JPH0244223Y2 - - 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]

Generally, this type of ultrasonic azimuth sensor uses a plurality of transducers to convert ultrasonic waves into electrical signals, detects the phase difference between these signals, and detects the propagated azimuth.

2 to 5 are views showing a conventional example, in which the upper surface 6 which is the detection surface of two vibrators 1a and 1b having cylindrical sensor bodies 8a and 8b.
a, 6b are arranged in the same plane, one of the two output terminals 7a, 7b protruding from the lower part of the sensor bodies 8a, 8b is grounded, and the other is connected to the amplifier 2a, 2b with a cable, respectively. It is connected at 5. Therefore, the upper surface 6a of the vibrator 1a, 1b,
The ultrasonic waves incident on 6b are converted into electrical signals by transducers 1a and 1b, respectively, and the respective electrical signals are amplified by amplifiers 2a and 2b. Here, the outputs of the amplifiers 2a and 2b are V ₀₁ and V ₀₂ respectively, and when ultrasonic waves are incident from the front direction as shown by the solid line arrow in Figure 2, the outputs V ₀₁ and V ₀₂ of the amplifiers 2a and 2b are As shown in FIG. 3, the waveforms have the same phase. Next, from the direction tilted by α degrees from the front direction, the second
When an ultrasonic wave is incident as indicated by a broken line arrow in the figure, the output V ₀₂ lags behind the output V ₀₁ in phase as shown in FIG. 4, and a phase difference (φα) occurs. here,
As shown in the top view of FIG. 5a, vibrators 1a and 1b
Let the distance between the centers of oscillators 1a and 1 be l ₀ .
b are in contact. ), and the difference in the distance traveled by the ultrasonic waves is Δl, then the azimuth α is sinα≈Δl/l ₀ . However, the phase difference (φα) can only be detected within the range of ±π (for example, a phase advanced by 2/3π and a phase delayed by π/3 cannot be distinguished).
If the wavelength of the ultrasonic wave is λ, then the condition Δl<|λ/2| must be satisfied.

Therefore, the maximum detectable azimuth (αmax)′
becomes sin(αmax′)≒|λ/2l ₀ |. That is, when detecting the orientation as described above, the wavelength (λ) of the ultrasonic wave and the transducers 1a, 1b
The maximum detectable azimuth (αmax') is determined by the distance _{l 0 between} the centers of Therefore, the maximum detectable azimuth (αmax') is limited.

[Purpose of invention]

The present invention was devised in view of the above-mentioned problems, and its purpose is to provide an ultrasonic azimuth sensor capable of widening the maximum detectable azimuth angle.

[Disclosure of invention]

FIG. 1 is a diagram showing an embodiment of the present invention, and except for the mask 3, the structure is the same as that of the conventional example. The mask 3 covers the upper surfaces 6a, 6b of the transducers 1a, 1b, makes contact with the transducers 1a, 1b at the same point, and provides detection holes 3a, 3b with a small radius on each of the transducers 1a, 1b. Provided on the upper surfaces 6a and 6b,
The distance between the centers of the detection holes 3a and 3b is defined as _l1 .

Due to the structure of the mask 3 described above, the maximum detectable azimuth (αmax') of this embodiment is expressed as sin(αmax)≒|λ/2l ₁ |, where, since l ₁ <l ₀ , αmax>αmax (However, αmax' is the maximum detectable azimuth when there is no mask 3.) The maximum detectable azimuth (αmax) can be expanded.

For example, if the frequency (f) of the ultrasonic wave is f = 25 kHz, the wavelength (λ) is λ = 13.3 [m/m], and the distance l ₁ between the centers of holes 3a and 3b of the mask 3 is l ₁ = 8.
[m/m], the distance l ₀ between the centers of vibrators 1a and 1b is
When l ₀ =16 [m/m], the maximum detectable azimuth (αmax) and the maximum detectable azimuth (αmax') without the mask 3 are αmax=56° and αmax'=24°. Note that the detection direction is not limited to the upward direction as shown in FIG.

[Effect of idea]

The present invention has a mask that covers the detection surface of the transducer and blocks ultrasonic waves, and the mask includes two pieces having a center-to-center distance shorter than the center-to-center distance of the transducer and a diameter smaller than the outer diameter of the transducer. Since the detection hole is drilled in the mask corresponding to the detection surface of each transducer, the distance between the centers of the transducers when determining the maximum detectable azimuth can be substantially shortened. This has the effect of widening the maximum detectable azimuth, which had been determined based on the distance between the two.

[Brief explanation of drawings]

Fig. 1a is a top view showing an embodiment of the present invention, Fig. 1b is a side view, Fig. 2 is a schematic configuration diagram of a conventional example, and Fig. 3 is a top view showing an embodiment of the present invention.
5 to 5 are explanatory views of the same operation as above. 1a, 1b are vibrators, 3 are masks, 3a, 3b
is the detection hole, and 6a and 6b are the upper surfaces.

Claims (1)

[Scope of utility model registration request] It has two transducers with detection surfaces disposed in the same plane and converts incoming ultrasonic waves into electrical signals, and a mask that covers the detection surfaces of the transducers to shield the ultrasonic waves. Two detection holes with a center-to-center distance shorter than the center-to-center distance and a diameter smaller than the outer diameter of the transducer are drilled in the mask corresponding to the detection surface of each transducer,
An ultrasonic azimuth sensor that compares the phase difference between signals detected by the vibrator and detects the direction in which the ultrasonic waves are incident.