JPH05309096A - Impulse wave generating source - Google Patents

Abstract

PURPOSE:To decrease the stress at the boundary surface between a piezoelectric ceramic vibrator and an acoustic matching layer and to prevent the peeling of the acoustic matching layer by forming an insulator having a specific coefft. of thermal expansion as the acoustic matching layer on the impulse wave radiation side surface of the piezoelectric ceramic vibrator. CONSTITUTION:The vibrator 1 is a piezoelectric material of a PZT system and is so constructed that a rear surface side 1b on the projecting surface of the vibrator 1 comes into contact with a packing layer 3 which is the air in a support 2. The vibrator 1 is subjected to the polarization treatment to make the recessed surface side 1c serve as the ground. Silver electrodes are formed on the front and rear surfaces. The silver electrodes are formed by applying silver paste thereon and baking the paste. The electric pulses from a driving circuit 6 are impressed via lead wires 5 to the silver electrodes of the vibrator 1. As a result, the vibrator 1 is driven to vibrate. An epoxy resin having, for example, <=39X10<-6>/ deg.C coefft. of thermal expansion is formed as the acoustic matching layer 4 on the surface of the recessed surface side 1c of the vibrator 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic vibration device mounted on an extracorporeal calculus crushing device (hereinafter referred to as calculus crushing device) for irradiating a shock wave from the outside of a calculus in the body to treat calculus. The present invention relates to a shock wave generation source using a child.

[0002]

2. Description of the Related Art As a shock wave source constituting a calculus breaking device, a device using electric spark, electromagnetic induction, micro explosion, etc. has been developed. In recent years, shock wave generators using piezoelectric ceramic oscillators have been able to obtain stable output,
Moreover, it has been put to practical use because it has no consumable parts, is inexpensive, and can downsize the device.

In a shock wave generation source using a piezoelectric ceramics oscillator, a plurality of concave piezoelectric ceramics oscillators are fixed to a support, and an epoxy resin is formed as an acoustic matching layer on the concave side surface of the piezoelectric ceramics oscillator. There is. The support is brought into contact with the patient via a container, for example made of rubber, which holds a liquid (for example, water) used as a propagation medium, and generates ultrasonic waves. A shock wave is generated by focusing this ultrasonic wave to form a focal point, and crushing can be realized by irradiating the ultrasonic wave with the focal point aligned with the calculus.

[0004]

However, in the conventional shock wave source, about 300 mm is required to maintain the crushing force.
Because of the large diameter, and the large difference in the coefficient of thermal expansion between the piezoelectric ceramics vibrator and the acoustic matching layer, the expansion and contraction rates of the two also differ due to changes in the operating environment temperature. Therefore, there is a problem that stress is applied to the boundary surface between the piezoelectric ceramics vibrator and the acoustic matching layer, and the acoustic matching layer peels off. As a result, the output sound pressure of the shock wave at the focal point decreased, leading to the inability to withstand long-term use.

The present invention reduces the stress on the boundary surface between the piezoelectric ceramics oscillator and the acoustic matching layer, suppresses the separation of the acoustic matching layer, reduces the decrease in the output sound pressure, and is capable of withstanding long-term use. The purpose is to provide.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a shock wave source using a piezoelectric ceramic oscillator mounted on an extracorporeal calculus breaking device for irradiating a calculus inside the body with a shock wave to crush the calculus. Oscillator
An acoustic matching layer is formed on the surface of the piezoelectric ceramic oscillator on the side of the shock wave radiation, which has a support for fixing the periphery of the oscillator with an opening, and an insulator having a thermal expansion coefficient of 39 × 10 ⁻⁶ / ° C. or less. The gist is a shock wave generation source characterized by this.

[0007]

[Function] Since an insulator having a coefficient of thermal expansion of 39 × 10 ⁻⁶ / ° C. or less is formed as an acoustic matching layer on the surface of the piezoelectric ceramic vibrator on the side of shock wave radiation, the optimum coefficient of thermal expansion is selected. The stress at the boundary surface between the piezoelectric ceramic oscillator and the acoustic matching layer is reduced, and peeling of the acoustic matching layer is suppressed.

[0008]

The preferred embodiments of the shock wave source of the present invention will be described below.

FIG. 1 is a sectional view conceptually showing for explaining a preferred embodiment of a shock wave source (hereinafter referred to as a shock wave source) of the present invention. This shock wave source is mounted on a calculus breaking device that crushes a calculus inside the body by irradiating it with a shock wave.

In FIG. 1, reference numeral 2 denotes, for example, an outer diameter of about 3.
A support having an opening 2a of 00 mm and an inner diameter of about 100 mm is shown. A peripheral portion 1 a of a concave piezoelectric ceramics oscillator (hereinafter referred to as “vibrator”) 1 having a curvature of about 250 mm is supported and fixed to the support 2 on the side of the opening 2 a in the support 2.

The vibrator 1 has, for example, a relative dielectric constant of about 200.
0, an antiresonance frequency of about 560 kHz, a PZT-based piezoelectric material having an electromechanical coupling coefficient of about 50% in the thickness direction, and the convex back surface 1b of the vibrator 1 is the air in the support 2 backing layer 3 It has a so-called air backing structure.

The vibrator 1 is polarized so that the concave surface 1c is grounded (-), and silver electrodes are formed on the front and back surfaces thereof. The silver electrode is formed by applying a silver paste and baking it, and the thickness of the silver electrode is set to, for example, 10 to 20 μm. The lead wire 5 from the drive circuit 6 is connected to this silver electrode.
5 are connected to each other, and an electric pulse from the drive circuit 6 is applied to the vibrator 1 via the lead wires 5 and 5. As a result, the vibrator 1 is driven and vibrates.

On the surface of the concave surface 1c of the vibrator 1, for example, an epoxy resin having a thermal expansion coefficient of about 55 × 10 ^-6 / ° C. is formed as an acoustic matching layer 4 (hereinafter referred to as matching layer).

When using such a shock wave source, a rubber container (not shown) is attached to the end of the opening 2a of the support 2 over the entire circumference, and ultrasonic waves from the vibrator 1 ( A liquid such as water is filled as a propagating medium of (shock wave). The container constitutes a calculus breaking device together with the drive circuit 6 and a system controller (not shown), the container is pressed against the body surface of the patient, and the transducer 1 is driven by electric pulses from the drive circuit to generate ultrasonic waves. Generate. Then, the shock wave generated at the focal point is applied to the stones existing in the kidney to crush them. Since the electric pulse that drives the vibrator 1 is transmitted to the patient via the propagation medium, the matching layer 4 is generally made of an insulator in order to ensure safety.

The resin forming the matching layer 4 is preferably 6 × 10 ⁶ kg / m ² · in terms of securing shock wave output sound pressure.
It has an acoustic impedance of s-9 × 10 ⁶ kg / m ² · s. If the acoustic impedance of the resin is 6 × 10 ⁶ k
If it is smaller than g / m ² · s, it is 1 compared to the maximum output sound pressure.
It is not good because it leads to a decrease in shock wave output sound pressure of 0% or more. Moreover, the acoustic impedance of the resin is 9 × 10 ⁶ kg /
When it is larger than m ² · s, the same shock wave output sound pressure drop occurs, which is not preferable. Acoustic impedance is the product of the density and the speed of sound. Epoxy resin is most preferable as the resin having the above acoustic impedance range. Hereinafter, an epoxy resin and alumina powder as a filler material for obtaining a matching layer by mixing the epoxy resin with each other to form a mixture will be described as an example.

The thermal expansion coefficient of the mixture of the epoxy resin and the alumina powder forming the matching layer 4 on the concave surface 1c of the vibrator 1 will be described.

FIG. 2 shows the relationship between the weight ratio of alumina powder to epoxy resin and the coefficient of thermal expansion for a mixture of epoxy resin and alumina powder as a preferred embodiment. The thermal expansion coefficient is obtained by measuring the thermal expansion coefficient of a small piece of a liquid epoxy resin mixed with alumina powder and then cured.

As shown in FIG. 2, the coefficient of thermal expansion tends to decrease as the weight ratio of the alumina powder to the epoxy resin increases. A weight ratio of 0% is a characteristic of the epoxy resin itself and has a thermal expansion coefficient of 55 × 10 ⁻⁶ / ° C.
By mixing the alumina powder with the epoxy resin, it is possible to obtain the effect of reducing the thermal expansion coefficient. In the range where the weight ratio of the alumina powder exceeds 80%, it is very difficult to mix, and there is a defect in productivity. Figure 2
As is clear from the above, by appropriately selecting the weight ratio of the alumina powder to be mixed with the epoxy resin in the range of 80% to 0%, the mixture has a weight ratio of 26 × 10 ^{−6 to} 55 × 10 ⁻⁶ / ° C. It can be seen that the coefficient of thermal expansion can be controlled to an arbitrary value.

Next, a shock wave source was prepared in which the weight ratio of the alumina powder to the epoxy resin was changed, that is, a matching layer having a different thermal expansion coefficient was formed, and a temperature cycle test was carried out for each shock wave source. The results will be described here.

FIG. 3 shows the change in the ratio of the output sound pressure at the shock wave focus to the number of cycles. The temperature range was tested at -20 to 60 ° C.

As is apparent from FIG. 3, the coefficient of thermal expansion is 4
When it is 3 × 10 ⁻⁶ / ° C. or higher, the output sound pressure ratio is already reduced to 90% or less after 5 cycles. On the other hand, when the thermal expansion coefficient is 39 × 10 ⁻⁶ / ° C. or less, the output sound pressure ratio does not decrease to 90% or less in at least 15 cycles or less. Further, as shown in FIG. 2, when the weight ratio of the alumina powder to the epoxy resin is increased and the coefficient of thermal expansion is lowered, the number of temperature cycles that can be endured is further increased as shown in FIG. It can be seen that the effect of increasing the number of temperature cycles is remarkable when the coefficient of thermal expansion is 39 × 10 ⁻⁶ / ° C. or less. That is, the coefficient of thermal expansion is 39 × 10 ^-6 / ° C.
The following matching layers are less likely to be separated at the boundary surface between the vibrator and the matching layer due to environmental temperature changes, and it is possible to reliably reduce the decrease in output sound pressure that is closely related to the crushing force. In this case, in order to form a matching layer having a coefficient of thermal expansion of 39 × 10 ⁻⁶ / ° C. or less, the weight ratio of alumina powder to epoxy resin in FIG. 2 is 40% to 80%. In the present invention, when the weight ratio of the alumina powder to the epoxy resin exceeds 80%, it is difficult to mix, so that 26 × 1
It is difficult to produce a matching layer having a coefficient of thermal expansion of 0 ⁻⁶ / ° C. or less. Therefore, when the epoxy resin and the alumina powder are used in the present invention, the coefficient of thermal expansion is 26 × 1.
It can be said that the range of 0 ⁻⁶ / ° C. to 39 × 10 ⁻⁶ / ° C. is feasible and effective.

According to the above-mentioned embodiment of the present invention, the epoxy resin is mixed with alumina powder in a weight ratio of 40-80%,
Since the matching layer having a thermal expansion coefficient of 26 × 10 ⁻⁶ / ° C. to 39 × 10 ⁻⁶ / ° C. is formed on the shock wave radiation side surface of the vibrator, the stress at the boundary surface with the vibrator is reduced and the acoustic matching layer is formed. The effect of suppressing peeling is obtained. As a result, the decrease in the output sound pressure, which is closely related to the crushing force, can be reduced, and even a shock wave source with a large diameter can withstand long-term use. Further, since the present invention can be easily realized, it is also effective in terms of productivity.

The present invention is not limited to the above embodiment. For example, the same effect can be obtained by using a ceramic powder such as zirconia or silica in place of alumina powder as the filler material for the epoxy resin and selecting an optimal weight ratio range.

Further, for example, quartz glass or the like having a coefficient of thermal expansion smaller than ^{26.times.10.sup.-6} / .degree. C. of the matching layer described in the above embodiment may be formed as the matching layer. As a matter of course, the effect of not lowering the output sound pressure ratio for a long time can be obtained. Quartz glass has a coefficient of thermal expansion of, for example, about 0.5 × 10 ^-6 / ° C.

[0025]

According to the present invention, the coefficient of thermal expansion of 39 × 10 ⁻⁶ / ° C. is formed on the surface of the piezoelectric ceramic vibrator on the side of the shock wave radiation.
Since the following insulator is formed as an acoustic matching layer,
The stress on the boundary surface between the piezoelectric ceramics oscillator and the acoustic matching layer is reduced, and the effect of suppressing peeling of the acoustic matching layer is obtained. As a result, it is possible to reduce the decrease in the output sound pressure, which is closely related to the crushing force, and it is possible to endure long-term use even with a large-diameter shock wave source. Further, since the present invention can be easily realized, it is also effective in terms of productivity.

[Brief description of drawings]

FIG. 1 is a sectional view conceptually showing a preferred embodiment of a shock wave source of the present invention.

FIG. 2 is a diagram showing a relationship between a thermal expansion coefficient and a weight ratio of alumina powder to epoxy resin which constitutes an acoustic matching layer in a preferred embodiment of the shock wave generating source of the present invention.

FIG. 3 is a diagram showing the relationship between the number of temperature cycles applied to the shock wave source and the ratio of the obtained output sound pressure in the present invention.

[Explanation of symbols]

 1 Piezoelectric ceramic vibrator (vibrator) 1a Peripheral part 1b Back side 1c Concave side 2 Support 2a Opening 3 Backing layer 4 Acoustic matching layer (matching layer) 5 Lead wire 6 Drive circuit ◆

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuzo Kimoto 1573-8 Inoue, Onuma, Togane-shi, Chiba Toshiba Ceramics Co., Ltd. Togane Factory

Claims (1)

[Claims] 1. A shock wave source using a piezoelectric ceramics oscillator mounted on an extracorporeal calculus breaking device for irradiating and crushing a calculus in the body from outside the body,
An insulator having a coefficient of thermal expansion of 39 × 10 ⁻⁶ / ° C. or less is provided on the surface of the piezoelectric ceramic oscillator on the shock wave emission side, which includes a piezoelectric ceramic oscillator and a support body having an opening and fixing the periphery of the oscillator. A shock wave source characterized by being formed as an acoustic matching layer.