JPS5856445B2 - ultrasonic switch - Google Patents

Description

[Detailed description of the invention] The present invention relates to an ultrasonic switch.

Conventionally, in this type of reflective ultrasonic switch, the first
As shown in the figure, in order to improve directivity, an electroacoustic transducer 1 such as a microphone was attached inside the rear end of a trumpet-shaped horn 2 to constitute a transducer 3. , the directivity changes when the ambient temperature changes, the object to be detected and the transducer 3
The detection area used to detect nearby fixed obstacles changes with the ambient temperature and sometimes becomes distorted.

In other words, the shape of the directivity at T1°C' shown in Figure 2a is sharper than the directivity at T2'c shown in Figure 2S, and is suitable for detecting objects such as humans. Comparing the directivity with respect to the gain required for 72°C, it is wider at 72°C.

Therefore, if the detection area at the time of construction is set at an ambient temperature of T1℃, for example, and the ambient temperature later changes to T2℃, the detection area will change accordingly, and as a result, the detection area will expand and fixed obstacles will enter the detection area. There was a risk that the device would receive a reflected signal and malfunction.

In Figure 2 a and b, θ1 and θ2 indicate the respective directivity angles. For example, if the angle widens and there is a possibility that a fixed obstacle may be included in the detection area, the transmission/reception will be changed as shown in Figure 3. The mounting angle a of the wave device 3 had to be set at the position indicated by the broken line based on experiments, and in this case, there was a drawback that a predetermined detection area could not be set.

In order to eliminate these drawbacks, it is sufficient to maintain the directivity even when the ambient temperature fluctuates, but the present invention has been made in view of the above points, and its purpose is to maintain the directivity even when the ambient temperature fluctuates. An object of the present invention is to provide an ultrasonic switch capable of keeping the directivity of a transducer substantially constant even when the directionality of the transducer varies.

By the way, the basic principle of the present invention is that when the horn 2 is provided with an electroacoustic transducer 1 such as a microphone, the wavelength of the ultrasonic signal changes and its directivity changes. At the time of wave transmission, r, r (correction is made by varying the frequency of the ultrasonic frequency signal applied to the electroacoustic transducer 1) to suppress changes in directivity.

The present invention will be explained below with reference to Examples.

FIG. 4 shows a circuit block diagram of one embodiment, where A is a wave transmitting circuit section and B is a wave receiving circuit section.

The transmitting circuit section A includes an oscillator 4 that oscillates and outputs an ultrasonic frequency signal, amplifies the ultrasonic frequency signal output from the oscillator 4, and transmits the electroacoustic transducer 1 with the amplified output.
It is composed of an amplifier 6 to be driven.

The force receiving circuit section B includes an amplification circuit that amplifies the output signal of the electroacoustic transducer 1, which receives a reflected signal obtained when an ultrasonic signal emitted into space is reflected from a fixed obstacle or an object to be detected 6. a detector 8 that receives a target signal from the amplified output of the amplifier 7, and an A-D converter circuit 9 that converts the analog value of the detected signal of the detector 8 into the number of pulse signals; A flip-flop circuit 12 that operates the output relay 11 via the switching circuit 10 when the pulse signal of the A-D conversion circuit 9 is, for example, 2 or more, the switching circuit 10, the output relay 11, and a direct wrap-around circuit. It is provided for the purpose of removing reflected signals from waves and fixed obstacles such as the floor surface, and is the time during which the reflected signal from the detected object 6 in the space between the transducer 3 and the floor surface is to be received. The distance setting section 13 is configured to generate an output signal only in the band, and input the output of the detector 8 to the A/D conversion circuit 9 only when this output signal is generated.

When the transmitted ultrasonic signal is reflected by the object to be detected 6 and received, the output relay 11 operates due to the movement of the wave receiving circuit section B to operate the load.

By the way, the detection area set at the time of construction changes as the directivity of the transducer 30 fluctuates depending on the ambient temperature as described above.
As shown in the figure, a negative characteristic thermistor 14 is used as part of the time constant resistor that configures the C-R oscillation circuit and sets its oscillation frequency, and the oscillation frequency is adjusted in response to changes in ambient temperature. It is set to change automatically.

That is, in order to prevent the directivity of the transducer 3 from changing due to the wavelength of the ultrasonic signal changing depending on the ambient temperature, the oscillation frequency is changed in a direction that suppresses the change in the wavelength of the ultrasonic signal. As a result, the directivity of the transducer 3 can be held substantially constant, and the set detection area will not change.

The electroacoustic transducer 1 used in the above-mentioned transducer 3 may be provided for wave transmission and wave reception, or one may be switched between wave transmission and wave reception.

As described above, the present invention changes the oscillation frequency in response to the ambient temperature so that the directivity of the transducer remains constant by suppressing the fluctuation in the wavelength of the ultrasonic signal that varies depending on the ambient temperature. Equipped with an oscillator, the oscillation output of this oscillator drives the electroacoustic transducer of the transducer and emits an ultrasonic signal into space, so there is little change in directivity due to ambient temperature and the detection area is stable. However, when the button is pressed after installation, the detection area expands due to changes in the ambient temperature and there is no possibility of malfunction due to detection of fixed obstacles.Moreover, no special structure is required for the horn. Compared to the structure of the horn that prevents changes in directivity, this has the effect that the oscillation frequency of the oscillator can respond to a wide range of changes in ambient temperature depending on the ambient temperature.

[Brief explanation of drawings]

Figure 1 is a new view of the transducer used in the ultrasonic switch, Figure 2 is a characteristic diagram of the relationship between the directivity of the ultrasonic switch's transmitter and the ambient temperature, and Figure 3 is the transducer of the ultrasonic switch. 4 is a circuit block diagram of the ultrasonic switch of the present invention, and FIG. 5 is a specific circuit diagram of the same oscillator as described above, 1 is an electroacoustic transducer, 2 is an electroacoustic transducer, A horn, 3 a transducer, and 4 an oscillator.

Claims (1)

[Claims] 1. An electroacoustic transducer such as a microphone phono is housed inside the rear end of a trumpet-shaped horn to form a transducer, and the reflected signal of the ultrasonic signal transmitted into the space is received to detect the detected object. In an ultrasonic switch that generates an output signal when detecting the An ultrasonic switch comprising an oscillator that changes the frequency, and the oscillation output of the oscillator drives an electroacoustic transducer of a transducer to emit an ultrasonic signal into space.