JPH0548143Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a reflection type ultrasonic switch that detects objects in a wide range from short distances to long distances.

[Prior art and its problems]

(Prior Art) As a conventional ultrasonic switch, a reflection type ultrasonic switch is known, which oscillates ultrasonic waves in a fixed direction at predetermined intervals and receives the reflected waves. Such an ultrasonic switch defines an object detection range based on the time it takes to receive ultrasonic waves after oscillating them.

FIG. 4 is a block diagram showing the main parts for setting the object detection range of such a conventional ultrasonic switch. In this figure, the transmission gate generation circuit 1
The transmission gate signal generated by the transmitting gate signal determines the timing for driving an ultrasonic element (not shown) and is also applied to the inhibition gate generating circuit 2. The inhibition gate generation circuit 2 determines the time width until the start of measurement, and its output is given to the detection gate generation circuit 3. The detection gate generation circuit 3 is triggered by the output signal of the inhibition gate generation circuit 2 and determines the object detection time. FIG. 5 is a time chart showing these operations, in which the output of the detection gate generation circuit 3 is given to the gate circuit 4, and the presence or absence of an object is detected by logical product with the received signal.

(Problems to be Solved by the Invention) However, in such conventional ultrasonic switches, the range in which objects are detected is determined by the timing of opening the detection gate after transmitting waves. When trying to detect a nearby object, a reflected wave signal is transmitted within a relatively short period of time after being transmitted, so it is necessary to stop driving the ultrasonic transducer within a short period of time in order to receive the signal. There is. On the other hand, if a distant object is to be detected, sufficient ultrasonic power is required, and since reverberation time is not a problem, it is necessary to lengthen the transmission time. In conventional ultrasonic switches, the driving time of such ultrasonic elements is fixed,
It was not possible to change this freely. Another problem is that a single ultrasonic switch cannot detect objects over a wide range from long distances to short distances.

[Purpose of invention]

The present invention was developed in view of the problems of conventional ultrasonic switches, and aims to widen the range in which objects can be detected and to detect objects over a wide range from short distances to long distances. is a technical issue.

[Structure and effect of the idea]

(Means for solving the problem) The present invention includes an ultrasonic wave transmitting means and a long-time and short-time wave transmitting gate signal for driving the ultrasonic wave transmitting means to transmit ultrasonic waves in one cycle. A transmitting gate generating means that generates a transmitting signal respectively, an ultrasonic receiving/transmitting means that receives the reflected wave reflected by the sensing object and outputs a received signal, and a predetermined output of the ultrasonic receiving/transmitting means. Comparison means for comparing with a threshold value and outputting a signal for determining the presence or absence of a received wave signal; and detection gate generation means for generating a detection gate signal of a predetermined time width after a predetermined time has elapsed from the activation point of each transmission gate signal. , a signal processing means into which the discrimination signal and each detection gate signal are input, and performs output processing of the object detection signal according to a result of whether or not the discrimination signal is input during the input period of each detection gate signal;
It is characterized by comprising the following.

(Function) According to the present invention having such characteristics, the wave transmission gate generation circuit outputs a wave transmission gate signal whose time width is alternately switched to long and short times for each oscillation,
It drives the ultrasonic wave transmitting means. Since the ultrasonic wave transmitting means is driven for a long time in a long-time wave transmission gate signal, its peak amplitude level also becomes large. In addition, when driving for a short time, the amplitude value of the ultrasonic waves transmitted by the ultrasonic wave transmitting means also becomes small. In this way, long-time and short-time wave transmission gate signals are alternately generated and transmitted as one-cycle transmission signals. Then, the received wave signal reflected by the detection object is received by the ultrasonic wave receiving means, and the reflected wave signal exceeding a predetermined level is detected by the comparing means. Further, a detection gate signal having a predetermined time width is generated by the detection gate generating means after a predetermined time has elapsed from the start of the transmission gate signal. Based on these signals, when a discrimination signal is obtained from the comparison means in any of the transmission signals of one cycle, an object detection signal is output.

(Effect of the invention) Therefore, according to the invention, an object located close to the ultrasonic switch can be detected by the reflected wave signal after the ultrasonic transmitting means is driven for a short time and the reverberation ends. . In addition, when the position is away from the ultrasonic switch, after driving the ultrasonic wave transmitting means for a long time, the reflected wave can be detected after the reverberation ends. Since these operations are repeated alternately, it is possible to detect objects in a wide range from long distances to short distances.

[Description of Embodiment] FIG. 1 is a block diagram showing the configuration of an ultrasonic switch according to an embodiment of the present invention. In this figure, a transmission gate generation circuit 11 generates transmission gate signals having different timings alternately, and its output is transmitted to a suppression gate generation circuit 12,
It is applied to the inhibition gate generation circuit 13, the vibrator drive circuit 14, and the amplifier circuit 15. The transducer drive circuit 14 drives the ultrasonic element 16, which serves as ultrasonic wave transmitting means and ultrasonic receiving/transmitting means, based on the timing of the wave transmission gate signal. Ultrasonic element 1
One end of 6 is also provided to an amplifier circuit 15. The amplifier circuit 15 is connected to the ultrasonic element 16 except for the wave transmission timing period given by the wave transmission gate generation circuit 11.
It amplifies the ultrasonic signal obtained from
The output is given to the detection circuit 17. Detection circuit 17
detects the received ultrasonic wave to obtain an envelope signal, the output of which is given to the comparator circuit 18. Comparison circuit 18 discriminates signals exceeding a predetermined threshold level and supplies them to signal processing circuit 19 .
Now, the suppression gate generation circuit 12 is triggered by the fall of the wave transmission gate signal, and the ultrasonic transducer 16
It outputs a suppression gate signal with a time width corresponding to the reverberation time of , and its output is given to the signal processing circuit 19. The prohibition gate generation circuit 13 is triggered by the rising edge output of the wave transmission gate signal, and generates a prohibition gate signal for a period until the start of object detection determined by the user, and its output is triggered by the rising edge output of the wave transmission gate signal. The signal is applied to the circuit 20 and the signal processing circuit 19 . The detection gate generation circuit 20 outputs a detection gate signal having a time width corresponding to a detection range determined by the user.

The signal processing circuit 19 includes a D-type flip-flop 2 to which the output of the comparison circuit 18 is applied to the clock input terminal.
1 and a shift register 22 whose output is given to the input terminal. D-type flip-flop 2
The output of the detection gate generation circuit 20 is given to the input terminal of 1, and the OR signal of the suppression gate generation circuit 12 and the prohibition gate generation circuit 13 is given to the clear input terminal via the OR circuit 23. . The Q output is connected to a preset input terminal and is further applied to a 2-bit shift register 22. The detection gate signal of the detection gate generation circuit 20 is input to the clock input terminal of the shift register 22.
The outputs of Q1 and Q2 are applied to the OR circuit 25. The OR circuit 25 provides an OR signal of these outputs to the output circuit 26.

In the present invention, the wave transmission gate generating circuit 11 is configured as a circuit that alternately outputs long-time and short-time wave transmission gate signals as one cycle. Second
The figure is a diagram showing the circuit configuration of the wave transmission gate generation circuit 11. As shown in FIG. As shown in this figure, the transmission gate generation circuit 1
1 has an operational amplifier 31 to which a predetermined level voltage obtained by dividing the power supply voltage by resistors R1 and R2 is applied to the non-inverting input terminal. A capacitor C1 is connected to the inverting input terminal of the operational amplifier 31, and the output terminal and the inverting input terminal are further connected to a resistor R3 for charging the capacitor C1, a diode D1, a diode D2 for discharging the charge of the capacitor C1, a resistor R4, and a diode D3. and resistor R5 and switching
The series-connected bodies of FET32 are connected in parallel.
The resistor R6 is a feedback resistor, and the resistor R7 is a resistor for charging the capacitor. The output of the operational amplifier 31 is applied to the clock input terminal of a D-type flip-flop 33. flip flop 33
is a binary counter whose state changes depending on the fall of the input signal, and its output is given to the gate of FET 32 as its control signal. The output of the operational amplifier 31 is then provided to the above-mentioned suppression gate generation circuit 12 and the like via the inverter 34.

Next, the operation of the ultrasonic switch of this embodiment will be explained with reference to the time chart of FIG.
FIG. 3a is a diagram showing the output of the operational amplifier 31 of the transmitting gate generation circuit 11. If the terminal voltage of the capacitor C1 is lower than the divided voltage of the resistors R1 and R2, the operational amplifier 31 goes to "H" level. A signal is output, and capacitor C1 is gradually charged via resistor R3 and diode D1. and resistance R1, R
When the reference voltage determined by 2 is reached, the output is inverted. And the Q output of flip-flop 33 is “H”
If the level is the same, the capacitor C1 is rapidly discharged via the diode D2 and the resistor R4, and the diode D2 and the resistor R5. Further, if the Q output of the flip-flop 33 is at the "L" level, the capacitor C1 is gradually discharged via the diode D2 and the resistor R4.
Therefore, the wave transmission gate generation circuit 11 outputs wave transmission gate signals which alternately reach the "H" level at different times, as shown in FIG. 3c. The ultrasonic element 16 is then driven based on this transmission gate signal. Since the rise of the ultrasonic element 16 is slow and it takes time for the amplitude level to increase, the output level of the ultrasonic amplitude is small when driven for a short time, and the output level of the amplitude becomes large when driven for a long time.
On the other hand, the suppression gate generation circuit 12 supplies a suppression gate signal to the signal processing circuit 19 for a certain period of time in response to the fall of this signal, as shown in FIG. 3d. Further, the inhibition gate generation circuit 13 generates an inhibition gate signal for a certain period of time determined by the user after the rise time of this signal, as shown in FIG.
0 also outputs a detection gate signal as shown in FIG. 3f.

Now, if an object exists near the ultrasonic transducer 16, the ultrasonic element 16 for a short period of time t ₁ to _{t 2}
The reflected wave is obtained at time _t3 after driving. Third
Figure h shows the waveform detected by the detection circuit 17 after the reflected wave signal is amplified by the amplifier circuit 15. If the reflected wave level is higher than the threshold level of the comparison circuit 18, the waveform shown in Figure 3 i is shown. Comparison circuit 1
Output is obtained from 8. At this point, OR circuit 2
Since the output of D flip-flop 21 is at the "L" level and the output is transmitted from the detection gate generation circuit 20 to the D flip-flop 21, the Q output of the D flip-flop 21 is inverted and its output is shifted, as shown in FIG. It is transmitted to the register 22. Since the shift register 22 uses the detection gate signal shown in FIG. 3(f) as a clock signal, this output is transmitted to the shift register 22 at the falling time _t4 , and the Q1 output becomes "L" as shown in FIG. 3(k). “It becomes a level. Therefore, the output is given to the output circuit 26 via the OR circuit 25, and the object detection signal can be outputted to the outside. However, if the object is near the ultrasonic switch and the ultrasonic transducer 16 is driven for a relatively long period of time, such as between time _t5 and _t6 , the reflected wave signal will be buried in reverberation and almost no reflection will occur. Unable to identify wave signals. Then, the output of the shaft register 22 is shifted to time _t7 , and the Q1 output becomes the "L" level and the Q2 output becomes the "H" level, as shown in FIG. 3k and l.
However, since the OR circuit 25 provides a signal to the output circuit 26 using these logical sum signals, it is possible to continuously output the object detection signal as shown in FIG. 3m. When the comparison output from the object is given within the detection gate time of the detection gate signal, the output circuit 26 can continuously output the object detection signal.

On the other hand, as shown after time _t8 , depending on the short-term transmission gate signal from time _t8 to time _t9 , as shown in FIG _.
As shown in the figure, the reflected wave level is low and cannot be detected. However, as shown at times t ₁₁ to _{t 12} , the reflected wave level is high after long-time driving, so a reflected wave signal exceeding the threshold level of the comparator circuit 18 is obtained and an object can be detected. In this case as well, the flip-flop 21 is set in the same manner, and during long-term and short-term driving, signals are sequentially transmitted to the shift register 22 and the output is held. The object is detected using the transmission gate signal as one cycle. Therefore, objects can be detected over a wide range from near the ultrasonic switch to far away.

In this embodiment, a self-excited oscillation circuit is formed using an operational amplifier and a flip-flop to change the discharge time of a capacitor to periodically obtain long and short time gate signals, but various other methods may also be used. It is also possible to obtain the transmission gate signal by It goes without saying that, for example, by providing a plurality of counters in the clock generator and switching their outputs, long-term and short-term transmission gate signals can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall configuration of an ultrasonic switch according to an embodiment of the present invention, Fig. 2 is a circuit diagram showing the circuit structure of a transmission gate generation circuit, and Fig. 3 shows the operation of this embodiment. 4 is a block diagram showing the main parts of a conventional ultrasonic switch, and FIG. 5 is a time chart showing its operation. 11... Transmission gate generation circuit, 13... Prohibition gate generation circuit, 16... Ultrasonic transducer, 17...
Detection circuit, 18... Comparison circuit, 19... Signal processing circuit, 20... Detection gate generation circuit, 21, 32
... flip-flop, 22 ... shift register, 23, 25 ... OR circuit, 31 ... operational amplifier, 33 ... FET, 34 ... inverter.

Claims (1)

[Claims for Utility Model Registration] (1) Ultrasonic wave transmitting means, and long-time and short-time wave transmission gate signals for driving the ultrasonic wave transmitting means to transmit ultrasonic waves in one cycle. A transmitting gate generating means that generates a transmitting signal, an ultrasonic transmitting means that receives a reflected wave reflected by a sensing object and outputs a received signal, and a predetermined output of the ultrasonic receiving and transmitting means. Comparing means for comparing with a threshold value and outputting a signal for determining the presence or absence of a reception signal; and detection gate generation means for generating a detection gate signal of a predetermined time width after a predetermined time has elapsed from the activation time of each of the transmission gate signals. and a signal processing means into which the discrimination signal and each of the detection gate signals are input, and outputs an object detection signal according to a result of whether or not the discrimination signal is input during the input period of each of the detection gate signals. An ultrasonic switch comprising: (2) The signal processing means includes a holding means for holding the discrimination output when a discrimination signal is input from the comparison means while the detection gate signal is being input, and an output of the holding means for the next cycle. It has a continuation means that continues until the discrimination output is given by the comparison means between the detection gate signals activated by the corresponding short-time or long-time transmission gate signals, and the output of the continuation means is The ultrasonic switch according to claim 1, wherein the ultrasonic switch outputs a detection signal. (3) The holding means of the signal processing means is a flip-flop that holds the output of the comparison means at the timing of the detection gate signal, and the continuation means of the signal processing means converts the held output of the flip-flop into the detection gate signal. 3. The ultrasonic switch according to claim 2, characterized in that it has a 2-bit shift register for shifting the outputs of the shift register and an OR circuit for calculating the logical sum of the respective outputs of the shift register.