JPH0365900A - Ultrasonic doppler sensor - Google Patents

Abstract

PURPOSE:To prevent a broken fault by fitting a metallic plate whose acoustic impedance is 15X10<6>kg/m<2>.S or over and whose thickness is 10-300mu to at least one side of a film shaped high polymer group piezoelectric material and coating them with a flexible high polymer material so as to avoid generation of elongation to the piezoelectric material even in the case of bent. CONSTITUTION:A metallic plate whose acoustic impedance is 15X10<6>kg/m<2>.S or over and whose thickness is 10-300mu is fitted on at least one side of a film shaped high polymer group piezoelectric material and they are coated with a flexible high polymer material. In this case, since elongation/contraction is caused around the film metallic plate 2 fitted on the high polymer group piezoelectric material 1 even when the sensor is bent, the elongation of the piezoelectric material 1 is small and the possibility of broken material is precluded. Moreover, when the film metallic plate 2 with a large acoustic impedance is fitted on the high polymer group piezoelectric material 1, the amplitude is suppressed, the frequency is lowered and it is possible for vibration at desired frequencies of 1-3.5MHz to generate an ultrasonic wave and the thickness of the piezoelectric material is thin. Thus, the sensor with excellent flexibility is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a delivery monitoring device, and more particularly to an ultrasonic Doppler sensor for measuring fetal heartbeat information.

[Conventional technology and its issues]

Ultrasonic Doppler sensors using ceramic piezoelectric elements have been widely used clinically as a means of obtaining fetal heartbeat information. However, since the piezoelectric element itself is hard and brittle, it is difficult to create a sensor with a large area.

Therefore, when a polymeric piezoelectric material is used, the frequency in this application field is mainly 1 to 3.5 μHz, and the thickness of the polymeric piezoelectric material is required to be 300 to 1000 μm.

Therefore, not only is the thickness easy to cause dielectric breakdown during polarization, resulting in poor yields, but also the thickness is 400 to 1000 μm.
In this case, even though it is a polymeric material, it becomes rigid, and if it is bent to a bending radius of about 5 mm, for example, cracks may occur in the piezoelectric film and there is a risk that the piezoelectric film will break.

[Summary of the invention]

In order to solve the above problems, the sensor of the present invention has two
As shown in the figure, the acoustic impedance of at least one side of the film-like polymeric piezoelectric material is 15X106kg/m2・S.
In the above configuration, a metal plate having a thickness of 10 to 300 μm is attached and coated with a flexible polymer material.

With such a configuration, even when the sensor is bent, expansion and contraction occurs centering around the membrane metal plate 2 attached to the polymeric piezoelectric material 1, so the expansion and contraction of the piezoelectric material 1 becomes small, and breakage occurs. The fear of

Furthermore, when a film-like metal plate 2 with a large acoustic impedance is attached to the polymeric piezoelectric material 1, the amplitude is suppressed and the frequency becomes lower than that of the conventional one, and the desired frequency l to 3.
It is possible to generate ultrasonic waves by vibrating at 5 MHz, and the piezoelectric material can be made thinner.

[Detailed description of the invention]

The present invention will be described in detail below based on the drawings.

FIG. 1 is a sectional view showing the configuration of an embodiment of the sensor of the present invention;
FIG. 2 is a detailed sectional view showing the configuration of an example of the sensor section.

1 in Figure 1 is a film-like polymeric piezoelectric material, and at least one side thereof has an acoustic impedance of 15X10'kg/m2.
- A metal plate 2 having a thickness of 10 to 300 μm, for example, a copper plate 2 having a thickness of 80 μm is attached. A shielding material 3°, for example a film-like mesh copper plate 3, is attached to the other surface of the polymeric piezoelectric material 1. These copper plates 2.3 are covered with a plastic film 4 such as a white polyester film, and the areas other than the central portion on the award copper plate 2 side are covered with a flexible polymeric material 5 such as urethane rubber.

The polymer-based piezoelectric material 1 refers to a piezoelectric material made of a synthetic polymer material or a composite piezoelectric material made by kneading ferroelectric ceramic powder into a polymer material. Vinylidene resin films, copolymers of vinylidene cyanide and monomers copolymerizable with vinylidene, such as vinyl acetate, and copolymers of vinylidene fluoride with other copolymerizable monomers (e.g., evatrifluoroethylene, vinylidene cyanide, etc.). Piezoelectric materials made by stretching and polarizing copolymer resin films, ferroelectric ceramics (e.g. titanium lead zirconate) and polymers (e.g. polyvinylidene fluoride resin, vinylidene fluoride copolymer resin, nylon resin, polyacetal resin, A piezoelectric polymer composite material is used, which is obtained by polarizing a composite material consisting of one or a combination of two or more of fluorine-based comb, NBR, chloroprene rubber, chlorohydrin rubber, and chlorinated polyethylene elastomer. The thickness is preferably about 30 to 350 μm.

The film metal plate 2 is made of copper, lead, or stainless steel.

Phosphor bronze, nickel, etc. can be used, and if the acoustic impedance is small, the effect of lowering the resonance frequency will be small. Therefore, the membrane metal plate 2 needs to have an acoustic impedance of 15×10' kg/m2·S or more. The thickness of this metal plate 2 is generally 10 to 300 μm.
In particular, 30 to 200 μm is suitable, and 1 to 3.5 μHz
It is possible to oscillate at a frequency of , and it is difficult to cause dielectric breakdown during polarization, and the electromechanical coupling constant is significantly improved, and the yield is also improved.

The plastic film 4 is polyester.

Polyimide is suitable.

Further, as the flexible polymer material, urethane rubber, silicone rubber, thermoplastic elastomer, etc. can be used.

3(a) to 3(a) show an example of a structure in which a polymeric piezoelectric material and a film-like metal plate are bonded together in the present invention, and FIG. FIG. 3 (5) shows an example in which metal plates 2 are attached to both sides of the polymeric piezoelectric material 10.
3 (C) is an example in which the polymeric piezoelectric material 1 is attached to both sides of the metal plate 2, and FIG. 3 (A) is an example in which the metal plate 2 is attached.
This is an example in which two polymer-based piezoelectric materials 1 are attached in two layers to one surface of the structure, and any structure may be used.

FIG. 4 shows the transmission of ultrasonic waves constituting the sensor of the present invention.

This is a cross-sectional view showing an example of the structure of a receiving section, and the sensor 13 of the present invention is composed of an ultrasonic transmitting section 6 and an ultrasonic receiving section 7, and the transmitting and receiving sections 6.7 are constructed using a polymeric piezoelectric material l. It is something.

The transmitting part 6 and the receiving part 7 in the present invention have a common electrode 8 attached to the back surface of the polymeric piezoelectric material 1 as shown in FIG. The receiving electrodes 10 constituting the portion 7 are formed with a slight gap therebetween.

Further, as shown in FIG. 4, the transmitting electrode 9 and the receiving electrode 10 are arranged in a comb shape so as to fit into each other.

The common electrode 89, the transmitting electrode 9, and the receiving electrode 10 can be formed by vapor deposition of aluminum, adhesion of conductive rubber, or the like.

Lead wires 8a, 9a, 10 for each electrode 8.9.10
a is connected to a plug 12 via a cable 11. 14
are the cable terminals, and 8a-10a are the ground wires.

It is connected to the cable 11 as a transmission signal line and a reception signal line. 15 is a ground terminal connected to the lead wire (ground wire) 8a, 16 is a transmission terminal connected to the lead wire (transmission signal line) 9a, and 17 is a lead wire (reception signal line) 10
This is a receiving terminal connected to a.

The plug 12 is connected to a device main body (not shown) that transmits high frequency waves in the ultrasonic range and applies them to the common electrode 8 and the transmitting electrode 9 to generate ultrasonic waves.

Further, the reflected waves of the generated ultrasonic waves are received by the receiving section 7,
An electrical signal is generated between the common electrode 8 and the receiving electrode 10.

The generated electrical signal is input to the main body of the apparatus and is configured to be displayed on a display such as an oscilloscope.

In the above embodiment, the transmitting section 6 and the receiving section 7 are divided, but the division may be omitted and a single electrode may be formed on the entire surface to serve both the transmitting and receiving functions.

With such a configuration, even when the sensor is bent, expansion and contraction occurs centering around the membrane metal plate 2 attached to the polymeric piezoelectric material 1, so the expansion and contraction of the piezoelectric material 1 becomes small, and breakage occurs. The fear of

Furthermore, when a film-like metal plate 2 with large acoustic impedance is attached to a polymer-based piezoelectric material 1, the amplitude is suppressed and the frequency becomes lower than that of conventional ones, making it possible to generate low-frequency ultrasonic waves. .

FIG. 6 is a diagram showing the relationship between the thickness and frequency of a polymeric piezoelectric material, where the a line shows only the piezoelectric material and the b line shows a case where a metal plate is attached to the piezoelectric material. FIG. 7 is a sectional view showing the state of use of the present invention.

The sensor 13 of the present invention is a main body as shown in FIG. Wall surface 18
Attach it in accordance with the A high frequency pulse wave or burst wave voltage is applied to the transmitter 6 through a cable 11. When applied through the plug 12, ultrasonic waves are generated and are irradiated to the heart of the fetus 19 within the mother's body. The Doppler signal (acoustic signal) reflected by the surface of the fetal heart, valves, etc. and modulated by the movement of the heart is converted into a fetal heartbeat signal (electrical signal) at the receiving section of the sensor, and then sent to the cable 11. The plug 12 leads to the main body of the device. The transmitting section 6 and the receiving section 7 are constructed using a polymeric piezoelectric material 1, and are entirely covered with a flexible polymeric material 5 to a thickness of several meters.
m, the entire device is flexible, and by increasing the area of the element, it is possible to collect fetal heartbeat information over a very wide range.

〔Effect of the invention〕

As described above, according to the present invention, the area of the transmitting part and the receiving part is large and flexible. There is no need to change (readjust) the position of the sensor each time the fetus gradually moves, and optimal heartbeat information can be obtained, leading to labor-saving management. In addition, even during pregnancy tests, even if the fetus moves slightly, the area of the ultrasound transmitting and receiving sections is large, so the frequency of readjusting the position of the fetus during delivery and the position of the sensor can be extremely reduced. In addition, since the entire sensor is flexible, it is possible to significantly improve the strong pressure and discomfort felt on the surface of the base body with conventional ceramic sensors.

In addition, since the metal plate is attached, it is possible to oscillate low frequencies using a thin piezoelectric material, and even when using high frequencies of about 1 to 3.5 MHz, the sensor can be made with excellent flexibility. . Furthermore, the piezoelectric material does not elongate when bent, and breakage accidents can be prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the sensor of the present invention;
FIG. 2 is a detailed cross-sectional view showing the configuration of an example of the sensor part, and FIGS. 3(a) to (d) are cross-sectional views showing an example of the lamination structure of the polymeric piezoelectric material and the film-like metal plate in the present invention. FIG. 4 is a cross-sectional view showing an example of the structure of the ultrasonic transmitting and receiving part constituting the sensor of the present invention, FIG. 5 is a cross-sectional view showing the structure of the piezoelectric element part of the present invention, and FIG. A diagram showing the relationship between material thickness and frequency, and FIG. 7 is a sectional view showing the state of use of the present invention. 1... Polymer piezoelectric material, 2... Membrane metal plate (copper plate), 3... Shielding material (membrane mesh copper plate), 4...・Plastic film (white polyester film), 5... Flexible polymer material (urethane rubber), 6... Transmission section, 7...
...Receiving section, 8...Common electrode, 8a = 9
a, 10a... Lead wire, 9... Electrode for transmitting, 10... Electrode for receiving, 11...
...Cable, 13...Sensor of the present invention. Sha 9 Minister Sha 5 Rōgo θ Rei's 4I Kirihipan Tsukidai Shinshi

Claims (1)

[Claims] A metal plate with an acoustic impedance of 15 x 10^6 kg/m^2 S or more and a thickness of 10 to 300μ is attached to at least one side of a film-like polymeric piezoelectric material, and the metal plate is covered with a flexible polymeric material. Ultrasonic Doppler sensor.