic distance measuring device can be made smaller, and therefore it is more effective when mounted on a vehicle or the like.

In the ultrasonic distance measuring apparatus of this embodiment, the amplifier 14, the bandpass filter 15, the detection circuit 16, the gate circuit 17, the comparator 18 and the distance indicator 19 are provided.
Is similar to the embodiment of FIG.

The present embodiment further includes a transmission / reception switching circuit 31 for switching the transmission / reception ultrasonic transducer 32 between transmission and reception. Microcomputer 30
Are signals S1 and S for driving the ultrasonic transducer 32 for both transmission and reception.
In addition to the terminals P1 and P2 for outputting 2, the transmission / reception switching circuit 3
It has a terminal P5 for outputting a control signal S6 for controlling 1.

The transmission / reception switching circuit 31 is provided with terminals t1 to t4 for switching the transmission state and the reception state of the ultrasonic transducer 32 for both transmission and reception. In FIG.
Although this switching mechanism is schematically shown, various mechanical and electrical configurations are possible.

First, the microcomputer 30 outputs the signals S1 and S2 whose phases are mutually inverted from the terminals P1 and P2, and outputs the high level signal S6 to the transmission / reception switching circuit 31 while the signals S1 and S2 are being output. Input (see Fig. 4). When the high-level signal S6 is input to the transmission / reception switching circuit 31, the terminals t1 and t3 are connected to each other, and the signal S is transmitted to the ultrasonic transducer 32 for both transmission and reception.
1 and S2 are supplied.

Therefore, the signal voltage applied to both terminals of the ultrasonic transducer 32 for both transmission and reception is as shown by S3 in FIG. Next, at the same time when the output of the signals S1 and S2 ends, the signal S6 also becomes low level. When the signal S6 becomes low level, in the transmission / reception switching circuit 31, the terminals t2 and t4 are in the connected state, and the ultrasonic transducer 32 for both transmission and reception is in the receivable state.

The received ultrasonic wave is an electric signal S in FIG.
The signal indicated by 7 is input to the amplifier 14. S in FIG.
In the signal of No. 7, the signal due to the electric sneak does not appear only for the time T ₂ . This is because the electrical sneak signal does not flow to the amplifier 14 side during the time T ₂ because the switches at the terminals t2 and t4 are open inside the transmission / reception switching circuit 31. Further, in the case of the present embodiment, the electrical sneak signal includes the reverberation of the ultrasonic transducer.

Thereafter, the signal is amplified by the amplifier 14, filtered by the bandpass filter 15, shaped by the detection circuit 16 and input to the gate circuit 17, as in the embodiment of FIG. The gate circuit 17 controls the gate opening timing by the signal output from the terminal P3 of the microcomputer 30 so as not to pass the electric sneak signal, and passes only the signal by the reflected wave.

In the comparator 18, the signal sent from the gate circuit 17 is shaped into a waveform that can be processed by the microcomputer and is input to the terminal P4 of the microcomputer 30 as the signal S5. Then, the microcomputer 30 calculates the distance to the measurement target 13 and displays it on the distance display 19.

As described above, by outputting signals whose phases are inverted from each other from the microcomputer 30 and applying them to both terminals of the ultrasonic transducer, it is possible to simplify the circuit structure without the need for a booster circuit. By using the ultrasonic transducers for both transmission and reception, the number of ultrasonic transducers can be reduced to one, so that the ultrasonic distance measuring device can be further downsized.

[0044]

In an ultrasonic distance measuring device driven by a microcomputer, the microcomputer is provided with two output terminals for driving an ultrasonic oscillator, and a signal output from one terminal is output from the other terminal. It is assumed that the signals have inverted phases. Then, by inputting the signals output from these two terminals to both terminals of the ultrasonic vibrator, it is possible to obtain a voltage amplitude sufficient to drive the ultrasonic vibrator without providing a booster circuit. it can.

Therefore, since it is not necessary to provide the booster circuit and the signal generation source is the microcomputer 10 itself, it is not necessary to separately provide a signal generation circuit, and the circuit can be simplified and downsized.

Further, since the ultrasonic transducer has both a transmitting function and a receiving function, it is possible to reduce the number of ultrasonic transducers to one.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a state of a signal at each point in the configuration of the embodiment of FIG.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

FIG. 4 is a diagram showing a signal state at each point in the configuration of the embodiment of FIG.

FIG. 5 is a diagram showing a configuration of a conventional ultrasonic distance measuring device.

[Explanation of symbols]

 10, 30 Microcomputer 11 Ultrasonic transducer for transmission 12 Ultrasonic transducer for reception 13 Measurement target 14 Amplifier 15 Band filter 16 Detection circuit 17 Gate circuit 18 Comparator 19 Distance indicator 31 Transmission / reception switching circuit 32 Transmit / receive ultrasonic transducer

Claims (4)

[Claims] 1. An ultrasonic distance measuring device for measuring a distance to an object based on a time required for an emitted ultrasonic wave to be reflected and returned, wherein a first signal having a predetermined frequency and the first signal are provided. A microcomputer that outputs a second signal whose phase is inverted with respect to the signal of, and is driven by the first signal and the second signal,
A first ultrasonic transducer that emits ultrasonic waves based on a signal having an amplitude that is the sum of the amplitude of the first signal and the amplitude of the second signal; An ultrasonic distance measuring apparatus, comprising: a second ultrasonic transducer for receiving the ultrasonic wave. 2. The first ultrasonic transducer receives the first signal and the second signal output from the microcomputer, and the transducer receives the first signal and the second signal depending on the voltages of the first and second signals. The ultrasonic distance measuring device according to claim 1, wherein the ultrasonic wave is emitted by vibrating the ultrasonic wave. 3. An ultrasonic distance measuring device for measuring a distance to an object based on a time required for an emitted ultrasonic wave to be reflected and returned, wherein a first signal having a predetermined frequency and the first signal are provided. Of the microcomputer, which outputs a second signal whose phase is inverted with respect to the signal of 1., and also performs the transmission and reception of ultrasonic waves. At the time of transmitting ultrasonic waves, the first signal and the second signal are transmitted. An ultrasonic transducer that is driven by a signal and that emits ultrasonic waves based on a signal having an amplitude that is the sum of the amplitude of the first signal and the amplitude of the second signal. An ultrasonic distance measuring apparatus comprising: a transmission / reception switching unit that switches circuit connection between transmission and reception of the ultrasonic transducer. 4. The ultrasonic vibrator receives the first signal and the second signal output from the microcomputer, and vibrates the vibrator according to the voltages of the first and second signals. The ultrasonic distance measuring device according to claim 3, wherein the ultrasonic wave is emitted thereby.