JPH11319081A - Ultrasonic bubble detector, ultrasonic bubble detector and artificial dialysis device using the same - Google Patents

Abstract

(57) [abstract] (with correction) [PROBLEMS] An ultrasonic bubble detector capable of performing stable bubble detection in which bubbles flow smoothly and capable of accurate bubble detection.
An ultrasonic bubble detector and an artificial dialysis device are provided. An ultrasonic bubble detector for detecting a bubble passing through a liquid transport pipe such that vibrating portions of a pair of ultrasonic vibrating elements facing each other across a liquid transport pipe through which a liquid flows is detected. Are arranged in a direction intersecting the flow direction of the liquid in the liquid transport pipe, and the inside of the liquid transport pipe in a state where the length of the belt-shaped vibrator is sandwiched. The liquid transport tube is longer than the width (inner diameter), and the portion other than the vibrating portion of the ultrasonic vibration element in the detector has the same surface (height) H as the contact surface of the vibrating portion with the liquid transport tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic bubble detector for detecting bubbles passing through a liquid transport tube at a holding portion of a pair of ultrasonic vibrating elements opposed to each other while sandwiching a liquid transport tube through which a liquid flows. The present invention relates to an ultrasonic bubble detector, an ultrasonic bubble detector, and an artificial dialysis device for stably detecting the pressure.

[0002]

2. Description of the Related Art As is well known, the principle of a bubble detector using ultrasonic waves is as shown in FIG. 2 showing an embodiment of the present invention.
When the ultrasonic wave transmitted from one ultrasonic vibration element 2 passes through the liquid transport pipe 8 and the liquid and is received by the other ultrasonic vibration element 2, and there is a bubble in the liquid, This utilizes a phenomenon in which the intensity of the ultrasonic wave received by the ultrasonic wave reflected by the air bubble is reduced.

Conventionally, it is used for an ultrasonic bubble detector or an ultrasonic bubble detector which detects bubbles passing through a liquid transport tube at a holding portion of a pair of ultrasonic vibrating elements opposed to each other across a liquid transport tube through which a liquid flows. The ultrasonic vibration element generally has a shape as shown in FIG. 9, for example, and is used as shown in FIG.

That is, a pair of ultrasonic waves in which a cylindrical ultrasonic wave transmitter 9 is added to a disk-shaped ultrasonic vibrating section 10 and the shape of a portion that comes into contact with the liquid transport pipe 8 is devised as shown in FIG. A vibration element 11 is used. In FIG. 9A, both ends of the ultrasonic transmission body 9 are flat, and in FIG. 9B, both are also spherical. FIG. 9 (c) a is spherical in shape, but one is convex, and FIG. 9 (b) is characterized in that the other is concave.

In the conventional method, ultrasonic waves are transmitted and received over a wide area, and it is considered difficult to detect a microbubble whose measurement object is small with respect to the area of the ultrasonic transmission body 9. As a means for solving this problem, FIG. An ultrasonic vibration element 13 to which an ultrasonic transmission body 14 as shown in FIG. 10 is added is proposed in Japanese Utility Model Publication No. 5-29717. That is, a convex ultrasonic transmitter 14 is added to the ultrasonic vibrating section 10, and a portion that comes into contact with the liquid transport pipe 8 is formed in a belt shape, and its longitudinal direction is set in the flow direction of the liquid in the liquid transport pipe 8. It is characterized in that it is arranged in the direction perpendicular to the direction, the area where the ultrasonic wave is transmitted is reduced, and the rate at which the intensity of the ultrasonic wave is reduced by the bubble is increased. However, conventional ultrasonic bubble detectors, including this new proposal, have the following problems, and these bubble detectors are mainly used for detecting bubbles present in blood in blood tubes. It is not just a performance problem of the bubble detector, but a serious problem related to human life.

1) There are many malfunctions. That is, many reports have been made that the number of detection pulses is small even though there are many bubbles, or that a detection pulse is generated without bubbles.

2) There is a change in sensitivity due to a temperature change in the ultrasonic detector and the signal processing circuit of the ultrasonic detector,
As the temperature increases, bubble detection becomes unstable.

3) As shown in FIGS. 11 (A) and 11 (B), the liquid transport tube 8 is strongly pinched to detect microbubbles, or bubbles stay at the bent portions to bend. In some cases, the passage time of the bubble through the holding portion may be long.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, namely,
Eliminate erroneous operations such as a small number of detection pulses even though there are many bubbles, or conversely, the generation of a detection pulse when there are no bubbles, such as an ultrasonic bubble detector and a signal processing circuit of an ultrasonic bubble detection device. Since it is difficult to take measures to reduce the change in sensitivity due to temperature change, measures must be taken to respond to this change in sensitivity so that stable air bubble detection can be performed even with temperature changes. The liquid transport tube should be so tight that the liquid transport tube is not pinched or bent in order to detect any An ultrasonic bubble detector that can stably detect bubbles by solving these problems by examining these issues is to enable bubbles to flow smoothly and to accurately detect bubbles without holding strongly. To And to provide an ultrasonic bubble detection apparatus and dialysis apparatus use.

[0010]

In order to achieve the above object, the present invention employs the following constitution. (1) In the ultrasonic bubble detector for detecting bubbles passing through the liquid transport pipe such that the vibrating portions of a pair of ultrasonic vibrating elements opposed to each other with the liquid transport pipe through which the liquid flows are formed in a belt shape, The longitudinal direction of the vibrating portion is arranged in a direction intersecting the flow direction of the liquid in the liquid transport tube, and the width (inner diameter) of the inside of the liquid transport tube in a state where the length of the band-shaped vibrating portion is sandwiched. ) It is longer than T, and the portion other than the vibrating portion of the ultrasonic vibrating element in the above-mentioned detector sandwiches the liquid transport tube on substantially the same plane (height) H as the contact surface of the vibrating portion with the liquid transport tube. Ultrasonic bubble detector featuring.

(2) In the ultrasonic bubble detector according to the above (1), a pair of ultrasonic vibrating elements receive and transmit the ultrasonic vibrating element using a polymer ferroelectric thin film or an inorganic ferroelectric on both transmitting sides. An ultrasonic bubble detector equipped with an ultrasonic vibrating element that uses an inorganic ferroelectric substance on either the transmitting or receiving side and uses a polymer ferroelectric thin film on the receiving or transmitting side. In the above, the vibrating part is an ultrasonic vibration element formed in a substantially band shape on a flat plate, or a substantially band-shaped tip of an ultrasonic transmission body attached to a side used as a reception surface or a transmission surface of the ultrasonic vibration element. An ultrasonic bubble detector, which is an ultrasonic vibration element.

(3) In the ultrasonic bubble detector according to the above (2), a protective film having the same shape and the same area or more covering the entire surface of the ultrasonic vibrating element on the receiving or transmitting side is provided. Ultrasonic bubble detector.

(4) In the ultrasonic bubble detector according to (3), an electrode is formed on the side of the protective film attached to the receiving or transmitting side of the ultrasonic vibrating element, which is in contact with the ferroelectric substance. An ultrasonic bubble detector comprising an electrode on one surface of an ultrasonic vibration element.

(5) In the ultrasonic bubble detector according to any one of the above (2) to (4), the ferroelectric substance of the ultrasonic vibrating element used alone or with a protective film. The thickness of the combined ferroelectric and protective film is approximately one quarter of the wavelength at the ultrasonic frequency to be used, which is determined by the material of the ferroelectric or the ferroelectric and the protective film. Sonic bubble detector.

(6) In the ultrasonic bubble detector according to any one of the above (2) to (5), a surface opposite to a surface of the ultrasonic vibration element using a ferroelectric material which receives or transmits ultrasonic waves. An ultrasonic bubble detector characterized in that the thickness of the electrode is approximately one half of the wavelength at the ultrasonic frequency to be used, which is determined by the electrode material.

(7) In the ultrasonic bubble detector according to any one of the above (1) to (6), as a resonance coil for determining a vibration frequency of the acoustic vibration element, a core or a filling material around the core is used as a resonance coil. An ultrasonic bubble detector characterized in that ferrite is used for the ultrasonic bubble detector.

(8) In the acoustic bubble detector according to any one of (1) to (7), the Q value of the coil at the resonance frequency of the ultrasonic vibration element using the coil is 1 to 10.
An ultrasonic bubble detector characterized by being 0.

(9) The ultrasonic bubble detector according to any one of (1) to (8), wherein the conductance at the resonance frequency of the ultrasonic vibration element is 0.1 milliSiemens or more. Sonic bubble detector.

(10) Detecting air bubbles passing through the liquid transport pipe at the holding portion of the pair of ultrasonic vibrating elements opposed to each other with the liquid transport pipe through which the liquid flows according to any one of (1) to (9) interposed therebetween. In the ultrasonic bubble detector, the material of the liquid transport tube is a polymer resin or rubber, and the liquid transport tube is a tube through which blood or the like flows.

(11) Bubbles passing through the liquid transport tube of the pair of ultrasonic vibrating elements opposed to each other with the liquid transport tube according to any one of (1) to (10) interposed therebetween are detected. In the ultrasonic bubble detector, the guide of the liquid transport tube has a substantially concave cross-sectional shape, and the guide has a gap (width) S at a central portion in the longitudinal direction that sandwiches the liquid transport tube. Ultrasonic bubble detector.

(12) In the ultrasonic bubble detector according to any one of the above (1) to (11), one of the pair of ultrasonic vibrating elements moves with respect to the other, or both of them move. An ultrasonic bubble detector comprising a mechanism which moves in parallel with each other and clamps a liquid transport tube.

(13) In the ultrasonic bubble detector according to any one of the above (1) to (12), the electric signal applied to the ultrasonic vibration element on the transmitting side is a substantially sinusoidal signal. Ultrasonic bubble detector.

(14) In the ultrasonic bubble detector according to any one of (1) to (13), an amplifier circuit 20 of a signal processing circuit for performing signal processing obtained by the ultrasonic wave received by the ultrasonic vibration element. Has two signal holding circuits with different signal holding times for detecting the output of
An ultrasonic bubble, comprising: a voltage comparator for comparing the output of the signal holding circuit 1 having a short holding time with an arbitrary ratio of the output of the signal holding circuit 2 having a long holding time as a reference and binarizing the output. Detector.

(15) An ultrasonic bubble detector comprising the ultrasonic bubble detector according to any one of (1) to (14) for detecting bubbles in a tube.

(16) The method for detecting bubbles in a tube of an ultrasonic bubble detector having a blood pump for circulating blood between the artificial kidney and the tube according to any one of the above (1) to (14). An artificial dialysis device comprising an ultrasonic bubble detector.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to facilitate understanding of the present invention, an ultrasonic vibration element using the polymer ferroelectric thin film shown in FIG. 1 and FIGS. 2, 4, 6 and 7
The following description is based on the embodiment of the ultrasonic bubble detector shown in FIG.

FIG. 1 is a structural view (exploded view) of an ultrasonic vibration element using a polymer ferroelectric thin film, (A) is an exploded view, and (B) is a sectional view.

FIG. 2 is a block diagram showing an embodiment of an ultrasonic bubble detector using a polymer ferroelectric thin film.

FIGS. 3A and 3B are configuration diagrams showing an example of an ultrasonic vibration element having a cylindrical ultrasonic transmitter with a mask. FIG. 3A shows a mask, and FIG. 3B shows a cylindrical ultrasonic transmitter. (C) shows an assembled sectional view.

FIG. 4 is a block diagram showing an embodiment of an ultrasonic bubble detector using an ultrasonic vibrating element having a cylindrical ultrasonic transmitter with a mask.

FIG. 6 is a block diagram showing an embodiment of an ultrasonic bubble detector using an ultrasonic vibration element having a convex ultrasonic transmitter with a mask.

FIGS. 7A and 7B are configuration diagrams showing an example of a guide for a blood tube of an ultrasonic bubble detector. FIG. 7A is a plan view of one side of an ultrasonic bubble detector having a guide, and FIG. is there.

The ultrasonic bubble detector of the present invention will be described with reference to FIGS. 1 and 2 so that the vibrating portions 2-a of a pair of ultrasonic vibrating elements 2 opposed to each other across a liquid transport pipe 8 through which liquid flows are formed in a band shape. In the ultrasonic bubble detector 1 for detecting bubbles passing through the liquid transport pipe 8, the longitudinal direction of the vibrating portion 2-a is arranged in a direction intersecting the flow direction of the liquid in the liquid transport pipe 8. And the width (inner diameter) T inside the liquid transport pipe 8 in a state where the length of the belt-shaped vibrating portion 2-a is clamped.
It is longer that a portion other than the vibrating portion 2-a in the detector 1 sandwiches the liquid transport pipe 8 on the substantially same plane (height) H as a contact surface of the vibrating portion with the liquid transport pipe 8. It is a feature. As shown in FIG. 1, the surface of the ultrasonic vibrating element 2 other than the vibrating part 2-a is flat, in which the vibrating part 2-a is formed on the substrate 6-a and the electrode formed on the protective film. Is formed by the opposing portions, and thus indicates the surface of the ultrasonic vibration element 2 excluding the vibration portion 2-a.

The belt-shaped vibrating part 2 of the ultrasonic vibration element 2
The width of -a is 10 μm or more and is arbitrarily determined according to the size of the bubble to be detected.

It is preferable that the pair of ultrasonic vibrating elements 2 have substantially the same band width or have a pair of widths different from each other.

A pair of ultrasonic vibrating elements receive and transmit an ultrasonic vibrating element using a polymer ferroelectric thin film or an inorganic ferroelectric on both transmitting and receiving sides, or an inorganic ferroelectric substance on either the transmitting or receiving side. And an ultrasonic bubble detector 1 having an ultrasonic vibrating element using a polymer ferroelectric thin film on the receiving and transmitting sides of the ultrasonic bubble detector, wherein the vibrating portion is formed in a substantially band shape on a flat plate. FIGS. 2, 4, and 4, which are vibration elements or ultrasonic vibration elements 13 which are substantially band-shaped tips of ultrasonic transmission bodies 14 attached to a side used as a reception surface or a transmission surface of the ultrasonic vibration element. 6 and the ultrasonic bubble detector 1 shown in FIG.

For example, these ultrasonic bubble detectors 1
A protective film 5 having the same shape and the same area or more covering the entire surface of the ultrasonic vibration element 2 shown in FIG.

An electrode is formed on the side of the protective film 5 which is in contact with the ferroelectric 4, and is used as an electrode on one surface of the ultrasonic vibrating element 2, so that the thickness of the ferroelectric 4 alone or the ferroelectric 4 and the protection The combined thickness of the film 5 and the ferroelectric material 4 of the ultrasonic vibration element 2 to be used or the material of the ferroelectric material 4 and the protective film 5 is approximately 4 wavelengths at the ultrasonic frequency to be used.
An electrode having a high sensitivity is obtained by reducing the thickness of the electrode on the surface opposite to the surface receiving or transmitting the ultrasonic wave to about one half of the wavelength at the ultrasonic frequency used, which is determined by the electrode material used. It is preferable that sound waves can be transmitted and received.

It is preferable to use ferrite in the core or in the filling around the core as a resonance coil for determining the vibration frequency of the ultrasonic vibration element 2 for transmitting and receiving ultrasonic waves with low noise and high sensitivity. . However, FIG.
6, the coil 7 is not shown in the drawings of the ultrasonic vibration element.

It is more preferable that the Q value of the coil 7 at the resonance frequency is 1 to 100 and the conductance of the ultrasonic vibrating element 2 is 0.1 millisiemens or more. Vibration element 2
When the resonance frequency is determined by measuring near the temperature where is used and combining them, stable measurement can be performed.

A polymer resin or rubber tube is used for the material of the liquid transport tube 8 for stable detection of microbubbles.
The cross-sectional shape of the guide 15 of the liquid transport pipe 8 is substantially concave as shown in FIG. 7 (a portion surrounding the liquid transport pipe 8 in FIG. 7B, which is surrounded by two guides 15 from above and below). Preferably, the guide 1 has a gap (width) S at the center in the longitudinal direction that sandwiches the liquid transport pipe 8.
It is five.

The guide 15 is arranged so that the liquid transport pipe 8 is perpendicular to the vibrating part 2-a of the ultrasonic vibration element 2 and the liquid transport pipe 8 when held is in contact with the vibrating part 2-a. It is installed on the upper side of the ultrasonic vibrating element 2 and on the side where the vibrating part 2-a is located so that the inner diameter falls within the vibrating part 2-a in the longitudinal direction.

In order to stably hold the liquid transport pipe 8, one of the ultrasonic vibrating elements 2 moves with respect to the other, or both move in parallel with each other. It is important to provide a mechanism for holding the liquid transport pipe 8.

FIG. 8 is a block diagram showing an example of the signal processing circuit.

For stable detection of microbubbles against fluctuations in sensitivity of the ultrasonic detector 1 due to changes in the ambient temperature, the output of the amplifier circuit 20 of the signal processing circuit shown in FIG.
It has two signal holding circuits 22 and 23 having different signal holding times for holding for an arbitrary time, and the signal holding circuit 22 having a short holding time with reference to an arbitrary ratio of the output of the signal holding circuit 2 having a long signal holding time. An electrical signal to be applied to the transmitting-side ultrasonic vibrating element 2 so as to compare the output of the holding circuit 1 and binarize the voltage, and to prevent electromagnetic waves due to harmonics from leaking to the outside as much as possible. Is provided with a sinusoidal wave transmitting circuit 26 which makes the signal a substantially sinusoidal signal.

As described above, the ultrasonic bubble detector 1 is provided for detecting bubbles in a tube of an ultrasonic bubble detector having a blood pump for circulating blood mainly between the artificial kidney and the human body through a tube. And an ultrasonic bubble detecting device provided with the above-described signal processing circuit, and further provides an artificial dialysis device using the same.

Hereinafter, embodiments of the present invention will be further described. As the ultrasonic bubble detector and the artificial dialysis device using the ultrasonic bubble detector 1 as one component, those conventionally used can be applied, and the description will be omitted.

The ultrasonic bubble detector 1 according to the present invention introduces blood from a human body to an artificial kidney attached to an artificial dialysis apparatus, and transports the blood again to the human body by a blood pump (blood circuit: blood tube # 8). It can be suitably implemented for those that are used to monitor and detect bubbles and issue an alarm.However, since malfunctions have a large effect on the human body, the present invention relates to a method for stabilizing small This study was conducted from the viewpoint of whether bubbles can be detected.

As is well known, the principle of the bubble detector 1 is shown in FIG.
As shown in (1), an ultrasonic wave (generally using 1 to 5 MHz) transmitted from one ultrasonic vibration element 2 passes through a liquid transport tube (hereinafter, referred to as a blood tube) 8 and a liquid, and the other one. When there is a bubble in the liquid received by the ultrasonic vibrating element 2, the ultrasonic wave is reflected by the bubble to utilize a phenomenon that the intensity of the received ultrasonic wave is reduced. Therefore, in order to detect minute bubbles, it is preferable to transmit and receive the ultrasonic waves on the narrowest possible band-like surface so that the rate of decrease in the ultrasonic intensity due to the bubbles increases.

There are several methods for realizing this. (1) When a ferroelectric thin film, particularly a polymer ferroelectric thin film 4 is used as a material of the ultrasonic vibration element 2 shown in FIGS. 1, 2 and 7, electrodes are provided on both sides of the ferroelectric. Only the portion where the position overlaps and coincides becomes the vibrating portion 2-a, and the portion for transmitting and receiving the ultrasonic wave may be formed in a shape that requires the electrode 6-a. Therefore, it is easy to form a band-shaped reception surface or transmission surface.

Although it depends on the application, if the accuracy of bubble detection is required, the width of the electrode 6-a of the vibrating part is formed narrow.
Generally, the unit is 0.1 mm, but the unit is μm (10 μm).
m or more) is also possible. In addition, it is possible to easily use the ultrasonic vibration element 2 that performs transmission / reception with different widths of the electrodes 6-a of the vibrating portion.

Further, the polymer ferroelectric thin film 4 is provided with a protective film 5 having the same shape and the same area or more covering the entire band-shaped receiving surface or transmitting surface. An electrode is formed on the contacting side to form an electrode which also serves as a shield electrode on one surface of the ultrasonic vibration element. That is, it has the same potential as the shield electrode 6-b. In particular, when copper is used as a material of the shielding electrode, the shielding effect of electromagnetic waves is high.

The thickness of the ferroelectric material 4 or the total thickness of the ferroelectric material 4 and the protective film 5 is determined by the material of the ferroelectric material 4 and the protective film 5 to be used. It is preferable that the receiving surface or the transmitting surface be the abdomen of the sound wave as a quarter, because it has the effect of increasing the intensity of the transmission and reception of the ultrasonic wave.

As the material of the protective film 5, it is preferable to use a high-strength plastic thin film such as polyester or polyimide. This is because the density of the blood tube 8 used is almost the same as that of the blood tube and the acoustic impedance, which is an index of the degree of sound penetration, is small, and the sound attenuation is reduced.

Further, in order to reduce the leakage of sound from the ultrasonic vibration element 2, the thickness of the electrode on the surface opposite to the surface for receiving or transmitting the ultrasonic wave is determined by the material of the electrode to be used. About one-half wavelength at
Is preferable.

In practice, a commercially available material having a thickness close to the calculated value is used for the protective film 5 and the electrode. This slightly changes the sensitivity, but does not cause a malfunction.

(2) On the other hand, when an inorganic ferroelectric material is used as the material of the ultrasonic vibrating elements 11 and 13 shown in FIGS. 3 to 6 (the inorganic ferroelectric material is used as the material of the flat ultrasonic vibrating element 2). When a body is used, an inorganic ferroelectric material of substantially the same type is connected to the electrode 6-a of the vibrating part, and the polymer ferroelectric thin film 4 is not used at this time. In some cases, the ferroelectric and the polymer ferroelectric thin film 4 are used together, but will not be described in detail here).
Generally, since the density of the blood tube 8 and the blood is significantly different from each other and the acoustic impedance is large, the acoustic impedance is reduced by adding plastic ultrasonic transmitters 9 and 14. However, when the transmission intensity is high or the reception sensitivity is high, the ultrasonic transmitters 9 and 14 may not use plastic or may not add the ultrasonic transmitters 9 and 14.

As shown in FIG. 11 (A), if the blood tube 8 is merely held in the same manner as in the prior art, the blood tube 8 may be strongly held to detect microbubbles. Due to the bending, the air bubbles may stay at the bent portion or the air bubbles may pass through the holding portion for a long time.

This is because, as shown in FIGS. 1 and 2, the ultrasonic vibrating element 2 in which the vibrating portion 2-a is formed on a flat plate using a ferroelectric thin film, particularly a polymer ferroelectric thin film 4, is used. No problem.

Accordingly, in order to prevent such a problem in the ultrasonic bubble detector 1 using the conventional ultrasonic transducers 11 and 13 as shown in FIGS. As shown in FIG. 4, (2-1) regardless of whether the material of the ultrasonic transducer is organic or inorganic, when using the ultrasonic transducer 11 having the cylindrical ultrasonic transmitter 9, When the blood tube 8 is used, an ultrasonic transmission body 9 as a vibrating portion in a band shape orthogonal to the longitudinal direction of the blood tube 8 is passed through a mask 12 having a substantially band-shaped gap so as to contact the blood tube 8. The length of the vibrating part is longer than the inner width (inner diameter) T of the blood tube 8 in the sandwiched state, and the portion other than the vibrating part of the ultrasonic vibrating element 11 in the detector 1 The blood tube 8 is held on the same surface (height) H as the contact surface of the vibrating portion of the holding portion with the blood tube 8.

(2-2) As shown in FIGS. 5 and 6, regardless of whether the material of the ultrasonic vibrator is organic or inorganic, a convex type as shown in Japanese Utility Model Publication No. 5-29717 is used. When the ultrasonic vibrating element 13 having the ultrasonic transmitting body 14 as the vibrating portion is used, similarly to the above, when the blood tube 8 is held, The ultrasonic transmitter 14 comes into contact with the blood tube 8 in a belt shape, and the portion other than the vibrating portion of the ultrasonic vibrating element 13 in the detector 1 is connected to the blood tube 8 of the vibrating portion of the holding portion of the ultrasonic vibrating element 13. The mask 12 having a gap so that the blood tube 8 is clamped on the same plane (height) H as the contact surface of the mask 12
Through.

As described above, the ultrasonic vibration elements 2, 11, and
The shape of the thirteenth element has been described. Next, the structure and signal processing of elements related to malfunction will be described.

Generally, an ultrasonic bubble detector is 1 MHz.
The above-described ultrasonic waves are used, and the leakage of the electromagnetic waves is a problem, and at the same time, the penetration of the electromagnetic waves from the outside is also a problem, which is one of the causes of malfunction.

The present inventors have examined the degree of leakage of electromagnetic waves with respect to a commercially available ultrasonic bubble detector. %. This means that even if the sensitivity is improved by making the ultrasonic vibrating element band-shaped, there is always as much as 20% of the signal, the rate of signal attenuation due to bubble detection is reduced, and the signal may fluctuate due to the penetration of electromagnetic waves from the outside. Indicates that malfunctions are likely to occur.

On the other hand, in the present invention, by adding the coil 7 for resonance and using the coil 7 using ferrite in the core or the filling around the core, the blood tube 8 has no liquid. Received signal at 0.3% or less when liquid was full (almost no frequency component of ultrasonic wave, only frequency component of commercial power supply on probe for measurement) .

That is, even in the conventional ultrasonic vibration element 11 shown in FIG. 9 to which the conventional cylindrical ultrasonic wave transmitter 9 is added, a signal having a high SN ratio is obtained if there is no leakage of electromagnetic waves and no invasion of electromagnetic waves from the outside. Can be obtained. In other words, this indicates that the detection of microbubbles equivalent to that of the present invention is possible depending on the method of signal processing. However, since the sensitivity is low, it is considered that the signal processing is simplified by using the configuration like the ultrasonic vibration element 11 of the present invention and improving the sensitivity.

Even when the coil 7 is not used, the transmission and reception of electromagnetic noise can be greatly reduced by using a filler containing ferrite around the ultrasonic vibration element 11.

In order to obtain the required sensitivity for transmitting and receiving ultrasonic waves, the Q value of the coil 7 at the frequency to be used is 1 to 1
00 is appropriate, and the conductance at the resonance frequency of the ultrasonic vibration element is suitably 0.1 milliSiemens or more. Of course, it goes without saying that it can be used outside of this range.

Another cause of malfunction is temperature dependence of the resonance frequency of the ultrasonic vibration element, the amplification factor of the amplifier circuit 20 of the signal processing circuit shown in FIG. 8, that is, the temperature of the sensitivity of the ultrasonic detector. If the sensitivity greatly changes depending on the temperature, the operation of the voltage comparator for generating the bubble detection pulse becomes unstable and malfunctions.
This is considered to be the reason why bubble detection at high temperature becomes unstable.

On the other hand, there are two signal holding circuits 22 and 23 which detect the output of the amplifying circuit 20 and hold the signal for an arbitrary time and have different signal holding times. The output of the signal holding circuit 122 having a short holding time is compared with an arbitrary ratio of the output, and the output of the signal holding circuit 122 having a short holding time is provided. The pulse generation level (threshold) is always kept at a constant ratio even if the sensitivity of the ultrasonic detector has temperature dependency
Is determined, so that stable bubble detection can be performed.

In this method, stable bubble detection can be performed even when the sensitivity is lowered due to other factors of sensitivity change, for example, the positional relationship between the two ultrasonic transducers is shifted from each other.

The signal holding circuits 22 and 23 of the present invention are primary delay circuits and are employed as envelope circuits in which the detection circuit 21 is combined. Apart from the presence or absence of the detection circuit 21, a moving average circuit (including a first-order delay circuit) and a hold circuit can also be used as the signal holding circuit. In addition, a digital system or an analog system may be adopted as needed.

In addition, when the resonance frequency is determined by measuring and combining the capacitance of the ultrasonic vibrating element and the inductance of the coil near the temperature at which the ultrasonic vibrating element is used, fluctuation of the resonance frequency is small and stable. A measurement can be made.

As is well known, it is known that a pulse or a rectangular wave has the same electromagnetic wave intensity as that of a fundamental frequency even at a higher harmonic. In recent years, high-frequency (30 to 300 MH), which is attracting attention as a cause of malfunction of medical equipment,
The electromagnetic wave z) is generated and easily leaks to the outside. In the present invention, as a countermeasure, a sine wave oscillating circuit 26 is provided which generates a substantially sine wave signal of an electric signal applied to the transmitting-side ultrasonic vibrating element so that high-frequency electromagnetic waves are not leaked to the outside as much as possible.

Next, regarding the material and shape of the blood tube 8, the material is such that the acoustic impedance having a density close to the material of the surface of the ultrasonic vibrating element in contact with the blood tube 8, such as a silicon tube, is small. Is preferred. In addition, regarding the shape, in order not to distort the blood tube 8 or to bite the tube,
As shown in FIG. 7, the guide 15 of the blood tube of the bubble detector is formed in a concave shape, and more preferably, a guide having a gap (width) S at a central portion in the longitudinal direction for holding the liquid transport tube, Further, in order to stably hold the blood tube 8, there is provided a mechanism that moves in parallel with the ultrasonic vibration elements 2, 12, and 13 to hold the blood tube.

Although the signal processing circuit has been described as a part of the bubble detector, the oscillation circuit of the signal processing circuit, the amplifying circuit 20 and the voltage comparator are built in the bubble detector to supply power. Even in a configuration that outputs a bubble detection pulse, stable bubble detection as described above can be performed.

[0077]

Embodiment An embodiment will be described with reference to FIGS. 1 to 7 and FIG.

First, referring to FIG.
It will be explained first. A band-shaped (2 mm × 9.6 mm) electrode 6 is formed on one surface of the substrate 3 formed of glass epoxy resin or the like.
a and a shielding electrode 6 serving as a reference potential (0 V) electrode
-B.

Although copper foil is used for these electrodes, the thickness of the electrode is two times the wavelength of the ultrasonic wave (frequency: 5 MHz) used in the copper foil to reduce the leakage of sound from the ultrasonic vibration element. It was reduced to 1/200 μm.

Then, a polymer ferroelectric thin film 4 of about 40 μm was attached to these electrode surfaces using an epoxy adhesive.
Further, an approximately 80 μm “Kapton” (registered trademark of DuPont) (polyimide) film having a protective film (a copper thin film (evaporation film, etc.)) 5 formed on one surface from above is used as the copper ferroelectric thin film 4. The total thickness of the polymer ferroelectric thin film 4 and the protective film 5 is about 120 μm, which is about １ ／ wavelength of the ultrasonic wave in the material used. Equivalent to.

As the polymer ferroelectric, a copolymer of vinylidene fluoride and ethylene trifluoride was used, but the type is not particularly limited. Similarly, no particular type of epoxy adhesive is selected,
Other methods such as direct application of a polymer ferroelectric on the substrate 3 or direct evaporation of copper may be sufficient as long as the electrode and the polymer ferroelectric thin film 4 and the protective film 5 are sufficiently adhered.

Next, an electrode 6-a corresponding to the vibrating portion 2-a of one surface is connected to the other surface of the substrate 3 by a through-hole, and a shield electrode 6-b is also connected by a through-hole. Yes. Here, the electrode and the core or the coil 7 using ferrite in the filling around the core were connected by soldering to form the ultrasonic vibration element 2.

The independent Q value of the coil 7 was 47 at the resonance frequency, and the conductance of the ultrasonic vibration element 2 configured as described above was 3 milliSiemens. This value is measured at the operating temperature of the bubble detector of 30 ° C.

Next, the signal processing circuit will be described with reference to FIG. In this embodiment, an amplifying circuit 20 having a constant gain below the basic operating frequency range is employed. Then, the amplified signal is detected, and the signal holding time is changed to 2
The reference voltage of the voltage comparator is set with reference to an arbitrary ratio of the output of the signal holding circuit 2 having a long signal holding time to the signal holding circuits 22 and 23 having a long signal holding time. A voltage comparison for comparing the output of the signal holding circuit 1 and binarizing the output is provided. When the output of one short 22 signal holding circuit 1 becomes equal to or less than an arbitrary fixed ratio value of the other long 23 signal holding circuit 2, a detection pulse is generated. This method is characterized in that a stable voltage comparison can be made with respect to a change in sensitivity due to temperature dependence of the ultrasonic vibration element and the signal processing circuit.

The signal holding circuits 22 and 23 used here are primary delay circuits, and are combined with the detection circuit 21 to form an envelope circuit. Since there are various other circuit configurations, an appropriate circuit may be adopted in view of the overall configuration.

However, a general voltage comparison circuit 24 may be used when the influence of the change in sensitivity due to temperature change is small or the influence of the sensitivity is examined depending on the use environment.

Although the resonance coil 7 is not shown in FIGS. 3 to 6 of the other embodiments, the coil 7 is connected to the ultrasonic vibration element 10 to the amplification circuit 20 of the signal processing circuit as much as possible. Connect near the vibrating element 10.

As an embodiment relating to the ultrasonic vibrating elements 11 and 13 which are not in the form of a flat plate, the ultrasonic vibrating element 1
The portions other than the oscillating portions 1 and 13 are substantially flush with the contact surface of the portion as the oscillating portion with the blood tube 8 (height).
The blood tube 8 is pinched with H, and the blood tube 8 is not strongly pinched or bent to detect microbubbles as in the related art so that the bubbles do not stay in the bent portion. It is a device to do.

As one of them, when the blood tube 8 is clamped by the ultrasonic bubble detector 1 using the conventional ultrasonic vibration element 11 to which the ultrasonic transmitter 9 shown in FIGS. 3 and 4 is added. A mask 12 having a gap so that the ultrasonic transmitter 9 of the ultrasonic vibration element 11 comes into contact with the blood tube 8 in a band shape orthogonal to the longitudinal direction of the tube 8 is provided. The length of the element 11 is longer than the inner width (inner diameter) T of the blood tube 8 in a sandwiched state, and serves as a vibrating portion of the ultrasonic vibration element 11 that contacts the blood tube 8 in the ultrasonic bubble detector 1. The other part of the vibrating part held the blood tube 8 on substantially the same plane (height) H as the contact surface with the blood tube 8.

Second, when the ultrasonic vibrating element 13 having the ultrasonic transmitting body 14 as the convex vibrating portion shown in FIGS. 5 and 6 is used, the blood tube 8 is held in the same manner as described above. In addition, the ultrasonic transmission body 14 as a band-shaped vibrating section orthogonal to the longitudinal direction of the blood tube 8
And the portion other than the ultrasonic vibration element 13 in the detector 1 is the blood tube 8 of the holding portion of the ultrasonic vibration element 13.
The blood tube 8 was sandwiched by a mask 12 having a gap on the substantially same surface (height) H as the contact surface with the blood tube.

The materials and shapes for improving the detection sensitivity of the ultrasonic bubble detector 1 are related to the ultrasonic vibration elements 2, 11,
The material of the blood tube (liquid transport tube) 8 that comes into contact with 13 was a polymer resin (silicon, polytetrafluoroethylene, polyethylene, or the like) having a density almost the same as that of the liquid (blood).

Then, the transmitted ultrasonic wave is transmitted to the blood tube 8.
As shown in FIG. 7, a guide 15 of a blood tube 8 is formed in a concave shape in the ultrasonic bubble detector 1 so that the ultrasonic wave passes through the entire liquid therein, and a central portion in a longitudinal direction for holding the blood tube 8 therebetween. Using a guide having a gap (width) S: 9 mm
In order to eliminate the distortion and biting of the tube and to stably hold the liquid transport tube, one of the ultrasonic vibration elements 2 moves with respect to the other, or both of them move in parallel with each other. And a mechanism for holding the liquid transport pipe. A similar mechanism is provided for the ultrasonic elements 11 and 13. Conventional ultrasonic bubble detectors as shown in FIG. 9 including the comparative example and the ultrasonic bubble detector as shown in FIG. 10 are respectively shown in FIGS. 7, 11B and 11A. When the blood tubes 8 were clamped and compared, the following performance and functional differences became apparent.

A) The conventional ultrasonic bubble detectors shown in FIGS. 9 and 10 have no countermeasures other than the electrostatic shield, and there is no liquid between the blood tube due to the leakage of the ultrasonic wave and the reception of the electromagnetic wave from the outside. Is satisfied, the amplitude ratio of the received signal is 18: 100 when the ratio is small, and 40: 100 when the ratio is large.
That was all. On the other hand, in the present invention, 0.3: 1
00.

B) The bubble diameter which can be detected is 0.5 mm in the conventional ultrasonic bubble detector using the ultrasonic vibration element shown in FIG.
At the lower limit, including 0.5 mm, and below that, air bubbles passed through the blood tube in the ultrasonic bubble detector, but the air bubble could not be detected, or the blood tube could not be detected in the blood tube in the detector. On the other hand, in the present invention, the bubble diameter is about 0.35.
mm.

C) In an environmental test of an ultrasonic bubble detector incorporated in an artificial dialysis device, a product having high sensitivity of a conventional ultrasonic bubble detector was compared with the present invention. At 5 to 20 ° C., both the conventional ultrasonic bubble detector and the present invention detect stable bubbles. However, at 40 ° C., the conventional ultrasonic bubble detector detects or does not detect microbubbles, which is unstable. Detect now.

On the other hand, the present invention operates stably,
Even bubbles having a diameter of 5 mm or less could be detected by changing the comparison voltage of the voltage comparator.

[0097]

The ultrasonic vibrating elements 2, 11 and 13 of the ultrasonic bubble detector 1 according to the present invention have a resonance coil for determining a vibration frequency and a coil using ferrite in a core or a filling material around the core. The use of 7 eliminates the leakage of electromagnetic waves and minimizes the effect of electromagnetic waves received from outside, so there is no sensitivity reduction due to the transmission and reception of electromagnetic waves, and ultrasonic vibration on the transmitting side so that high-frequency electromagnetic waves are not leaked to the outside as much as possible. Since a sine wave oscillating circuit 26 for generating a substantially sine wave signal is provided for an electric signal to be applied to the element, generation of high frequency electromagnetic waves is reduced, and an amplified signal is detected and held for an arbitrary time. The comparison voltage of the voltage comparator is set on the basis of an arbitrary ratio of the output of the signal holding circuit 2 which is input to two signal holding circuits having different time and has a long signal holding time, and the other short is set. When the output of the signal holding circuit 122 becomes equal to or less than an arbitrary fixed ratio, the voltage comparison circuit 24 generates a detection pulse and generates a detection pulse. The detection is lost, and the ultrasonic vibration elements 2, 11, and
13 is a part other than the vibrating part.
In order to hold the blood tube 8 on the same surface (height) H as the contact surface of the holding portions 1 and 13 with the blood tube 8, a supersonic wave using the flat ultrasonic vibration element 2 or the mask 12-a is used. Ultrasonic vibrating elements 11, 13 to which sound wave transmitting bodies 9, 14 are added
And the blood tube 8 in the ultrasonic bubble detector 1
The guide 15 is formed in a concave shape, and a gap is provided at a central portion in the longitudinal direction for holding the blood tube 8, and further, in order to stably hold the blood tube 8, the ultrasonic vibrating elements 2, 11,.
13 is a blood tube 8 which has been moved in one of the movements of the other, or both of them in parallel with respect to each other, and which has arisen in the scissors-like clamping structure which has been commonly used in the past. The blood tube 8 and the vibrating parts of the sound wave vibrating elements 2, 11, and 13 are no longer in poor contact with each other. Stable bubble detection was eliminated.

According to the present invention, a stable ultrasonic bubble detector, an ultrasonic bubble detector and an artificial dialysis apparatus can be provided without malfunction of bubble detection. In addition, the cause of the malfunction becomes clear, and continuous change can be measured instead of pulse output such as bubble detection. If continuous measurement is desired in an atmosphere having a large temperature change, two signals having different signal holding times are required. This is made possible by using a signal processing circuit having a signal holding circuit, and as an ultrasonic bubble detector including the ultrasonic bubble detector, not only for medical use, but also for bubbles and liquid transport in an oil supply pipe in a spinning process. It can be used in a wide range of fields such as detection of foreign matter in liquid in a pipe and measurement of density change.

[Brief description of the drawings]

FIG. 1 is a configuration diagram (exploded explanatory view) of an ultrasonic vibration element using a polymer ferroelectric thin film, (A) is an exploded view,
(B) is a sectional view.

FIG. 2 is a configuration diagram showing an embodiment of an ultrasonic bubble detector using a polymer ferroelectric thin film.

FIG. 3 is a configuration diagram of an ultrasonic vibration element having a cylindrical ultrasonic transmission body to which a mask is added.
(B) shows an ultrasonic vibration element having a cylindrical ultrasonic transmitter, and (C) shows an assembled sectional view.

FIG. 4 is a configuration diagram showing an embodiment of an ultrasonic bubble detector using an ultrasonic vibration element having a cylindrical ultrasonic transmitter with a mask.

FIG. 5 is a configuration diagram of an ultrasonic vibration element having a conventional convex ultrasonic transmission body to which a mask is added.
(B) is an ultrasonic vibration element having a convex ultrasonic transmitter,
(C) is an assembly sectional view.

FIG. 6 is a configuration diagram showing an embodiment of an ultrasonic bubble detector using an ultrasonic vibration element having a convex ultrasonic transmitter with a mask.

FIGS. 7A and 7B are configuration diagrams showing an example of a blood tube guide of the ultrasonic bubble detector. FIG. 7A is a plan view of one of the ultrasonic bubble detectors having the guide, and FIG. 7B is a cross-sectional view.

FIG. 8 is a configuration diagram of a signal processing circuit.

9A and 9B are configuration diagrams of a conventional ultrasonic transducer having a cylindrical ultrasonic transmitter, wherein FIG. 9A is an ultrasonic transducer having a cylindrical ultrasonic transmitter having a flat tip, and FIG. Ultrasonic vibrating element in which the tip of a cylindrical ultrasonic transmitter has a spherical shape, (C)
-A is a convex ultrasonic vibrating element having a cylindrical ultrasonic transmitter having a spherical tip, and (C) -b is a concave ultrasonic vibrating element having a cylindrical ultrasonic transmitter having a spherical tip. Show.

10A and 10B are configuration diagrams of a conventional ultrasonic transducer having a convex ultrasonic transmitter, wherein FIG. 10A is a plan view, FIG. 10B is a front view, and FIG. 10C is a side view.

11A and 11B are configuration diagrams illustrating an example of conventional ultrasonic bubble detection, in which FIG. 11A is an example of use of an ultrasonic vibration element having a cylindrical ultrasonic transmitter, and FIG. An example of using an ultrasonic vibration element having an ultrasonic transmitter will be described.

[Explanation of symbols]

1: ultrasonic bubble detector 2: (flat) ultrasonic vibrating element 2-a: vibrating part of (flat) ultrasonic vibrating element 3: substrate 4: polymer ferroelectric thin film 5: protective film 6: electrode 6-a: Electrode of vibrating part 6-b: Electrode for shielding (0V) 7: Coil 8: Liquid transport tube (blood tube) 9: Cylindrical ultrasonic transmitter 10: Inorganic ultrasonic transducer 11: Cylindrical super Ultrasonic vibrating element having an ultrasonic transmitting body added 12: Mask 13: Ultrasonic vibrating element having a convex ultrasonic transmitting body 14: Convex type ultrasonic transmitting body 15: Guide 20: Amplifying circuit 21: Detection circuit 22: Signal Holding circuit 1 (short holding time) 23: Signal holding circuit 2 (long holding time) 24: Voltage comparison circuit 25: Level setter 26: Sine wave oscillation circuit T: Width (inner diameter) inside liquid transport pipe H: Super The same level as the contact surface of the sandwiching part of the acoustic transducer (high S) S: Clearance (width) of the central part in the longitudinal direction that holds the liquid transport pipe of the guide

Claims (16)

[Claims] 1. An ultrasonic bubble detector for detecting bubbles passing through a liquid transport tube such that vibrating portions of a pair of ultrasonic vibrating elements opposed to each other across a liquid transport tube through which a liquid flows is detected. The longitudinal direction of the vibrating portion is arranged in a direction intersecting the flow direction of the liquid in the liquid transport tube, and the width (inner diameter) of the inside of the liquid transport tube in a state where the length of the band-shaped vibrating portion is sandwiched. ) It is longer than T, and the portion other than the vibrating portion of the ultrasonic vibrating element in the above-mentioned detector sandwiches the liquid transport tube on substantially the same plane (height) H as the contact surface of the vibrating portion with the liquid transport tube. Ultrasonic bubble detector featuring. 2. An ultrasonic bubble detector according to claim 1, wherein said pair of ultrasonic vibrating elements receive and use an ultrasonic vibrating element using a polymer ferroelectric thin film or an inorganic ferroelectric on both transmitting sides. Or, in the ultrasonic bubble detector equipped with an ultrasonic vibrating element using a polymer ferroelectric thin film on the receiving and transmitting side, using an inorganic ferroelectric substance on either side of transmission or reception, and vice versa, The vibrating part is an ultrasonic vibrating element formed in a substantially band shape on a flat plate, or a supersonic wave-shaped tip of an ultrasonic transmitting body attached to a side used as a receiving surface or a transmitting surface of the ultrasonic vibrating element. An ultrasonic bubble detector, which is an ultrasonic vibration element. 3. An ultrasonic bubble detector according to claim 2, wherein a protective film having the same shape and the same area or more covering the entire surface of the ultrasonic vibrating element on the receiving or transmitting side is provided. Ultrasonic bubble detector. 4. An ultrasonic bubble detector according to claim 3, wherein an electrode is formed on a side of the protective film attached to the receiving or transmitting side of the ultrasonic vibrating element, the electrode being in contact with the ferroelectric substance. An ultrasonic bubble detector comprising an electrode on one surface of an element. 5. A ferroelectric substance or a ferroelectric substance of an ultrasonic vibrating element according to claim 2, wherein the ferroelectric substance is used alone or with a protective film. Ultrasonic bubble detection characterized in that the combined thickness of the protective film and the protective film is approximately one-fourth of the wavelength at the ultrasonic frequency to be used, which is determined by the material of the ferroelectric or the ferroelectric and the protective film. vessel. 6. The ultrasonic bubble detector according to claim 2, wherein an electrode thickness of a surface of the ultrasonic vibration element using a ferroelectric material, which is opposite to a surface for receiving or transmitting ultrasonic waves, is adjusted. An ultrasonic bubble detector which is determined by an electrode material and has a wavelength substantially equal to one half of a wavelength at an ultrasonic frequency to be used. 7. The ultrasonic bubble detector according to claim 1, wherein ferrite is contained in a core or a filler around the core as a resonance coil for determining a vibration frequency of the ultrasonic vibration element. An ultrasonic bubble detector characterized by being used. 8. The ultrasonic bubble detector according to claim 1, wherein the Q value of the coil at the resonance frequency of the ultrasonic vibration element using the coil is 1 to 100. Ultrasonic bubble detector. 9. The ultrasonic bubble detector according to claim 1, wherein a conductance at a resonance frequency of the ultrasonic vibration element is 0.1 milliSiemens or more. vessel. 10. An ultrasonic bubble detector for detecting air bubbles passing through a liquid transport tube at a holding portion of a pair of ultrasonic vibrating elements opposed to each other with the liquid transport tube according to claim 1 interposed therebetween. An ultrasonic bubble detector, wherein a material of a liquid transport tube is a polymer resin or rubber, and the liquid transport tube is a tube through which blood or the like flows. 11. An ultrasonic bubble detector for detecting a bubble passing through a liquid transport tube at a holding portion of a pair of ultrasonic vibrating elements opposed to each other while sandwiching the liquid transport tube according to any one of claims 1 to 10. An ultrasonic bubble, wherein a cross section of a guide of the liquid transport pipe is substantially concave, and the gap has a width (width) S at a central portion in a longitudinal direction for holding the liquid transport pipe. Detector. 12. An ultrasonic bubble detector according to claim 1, wherein one of said pair of ultrasonic vibrating elements moves relative to the other, or both are parallel to each other. An ultrasonic bubble detector comprising a mechanism for moving and moving and holding a liquid transport pipe. 13. An ultrasonic bubble detector according to claim 1, wherein the electric signal applied to the ultrasonic vibration element on the transmitting side is a substantially sinusoidal signal. Detector. 14. An ultrasonic bubble detector according to claim 1, wherein an output of an amplifier circuit of a signal processing circuit for performing signal processing obtained by the ultrasonic wave received by the ultrasonic vibration element is detected. Has two signal holding circuits with different signal holding times to hold for an arbitrary time, and compares the output of the signal holding circuit with a short holding time with reference to an arbitrary ratio of the output of the signal holding circuit with a long holding time An ultrasonic bubble detector comprising a voltage comparator for binarization. 15. A method for detecting bubbles in a tube.
An ultrasonic bubble detector comprising the ultrasonic bubble detector according to any one of the above. 16. An ultrasonic bubble detecting apparatus according to claim 1, wherein said ultrasonic bubble detecting apparatus has a blood pump for circulating blood between said artificial kidney and said artificial kidney. An artificial dialysis device comprising a vessel.