JP6856995B2 - An ultrasonic sensor head and an ultrasonic detector including the ultrasonic sensor head - Google Patents

Description

The present invention relates to an ultrasonic sensor head used for detecting air bubbles in a liquid flowing through a conduit and an ultrasonic detector including the ultrasonic sensor head.

Conventionally, in medical facilities, a bubble detector that detects bubbles has been used so as not to accidentally inject air (bubbles) into the patient's body when performing infusion, blood transfusion, or the like. Ultrasonic waves have been used as one of the detection means for such bubble detectors so that they can be applied to non-transparent chemicals and blood.

For example, as an ultrasonic detector for detecting microbubbles, in a pair of ultrasonic sensor heads arranged to face each other across a conduit through which a liquid flows, a strip-shaped sensor head transmission / reception surface having a narrow width in the liquid flow direction. (See Patent Document 1). With this configuration, the area through which ultrasonic waves are transmitted becomes smaller and the intensity of ultrasonic waves due to microbubbles decreases, compared to the conventional configuration in which the transmitting and receiving surfaces of the sensor head are formed to have the same width in the vertical and horizontal directions. Therefore, the detection sensitivity of minute bubbles can be improved.

Jitsufuku No. 5-29717

As described above, when the width of the transmission / reception surface of the sensor head is narrowed in the liquid flow direction to increase the sensitivity of bubble detection, the transmitted ultrasonic waves are weak and the reception voltage is small because the transmission / reception surface is small. Therefore, the voltage difference for determining the presence or absence of air bubbles is also small. Therefore, the received voltage changes or becomes unstable due to changes in the material and type of the conduit, the contact state between the conduit and the sensor head, and the ambient environment such as temperature and humidity, and erroneous detection is likely to occur.
In order to prevent such false detections from occurring, it is generally necessary for an ultrasonic detector to have a complicated circuit design in hardware and to devise an algorithm in software.

Therefore, an object of the present invention is to provide an ultrasonic sensor head having high bubble detection sensitivity and less false detection, and an ultrasonic detector including the ultrasonic sensor head.

The present invention is a pair of ultrasonic sensor heads that are arranged to face each other with a conduit through which a liquid flows and can transmit and receive ultrasonic waves, and one of the pair of ultrasonic sensor heads faces the conduit. The other of the pair of ultrasonic sensor heads is provided with a vibration surface, and the other of the pair of ultrasonic sensor heads is provided with a second vibration surface facing the conduit, and the width of the second vibration surface is the width of the first vibration surface in the flow direction of the liquid. A pair of ultrasonic sensors that are smaller than the width of the vibrating surface and one of the first vibrating surface and the second vibrating surface is used as an ultrasonic transmitting surface and the other is used as an ultrasonic receiving surface. Regarding the head.

Further, it is preferable that the first vibrating surface is used as an ultrasonic wave transmitting surface and the second vibrating surface is used as an ultrasonic wave receiving surface.

Further, the pair of ultrasonic sensor heads are arranged so as to be in contact with the conduit on the first vibration surface and the second vibration surface, and the first vibration surface is perpendicular to the flow direction of the liquid. It is preferable that the cross-sectional shape cut by the surface is formed into a concave curve or a convex curve.

Further, the conduit has flexibility, and the second vibration surface has a convex curve or a straight cross-sectional shape cut by a surface parallel to the ultrasonic wave transmission / reception direction and the liquid flow direction. It is preferably formed.

The present invention also relates to an ultrasonic detector provided with any of the above-mentioned pair of ultrasonic sensor heads and detecting bubbles in a liquid flowing through the duct.

According to the present invention, it is possible to provide an ultrasonic sensor head having high bubble detection sensitivity and less false detection, and an ultrasonic detector including the ultrasonic sensor head.

It is a block diagram which shows the embodiment of the ultrasonic sensor head of this invention, and is the figure which shows the pair of ultrasonic sensor heads which are arranged facing each other across a conduit. It is a YY cross-sectional view of FIG. 1A. It is a block diagram which shows the embodiment of the ultrasonic sensor head of this invention, and is the figure which looked at the 1st sensor head from the 1st vibration surface side. It is a block diagram which shows the embodiment of the ultrasonic sensor head of this invention, and is the figure which looked at the 2nd sensor head from the 2nd vibration surface side. It is a figure which shows the 1st Embodiment of the ultrasonic sensor head of this invention, and is the figure which shows the pair of ultrasonic sensor heads 1A which are arranged facing each other across a conduit. FIG. 2 is a sectional view taken along line YY of FIG. 2A. It is a figure which shows the 1st Embodiment of the ultrasonic sensor head of this invention, and is the figure which looked at the 1st sensor head from the 1st vibration surface side. It is a figure which shows the 1st Embodiment of the ultrasonic sensor head of this invention, and is the figure which looked at the 2nd sensor head from the 2nd vibration surface side. It is a figure which shows the 2nd Embodiment of the ultrasonic sensor head of this invention, and is the figure which shows the pair of ultrasonic sensor heads 1B which are arranged facing each other across a conduit. FIG. 3A is a sectional view taken along line YY of FIG. 3A. It is a figure which shows the 2nd Embodiment of the ultrasonic sensor head of this invention, and is the figure which looked at the 1st sensor head from the 1st vibration surface side. It is a figure which shows the 2nd Embodiment of the ultrasonic sensor head of this invention, and is the figure which looked at the 2nd sensor head from the 2nd vibration surface side. It is a figure explaining the projection surface of the microbubbles when the directivity of the transmission wave from the 2nd vibration surface 211B (transmission surface) is high in the 2nd Embodiment of this invention. It is a figure explaining the projection surface of the microbubbles when the directivity of the transmitted wave from the 2nd vibration surface 211B (transmission surface) is low in the 2nd Embodiment of this invention. It is a figure which shows the modification of the ultrasonic sensor head of this invention, and is the figure which shows the pair of ultrasonic sensor heads 1C which are arranged facing each other across a conduit. 5A is a cross-sectional view taken along the line YY of FIG. 5A.

Hereinafter, embodiments of the pair of ultrasonic sensor heads of the present invention will be described with reference to FIGS. 1A to 1D.
The pair of ultrasonic sensor heads 1 includes a first sensor head 10 and a second sensor head 20, and are arranged so as to face each other with the conduit 30 interposed therebetween.

The first sensor head 10 includes an ultrasonic transmitter 110 on which a first vibration surface 111 is formed, and an ultrasonic vibrator 120 that converts an electric signal and vibration.
The second sensor head 20 includes an ultrasonic transmitter 210 on which a second vibration surface 211 is formed, and an ultrasonic vibrator 220 that converts an electric signal and vibration.

The ultrasonic transmitters 110 and 210 transmit ultrasonic waves between the ultrasonic transducers (120, 220) and the vibrating surfaces (111, 211). The ultrasonic transmitters 110 and 210 are formed of a resin such as acrylic, hard polyvinyl chloride, or modified polyphenylene ether. In this embodiment, the ultrasonic transmitters 110 and 210 are made of acrylic resin.
Further, the ultrasonic transmitters 110 and 210 not only transmit ultrasonic waves, but also have a vibrating surface having a concave curved surface shape or a convex curved surface shape, for example, as described in the first embodiment and the second embodiment described later. By doing so, it is possible to function as an acoustic lens that focuses or diffuses ultrasonic waves.

The first vibrating surface 111 and the second vibrating surface 211 are formed on the ultrasonic transmitters 110 and 210 so as to face the side surfaces of the conduit 30, respectively, and come into contact with the conduit 30 to transmit ultrasonic waves. The first vibrating surface 111 is formed in a circular shape as shown in FIG. 1C, and the second vibrating surface 211 is formed in a rectangular shape as shown in FIG. 1D.

As shown in FIGS. 1C and 1D, the width w2 of the second vibrating surface 211 is formed smaller than the width w1 of the first vibrating surface 111 in the liquid flow direction (y direction). Specifically, the ratio of the width w2 to the width w1 is preferably about 0.1 to 0.7. When the ratio is larger than 0.1, the area of the second vibrating surface 211 becomes large, the intensity of ultrasonic wave transmission / reception becomes large, and the reception voltage is easily stabilized, which is preferable. Further, when the ratio is smaller than 0.7, the width w2 becomes small and the sensitivity for detecting minute bubbles can be obtained, which is preferable.
Further, when the first sensor head 10 and the second sensor head 20 are arranged so as to face each other, one of the transmitting surface and the receiving surface is wide in the liquid flow direction (y direction), so that the position is precise. Transmission and reception can be reliably performed without matching.

As shown in FIGS. 1B to 1D, the widths h1 and the second of the first vibrating surface 111 are taken as an example for the z direction perpendicular to the liquid flow direction (y direction) and the ultrasonic wave transmission direction (x direction). The width h2 of the vibrating surface 211 of the above is configured to have the same size.
When detecting air bubbles in a liquid having a low viscosity with respect to the width h1 and the width h2, at least in a state where the flexible conduit 30 is sandwiched between the first vibrating surface 111 and the second vibrating surface 211. It is desirable that the width is equivalent to the inner diameter of the conduit 30 in the z direction. With this configuration, the ultrasonic waves pass through most of the inside of the conduit 30 in the z direction, so that the detection omission of bubbles can be reduced.
In addition, air bubbles in the highly viscous liquid easily pass through the central portion of the conduit 30. Therefore, when detecting bubbles in a highly viscous liquid, the widths h1 and h2 may be at least about half the inner diameter of the conduit 30 so that ultrasonic waves can pass through the central portion of the conduit 30. .. However, practically, it is preferable that the width h1 and the width h2 have the same width as the inner diameter of the conduit 30 in the z direction, giving priority to safety again.

Disc-shaped piezoelectric elements are used as the ultrasonic vibrators 120 and 220, and electrodes (not shown) are attached to both sides thereof, and the input electric signal is converted into mechanical vibration and transmitted. The generated mechanical vibration can be converted into an electric signal and output. The ultrasonic vibrators 120 and 220 are embedded and arranged inside the ultrasonic transmitters 110 and 210, respectively. As the material of the piezoelectric element, piezoelectric ceramics such as lead zirconate titanate, piezoelectric thin films such as zinc oxide, and piezoelectric polymer films such as vinylidene fluoride can be applied. In this embodiment, lead zirconate titanate was used as the material of the piezoelectric element, and silver and platinum were used as the electrodes.

The conduit 30 is formed of a flexible tube such as soft vinyl chloride (PVC) or silicon (Si). For example, as a medical tube, the outer diameter is 5.5 to 6.5 mm and the inner diameter is 3. Those having a diameter of 5 to 4.5 mm are used.

The first sensor head 10 and the second sensor head 20 constituting the pair of ultrasonic sensor heads 1 described above can be used as a transmission head and a reception head of the ultrasonic detector, respectively.
Next, a configuration in which the first sensor head is used as the transmitting head and the second sensor head is used as the receiving head will be described in the first embodiment, and the second sensor head is used as the transmitting head and the first sensor head is used. Will be described in the second embodiment.

<First Embodiment>
The first embodiment of the present invention will be described with reference to FIG. The same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.
FIG. 2A shows a pair of ultrasonic sensor heads 1A arranged to face each other with the conduit in between, and FIG. 2B is a YY cross-sectional view of FIG. 2A.

The pair of ultrasonic sensor heads 1A includes a first sensor head 10A as a transmitting head and a second sensor head 20A as a receiving head, and is a tube (outer diameter 5.5 mm) as a conduit 30. , Inner diameter 3.5 mm) are placed opposite each other.

The first sensor head 10A includes an ultrasonic transmitter 110A on which a first vibration surface 111A serving as a transmission surface is formed, and an ultrasonic vibrator 120 that converts an electric signal and vibration.
The second sensor head 20A includes an ultrasonic transmitter 210A on which a second vibration surface 211A serving as a receiving surface is formed, and an ultrasonic vibrator 220 that converts an electric signal and vibration.
The ultrasonic transmitters 110A and 210A are configured in the same manner as the ultrasonic transmitters 110 and 210, except that the shapes of the vibration surfaces are different from each other.

As shown in FIG. 2B, the first vibration surface 111A is formed on the ultrasonic transmitter 110A in a concave curved surface shape, and the projection surface viewed from the x direction is a circle with a diameter of 6.9 mm (= h1A = w1A). .. More specifically, the first vibration surface 111A is formed in a concave curved shape so that the cross-sectional shape cut by the surface perpendicular to the liquid flow direction (y direction) is along the side surface of the conduit 30. With this configuration, the adhesion between the side surface of the conduit 30 and the first vibrating surface 111A is improved, so that ultrasonic waves can be efficiently transmitted to the liquid in the conduit 30.
Further, since the contact area between the side surface of the conduit 30 and the first vibrating surface 111A can be increased, ultrasonic waves can be efficiently transmitted to the liquid in the conduit 30 and the directivity of the ultrasonic waves is improved. Further, the lens effect on the first vibrating surface 111A formed in a concave curved surface makes it easier for ultrasonic waves to be focused. Therefore, the transmission intensity of ultrasonic waves can be improved.

As shown in FIGS. 2A and 2B, the second vibration surface 211A is formed on the ultrasonic transmitter 210A in a convex curved surface shape, and the projection surface viewed from the −x direction has a width w2A = 1.4 mm and a width h2A. = 6.9 mm rectangular shape. More specifically, as shown in FIG. 2A, the second vibration surface 211A is a cross section cut along a plane (xy plane) parallel to the ultrasonic transmission / reception direction (x direction) and the liquid flow direction (y direction). The shape is formed in a convex curve with respect to the side surface of the conduit 30 having flexibility. With such a configuration, the adhesion between the side surface of the conduit 30 and the second vibrating surface 211A is improved, so that ultrasonic waves transmitted through the liquid can be efficiently transmitted. Therefore, the reception strength can be improved.

Further, since the width w2A of the second vibration surface 211A (reception surface) is small in the liquid flow direction (y direction), the proportion of the microbubbles on the projection surface on the reception surface increases. Therefore, the ultrasonic waves that pass through the liquid are reflected by the fine bubbles and the ultrasonic waves that reach the receiving surface are attenuated at a large rate, and the fine bubbles can be detected with high sensitivity.

According to the pair of ultrasonic sensor heads 1A according to the first embodiment, the following effects are achieved.

(1) With respect to the liquid flow direction (y direction), the width w2A of the second vibrating surface 211A (receiving surface) is smaller than the width w1A of the first vibrating surface 111A (transmitting surface). With this configuration, when the first sensor head 10A (transmission head) and the second sensor head 20A (reception head) are arranged to face each other, the transmission surface is arranged in the liquid flow direction (y direction). Therefore, it is possible to transmit and receive waves so that the transmitted wave does not deviate from the receiving surface without precisely aligning the transmitting surface and the receiving surface. Therefore, the intensity of transmitting and receiving ultrasonic waves can be increased, and the receiving voltage from the receiving head becomes stable when the pair of ultrasonic sensor heads 1A is applied to the ultrasonic detector.

(2) Regarding the liquid flow direction (y direction) Since the width w2A of the second vibration surface 211A (reception surface) is small, the proportion of the microbubbles on the projection surface on the reception surface is large. Therefore, since the ultrasonic waves that pass through the liquid are reflected by the minute bubbles and the ultrasonic waves that reach the receiving surface are attenuated at a large rate, the fine bubbles can be detected with high sensitivity.

(3) The first vibration surface 111A (transmission surface) is formed in a concave curved shape so that the cross-sectional shape cut by a surface perpendicular to the liquid flow direction (y direction) is along the side surface of the conduit 30. With this configuration, the adhesion between the side surface of the conduit 30 and the transmission surface can be improved, and the contact area between the two can be increased, so that ultrasonic waves can be efficiently transmitted to the liquid in the conduit 30. Moreover, since the transmitting surface is large, the directivity of ultrasonic waves is improved. Further, since the transmitting surface is formed in a concave curved surface shape, the ultrasonic waves are focused by the lens effect, and the directivity is further improved. Therefore, the transmission intensity of ultrasonic waves can be increased, and the output voltage in the ultrasonic detector becomes stable.

(4) The conduit 30 has flexibility, and the second vibration surface 211A (reception surface) is a surface (xy) parallel to the ultrasonic wave transmission / reception direction (x direction) and the liquid flow direction (y direction). The cross-sectional shape cut by (planar) is formed into a convex curve. With such a configuration, the adhesion between the side surface of the conduit 30 and the receiving surface is improved, so that ultrasonic waves transmitted through the liquid can be efficiently transmitted. Therefore, the reception intensity can be increased and the output voltage in the ultrasonic detector becomes stable.
Further, since the width w2A of the receiving surface in the liquid flow direction (y direction) is small, the proportion of the microbubbles on the projection surface on the receiving surface increases. Therefore, the ultrasonic waves that pass through the liquid are reflected by the fine bubbles and the ultrasonic waves that reach the receiving surface are attenuated at a large rate, and the fine bubbles can be detected with high sensitivity.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIGS. 3 and 4. The same components as those in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof will be omitted.
FIG. 3A shows a pair of ultrasonic sensor heads 1B arranged to face each other with the conduit in between, and FIG. 3B is a YY cross-sectional view of FIG. 3A.

The pair of ultrasonic sensor heads 1B includes a second sensor head 20B (20A) as a transmitting head and a first sensor head 10B (10A) as a receiving head, and is a tube as a conduit 30. (Outer diameter 5.5 mm, inner diameter 3.5 mm) are arranged so as to face each other.

In the second embodiment, the first sensor head 10A used as the transmission head in the first embodiment is used as the receiving head (first sensor head 10B), and the second sensor head 10A used as the receiving head in the first embodiment. It differs from the first embodiment in that the sensor head 20A is used as the transmission head (second sensor head 20B). Since the shape and the like of each vibrating surface are the same as those in the first embodiment, the description thereof will be omitted.

As shown in FIGS. 3A and 3B, the second vibration surface 211B (211A) is formed on the ultrasonic transmitter 210B (210A) in a convex curved surface shape. More specifically, as shown in FIG. 3A, the second vibration surface 211B (211A) is a plane (xy plane) parallel to the ultrasonic transmission / reception direction (x direction) and the liquid flow direction (y direction). The cut cross-sectional shape is formed in a convex curve with respect to the side surface of the flexible conduit 30. With this configuration, the adhesion between the side surface of the conduit 30 and the second vibrating surface 211B (211A) is improved, so that ultrasonic waves can be efficiently transmitted to the liquid in the conduit 30. Therefore, the transmission strength can be increased.

The first vibrating surface 111B (111A) is formed on the ultrasonic transmitter 110B in a concave curved surface shape as shown in FIG. 3B. More specifically, the first vibrating surface 111B (111A) is formed in a concave curved shape so that the cross-sectional shape cut by the surface perpendicular to the liquid flow direction (y direction) is along the side surface of the conduit 30. With such a configuration, the adhesion between the side surface of the conduit 30 and the first vibrating surface 111B (111A) is improved, so that the ultrasonic waves transmitted through the liquid in the conduit 30 can be efficiently transmitted. Therefore, the reception strength can be increased.

In the second embodiment, a mechanism for detecting microbubbles with high sensitivity will be described with reference to FIG. FIG. 4A is a diagram illustrating a projection surface of microbubbles when the directivity of the transmitted wave from the second vibration surface 211B (transmission surface) is high, and FIG. 4B is a diagram showing a second vibration surface 211B (transmission surface). It is a figure explaining the projection plane of the microbubbles when the directivity of the transmitted wave from) is low.

As shown in FIG. 4A, when the ultrasonic wave transmitted from the transmission side is of high directivity, in a portion of the receiving surface (hatched portion P _A), to receive transmission waves. In this case, the projection surface of the microbubbles in the entire receiving surface, the proportion is considered to be negligible, with respect to the hatched portions P _A which receives the transmission wave at the receiving side, the ratio of the projection surface of the microbubbles occupied , It can be said that it is large enough to be detected. Therefore, the ultrasonic waves transmitted through the liquid is reflected by microbubbles, the ultrasonic wave reaches the hatched portion P _A which receives the transmission wave of the reception surface is the ratio of attenuation is large, it can detect microbubbles with high sensitivity.

When the ultrasonic wave transmitted from the transmitting surface has low directivity, for example, when _{the directivity of the transmitted wave is lowered due to the small width w2 B} of the transmitting surface, or when the transmitting surface has a convex curved surface shape. Since it is formed in, it is conceivable that the ultrasonic wave may be easily diffused due to the lens effect.
As shown in FIG. 4B, when the ultrasonic wave transmitted from the transmitting side is low in directivity, in most receiving surface (hatched portion P _B), receives the transmission wave. Receiving surface, since wider width for the liquid in the flow direction (y-direction) than the transmission surface, ultrasonic waves transmitted through the liquid is received by the receiving surface of which the hatched portion P _B be spread along the y-direction It is possible. Further, when microbubbles are present, the microbubbles are enlarged and projected in the y direction with the diffusion of ultrasonic waves on the receiving surface. Therefore, the ultrasonic waves transmitted through the liquid is reflected by microbubbles, since ultrasonic waves spread in the y-direction to reach the hatched portion P _B which receives the transmission wave of the reception surface proportion to attenuation increases, high microbubbles It can be detected by sensitivity.

According to the pair of ultrasonic sensor heads 1B according to the second embodiment, the following effects are obtained.

(5) With respect to the liquid flow direction (y direction), the width w1B of the first vibrating surface 111B (reception surface) is smaller than the width w2B of the second vibrating surface 211B (transmission surface). With this configuration, when the second sensor head 20B (transmission head) and the first sensor head 10B (reception head) are arranged to face each other, the reception surface is arranged in the liquid flow direction (y direction). Therefore, it is possible to transmit and receive waves so that the transmitted wave does not deviate from the receiving surface without precisely aligning the transmitting surface and the receiving surface. Therefore, the intensity of ultrasonic wave transmission / reception can be increased, and the reception voltage from the reception head becomes stable when the pair of ultrasonic sensor heads 1B are applied to the ultrasonic wave detector.

(6) The first vibration surface 111B (reception surface) is formed in a concave curved shape so that the cross-sectional shape cut by a surface perpendicular to the liquid flow direction (y direction) is along the side surface of the conduit 30. With such a configuration, the adhesion between the side surface of the conduit 30 and the transmitting surface is improved, so that the ultrasonic waves transmitted through the liquid in the conduit 30 can be efficiently transmitted. Therefore, the reception intensity of ultrasonic waves can be increased, and the output voltage in the ultrasonic detector becomes stable.

(7) The conduit 30 has flexibility, and the second vibration surface 211B (transmission surface) is a surface (xy) parallel to the ultrasonic transmission / reception direction (x direction) and the liquid flow direction (y direction). The cross-sectional shape cut by (planar) is formed into a convex curve. With this configuration, the adhesion between the side surface of the conduit 30 and the receiving surface is improved, so that ultrasonic waves can be efficiently transmitted to the liquid in the conduit 30. Therefore, the transmission intensity can be increased and the output voltage in the bubble detector becomes stable.

(8) With respect to the liquid flow direction (y direction), the width w1B of the first vibrating surface 111B (receiving surface) is smaller than the width w2B of the second vibrating surface 211 (transmitting surface). With this configuration, when the directivity of the ultrasonic waves transmitted from the transmitting surface is high, when the ultrasonic waves passing through the liquid are reflected by minute bubbles, a part of the receiving surface that receives the transmitted waves (diagonal line). since ultrasonic waves reaching the portion P _a) the rate of attenuation is large, it can detect microbubbles with high sensitivity.
Further, when the directivity of the ultrasonic waves is low, the ultrasonic waves transmitted through the liquid is reflected by microbubbles and diffused in the y-direction to reach the most receiving transmission waves of the receiving surface (hatched portion P _B) Since the rate at which ultrasonic waves are attenuated increases, minute bubbles can be detected with high sensitivity.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to such examples.
A bubble detection experiment was performed using the pair of ultrasonic sensor heads described in the first and second embodiments described above and the ultrasonic sensor heads corresponding to the configurations of the prior art. The bubble detection experiment was performed using a hemodialysis machine (not shown).

[Example 1]
The hemodialysis apparatus includes a tube having flexibility as a conduit 30 and an ultrasonic detector having an ultrasonic sensor head 1A described in the first embodiment. A flexible vinyl chloride tube having an outer diameter of 5.5 mm and an inner diameter of 3.5 mm was prepared. As a substitute for blood or a drug solution, water at about 36 ° C. heated to a temperature similar to that of body fluid was flowed into a tube at a flow rate of 250 mL / min.
A pair of ultrasonic sensor heads 1A were arranged and attached so as to sandwich the tube. With water flowing through the tube, use a microsyringe to inject 0.3 μL of microbubbles (bubble diameter of about 0.83 mm) in a single shot, and check the bubble detection rate and voltage changes with a hemodialysis machine. A bubble detection experiment was conducted. This was repeated 30 times to evaluate the bubble detection rate and the voltage stability.

[Example 2]
Using the pair of ultrasonic sensor heads 1B described in the second embodiment as the ultrasonic sensor heads, a bubble detection experiment was performed in the same manner as in Example 1.

[Comparative Example 1]
As the ultrasonic sensor head, a bubble detection experiment was conducted in the same manner as in Example 1 using a pair of ultrasonic sensor heads composed of the first sensor head 10A described in the first embodiment.

[Comparative Example 2]
As the ultrasonic sensor head, a bubble detection experiment was conducted in the same manner as in Example 1 using a pair of ultrasonic sensor heads composed of the second sensor head 20A described in the first embodiment.
The experimental results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

As shown in Table 1, the bubble detection rate was significantly improved in Examples 1 and 2 as compared with Comparative Example 1. Since the bubble detection experiment in this example was performed using water having a low viscosity, the bubble detection rate was 93% and 87%, but in the liquid or blood used for the infusion solution having a viscosity higher than that of water. Since microbubbles easily pass through the central part of the tube, the detection rate is estimated to be 100%.
Further, as compared with Comparative Example 2, in Examples 1 and 2, the change in the received voltage was stable at ± 0.1 V, so that the ultrasonic detector provided with the pair of ultrasonic sensor heads of the present invention was erroneous. The occurrence of detection can be suppressed. Therefore, it is not necessary to perform complicated circuit design in hardware and devise of algorithms in software, which are necessary to prevent false detection, and the configuration of the ultrasonic detector can be simplified.

Although the preferred embodiment of the pair of ultrasonic sensor heads 1 and the ultrasonic detector of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be changed as appropriate.
For example, although the first vibrating surface 111 in the embodiment is shown in a circular shape as an example, it may be in an elliptical shape or a rectangular shape.

Further, in the first embodiment and the second embodiment, the first vibration surface is formed on the ultrasonic wave transmitter in a concave curved surface shape, but the present invention is not limited to this. That is, as shown in FIGS. 5A and 5B, the first vibration surface 111C may be formed on the ultrasonic transmitter 110C in a convex curved surface shape.
Further, in the first embodiment, the second vibration surface is formed on the ultrasonic transmitter in a convex curved surface shape, but the present invention is not limited to this. That is, as shown in FIGS. 5A and 5B, the second vibration surface 211C may be formed on the ultrasonic transmitter 210C in a planar shape (straight line).

Further, in the first and second embodiments, the structure of the contact type in which the ultrasonic sensor head contacts the conduit on the vibration surface and transmits the ultrasonic wave is shown, but the present invention also applies to the non-contact type ultrasonic sensor head. The concept of is applicable.

Further, in the first and second embodiments, a tube having flexibility as a conduit is shown as an example, but the present invention is not limited to this. As the conduit, the concept of the present invention can be applied not only to medical and industrial resin tubes but also to metal tubes, pipes and the like.

Further, as an example to which the ultrasonic detector provided with the ultrasonic sensor head of the present invention can be applied, a hemodialysis apparatus is shown, but the present invention is not limited to this. It can be applied to medical devices connected to blood circuits and infusion circuits where the presence of bubbles is a problem, and it can be widely applied to fields other than the medical field where it is necessary to detect bubbles.

1 Pair of ultrasonic sensor heads 10 First sensor head 20 Second sensor head 30 Conduit (tube)
110, 210 Ultrasonic transmitter 111 First vibrating surface 120, 220 Ultrasonic oscillator 211 Second vibrating surface

Claims (5)

A pair of ultrasonic sensor heads that are arranged facing each other across a conduit through which a liquid flows and can transmit and receive ultrasonic waves.
One of the pair of ultrasonic sensor heads comprises a first vibrating surface facing the conduit.
The other of the pair of ultrasonic sensor heads comprises a second vibrating surface facing the conduit.
The first vibration surface has a circular shape or an elliptical shape when viewed from the direction of transmitting and receiving ultrasonic waves.
The second vibration surface has a rectangular shape when viewed from the direction of transmitting and receiving ultrasonic waves.
With respect to the flow direction of the liquid, the width of the second vibrating surface is smaller than the width of the first vibrating surface.
A pair of ultrasonic sensor heads in which one of the first vibrating surface and the second vibrating surface is used as an ultrasonic transmitting surface and the other is used as an ultrasonic receiving surface. The pair of ultrasonic sensor heads according to claim 1, wherein the first vibrating surface is used as an ultrasonic wave transmitting surface, and the second vibrating surface is used as an ultrasonic wave receiving surface. The pair of ultrasonic sensor heads are arranged so as to be in contact with the conduit on the first vibrating surface and the second vibrating surface.
The pair of ultrasonic sensor heads according to claim 1 or 2, wherein the first vibration surface is formed into a concave curve or a convex curve in a cross-sectional shape cut by a surface perpendicular to the flow direction of the liquid. The conduit is flexible and
The pair of ultrasonic waves according to claim 3, wherein the second vibration surface has a convex curve or a linear cross-sectional shape cut by a surface parallel to the transmission / reception direction of the ultrasonic waves and the flow direction of the liquid. The sensor head. The pair of ultrasonic sensor heads according to any one of claims 1 to 4 is provided.
An ultrasonic detector that detects air bubbles in a liquid flowing through the duct.

Images