Composite focusing piezoelectric shock wave transducer

Abstract

The invention discloses a composite focusing piezoelectric shock wave transducer, and belongs to the technical field of extracorporeal shock wave lithotripsy treatment. The transducer comprises a spherical crown-shaped backing, a PVDF piezoelectric composite material spherical crown and PZT piezoelectric ceramic arrays densely arranged in round holes of the spherical crown-shaped backing. A circular hole is machined in the surface of the PVDF spherical crown to accommodate the PZT ceramic chip, and the thicknesses of the two are designed according to the half-wavelength resonance principle corresponding to the emission frequency. And the PZT array and the PVDF spherical crown are synchronously excited through an independent power supply, so that generated shock waves are coherently superposed and focused on a spherical crown focus. Through the PZT / PVDF composite structure, the utilization rate of the spherical crown surface is increased to 90% or above, the shock wave focusing effect and energy density are enhanced, meanwhile, energy loss is reduced, and the PZT / PVDF composite spherical crown is suitable for efficient non-invasive lithotripsy treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of extracorporeal shock wave lithotripsy, in particular to a composite focusing piezoelectric shock wave transducer, especially a PZT / PVDF composite focusing piezoelectric shock wave transducer, for improving shock wave energy density and focusing efficiency. BACKGROUND

[0002] Extracorporeal shock wave lithotripsy is a non-invasive treatment method that focuses shock wave energy on stones in the body to break them. This method has the advantages of short treatment time, high safety, and less pain for patients, and is widely used in the treatment of kidney stones, urinary stones and other diseases.

[0003] The focusing transducer is the core component of the extracorporeal shock wave treatment system, and its focusing performance directly affects the treatment effect. The commonly used focusing transducer is a single ball crown piezoelectric ceramic or an array composed of multiple small size piezoelectric ceramics. The single ball crown piezoelectric ceramic has the problem of low electro-acoustic conversion efficiency, and in the array splicing mode, the gap between the round piezoelectric ceramics will reduce the utilization rate of the ball crown, affecting the focusing effect and energy transfer efficiency of the shock wave.

[0004] Therefore, there is an urgent need for a composite piezoelectric transducer that can improve the utilization rate of the spherical surface and enhance the focusing effect of the shock wave. SUMMARY

[0005] The present application aims to provide a composite focusing piezoelectric shock wave transducer with high spherical surface utilization rate, which combines the advantages of lead zirconate titanate (PZT) piezoelectric ceramic and polyvinylidene fluoride (PVDF) piezoelectric material to achieve efficient focusing and energy transfer of shock waves.

[0006] The technical solution of the present application includes:

[0007] The ball crown-shaped backing is made of insulating material;

[0008] The PVDF piezoelectric composite material ball crown is attached to the inner surface of the backing, and the surface is provided with a plurality of round holes;

[0009] The PZT piezoelectric ceramic array is composed of multiple round PZT piezoelectric ceramics closely arranged in the round holes of the PVDF ball crown, and the surface normal of each PZT ceramic sheet points to the focal point of the ball crown;

[0010] The electrode system, the electrodes of the PZT array are connected in parallel, and the electrodes of the PVDF ball crown are independently set, and the two are excited by a synchronous power supply.

[0011] The diameter of the round hole of the PVDF piezoelectric composite material ball crown is 0.2-3mm larger than that of the PZT piezoelectric ceramic sheet, and the gap is filled with insulating glue or plastic.

[0012] The thicknesses of the PZT piezoelectric ceramic sheet and the PVDF piezoelectric composite spherical cap are determined according to the half-wave resonance principle corresponding to the transmission frequency, and the calculation formula is:

[0013] Thickness = speed of sound in the material / (2 x design frequency).

[0014] The PZT piezoelectric ceramic array adopts an equal-interval ring belt arrangement mode, which ensures that the center distance of each ceramic sheet does not exceed half a wavelength.

[0015] Blind holes are arranged on the back plate for fixing the PZT piezoelectric ceramic sheet, so that the inner surface of the PZT piezoelectric ceramic sheet is aligned with the inner surface of the PVDF spherical cap.

[0016] The inner and outer surfaces of the PVDF piezoelectric composite spherical cap are plated with metal electrodes.

[0017] The negative electrode of the PZT piezoelectric ceramic array is connected in parallel towards the focal point side, and the positive electrode is led out through the back plate.

[0018] The PVDF spherical cap and the PZT array are excited by a synchronous power supply, so that the shock waves generated by the two are in phase and superimposed and focused.

[0019] The material of the back plate is epoxy resin or insulating treated lightweight metal.

[0020] The transducer is suitable for extracorporeal shock wave lithotripsy treatment equipment.

[0021] The beneficial effects of the present application are:

[0022] Through the composite design of PZT piezoelectric ceramic and PVDF piezoelectric composite spherical cap, PVDF fills the gap between PZT, significantly improves the utilization rate of the spherical cap surface, the utilization rate is increased to more than 90%, the energy density is improved, and the energy loss is reduced.

[0023] The synchronous excitation technology is adopted, so that the shock waves generated by the PZT piezoelectric ceramic and the PVDF piezoelectric composite spherical cap are in phase and focused, the energy and focusing effect of the shock wave are enhanced, the composite structure makes the shock wave coherent superposition, and the energy at the focal point is increased by 30%-50%. The PZT array and the PVDF spherical cap are driven by independent power supplies, which simplifies the excitation mode.

[0024] The PVDF spherical cap is integrally formed, which reduces the assembly difficulty of the array, has a simple structure, low manufacturing cost, and is suitable for large-scale production and clinical application. DETAILED DESCRIPTION

[0025] Figure 1 It is a perspective view of the composite transducer of the present application;

[0026] Figure 2 It is a sectional view of the composite transducer of the present application;

[0027] Figure 3 Partial sectional view of the composite transducer of the present invention. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] Figure 1 Partial sectional view of the composite transducer of the present invention.

[0030] The composite focusing piezoelectric transducer of the present invention comprises:

[0031] Backing: made of insulating material, in the shape of a spherical cap, used to support and fix other components.

[0032] PVDF piezoelectric composite spherical cap: as a filler, in the shape of a spherical cap, the outer diameter of the PVDF piezoelectric composite spherical cap is equal to the inner diameter of the backing 1, the surface of the PVDF piezoelectric composite spherical cap is machined with a circular hole according to the arrangement position of the PZT piezoelectric ceramic, the radius of which is 0.2-3mm larger than that of the PZT piezoelectric ceramic 3, used to accommodate the PZT piezoelectric ceramic. The thickness of the PVDF piezoelectric composite spherical cap is determined according to the corresponding half wavelength of the transmission frequency.

[0033] PZT piezoelectric ceramic: in the shape of a circular sheet, densely arranged in the circular hole on the surface of the PVDF piezoelectric composite spherical cap, the surface normal of the PZT piezoelectric ceramic points to the focal point of the spherical cap. The thickness of the PZT piezoelectric ceramic is also determined according to the corresponding half wavelength of the transmission frequency.

[0034] According to the half wavelength resonance principle corresponding to the transmission frequency:

[0035] Thickness = propagation speed of sound in the material / (2 x design frequency)

[0036] For example: at 1MHz frequency, the thickness of PZT is about 2mm, and the thickness of PVDF is about 1mm.

[0037] The surface of the PZT piezoelectric ceramic is aligned with the inner surface of the spherical cap, all PZT piezoelectric ceramic sheets are connected in parallel, the inner and outer surfaces of the PVDF piezoelectric composite spherical cap are plated with metal electrodes (such as silver paste), and separate leads are provided.

[0038] The PZT piezoelectric ceramic array and the PVDF piezoelectric composite spherical cap are respectively excited by independent power sources synchronously, so that the shock waves generated by the two are coherently superimposed and focused at the focal point of the spherical cap, thereby improving the utilization rate of the spherical cap surface and the focusing effect of the shock wave.

[0039] Figure 2Figure 1 is a sectional view of the composite transducer of the present application. The backing 1 is tightly connected with the PVDF piezoelectric composite spherical cap 2. A blind hole is opened on the backing 1. The depth of the hole satisfies the requirement that the PZT piezoelectric ceramic 3 is placed in the hole to be normal to the focal point of the spherical cap surface, and the inner surface edge is aligned with the inner edge of the opening of the PVDF piezoelectric composite spherical cap 2.

[0040] Figure 3 Figure 2 is a partial sectional view of the composite transducer of the present application. The backing 1 is tightly connected with the PVDF piezoelectric composite spherical cap 2. A blind hole is opened on the backing 1. The depth of the hole satisfies the requirement that the PZT piezoelectric ceramic 3 is placed in the hole to be normal to the focal point of the spherical cap surface, and the inner surface edge is aligned with the inner edge of the opening of the PVDF piezoelectric composite spherical cap 2. The gap between the PZT piezoelectric ceramic 3 and the hole on the backing 1 and the PVDF piezoelectric composite spherical cap 2 is filled with insulating glue or plastic to achieve insulation.

[0041] Example 1

[0042] The backing 1 is made of insulating material (such as epoxy resin) into a spherical cap shape, and the inner diameter is equal to the outer diameter of the PVDF piezoelectric composite spherical cap 2.

[0043] PVDF piezoelectric composite spherical cap 2 processing: circular holes are processed on the surface of the PVDF spherical cap according to the arrangement position of the PZT. The gap between the circular hole and the PZT wafer is 0.2-3mm, which can be filled with insulating glue (such as epoxy resin) to avoid short circuit.

[0044] PZT piezoelectric ceramic 3 array installation: the PZT wafer is embedded into the circular hole of the PVDF spherical cap, ensuring that its surface is normal to the focal point of the spherical cap and aligned with the inner surface of the PVDF piezoelectric composite spherical cap. The PZT piezoelectric ceramic 3 array is arranged in an equal interval ring band, dividing the spherical cap surface into multiple ring bands. The center distance of the PZT wafer in each ring band satisfies: center distance ≤ wavelength / 2 (to avoid acoustic interference).

[0045] Electrode connection: the negative electrode (facing the focal point side) of the PZT piezoelectric ceramic array is connected in parallel through a wire, and the positive electrode is connected to the external power supply through the backing; the electrode of the PVDF spherical cap is separately connected to another power supply.

[0046] Synchronous excitation: by controlling the power supply, the PZT piezoelectric ceramic array and the PVDF piezoelectric composite spherical cap are excited at the same frequency, same phase or certain phase difference, realizing coherent superposition and focusing of the shock wave.

[0047] 1. Backing processing: epoxy resin is poured into a spherical cap shape (curvature radius 100mm), and a blind hole with a depth of 2.1mm is processed on the inner side.

[0048] 2. PVDF dome preparation: PVDF and PZT particles are compounded and pressed into shape, and silver electrodes are plated on the surface; drill holes according to ring belt arrangement (diameter 5.2 mm, spacing 6 mm, accommodate Φ5 mm PZT sheet).

[0049] 3. PZT array installation: embed the PZT sheet (thickness 2 mm) into the PVDF hole, and fill the gap with epoxy glue.

[0050] 4. Electrode connection: connect the negative poles of PZT in parallel and lead to the focal point side, and connect the positive poles through the backing blind hole.

[0051] 5. Synchronous excitation: PZT and PVDF are respectively connected to phase-adjustable power supply, and the driving frequency is 1 MHz.

[0052] Example 2

[0053] The PZT piezoelectric ceramic discs are arranged at equal intervals on the surface of the dome. The surface of the backing dome is divided into ring belts of equal width and greater than the diameter of the PZT disc, and the PZT piezoelectric ceramic discs are arranged at equal intervals along the ring belts, so that the center of the surface of the PZT piezoelectric ceramic disc is equal to the distance from the edge of the ring belt.

[0054] Example 3

[0055] The PVDF piezoelectric composite dome and the backing, and the PZT piezoelectric ceramic array and the backing are fixed by gluing, and the electrodes at the circular holes and the PZT electrodes are isolated by insulating glue or plastic to ensure electrical insulation.

[0056] The PZT piezoelectric ceramic discs and the PVDF piezoelectric composite dome both adopt thickness vibration mode, and the thicknesses are determined according to the half wavelength of the PZT piezoelectric ceramic and the PVDF piezoelectric composite dome corresponding to the designed transmission frequency, and blind holes are processed on the inner side of the backing facing the PZT piezoelectric ceramic discs, so that the PZT piezoelectric ceramic discs and the PVDF piezoelectric composite dome of different thicknesses are aligned on the side facing the focal point.

Claims

1. A composite focused piezoelectric shock wave transducer, characterized in that, include: The spherical backing is made of insulating material. A PVDF piezoelectric composite spherical cap is attached to the inner surface of the backing, and its surface is provided with multiple round holes; The PZT piezoelectric ceramic array consists of multiple circular PZT piezoelectric ceramic sheets densely packed in the circular hole of the PVDF spherical cap, with the surface normal of each PZT ceramic sheet pointing towards the focal point of the spherical cap; The electrode system consists of parallel connections of the PZT array electrodes and independently set electrodes of the PVDF spherical cap electrodes, both of which are excited by a synchronous power supply.

2. The transducer according to claim 1, characterized in that: The diameter of the circular hole in the PVDF piezoelectric composite material spherical cap is 0.2-3 mm larger than that of the PZT piezoelectric ceramic sheet, and the gap is filled with insulating glue or plastic.

3. The transducer according to claim 1, characterized in that: The thicknesses of the PZT piezoelectric ceramic sheet and the PVDF piezoelectric composite material spherical cap are determined according to the half-wavelength resonance principle corresponding to the emission frequency, and the calculation formula is as follows: Thickness = speed of sound propagation in the material / (2 × design frequency).

4. The transducer according to claim 1, characterized in that: The PZT piezoelectric ceramic array adopts an equally spaced ring arrangement to ensure that the center distance between each ceramic sheet does not exceed half a wavelength.

5. The transducer according to claim 1, characterized in that: The backing is provided with blind holes for fixing the PZT piezoelectric ceramic sheet so that its inner surface is aligned with the inner surface of the PVDF spherical cap.

6. The transducer according to claim 1, characterized in that: The PVDF piezoelectric composite material spherical crown has metal electrodes plated on its inner and outer surfaces.

7. The transducer according to claim 1, characterized in that: The negative electrode of the PZT piezoelectric ceramic array is connected in parallel towards the focal point, and the positive electrode is led out through the backing.

8. The transducer according to claim 1, characterized in that: The PVDF spherical cap and the PZT array are excited by a synchronous power supply, so that the shock waves generated by the two are superimposed in phase and focused.

9. The transducer according to claim 1, characterized in that: The backing material is epoxy resin or an insulating lightweight metal.

10. The transducer according to any one of claims 1-9, characterized in that: The transducer is suitable for extracorporeal shock wave lithotripsy equipment.

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