Airflow sensor and vital capacity detector

Abstract

The invention belongs to the field of medical care equipment, and particularly relates to an airflow sensor and a vital capacity detector. The airflow sensor comprises a shell, a magnetic field generating device and a coil film. Wherein the shell is made of a non-ferromagnetic material; and an air flow channel with a square section is formed on the inner side of the shell. The shell comprises an upper substrate and a lower substrate which are parallel to each other. The magnetic field generating device is used for generating a fixed magnetic field with the magnetic field intensity changing along with the distance between the upper substrate and the lower substrate of the shell. The coil film comprises a flexible base film and a coil printed on the base film. The coil film is located between the upper substrate and the lower substrate. When gas flows through the gas flow channel in the shell, the coil film vibrates up and down, and then induction signals with the mapping relation with the gas flow intensity are generated at the two ends of the coil. The problems that a sensor part of an existing vital capacity detector cannot be self-powered, and the detection precision is prone to being affected by factors such as environment humidity are solved.

Description

Technical Field

[0001] The invention belongs to the field of medical care equipment, and in particular relates to an airflow sensor and a vital capacity detector. Background Art

[0002] With the rapid development of technology, medical devices are evolving towards smaller and more portable devices, and the demand for seamless integration with wearable devices is growing. In this context, it is particularly important to develop a lung function assessment device that is portable, economical, low-power and highly stable.

[0003] Most of the spirometers currently used in daily life require additional energy-driven devices, which not only affects the portability of the device and limits the use time of the device, but also brings problems such as energy consumption and environmental pollution. In addition, traditional spirometers are easily affected by environmental temperature and humidity, which affects the accuracy of the measurement. Summary of the invention

[0004] In order to solve the problems that the sensor part of the existing vital capacity detector cannot be self-powered and the detection accuracy is easily affected by factors such as environmental humidity, the present invention provides an airflow sensor and a vital capacity detector.

[0005] The technical solution provided by the present invention is:

[0006] An airflow sensor comprises a shell, a magnetic field generating device, and a coil film.

[0007] The shell is made of non-ferromagnetic material and includes an upper base plate and a lower base plate which are parallel to each other, and the inner side of the shell forms an air flow channel with a square-shaped cross section.

[0008] The magnetic field generating device is used to generate a fixed magnetic field whose magnetic field strength varies with distance between the upper substrate and the lower substrate of the shell.

[0009] The coil film includes a flexible base film and a coil printed on the base film. Two ends of the coil film are fixed on two sides of the housing, and the coil film is located between the upper substrate and the lower substrate and is parallel to the two substrates.

[0010] In the airflow sensor, when the gas flows through the airflow channel in the shell, the coil film vibrates up and down, thereby generating an induction signal at both ends of the coil that has a mapping relationship with the airflow intensity.

[0011] As a further improvement of the present invention, the magnetic field generating device comprises a strip-shaped permanent magnet fixedly connected to the inner side of the upper substrate and / or the lower substrate, wherein the magnetic pole connection direction of the permanent magnet is perpendicular to the plane where the upper substrate and the lower substrate are located.

[0012] As a further improvement of the present invention, the magnetic field generating device includes two permanent magnets arranged in mirror images; and the coil film is located between the two permanent magnets at a position corresponding to the interface of the magnetic field distribution.

[0013] As a further improvement of the present invention, the upper substrate and the lower substrate in the housing are fixedly connected by screws and nuts. The housing also includes four washers, two washers are sleeved on each screw between the upper substrate and the lower substrate; the end of the coil film is clamped between the two washers on the corresponding side; the washers are used to control the spacing between the upper substrate, the coil film and the lower substrate.

[0014] As a further improvement of the present invention, the shell and its gasket are made of resin, ceramic or glass, or non-ferromagnetic metal material.

[0015] As a further improvement of the present invention, surfaces on opposite sides of the upper substrate and / or the lower substrate are provided with grooves for embedded installation of permanent magnets.

[0016] As a further improvement of the present invention, the base film includes a carrier layer located in the inner layer and a protective layer covering the outside of the coil. The base film of the coil film is any one of polytetrafluoroethylene film, polyester film, polyimide film and other films made of flexible resin materials.

[0017] As a further improvement of the present invention, the coils are distributed in multiple layers in the base film to increase the number of turns.

[0018] The present invention also includes a vital capacity detector, which includes the aforementioned airflow sensor, a mask, and a data processing module. The mask is connected to the front end of the airflow channel in the airflow sensor. The data processing module includes a signal acquisition unit, a signal conversion unit, and a vital capacity calculation unit. The signal acquisition unit is connected to the output port of the coil film in the airflow sensor, and is used to collect the electrical signal output by the coil film; the signal conversion unit is used to convert the electrical signal into a detection signal representing the airflow intensity using a preset conversion model. The vital capacity calculation unit is used to calculate the vital capacity and peak exhalation flow of the detected user according to the change curve of the detection signal.

[0019] As a further improvement of the present invention, the vital capacity detector also includes or is connected to a display module; the display module is electrically connected to the data processing module; the display module is used to visualize the data of the vital capacity detection process.

[0020] As a further improvement of the present invention, the spirometry detector also has an external power supply or a built-in power supply; the power supply is used to supply power to the data processing module.

[0021] As a further improvement of the present invention, the mask is made of flexible silicone material.

[0022] As a further improvement of the present invention, the spirometry instrument further includes a tailpipe, which is connected to the rear end of the airflow channel in the airflow sensor; a check valve is provided in the tailpipe, which only allows the gas to flow in one direction from the mask to the tailpipe.

[0023] As a further improvement of the present invention, the method for constructing the conversion model is:

[0024] A large number of synchronous tests are carried out on the spirometer and the standard equipment under different airflow environments; then, a mapping is established between the detection signal of the spirometer and the detection result of the standard equipment by mathematical analysis or machine learning in combination with the large amount of test data obtained; finally, the obtained mathematical model or network model is used as the required conversion model.

[0025] The technical solution provided by the present invention has the following beneficial effects:

[0026] The present invention designs a new type of air flow sensor based on the principle of electromagnetic induction. In the sensor, when gas enters the channel, the flexible coil film will vibrate up and down due to the Bernoulli effect, causing the magnetic flux passing through the coil to change, thereby generating an electrical signal. The peak value and cumulative value of the air flow can be obtained by analyzing the signal.

[0027] The air flow sensor of the present invention can be applied to a vital capacity detector. Compared with existing products, the sensor is not affected by the temperature and humidity in the air, has a stable signal, is not affected by the humidity of the exhaled gas, and improves the accuracy of vital capacity sensing.

[0028] The airflow sensor provided by the present invention can generate an induction signal by self-excitation under the action of airflow, which can not only detect the airflow volume, but also does not require external energy drive. It is a new type of self-driven vital capacity sensor with higher practical value.

[0029] The air flow sensor and vital capacity detector designed by the present invention have simple structure, low cost, high reliability, strong sensitivity, and can output high induced current. This solution effectively utilizes the electricity generated by human breathing and can sense indicators such as vital capacity, which has certain application value in the field of human health management. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of an airflow sensor with two mirror-image bar magnets designed for Example 1 of the present invention.

[0031] Figure 2 Schematic diagram of an airflow sensor with a bar magnet on the upper substrate.

[0032] Figure 3 Schematic diagram of an airflow sensor with a bar magnet on the lower substrate.

[0033] Figure 4 The schematic diagram of an airflow sensor having two bar magnets arranged in the same direction.

[0034] Figure 5 The figure shows the distribution diagram of the non-uniform magnetic field generated by two bar magnets arranged in mirror image and in the same direction between the upper substrate and the lower substrate.

[0035] Figure 6 This is a schematic diagram of the structure of the coil film used in Example 1 of the present invention.

[0036] Figure 7 This is a product structure diagram of the airflow sensor provided in Example 1 of the present invention.

[0037] Figure 8 This is a product structure diagram of the spirometry instrument provided in Example 2 of the present invention (excluding the data processing module).

[0038] Fig. 9 These are the signals of the induced current and induced voltage output by the sample device in the test experiment at a wind speed of 20 m / s.

[0039] Fig.10 This is the signal diagram after the induced current signal is stretched along the time domain.

[0040] Fig.11 It is a schematic diagram of the state change of the airflow sensor of the present invention under the influence of airflow.

[0041] Fig.12 The figure shows the signal strength comparison of the airflow sensor under the same conditions when using bar magnets with different numbers and pole arrangements.

[0042] Fig.13 The airflow sensor outputs the current sensing curve and charge change curve when the user blows hard.

[0043] Fig.14 Fitting curves of charge and vital capacity measured for different test subjects.

[0044] Fig.15 Fitting curves of peak current and peak expiratory flow measured for different test subjects.

[0045] Fig.16 This is a graph showing how the output signal of the airflow sensor changes with ambient humidity at the same flow rate.

[0046] The markings in the figure are:

[0047] 1. Shell; 2. Magnetic field generating device; 3. Coil film; 11. Upper substrate; 12. Lower substrate; 13. Washer; 14. Screw; 15. Nut; 32. Coil; 100. Airflow sensor; 200. Mask; 300. Tailpipe; 311. Carrier layer; 312. Protective layer. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] Example 1

[0050] In view of the shortcomings of the sensors used in the existing spirometry detectors, this embodiment designs a new type of airflow sensor 100 based on the principle of electromagnetic induction. The device can achieve self-excitation under the drive of airflow, and then generate an induction signal output. Therefore, the airflow sensor 100 designed in this embodiment can achieve signal detection and output without external power supply, which is more energy-saving and environmentally friendly. In addition, the airflow sensor 100 designed in this embodiment can still work stably under the condition of temperature and humidity changes, thereby ensuring the reliability of the measurement results.

[0051] Specifically, Figure 1 As shown, the airflow sensor 100 provided in this embodiment includes: a housing 1 , a magnetic field generating device 2 , and a coil film 3 .

[0052] The shell 1 is made of non-ferromagnetic material; the inner side of the shell 1 forms an airflow channel with a cross section in the shape of a square; the shell 1 includes an upper substrate 11 and a lower substrate 12 parallel to each other. The magnetic field generating device 2 is installed in the shell 1, and is used to generate a fixed magnetic field between the upper substrate 11 and the lower substrate 12 of the shell 1, and the magnetic field strength varies with the distance. The coil film 3 includes a flexible base film and a coil 32 printed on the base film. The two ends of the coil film 3 are fixed on both sides of the shell 1, and the coil film 3 is located between the upper substrate 11 and the lower substrate 12, and is parallel to the two.

[0053] exist Figure 1In the airflow sensor 100 shown, on the one hand, the base film in the coil film 3 is made of a flexible material and has good elasticity and toughness; therefore, when air flows through the airflow channel of the housing 1, the coil film 3 is deformed and vibrates in the airflow channel under the influence of the Bernoulli effect. On the other hand, the coil film 3 is located in an inhomogeneous magnetic field generated by the magnetic field generating device 2. When the coil film 3 vibrates, according to the principle of electromagnetic induction, the projected area of ​​the coil 32 along the magnetic field direction remains unchanged, while the magnetic field distribution is inhomogeneous. Therefore, the magnetic flux in the coil 32 changes, and an electromotive force ε related to the airflow intensity is generated at both ends of the coil 32. Finally, the induction signal output by the coil film 3 satisfies the following formula:

[0054]

[0055] Here, N represents the number of turns of the coil 32, Φ represents the magnetic flux, and t represents time.

[0056] In addition, considering that the faster the gas flow rate in the airflow channel is, the larger the deformation of the coil film 3 and the swing away from the initial position are, and the magnetic field distribution between the upper and lower substrates 12 can be kept constant in the time domain; therefore, there is a mapping relationship between the induction signal output by the coil film 3 and the airflow intensity (flow velocity) in the airflow channel; the airflow intensity can be quantitatively detected based on the induction signal output by the coil film 3.

[0057] 1. Magnetic field generating device

[0058] The core components of the airflow sensor 100 provided in this embodiment are the magnetic field generating device 2 and the coil film 3. In practical applications, a permanent magnet can be used to generate the required inhomogeneous magnetic field with a specific spatial distribution; for example, in a typical solution, Figure 2 and Figure 3 As shown, a bar magnet can be installed on the upper substrate 11 or the lower substrate 12 in the housing 1; the direction of the magnetic pole connection line of the permanent magnet is perpendicular to the plane where the upper substrate 11 and the lower substrate 12 are located. In this state, the magnetic induction generated by the permanent magnet points from one side of the substrate to the other side and gradually diverges, which causes the magnetic induction lines on one side of the upper substrate 11 and the lower substrate 12 in the airflow channel to be denser (higher magnetic field strength), and the magnetic induction lines on the other side to be sparser (lower magnetic field strength).

[0059] In other schemes of this embodiment, bar magnets can also be installed on the upper substrate 11 and the lower substrate 12 respectively, and the direction of the magnetic pole connection line of the two permanent magnets is perpendicular to the upper substrate 11 and the lower substrate 12. When the magnetic field generating device 2 includes two permanent magnets, the two permanent magnets can also be installed in two ways: one of which is to set the two permanent magnets in mirror image, such as Figure 1As shown, the other is that the magnetic poles of the two permanent magnets are arranged in the same direction, such as Figure 4 In these two permanent magnet installation methods, Figure 5 As shown, the former generates a larger gradient of change in magnetic field intensity between the upper substrate 11 and the lower substrate 12. Therefore, in practical applications, when the coil film 3 generates vibrations of the same amplitude and frequency, the induction signal output by the former is also stronger.

[0060] The above three magnetic field generating devices 2 can be respectively recorded as a single magnet solution, a mirror image dual magnet solution and a co-directional dual magnet solution, among which the mirror image dual magnet solution has the best performance, the single magnet solution is second, and the co-directional dual magnet solution is the worst. In the optimized magnetic field generating device 2 provided in this embodiment, the mirror image dual magnet solution should be adopted.

[0061] It should be particularly emphasized that the two magnets in the mirror double magnet solution can be two bar magnets of the same specifications, or two bar magnets of different specifications. Regardless of which combination is used, in order to obtain a stronger induction signal, the coil film 3 should be installed at the interface between the two permanent magnets corresponding to the magnetic field distribution. That is: when the two permanent magnets have the same specifications, the coil film 3 should be located in the middle of the upper substrate 11 and the lower substrate 12. When the two permanent magnets have different specifications, the coil film 3 should be located on the side close to the permanent magnet with weaker magnetism.

[0062] 2. Coil Film

[0063] In the solution of this embodiment, the coil film 3 is a flexible film device printed with a coil 32, and the coil film 3 includes a flexible base film and a coil 32 printed on the base film. The coil film 3 has two characteristics: one is that it has the electrical characteristics of the coil 32. When the coil film 3 moves in the uneven magnetic field between the upper substrate 11 and the lower substrate 12, it cuts the magnetic flux lines and generates an induced electromotive force. The second is that it has the characteristics of a flexible film. When the two sides of the coil film 3 are subjected to unbalanced stress, they will deform, and when the stress is removed, the deformation will be restored; thus, it will manifest as continuous tremor.

[0064] In actual products, coil film 3 is as Figure 6 As shown, the base film is a multi-layer structure, including a carrier layer 311 located in the inner layer, and a protective layer 312 covering the outside of the coil 32. The coil 32 is composed of a conductor material printed on one or both sides of the carrier layer 311. The conductor material can be made of metal materials such as gold, silver, copper, or conductive ink prepared from graphene, carbon nanotubes, metal nanowires, and conductive polymers. The base film of the coil film 3 can be any one of polytetrafluoroethylene film (PTFE), polyester film (PET), polyimide film (PI), and other films made of flexible resin materials.

[0065] When printing the coil 32, the coil 32 on each surface of the carrier layer 311 is distributed in a "backward" shape. For example, in this embodiment, the wire diameter of the copper coil 32 can be selected to be 50-150μm, and printed according to the designed number of turns. When the coil 32 is printed on both sides of the carrier layer 311, the two are electrically connected. In addition, considering that the induced electromotive force generated at both ends of the coil film 3 is positively correlated with the number of turns of the coil 32, the carrier layer 311 of the coil film 3 in this embodiment can also be further upgraded to a multi-layer. A group of multi-turn coils 32 is printed between every two carrier layers 311, and the coils 32 of each layer are electrically connected in sequence, thereby increasing the number of turns of the coil 32 in the coil film 3 and enhancing the intensity of the output induction signal.

[0066] 3. Shell

[0067] The shell 1 in this embodiment is essentially a pipe structure for gas circulation. In particular, the upper and lower sides of the shell 1 in this embodiment are provided with an upper substrate 11 and a lower substrate 12 for installing a magnetic field generating device 2. The installation of the magnetic field generating device 2 generates an unevenly distributed magnetic field between the upper substrate 11 and the lower substrate 12. The coil film 3 is located in the uneven magnetic field between the upper substrate 11 and the lower substrate 12. In order to make all airflows in the pipeline pass along the area where the magnetic field is distributed and effectively drive the coil film 3 therein to vibrate; in this embodiment, the cross-section of the local area corresponding to the upper substrate 11 and the lower substrate 12 in the airflow channel of the shell 1 is designed to be a square shape.

[0068] In order to facilitate product assembly, such as Figure 7 As shown, in a typical scheme of this embodiment, the housing 1 includes an upper substrate 11, a lower substrate 12, two sets of fasteners consisting of screws 14 and nuts 15, and four washers 13; wherein, through holes are provided at both ends of the upper substrate 11 and the lower substrate 12; two washers 13 are provided at the corresponding through hole positions between the upper substrate 11 and the lower substrate 12, and each screw 14 passes through the upper substrate 11, the two washers 13 and the lower substrate 12 in sequence, and is connected to the nut 15 below the lower substrate 12, thereby realizing the fixed connection of the upper substrate 11 and the lower substrate 12. The end of the coil film 3 is clamped between the two washers 13 on the corresponding side. Therefore, by selecting the appropriate height of the washer 13, the spacing between the upper substrate 11, the coil film 3 and the lower substrate 12 can be accurately controlled, so that the position distribution of the coil film 3 in the inhomogeneous magnetic field in the upper substrate 11 and the lower substrate 12 meets the requirements.

[0069] In this embodiment, the permanent magnets can be fixed on the upper substrate 11 and the lower substrate 12 in any manner, such as by gluing or by providing corresponding mounting structures in the upper substrate 11 and the lower substrate 12. Figure 7In the solution, grooves for embedded installation of permanent magnets are provided on the surfaces of the upper substrate 11 and the lower substrate 12 on the opposite sides.

[0070] In the scheme of this embodiment, in order to avoid the influence of the magnetic conductivity of the shell 1 material on the magnetic field distribution between the upper substrate 11 and the lower substrate 12, the shell 1 and its gasket 13 in this embodiment should be made of non-ferromagnetic materials, including various resins, ceramics or glasses, or non-ferromagnetic metal materials, such as aluminum alloys, magnesium alloys, copper alloys, etc.

[0071] Example 2

[0072] On the basis of the scheme in Example 1, Figure 8 As shown, this embodiment further provides a vital capacity detector, which includes the airflow sensor 100 as in Embodiment 1, and also includes a mask 200 and a data processing module.

[0073] The mask 200 is connected to the front end of the airflow channel in the airflow sensor 100. The data processing module includes a signal acquisition unit, a signal conversion unit and a vital capacity calculation unit. The signal acquisition unit is connected to the output port of the coil film 3 in the airflow sensor 100, and is used to collect the electrical signal output by the coil film 3; the signal conversion unit is used to convert the electrical signal into a detection signal representing the airflow intensity using a preset conversion model. The vital capacity calculation unit is used to calculate the vital capacity (FVC) and peak expiratory flow (PEF) of the detected user according to the change curve of the detection signal.

[0074] In the spirometry detector provided in this embodiment, the conversion model adopted by the signal conversion unit is capable of obtaining a digital value corresponding to the airflow in the detection signal based on the analog value of the induction signal output by the coil 32 module, and is therefore a key component in the data processing module. In a specific solution, the signal conversion unit first quantifies the analog value of the induction signal into a digital value of the current value through ADC, and then maps the current value to the airflow intensity through a pre-built conversion model. The method for building the conversion model is as follows:

[0075] A large number of simultaneous tests are conducted on the spirometer and standard equipment (referring to existing high-precision spirometer products) under different airflow environments. Then, a large amount of test data is obtained to establish a mapping between the detection signal of the spirometer and the detection result of the standard equipment through mathematical analysis or machine learning; finally, the obtained mathematical model or network model is used as the required conversion model.

[0076] The mathematical analysis method refers to using a large amount of "current value I-airflow intensity Q" data to perform linear regression on the two parameters, and then fit an IQ function, and then achieve mapping between the current value and the airflow intensity based on the IQ function. The machine learning method refers to using a neural network model to assist in completing the linear regression of the parameters, and then establish a mapping relationship between the two parameters. The trained network model is used to predict the sequence value of another parameter based on the sequence value of one of the input parameters.

[0077] In the scheme of the present embodiment, when the user uses the vital capacity detector, the mask 200 is first worn on the oral face. In order to make the mask 200 fit the facial contours of different users and avoid air leakage, the mask 200 in the present embodiment is made of flexible silicone material. After wearing, the user blows air into the airflow sensing component. During the blowing process of the user, the coil film 3 in the airflow sensor 100 vibrates with the airflow blown out by the user, and then generates an induction signal in the uneven magnetic field generated by the upper and lower permanent magnets. After the signal acquisition unit obtains the induction signal, it is processed by the signal conversion unit to obtain a detection signal characterizing the airflow intensity. In the present embodiment, the detection signal generated by the exhalation process of a complete vital capacity detection is continuous. When the user stops exhaling, the amplitude of the detection signal is also reset to zero (the coil film 3 is reset and no longer generates an induction signal). Finally, the vital capacity calculation unit calculates the user's vital capacity and peak exhalation flow rate according to the waveform diagram of the detection signal obtained during the entire detection process. The peak expiratory flow is the airflow corresponding to the peak value in the waveform of the entire detection signal; and the vital capacity is the integral of the waveform of the airflow in the entire detection signal in the time domain.

[0078] In the solution of this embodiment, the vital capacity detector also includes or is connected to a display module; the display module is electrically connected to the data processing module; the display module is used to visualize the data of the vital capacity detection process. In practical applications, the display module can adopt one or more of a digital tube, a liquid crystal display screen, and a dial pointer display. Using these display modules commonly used in electronic appliances, data such as vital capacity and expiratory peak flow during the user's detection process can be intuitively displayed.

[0079] In the spirometer of this embodiment, the airflow sensor 100 can generate self-excitation current when performing signal detection, so no external power supply is required. However, the data processing module still needs power supply when performing signal acquisition, analog-to-digital conversion and numerical synthesis; therefore, the spirometer of this embodiment also has an external power supply or a built-in power supply; the power supply is used to power part of the data processing module. In actual application, the power supply can be a dry cell or a rechargeable lithium battery.

[0080] In a further optimized solution of this embodiment, the spirometer further includes a tail pipe 300, which is connected to the rear end of the airflow channel in the airflow sensor 100; a check valve is provided in the tail pipe 300 to allow only one-way flow of gas from the mask 200 to the tail pipe 300. The airflow sensor 100 in Example 1 is a device that can perform bidirectional detection, that is, after the airflow enters from either side of the housing 1 and flows through the coil film 3, an induction signal output will be generated. This characteristic will bring a disadvantage after being applied to the spirometer, that is, when the user ends exhalation and starts inhalation during the spirometer detection process, the airflow sensor 100 will still generate an induction signal, which may affect the detection accuracy of the spirometer. In the optimized solution of this embodiment, the check valve is provided in the tail pipe 300 to prevent the airflow from entering the airflow sensor 100 when the user inhales, thereby ensuring the accuracy of the detection result.

[0081] Performance Testing

[0082] In order to verify the performance and advantages of the technical solution provided in this embodiment, technicians prepared corresponding samples and tested them. The experimental process is as follows:

[0083] 1. Sample preparation

[0084] This experiment was carried out according to Figure 6 The acrylic shell of the structure shown in the figure has a size of 130mm×12mm×5mm for the upper and lower substrates of the shell, and a through hole with a diameter of 5mm is provided at both ends of the upper and lower substrates. The washer is in a circular shape with an outer diameter of 9mm, an inner diameter of 5mm, and a thickness of 3mm. The diameter of the screw is 5mm and the length is 35mm.

[0085] 80mm×10mm×3mm grooves are set on the opposite sides of the upper and lower substrates of the shell, and then neodymium iron boron bar magnets of corresponding sizes are pasted in the grooves with shadowless adhesive. The two bar magnets are arranged in a mirror image, and the magnetic induction intensity is 3140Gs.

[0086] In this experiment, PCB technology is used to print the copper coil onto a flexible polyimide film to obtain a coil film. When printing the coil, the copper coil wire diameter is 60μm. The number of coil turns on each side is 80 turns. In order to achieve coils with more turns, the copper coils are printed on both sides of the PI in this implementation case, and the copper coils on both sides are connected. The effective working length of the printed flexible coil is selected to be 100mm, the width is 10mm, and the total coil resistance is 480Ω. Finally, the two sides of the PI film after printing the copper coil are covered with PI to form a protective layer to achieve insulation and protection of the coil. The actual area of ​​the flexible coil (including the area of ​​the PI film) is 150mm×12mm, and the area of ​​the effective part containing the coil is 100mm×10mm.

[0087] After assembling the shell, permanent magnet and coil film, a sample of the airflow sensor can be obtained. A trumpet-shaped air collecting hood and a pipe made of acrylic material are installed at both ends of the airflow sensor. During the experiment, the user blows air from one side of the air collecting hood, and the trumpet can gather the gas entering the airflow sensor.

[0088] 2. Induction signal output

[0089] In this experiment, the manufactured airflow sensor is first placed in a wind speed of 20m / s to test the sensitivity of the device to airflow; the current and voltage signals obtained are as follows: Fig. 9 As shown. Fig. 9 By stretching the time axis of the current signal, we can get Fig.10 The waveform diagram shown, combined with Fig. 9 and Fig.10 It can be seen that the sensing signal of the airflow sensor of the present invention is substantially in a sinusoidal waveform.

[0090] Combination Fig.11 The state diagram shown can be used to analyze the air flow sensor to generate Fig.10 The principle of the induction signal shown;

[0091] In the initial state, the coil film is located in the middle of the two bar magnets, which is the interface of the magnetic field in the two bar magnets, and the magnetic flux lines are the sparsest. Next, when the wind passes through the airflow sensor, it will cause the coil film to vibrate. When the flexible coil moves upward and approaches the upper bar magnet, the magnetic flux lines are the densest, the magnetic field gradient is large, the number of magnetic flux lines cut by the coil increases rapidly, and the rate of change of magnetic flux is high when the coil moves, so the induced electromotive force is high. When the flexible coil moves downward and away from the upper magnet, the magnetic flux lines around the coil become sparser. In this case, the number of magnetic flux lines cut by the coil decreases, the rate of change of magnetic flux is low when the coil moves, and the induced electromotive force generated is small. When the coil continues to move downward and approaches the lower bar magnet, the magnetic flux lines passing through the upper magnet become fewer, while the magnetic flux lines passing through the lower magnet will become more, causing the direction of the induced electromotive force to change. On this basis, the coil film reciprocates up and down under the action of wind, generating a periodically changing output signal.

[0092] 3. Influence of permanent magnet assembly method

[0093] Using the manufactured airflow sensor samples, technicians followed Figure 2-Figure 4 The number of bar magnets installed on the shell and the direction of magnetic pole arrangement were changed, and the current signal output by each sample at the same wind speed was tested. The experimental results are shown in Figure 2. Fig.12 shown.

[0094] contrast Fig.12 The experimental data show that when the two permanent magnets are set in mirror image, the output induction signal has a higher signal strength, the output signal strength of the single permanent magnet solution is second, and the signal output is the weakest when the two permanent magnets are set in the same direction. Figure 5 The reasons for this situation are:

[0095] (1) When a single permanent magnet is used, the number of magnetic flux lines around it will decrease gradually between the upper substrate and the lower substrate. (2) When two permanent magnets are arranged in a mirror image, the magnetic flux lines around the two permanent magnets are also distributed in a mirror image, and the middle position of the upper substrate and the lower substrate is used as the interface, and the magnetic flux lines decrease gradually along both sides. Therefore, compared with a single permanent magnet, the number of magnetic flux lines in the magnetic field generated by the two permanent magnets in a mirror image has a larger gradient change in the vertical direction. On this basis, the induction signal generated by the movement of the coil with the same number of turns is also stronger. (3) When the two permanent magnets are distributed in the same phase, the magnetic flux lines generated by the N pole of one permanent magnet will enter the S pole of the other permanent magnet in the vertical direction, and this part of the magnetic flux lines will not affect the magnetic flux of the coil when the coil moves up and down. Considering that the number of magnetic flux lines that each permanent magnet can emit is fixed, in this assembly state, the two permanent magnets arranged in the same direction actually cause mutual suppression of the gradient change of the number of magnetic flux lines between the upper substrate and the lower substrate, making the signal strength of the final induction signal even lower than that of a single permanent magnet.

[0096] 4. Blow test

[0097] This experiment studies the current output and charge generated by the airflow sensor when the user blows hard using the airflow sensor with an air collection hood. The data obtained are as follows: Fig.13 shown.

[0098] analyze Fig.13 The data in the figure shows that when the user starts to blow, the airflow through the airflow sensor is large. At this time, the amplitude of the current sensing signal is higher and the growth rate of the accumulated charge is relatively high. In the later stage of the user's blowing, the airflow gradually decreases, and the amplitude of the current sensing signal obtained by the image becomes lower, and the growth rate of the accumulated charge gradually slows down and returns to zero. Fig.13 The data in can prove that the signal strength output by the airflow sensor of this embodiment is positively correlated with the airflow strength, and the device can be used to quantitatively detect the airflow volume of the gas flowing through.

[0099] 5. FVC and PEF

[0100] This experiment selected 7 different test subjects, and used the device of the present invention and the standard lung capacity detection device to measure the lung capacity of each test subject. During the measurement, each experimental subject collected data four times and calculated the average value.

[0101] The detection data of the device according to the present invention can be plotted as follows Fig.13The output current and charge change curves are shown in FIG. 1 . Considering that the charge value can reflect the integral characteristic of the current sensing signal, it should be able to reflect the vital capacity of the test subject. In this embodiment, the charge value measured by the present invention and the vital capacity measured by the standard equipment of different test subjects are linearly regressed to obtain the following: Fig.14 The regression curve is shown.

[0102] analyze Fig.14 From the data, it can be seen that the charge and FVC measured when different test subjects blow hard are different, but the charge and vital capacity measured when the same subject exhales have an obvious linear relationship, which shows that the device provided by the present invention can be used to accurately measure the vital capacity of the user.

[0103] According to the above introduction, the peak value of the current sensing signal output by the airflow sensor of the present invention is the position corresponding to the user's peak vital capacity. Therefore, the technicians continued to perform linear regression on the peak current measured by the present invention and the peak exhalation flow measured by the standard equipment for different test subjects, and obtained the following: Fig.15 The regression curve of .

[0104] analyze Fig.15 From the data, it can be seen that the peak current and peak exhalation flow rate measured when different test subjects blow hard are different, but the peak current and peak exhalation flow rate measured when the same subject exhales have an obvious linear relationship, which shows that the device provided by the present invention can be used to accurately measure the user's peak exhalation flow rate.

[0105] 5. Humidity adaptability

[0106] This experiment further tested the stability of the signal output generated by the scheme under airflows of different humidity and the same flow rate. The experimental data obtained are as follows Fig.16 As shown, analysis Fig.16 It can be seen that the detection accuracy of the product of the present invention is hardly affected by the environmental humidity and has higher reliability.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An airflow sensor, characterized in that: It includes: The shell is made of non-ferromagnetic material; the shell comprises an upper base plate and a lower base plate which are parallel to each other; the inner side of the shell forms an air flow channel with a square-shaped cross section; A magnetic field generating device, which is used to generate a fixed magnetic field between the upper substrate and the lower substrate of the housing, the magnetic field strength of which varies with the distance; and A coil film, comprising a flexible base film and a coil printed on the base film; the coil film is fixed on the housing; the coil film is located between the upper substrate and the lower substrate and is parallel to the two substrates; In the airflow sensor, when the gas flows through the airflow channel in the shell, the coil film vibrates up and down to generate an induction signal at both ends of the coil that has a mapping relationship with the airflow intensity.

2. The airflow sensor according to claim 1, characterized in that: The magnetic field generating device comprises a strip-shaped permanent magnet fixedly connected to the inner side of the upper substrate and / or the lower substrate; the direction of the magnetic pole line of the permanent magnet is perpendicular to the plane where the upper substrate and the lower substrate are located.

3. The airflow sensor according to claim 2, characterized in that: The magnetic field generating device comprises two permanent magnets arranged in mirror image; and the coil film is located at a position between the two permanent magnets corresponding to the interface of the magnetic field distribution.

4. The airflow sensor according to claim 3, characterized in that: The upper substrate and the lower substrate in the shell are fixedly connected on both sides by screws and nuts; the shell also includes four washers, two washers are arranged on each screw between the upper substrate and the lower substrate; the end of the coil film is clamped between the two washers on the corresponding side; the washers are used to control the spacing between the upper substrate, the coil film and the lower substrate.

5. The airflow sensor according to claim 4, characterized in that: The shell and its gasket are made of resin, ceramic or glass, or non-ferromagnetic metal material; and / or Surfaces on opposite sides of the upper substrate and / or the lower substrate are provided with grooves for embedded installation of the permanent magnets.

6. The airflow sensor according to claim 1, characterized in that: The base film includes a carrier layer located in the inner layer and a protective layer covering the outside of the coil; the base film of the coil film is any one of polytetrafluoroethylene film, polyester film, polyimide film and other films made of flexible resin materials; and / or The coil is distributed in multiple layers in the base film to increase the number of turns.

7. A vital capacity detector, characterized in that: It includes: An airflow sensor as claimed in any one of claims 1 to 6; a mask in communication with a front end of an airflow passage in the airflow sensor; as well as The data processing module includes a signal acquisition unit, a signal conversion unit and a vital capacity calculation unit; the signal acquisition unit is connected to the output port of the coil film in the airflow sensor and is used to collect the electrical signal output by the coil film; the signal conversion unit is used to convert the electrical signal into a detection signal representing the airflow intensity using a preset conversion model; the vital capacity calculation unit is used to calculate the vital capacity and peak exhalation flow of the detected user according to the change curve of the detection signal.

8. The spirometry device according to claim 7, wherein: It also includes or is connected to a display module; the display module is electrically connected to the data processing module; the display module is used to visualize the data of the vital capacity detection process; and / or The spirometry detector is also connected to an external power supply or has a built-in power supply; the power supply is used to supply power to the data processing module; and / or The mask is made of flexible silicone material.

9. The spirometry device according to claim 7, wherein: It also includes a tail flow pipe, which is connected to the rear end of the air flow channel in the air flow sensor; a check valve is arranged in the tail flow pipe to only allow the gas to flow in one direction from the mask to the tail flow pipe.

10. The spirometry device according to claim 7, wherein: The construction method of the conversion model is: A large number of synchronous tests are performed on the spirometer and the standard equipment under different airflow environments; then, a mapping is established between the detection signal of the spirometer and the detection result of the standard equipment by mathematical analysis or machine learning in combination with the large amount of test data obtained; finally, the obtained mathematical model or network model is used as the required conversion model.

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