JP5149018B2 - Flow sensor - Google Patents

Description

  The present invention relates to a flow rate sensor capable of detecting a medium flow rate in a tube through which a medium such as gas or liquid flows, and in particular, a flow rate sensor that can be attached to a medical instrument (for example, an endoscope). It is about.

2. Description of the Related Art Conventionally, there is an endoscope as a means that enables in-situ observation of a disease in the body and enables examination and treatment with minimal invasiveness. For example, the following Patent Document 1 describes a method of diagnosing a respiratory disease by inserting an endoscope into a trachea.
In addition, a technique for miniaturizing and integrating a fluid machine such as a micropump and a flow sensor has been developed by using a micromachining technique in which a semiconductor fine processing technique is applied and developed. For example, Patent Document 2 below describes an example in which a small cantilever structure manufactured by a micromachining technique is applied to a flow sensor. Non-Patent Document 1 below describes a method in which a hot wire (heater) formed by photolithography is raised from the substrate surface and installed in the center of the tube in order to measure the flow rate in the tube. Patent Document 3 below describes a small diaphragm type flow sensor structure manufactured by a micromachining technique. In Patent Document 4 below, a method is described in which a heater formed on a flexible substrate is mounted on the inner wall surface of a pipe, and thereby the flow rate in the pipe is detected. Further, Patent Document 3 and Patent Document 5 below propose a method of achieving thermal insulation using a diaphragm structure.

JP 2005-514081 A JP 2002-257606 JP Three dimensional silicon triple-hot-wire anemometer based on polyimide joints, Proceeding of The Eleventh annual international conference on Micro Electro Mechanical Systems, (1998, pp. 93-98) JP 2000-275076 JP 2007-127538 A JP 62-43522 A

In the above prior art (Patent Document 1: Japanese Patent Application Laid-Open No. 2005-514081), there is a description of putting an endoscope into a trachea, thereby diagnosing a respiratory disease, but there is a description of a flow sensor to be inserted into an endoscope. Nothing at all. That is, there is no mention of a miniaturized structure of a flow sensor that can be inserted into an endoscope and a means for realizing it.
Patent Document 2 (Japanese Patent Laid-Open No. 2002-257606), Non-Patent Document 1, and Patent Document 3 (Japanese Patent Laid-Open No. 2000-275076) are conventional techniques that focus on means for measuring the flow rate flowing through industrial piping. Since these flow sensors all use micromachining technology, the size of the sensor can be reduced, and the flow rate in the pipe is measured by installing the sensor at the center of the pipe. For example, in Non-Patent Document 1, the flow rate in the tube is measured by installing a hot wire that is raised from the surface of the single crystal silicon substrate in the center of the tube. In these three conventional techniques, since the flow in the pipe is measured as point information by a sensor installed at the center of the pipe, it is difficult to measure the flow rate in the bent pipe. For this reason, the conventional method cannot be applied to flow measurement in a trachea formed by a winding path.
Patent Document 4 (Japanese Patent Application Laid-Open No. 2007-127538) describes a flow sensor having a structure in which a heater is formed on a flexible base material and the flexible base material is mounted on the inner wall of the tube so as to follow the shape of the inner wall of the tube. Unlike the above three conventional techniques, this conventional technique is characterized in that the flow rate can be measured even in a winding pipe because the flow rate is detected not by a point but by a line. However, originally, its use is aimed at industrial use like the above three conventional examples, and there is a problem of how to reduce the size of the sensor structure in order to use it by inserting it into the airway. Further, since the flexible substrate on which the heater is formed is directly mounted on the inner wall of the pipe, the thermal insulation of the heater substrate is not sufficiently taken into consideration. As a result, this conventional technique has a problem that the thermal response is not good, and it is difficult to evaluate the lung function by performing 10 to 20 reciprocal breaths per minute.
For conventional thermal sensors, as shown in Patent Document 3 (Japanese Patent Laid-Open No. 2000-275076) and Patent Document 5 (Japanese Patent Laid-Open No. 62-43522), a diaphragm structure is used for thermal insulation. The technique of being proposed is proposed. However, any conventional heat insulating diaphragm structure is a structure for a heater formed on a flat surface, and cannot be applied as it is to a flow sensor that is mounted along a wall surface having a curvature in the pipe.
To sum up the above, in the conventional method, it is difficult to reduce the size of the flow rate sensor based on bending tube measurement, and the response speed sufficient to measure respiration cannot be obtained. was there.

The present invention solves the above-described problems, and an object of the present invention is to provide a flow sensor that can be miniaturized and can obtain a sufficient response speed. It is another object of the present invention to allow the flow sensor to be mounted in, for example, an endoscope and to diagnose a respiratory disease locally by placing the endoscope in the lung.
In order to achieve the above object, in the present invention, a flexible base material on which a heater is formed is mounted on the inner wall of a tube so as to follow the shape of the inner wall of the tube through which the medium flows, and the amount of heat generated from the heater surrounding the inner wall of the tube. In the flow rate sensor that can measure the flow rate of the medium in the pipe by detecting the state in which the medium is dispersed by the medium, in order to insulate the heat transmitted from the heater to the pipe direction between the heater and the pipe, Is formed. In the above flow sensor, it is preferable to detect the flow rate in the pipe by detecting the resistance change of the heater. In this configuration, since the flexible base material is mounted on the inner wall of the pipe so as to follow the inner wall shape of the pipe, the flow rate can be measured even with a twisted pipe in order to detect the flow rate with a line instead of a point. Since a thermal insulation cavity is formed between the two, the heat response is determined by the heat capacity of the heater itself, and as a result, a high-speed response of 100 milliseconds or less can be realized.
In another configuration, a flexible base material on which one or more heaters and one or more detectors are formed is mounted on the inner wall of the tube so as to follow the shape of the inner wall of the tube through which the medium flows, and surrounds the inner wall of the tube. In the flow rate sensor that can measure the medium flow rate in the pipe by detecting the state in which the amount of heat generated from the heater is dispersed by the medium, the pipe direction from the heater to the pipe direction is between the heater and the pipe. A cavity is formed in order to insulate the heat transmitted to. In the above flow rate sensor, the heater is energized and heated, and the flow rate in the tube is measured by detecting a change in the resistance value of the detector, or the difference signal of the two or more heaters provided is detected in the tube. It is good to measure the flow of In this configuration as well, the flow rate is detected with a line and the heater portion is thermally insulated, so that the flow rate in the bent pipe can be measured with a high-speed response of 100 milliseconds or less. . In this configuration, since one or more heaters or one or more detectors are formed, the direction of flow in the pipe is detected by detecting the difference signal of the heater or the difference signal of one or more installed detectors. Can also be detected.

In the flow sensor described above, it is preferable that the tube surrounding the flow sensor is a heat shrinkable tube. Moreover, the whole sensor is reduced in size by using a heat-shrinkable tube. The outline of the flow sensor mounting method using the heat shrinkable tube is as follows. First, a metal thin film heater is formed on a film substrate to produce a flow sensor body. Then, a film-like flow sensor is put in the heat shrinkable tube. In this case, the size of the heat-shrinkable tube is large, for example, an inner diameter of 3 mm and an outer diameter of 3.5 mm, and a film sensor can be easily inserted. In addition, a cavity forming slit for heat insulation of the heater is formed in a part of the heat shrinkable tube. Next, heat is applied to the heat shrinkable tube to shrink the tube to a desired size. At this time, as the tube contracts, the film sensor that has been inserted into the tube is automatically mounted along the inner wall of the tube. Again, for the purpose of forming a cavity in the outer periphery of the sensor heater, a heat-shrinkable tube is prepared, and the heat-shrinkable flow sensor tube formed in the previous step is inserted therein. Thereafter, heat is applied again to shrink the outer heat-shrinkable tube and close contact with the inner tube to form a flow sensor having a cavity. By using the process as described above, the size of the catheter-type flow sensor can be reduced to 2 mm or less in outer diameter while achieving thermal insulation of the sensor. Unlike the conventional example, this process is a self-assembling method in which the sensor film automatically follows the inner wall of the tube when it heat shrinks. There is also a feature that it is possible to cope with.
In the above flow sensor, the flow sensor is attached to a distal end of a bronchoscope catheter, the catheter is inserted into a lung, and local lung function measurement is performed. Also, when measuring local lung function, it is preferable to fix the catheter in the bronchus with a balloon attached to the distal end of the catheter. In this configuration, since the flow sensor having the above-described small diameter (outer diameter of 2 mm or less) is used, it can be easily attached to the distal end portion of the bronchoscope catheter. In addition, local lung function measurement can be realized.
In the flow sensor described above, the flow sensor is attached to a stent structure, the stent-integrated flow sensor is inserted into a pipe, and then the flow sensor is fixed in the pipe with the stent. To do. The stent-integrated flow sensor is attached to a distal end portion of a catheter for bronchoscope, the catheter is inserted into a lung, and a respiratory disease is diagnosed by a local lung function test. In this configuration, since the flow sensor having the above-described small diameter (outer diameter of 2 mm or less) is used, it can be easily attached to the distal end portion of the bronchoscope catheter. In addition, local lung function measurement can be realized.
In the flow sensor described above, a bridge circuit is configured by the heater and three known resistors. The bridge circuit is in an equilibrium state when there is no flow, and when the flow occurs, the bridge is unbalanced, the difference signal is input to the operational amplifier circuit, and the output signal corresponding to the input signal is the heater sensor. As a result, the temperature of the heater is always kept constant. In this method, the flow rate is converted by detecting the output waveform of the operational amplifier circuit generated by the flow. The biggest feature of this system is that the temperature of the heater is always kept constant by the feedback mechanism, and as a result, the followability of the sensor to the flow is greatly improved.

Hereinafter, the best mode for carrying out the present invention will be described in more detail.
The usage concept of the endoscope flow sensor of the present invention is shown in FIG. In order to detect a diseased site in the lung 1 and evaluate its local function, first, an endoscope 10 having a size of about 1 centimeter is inserted through the mouth. Thereafter, after inserting the endoscope to the vicinity of the affected part of the bronchus 2, the catheter 11 including the flow sensor 30 smaller than the outer diameter of the endoscope is extended from the distal end portion of the endoscope 10, and inserted into the bronchi at the distal end. Assessment of pulmonary function at specific locations. It should be noted that the size of the endoscope 10 is preferably determined according to the type of treatment instrument to be inserted into the endoscope.
The structure of an endoscope flow sensor 30 embodying the present invention is shown in FIG.
A flow sensor 30 for evaluating pulmonary function in a local field is incorporated in the catheter 11, and the catheter 11 is arranged in one lumen 12 provided in the endoscope 10. The endoscope is provided with an endoscope optical system 14 such as a lens and a light, and the catheter 11 can be inserted while observing the bronchus to be measured. In the figure, a structure in which the catheter 11 extends from the lumen from the endoscope 10 is shown. The catheter 11 includes a flow sensor 30, a heat insulation structure cavity 33, and a flow path 35. The flow sensor 30 includes a heater 32 formed on the film substrate 31 and wiring 34 for supplying electric power to the heater. Further, the film substrate 31 is arranged along the inner wall of the catheter 11, thereby enabling the flow rate measurement in the bent tube and reducing the disturbance of the flow in the tube due to the installation of the sensor to the limit. In addition, in the catheter 11, a cavity 33 is formed on the outer periphery of the heater in order to insulate the heater 32 formed on the film substrate 31. In order to form the cavity 33, the catheter structure has a double structure made of a resin material. Thereby, the heat insulation with respect to a heater board | substrate is achieved and the pulmonary function evaluation which breathes 10-20 times per minute is attained. The catheter 11 is also provided with a flow path 35 for allowing the flow in the tube to flow in and out. By using the flow rate sensor structure as described above, it is possible to measure the flow rate in the bronchi that is winding. The remaining problem is how to realize the catheter structure with a diameter of 2 mm or less. This will be described below with reference to FIG.
FIG. 2 shows the case where only the heater 32 is arranged in the pipe. However, depending on the application, a plurality of heater wires may be provided, or resistance wires for detection may be provided on both sides of the heater. This is characterized in that it is possible to improve the responsiveness as well as to detect the direction. Although the figure shows a case where a cylindrical tube is used, this sensor utilizes the flexibility of the flexible substrate 31 even in the case of a tube having a shape other than this (for example, an ellipse and a square cross section). It can be deformed according to the wall structure and adapted to the inner wall. Therefore, it is desirable to change the sensor form installed on the inner wall of the pipe according to the shape of the pipe to be measured.

FIG. 3 shows a technique for downsizing the endoscope catheter flow sensor 30 of the present invention to an outer diameter of 2 mm or less. In a conventional example (Japanese Patent Laid-Open No. 2007-127538), a flow sensor having a structure in which a heater is formed on a flexible base material and the flexible base material is attached so as to follow the shape of the inner wall of the pipe is described. Further, the inner diameter of the pipe is 3 millimeters and the outer diameter is as large as about 6 millimeters as judged from the figure, and it is presumed that the film is manually inserted along the inside of the pipe. Therefore, with the manual method as it is, it is difficult to miniaturize the flow sensor itself. As a result, the flow sensor is inserted into the lumen 12 provided in the endoscope 10 as well as into the lung bronchus. It is impossible. In order to solve this problem, the present invention has devised a method using a heat-shrinkable resin tube as means for mounting and miniaturizing a film-like sensor. Details are described below.
In FIG. 3 (a), first, a metal thin film heater is formed on a polyimide film substrate having a thickness of several tens of microns using photolithography to produce a flow sensor. Thereafter, the film-like flow rate sensor 30 is placed in the heat shrinkable tube 13. In this case, the size of the heat-shrinkable tube is large, for example, an inner diameter of 3 mm and an outer diameter of 3.5 mm, and the film-like flow sensor 30 can be easily inserted. A cross-sectional view when the film-like flow sensor 30 is inserted into the pipe is shown on the right side of the figure. As described above, in this method, it is not necessary to place the film-like flow sensor 30 along the inner wall of the pipe at the time of insertion, and it is sufficient to simply insert a linear film into the pipe. In addition, a cavity forming slit 36 is formed in a part of the heat shrinkable tube 13 for heat insulation of the heater. Note that the size and material of the heat-shrinkable tube and the size of the flow sensor are desirably determined as appropriate according to the size of use of the catheter.
In FIG. 3 (b), heat is applied to the heat shrinkable tube 13 in which the film-like flow sensor 30 is inserted, and the tube is shrunk to a desired size. At this time, as the tube contracts, the film-like flow sensor 30 inserted in the tube is automatically mounted along the inner wall of the tube.
In FIG. 3 (c), a heat-shrinkable tube is prepared again for the purpose of forming the cavity 33 in the outer periphery of the sensor heater, and the heat-shrinkable flow sensor tube formed in the previous step is inserted therein. To do. Unlike the previous tube, this tube is not provided with a slit 36 for thermal insulation.
In FIG. 3 (d), heat is then applied again to shrink the outer heat-shrinkable tube, and the inner tube is brought into close contact to form the flow sensor 30 having the cavity 33.
By using the process as described above, the size of the catheter-type flow sensor can be reduced to 2 mm or less in outer diameter while achieving thermal insulation of the sensor. Unlike the conventional example, this process is a self-assembling method in which the sensor film automatically follows the inner wall of the tube when it heat shrinks. There is also a feature that it is possible to cope with.
A method for producing the film substrate 31 of the present invention is shown in FIG. The flexible sensor structure is fabricated using semiconductor microfabrication technology. Details are described below.

4A, first, a polyimide film having a thickness of several tens of microns is prepared as a flexible film substrate 31, and a photosensitive photoresist 41 for forming a heater metal film pattern is spin-coated thereon. The thickness and material of the film substrate 31 are preferably determined according to the operating environment used as the flow sensor, but generally the thickness is several tens to several hundreds of microns and is chemically stable. A polyimide film excellent in thermal insulation and electrical insulation is preferable.
In FIG. 4 (b), the electrode pattern of the heater (detector depending on the case) is formed using photolithography.
In FIG. 4 (c), a metal film 42 to be a heater (a detector according to circumstances) is formed on the photoresist pattern. In this method, either chromium or titanium is used for the base, and chemically stable platinum or gold is used for the heater and detector thereon. In addition, as for the material of the metal film 42, it is desirable to determine a material, a shape, thickness, etc. according to a use purpose similarly to board | substrate selection.
In FIG. 4D, a metal heater (detector depending on the case) is formed on the polyimide film by removing the photoresist 41 formed in the step (a).
As shown in FIG. 4 (e), finally, the flexible film substrate 31 is peeled off from the support substrate to complete the film flow sensor.
As described above, in this method, the heater and the resistance wire (not shown) are patterned using the lift-off method. However, after this, a metal thin film is first formed on the surface of the film substrate 31 and then patterned by photolithography. You can go. It is desirable to select one according to the patterning accuracy of the metal thin film and the metal thin film etching method.
A photograph of the flexible flow sensor of the present invention is shown in FIG. FIG. 5 (a) shows an enlarged photograph of the heater portion, and FIG. 5 (b) shows the entire flexible flow sensor. The figure shows a case where a heater 32 is formed of chromium (50 nanometers) and gold (250 nanometers) on a polyimide film having a thickness of 25 microns. The size of the heater 32 is about 0.45 mm × 2.04 mm. Further, the figure shows a case where a flexible printed circuit board 45 is used as an electrical signal wiring connection portion of the flexible flow sensor 30. In addition, by providing detection elements on both sides of the heater 32, a flow rate sensor can be obtained in which the direction of flow can be understood. It is desirable that the number of heater structures and detection resistance wirings provided on the flexible substrate is appropriately determined according to the usage environment of the sensor. In the case of measuring only the flow rate, the flow rate can be detected by the heater alone. However, if it is necessary to detect the flow direction with high-speed response, install two or more heaters, or use it for flow rate detection on both sides of the heater. It is desirable to provide resistance wiring.
FIG. 6 shows how the flexible flow sensor is mounted using the heat shrinkable tube of the present invention. Details are shown below.
FIG. 6A shows a state immediately after the polyimide flow sensor 30 having a thickness of 25 microns shown above is inserted into a heat shrinkable tube having an outer diameter of 2.8 mm and an inner diameter of 2.4 mm.
FIG. 6B shows a state after the tube is contracted by heating. FIG. 6 (c) shows an enlarged photograph of the heater portion. By shrinking the tube, the outer diameter is reduced to 1.7 millimeters, and the flow sensor 30 is automatically mounted along the inner wall surface of the tube. It is desirable to select not only the heater shape but also the heat shrinkable tube material according to the purpose of use.

FIG. 7 shows the resistance change characteristics of the flow sensor of the present invention. In this flow sensor, the flow rate is calculated based on the resistance change of the heater or detector. Therefore, as an example, the relationship between the heater temperature and the resistance change is shown in the figure. As shown in the figure, the resistance value of the heater itself changes according to the heater temperature, and by using this, an unknown flow rate is calculated. In addition, the value of the vertical axis | shaft of a figure is the value normalized by the value at the temperature of 30 degreeC. In addition, it is desirable to set the electric power applied to a heater according to a use range.
An example of the detection circuit of the flow sensor of the present invention is shown in FIG. In this flow sensor, a response characteristic of 100 milliseconds or less is required in order to evaluate the lung function of breathing 10 to 20 times per minute. As means for solving this problem, the thermal insulation structure shown in FIG. 3 is structurally constructed, and a feedback circuit as shown in FIG. 8 is devised for the electrical signal processing circuit. Hereinafter, an electrical signal processing circuit will be described. As shown in FIG. 8, the sensor heater and three known resistors constitute a bridge circuit. The bridge circuit is in an equilibrium state when there is no flow, but when a flow occurs, the balance of the bridge is lost, the difference signal is input to the operational amplifier circuit, and the output signal corresponding to the input signal is sent to the heater sensor. Reflected. Therefore, the flow rate can be converted by detecting the output waveform of the operational amplifier circuit generated by the flow. Further, the temperature of the heater sensor is always kept constant by the feedback mechanism, and as a result, the followability of the sensor to the flow is greatly improved.
An example of the relationship between the input power and the detected flow rate of the flow sensor of the present invention is shown in FIG. The figure shows the input power (output of the operational amplifier) to the sensor bridge circuit with respect to the flow rate when the heater element itself is used as a flow rate sensor. As shown in the figure, the input power changes according to the flow rate. By using this as a calibration curve, the sensor can calculate an unknown flow rate.
FIG. 10 shows the response characteristics of the flow sensor of the present invention. In this flexible flow rate sensor, the responsiveness of the sensor is improved by using the thermal insulation cavity 33 structure described in FIG. 3 and the feedback circuit described in FIG. By introducing the above two techniques, as shown in FIG. 10, a response waveform of 90% or more is obtained in 100 milliseconds or less.
The structure of another flow sensor of the present invention is shown in FIG. FIGS. 2 to 10 show the case where only a single heater 32 is arranged in the pipe on the film substrate 31. However, depending on the application, a plurality of heater wires are provided, or detection is provided on both sides of the heater. It is also possible to provide a resistance wire, thereby detecting the direction of flow and improving responsiveness. FIG. 11 (a) shows the former example, and FIG. 11 (b) shows the latter embodiment. The parts other than the heater 32 and the detector 37 are as described in FIG.

FIG. 12 shows a detection circuit example of another flow sensor of the present invention. As described above with reference to FIG. 8, this flow sensor requires a response characteristic of 100 milliseconds or less in order to evaluate the lung function of breathing 10 to 20 times per minute. Therefore, even in the flow rate sensor of another embodiment shown in FIG. 11, the response of the sensor is improved by using an electrical feedback circuit. An example of a detection circuit for the flow sensor having the double heater structure shown in FIG. 11A is shown in FIG. In the flow sensor of this double heater structure, the difference of the sensor signal in two heater parts is detected. As a result, this sensor structure has the following two features. One is the feature that the direction of the flow can be discriminated, and the other is that the signal components other than the signal component due to the flow can be canceled, and as a result, high-speed and high-sensitivity measurement for the flow can be achieved.
An example of the relationship between the input power and the detected flow rate of another flow sensor of the present invention is shown in FIG. The figure shows the input power to the sensor bridge circuit with respect to the flow rate when a double heater is used as the flow rate sensor. As shown in the figure, the input power changes according to the flow rate. By using this as a calibration curve, the sensor can calculate an unknown flow rate.
FIG. 14 shows the response characteristics of another flow sensor of the present invention. In the double heater flow rate sensor, as described with reference to FIG. 12, the responsiveness of the sensor is improved by using the thermal insulation cavity 33 structure, the feedback circuit, and the differential detection by the double heater structure. By introducing the above three technologies, the sensor can respond in 100 milliseconds or less as shown in FIG. The figure shows the response waveform of the sensor when a pulsed flow is generated.
FIG. 15 shows the response characteristics of another flow sensor of the present invention. As described with reference to FIG. 11, the double heater flow rate sensor can detect the flow direction by using the difference detection by the double heater. FIG. 15 shows the output waveform of the flow sensor when the flow in the pipe is moved back and forth. As shown in the figure, the magnitude relationship between the heater sensor output arranged on the upstream side and the heater sensor output arranged on the downstream side is reversed depending on before and after the flow. Can be determined.
FIG. 16 shows a method of fixing the endoscope flow rate sensor of the present invention in the bronchus.
By using the balloon 50 provided at the distal end portion of the catheter 11, the catheter 11 with a flow sensor is fixed in the bronchus. First, the catheter 11 with a flow sensor is extended from the distal end of the endoscope 10 near the bronchus to be measured (FIG. 16 (a)). Next, the balloon provided at the distal end of the catheter is inflated, thereby fixing the flow rate sensor at the target site and measuring the flow rate (FIG. 16 (b)). After the measurement is completed, the balloon is contracted to the original size (FIG. 16 (a)), and the catheter 11 is collected in the endoscope.
FIG. 17 shows another method for fixing the endoscope flow sensor of the present invention in the bronchus.

The fixing method shown in FIG. 16 is a simple method, but on the other hand, since a part of the bronchus is closed with a balloon, there is a problem that pressure loss before and after the balloon becomes large. FIG. 17 shows a method of fixing the catheter with flow sensor 11 in the bronchus 2 using a stent 52 instead of a balloon. As in the case of FIG. 16 described above, when the catheter with flow sensor 11 extended from the lumen of the endoscope 10 arrives at the bronchus to be measured (FIG. 17 (a)), the stent structure to which the flow sensor is attached becomes. The bulge is fixed in the vicinity of the target region, and the flow rate is measured (FIG. 17B). After completion of the measurement, the stent is folded back to the original size (FIG. 17 (a)), and the catheter 11 is collected in the endoscope. Since this structure uses a mesh-like stent for fixing the flow sensor, the pressure loss of the fluid in the fixing portion can be reduced to the limit. In addition, when using a stent, the stent is fixed in the bronchus using the spread of the mesh structure, so the heater sensor is not a ring that goes around the inside of the tube, but only on a part of the tube. It becomes a structure to do.
Note that the flow sensor fixing method shown in FIGS. 16 and 17 has a feature that it can be appropriately fixed in pipes having different inner diameters. Therefore, the fixing method is not limited to the bronchus and is generally used for industrial use. It can also be applied to piping. Moreover, since the flow sensor described in FIGS. 3 to 15 can be applied to a small-diameter pipe having an inner diameter of 2 mm or less, it can be widely applied not only to an endoscope but also to general uses such as a small analyzer and a small fuel cell. .
The matters described in FIG. 1 to FIG. 17 are examples of the present flow sensor, and it is desirable to change the specific specifications according to the purpose of use. In addition, the target fluid of the present sensor is mainly gas, and any type can be applied as long as it is gas. In addition, it is applicable also in the case of a liquid.
As described above, in this embodiment, by using the heat-shrinkable tube as the mounting means for the flexible flow sensor, the outer diameter of the flow sensor can be manufactured with 2 mm or less, and as a result, it can be stored in the lumen treatment instrument for bronchoscope. Local lung function evaluation became possible. Moreover, in order to improve the responsiveness of the flexible flow sensor, a cavity thermal insulation structure using a resin material was proposed. Specifically, by making the mounting tube into a double structure, a cavity structure was produced simultaneously with the sensor mounting. Thereby, the lung function evaluation which breathes 10 to 20 times per minute became possible.

  The flow sensor of the present invention is capable of detecting the flow of a medium such as a gas or liquid in a tube. In particular, when the flow sensor is attached to an endoscope of a medical instrument, the endoscope is used as a lung. By putting in, respiratory disease can be diagnosed by measuring lung function locally including the peripheral airway.

It is a figure which shows the usage concept of the flow sensor for endoscopes of this invention. It is a figure which shows the structure of the flow sensor for endoscopes which embodied this invention. It is a figure which shows the method of miniaturizing the catheter type flow sensor for endoscopes of this invention to outer diameter 2mm or less. It is a figure which shows the preparation methods of the film substrate of this invention. It is a figure which shows the photograph of the flexible flow sensor of this invention. It is a figure which shows the mode of mounting of the flexible flow sensor by the heat contraction tube of this invention. It is a figure which shows the resistance change characteristic of the flow sensor of this invention. It is a figure which shows the example of a detection circuit of the flow sensor of this invention. It is a figure which shows the example of a relationship between the input electric power of the flow sensor of this invention, and a detected flow volume. It is a figure which shows the response characteristic of the flow sensor of this invention. It is a figure which shows the structure of the other flow sensor of this invention. It is a figure which shows the example of a detection circuit of the other flow sensor of this invention. It is a figure which shows the example of a relationship between the input electric power and the detected flow volume of the other flow sensor of this invention. It is a figure which shows the response characteristic of the other flow sensor of this invention. It is a figure which shows the response characteristic of the other flow sensor of this invention. It is a figure which shows the method to fix the flow sensor for endoscopes of this invention in a bronchus. It is a figure which shows the other method of fixing the flow sensor for endoscopes of this invention within a bronchus.

Explanation of symbols

1 lung, 2 bronchi, 10 endoscope, 11 catheter, 12 lumen for treatment instrument, 13 tube, 14 endoscope optical system, 30 flow sensor, 31 film substrate, 32 heater, 33 cavity for thermal insulation, 34 wiring , 35 flow path, 36 cavity forming slit, 37 detector, 40 flexible substrate, 41 photoresist, 42 metal film, 45 flexible printed circuit board, 50 balloon, 51 flow by respiration, 52 stent, 53 stent flow sensor

Claims (4)

By mounting the flexible base material on which the heater is formed on the inner wall of the tube so as to follow the shape of the inner wall of the tube through which the medium flows, and detecting the state in which the amount of heat generated from the heater surrounding the inner wall of the tube is dispersed by the medium In the flow sensor that can measure the medium flow rate in the pipe,
Between the heater and the pipe, in order to insulate the heat transmitted from the heater in the pipe direction, a cavity for thermal insulation is formed ,
A flow sensor characterized in that a tube surrounding the flow rate sensor is formed of a heat shrinkable tube, and heat is applied to the heat shrinkable tube, whereby the tube is contracted and downsized . A flexible base material on which one or more heaters and one or more heat detectors are formed is mounted on the inner wall of the tube along the shape of the inner wall of the tube through which the medium flows, and the amount of heat generated from the heater surrounding the inner wall of the tube In the flow rate sensor that can measure the medium flow rate in the pipe by detecting the state in which the medium is dispersed by the medium,
Between the heater and the pipe, in order to insulate the heat transmitted from the heater in the pipe direction, a cavity for thermal insulation is formed ,
A flow sensor characterized in that a tube surrounding the flow rate sensor is formed of a heat shrinkable tube, and heat is applied to the heat shrinkable tube, whereby the tube is contracted and downsized . Flow sensor, characterized in that mounted for bronchoscope tip section in the flow rate sensor according to any one of claims 1 or 2. The flow sensor according to claim 3 , wherein a balloon is attached to the distal end portion of the catheter for bronchoscope.