JPS6122294Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an ultrasonic pulse echo device for industrial use, fishing or navigation in freshwater and saltwater areas, or medical use, and particularly relates to high-level pulse echo devices in the probe drive circuit and its surroundings. This invention relates to an improvement in an ultrasonic pulse echo system using an inductor or transformer installed in a circuit that has a magnetic core made of ferrite or the like for the purpose of downsizing.

In recent years, magnetic cores made of ferrite or the like have been used in pulse transformers, flyback transformers, and other transformers and inductors for everything from small signals to electric power, and the above-mentioned pulse echo system is no exception. A wide variety of ferrites are available as materials for the magnetic core, and those with various performances are available, and even the existence of air-core coils has become extremely rare.

However, although these ferrites are quite close to ideal magnetic materials, the existence of residual magnetization (the existence of hysteresis on the connecting BH curve) and the accompanying magnetostrictive effect have been denied as accompanying properties. I can't. This is found to a greater or lesser degree in all ferrite materials, even those not specifically designed for this purpose. This property is often overlooked because it is not necessarily harmful for general coil and transformer applications. However, in a circuit where high-level transmitted pulses and extremely low-level reflected wave reception signals coexist and appear alternately, which constitutes a pulse echo system like the one mentioned above, the properties of the ferrite material as described above are Woe to you.
This is because these ferrite magnetic cores are themselves ultrasonically excited by the energy of the transmitted pulse through the magnetostrictive effect, and are excited and even resonate. As is well known, ferrite materials are very hard and generally have a high mechanical Q, so once excited, they continue to vibrate for quite a long time due to their own resonance or internal multiple reflections. Meanwhile, the vibrational energy appears again at the terminals of the wound coil via the magnetostrictive effect. This actually becomes a kind of echo generator, which interferes with the normal reception of reflected waves as a pulse echo device, and adds false echoes that are confusing as fixed reflections returning from the target space.

For example, Figure 1 shows an example of the circuit configuration of the transmission pulse generation circuit, the probe matching circuit, and the first stage of the reception amplifier of a commonly used ultrasonic medical diagnostic device that does not require a deep metal wound instrument. However, the problem in this case is the inductor for conjugate matching of the probe TD (piezoelectric ceramic resonator).
L ₁ and/or L ₂ , or even a step-up transformer L ₃ in the first stage of the receiver. Although not all of these are always employed and arranged as shown in this schematic, in many cases
It is obvious that an inductor and/or a transformer are required in the same position. Therefore, it can be said that FIG. 1 shows a typical example.

Therefore, in any of these L ₁ to L ₃ ,
If an attempt is made to miniaturize it by using, for example, a toroidal core, the above-mentioned problem will occur, and in severe cases, pseudo echoes will be generated to the extent that they will mask all weak distant echoes.

Therefore, in the present invention, an ultrasonically effective sound absorbing material is tightly attached to the ferrite core used in these coils to prevent the generation of the above-mentioned false echoes. As a sound absorbing material, a single substance or suitable heavy metal powder (tungsten, copper,
Epoxy resin or other casting resin containing an appropriate amount of fine powder of lead, stainless steel, etc. is suitable. When using the resin alone, it is preferable to completely wrap the ferrite core so as to impregnate the entire ferrite core.

For example, as shown in FIG. 2a, the toroidal core 1 and the windings 2 are all placed in a mound of epoxy resin 3 so as to be densely impregnated, and at the same time, they are bonded to the base 4. This means that simply fixing the winding 2 and properly bonding the core 1 to the base 4 is not enough, as is generally said.
It is important that the resin is well distributed and impregnated throughout the area. Therefore, if this process is carried out in the atmosphere, air bubbles and residual air chambers are likely to form, so this process should be carried out after vacuuming, and the fluidity of the uncured epoxy resin is also important. In order to ensure this, it is desirable to heat the process to around 40-50°C. Note that if the temperature is too high, the fluidity will increase too much and it will not be possible to build up the mixture, which is not preferable.

However, instead of raising it up, a casting mold may be used, or it may be potted into a case 4' instead of using a base as shown in FIG. 2b. In that case as well, if there is poor adhesion of residual bubbles, this will significantly impede the sound absorption effect, so degassing and heating for fluidization before and after casting are essential.

Furthermore, the winding may be wound tightly around the core as shown in Figure 2a, but
It is more effective to leave a slight gap between the core 1 and the winding 2 and intentionally inject the sound absorbing material 3 between the core 1 and the winding 2, as shown in FIG.

As clarified from the above explanation, the present invention allows high-energy pulses and weak received signals to coexist and pass through a magnetic material that easily resonates ultrasonically, such as a toroidal core made of a hard material such as ferrite. It provides a technique for suppressing internal interference, which is essential for use in circuits. However, it is obvious that the invention can be implemented in a similar manner, particularly with respect to ferrite inductors employing magnetic cores of other shapes, or cored inductors or transformers made of other materials, in particular not only with toroidal cores. Furthermore, this is effective not only for the cited metal flaw detectors or ultrasonic medical diagnostic equipment, but also for all pulse echo equipment in general, including industrial,
This includes ultrasonic pulse echo devices for fishing and aquatic navigation.

[Brief explanation of the drawing]

FIG. 1 is a typical example of a part of the electric circuit of an ultrasonic pulse echo device, and FIG. 2 is an example of an internal interference suppression measure according to the present invention. TD...Ultrasonic probe, _L1 , _L2 ...Inductor, _L3 ...Transformer, 1...Troidal core,
2... Winding wire, 3... Sound absorbing material.

Claims (1)

[Scope of utility model registration request] An ultrasonic pulse having a conjugate matching inductor connected in parallel between a pair of electrodes of a probe that transmits ultrasonic waves excited by the transmitting pulse and receives reflected ultrasonic waves afterwards. An ultrasonic pulse echo device characterized in that the inductor is an inductor made of a coil having a magnetic core, the entire magnetic core of which is covered with a resin-like sound absorbing material.