JPH0219432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an ultrasonic azimuth sensor that detects azimuth using ultrasonic waves.

[Background technology] Conventionally, this type of ultrasonic direction sensor converts ultrasonic waves into electrical signals using two transducers, detects the phase difference between these signals, and determines the direction in which the ultrasonic waves are incident. was detected. A conventional example is shown in FIGS. 3 to 6, in which sensor bodies 8a and 8b have upper surfaces 6a and 6b, which are the detection surfaces of two cylindrical transducers 1a and 1b, on the same plane. One output terminal of the output terminals 7a and 7b provided and protruding from the lower surface is grounded, and the other output terminal is connected to the amplifiers 2a and 2b via a cable 5. Therefore, the ultrasonic waves incident on the upper surfaces 6a, 6b of the transducers 1a, 1b are converted into electrical signals by the transducers 1a, 1b, respectively, and the respective electrical signals are amplified by the amplifiers 2a, 2b. Here, the respective outputs of the amplifiers 2a and 2b are V ₀₁ and V ₀₂ , and when ultrasonic waves are incident from the front direction shown by the solid line in FIG.
The outputs V ₀₁ and V ₀₂ of 2b have the same phase waveforms as shown in FIG. Next, if an ultrasonic wave is incident from a direction tilted by α degree from the front direction as shown by the broken line in Fig. 3, the output V ₀₂ of amplifier 2b is the output of amplifier 2a as shown in Fig. 5. V ₀₁
The phase is further delayed, and a phase difference φα is generated. here,
As shown in the top view of FIG. 6a, vibrators 1a and 1b
_Let the distance between the centers of
1b are in contact. ), and the difference in the distance traveled by the ultrasonic waves is Δ, then the azimuth angle α is sinα=Δ/ ₀ . However, the phase difference φα can only be detected within the range of ±π (for example, a phase leading by 2π/3 and a phase delayed by π/3 cannot be distinguished), so if the wavelength of the ultrasound is λ, then Δ<|λ /2｜ must satisfy the following conditions.

Therefore, the maximum detectable azimuth αmax′ is sin(αmax′)≒|λ/2 ₀ |. That is, when detecting the azimuth as described above, the maximum detectable azimuth angle αmax' is determined by the wavelength λ of the ultrasonic wave and the distance ₀ between the centers of the transducers 1a and 1b. If it is constant, there is a drawback that the maximum detectable azimuth angle αmax' is limited by the distance ₀ between the centers of the vibrators 1a and 1b.

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to provide an ultrasonic azimuth sensor that can widen the maximum detectable azimuth angle. It is in.

[Disclosure of the Invention] (Embodiment) FIGS. 1 and 2 are diagrams showing an embodiment of the present invention, in which an upper surface 6a as a detection surface,
and 6b are arranged to convert incoming ultrasonic waves into electrical signals, and a mask 2 that covers the upper surfaces 6a and 6b of the transducers 1a and 1b to shield the ultrasonic waves. and the mask 2
Two openings 3a and 3b are bored on the two vibrators 1a and 1b, respectively, with a center-to-center distance shorter than the distance between the centers of the vibrators 1a and 1b, and the openings 3
The shapes of a and 3b are formed to be long in the direction orthogonal to the straight line connecting the vibrators 1a and 1b.

When the maximum detectable azimuth αmax in this embodiment configured as described above is found, sinα≒|λ/2 ₁ |. Here, ₁ is the distance between the center lines of the openings 3a and 3b. Furthermore, distance ₁ is oscillator 1
Since the distance between the centers of a and 1b is smaller than ₀ , sinαmax>sinαmax'. However, sinαmax' is the maximum detectable azimuth when the mask 2 is not present.

For example, if the frequency of ultrasound is 25kHz, the wavelength λ is 13.3mm, distance ₁ is 6.7mm, and distance ₀ is 6.7mm.
Assuming 16 mm, when the mask 2 is not used, αmax'= ²⁴⁰ , but when the mask 2 of this embodiment is attached, αmax= ⁹⁰⁰ , which makes it possible to widen the maximum detectable azimuth angle. Furthermore, the shapes of the openings 3a and 3b are changed to the shape of the vibrator 1.
Since the direction orthogonal to the straight line connecting a and 1b is formed to be long, the detection area of the ultrasonic waves incident from the detection direction becomes wider, so that the ultrasonic detection sensitivity of the transducers 1a and 1b can be improved. The distance between the apertures can be made considerably smaller, since the detection area will not be drastically reduced and the detection sensitivity will not be deteriorated by reducing the distance, as is the case with circular apertures. It is.

[Effects of the Invention] As described above, the present invention includes two transducers whose detection surfaces are arranged on the same plane and converts incident ultrasonic waves into electrical signals, and an ultrasonic transducer that covers the detection surfaces of the transducers. A mask that blocks sound waves is provided, two openings are formed in the mask on each of the two transducers at a distance shorter than the distance between the centers of the transducers, and the openings are placed between the centers of the transducers. By covering the detection surface of the transducer with a mask with perforated openings, the distance between the centers of the transducers, which determines the maximum detectable azimuth angle, can be effectively reduced. This makes it possible to widen the maximum detectable azimuth angle, and the opening is made longer in the direction perpendicular to the straight line connecting the centers of the vibrators. Since the detection area of the ultrasonic waves incident from the detection direction becomes wider, the detection sensitivity of the ultrasonic waves of the transducer can be improved. Since the detection sensitivity does not deteriorate to an extreme degree, the distance between the openings can be made considerably smaller.

[Brief explanation of drawings]

Fig. 1 is a top view of an embodiment of the present invention, Fig. 2 is a side view of the same as the above, Fig. 3 is an explanatory diagram of the operation of the conventional example, and Fig. 4 is a diagram showing the state in which ultrasonic waves are incident from the front. Figure 5 shows the output waveform when ultrasonic waves are incident from an oblique direction. Figure 6 shows the output waveform when the ultrasound is incident from an oblique direction.
Figures a and b are a top view and a side view of the same. 1a to 1c are vibrators, 2 is a mask, 3a to 3c
is an opening, and 6a to 6c are upper surfaces.

Claims (1)

[Claims] 1. Two transducers with detection surfaces disposed on the same plane and converting incoming ultrasonic waves into electrical signals, and a mask that covers the detection surfaces of the transducers and blocks the ultrasonic waves, are provided. Two openings are bored on each of the two vibrators at a distance shorter than the distance between the centers of the vibrators, and the openings are formed long in a direction perpendicular to a straight line connecting the centers of the vibrators. Ultrasonic direction sensor consisting of