JP6440488B2 - Pulse wave measuring device and pulse wave measuring method - Google Patents

Description

  The present invention relates to a pulse wave measuring device and a pulse wave measuring method that are mounted on the wrist or arm of a human body and measure a minute displacement of the skin surface due to pulsation with high accuracy.

  Devices that measure pulse waves are devices that are worn on the wrist and irradiate the wrist with light, measure fluctuations in the intensity of reflected light from blood vessels, or wrap a cuff around the arm and press it like a sphygmomanometer. There has been proposed an apparatus for measuring atmospheric pressure fluctuation in a cuff with an atmospheric pressure sensor. For example, in Patent Document 1, a device mounted on a wrist or a finger has a light emitting element and a light receiving element, irradiates the wrist with light from the light emitting element, and receives the reflected light by the light receiving element, so that the reflected light intensity due to pulsation is increased. A technique for obtaining a pulse by measuring fluctuation is disclosed. Patent Document 2 discloses a technique for obtaining a pulse wave by measuring a pressure in a cuff wound around an arm with a pressure sensor and measuring a fluctuation in the cuff pressure due to pulsation.

JP 2010-017602 A Japanese Patent Laid-Open No. 2004-223044

However, the conventional pulse wave measuring apparatus and method described above have the following problems. That is, in the pulse wave meter configured to detect the reflected light by irradiating light, power consumption due to light emission becomes large, and it is difficult to use for a long time. Further, in such a pulse wave meter, since the intensity of the detection light greatly fluctuates even if the mounting position is slightly shifted, there is a problem in measurement accuracy and stability.
Accordingly, an object of the present invention is to provide a pulse wave measuring device and a pulse wave measuring method capable of reducing power consumption and improving accuracy and sensitivity.

In order to solve the above-mentioned problem, a first feature of the present invention is a pulse wave measuring device that measures a pulse wave by calculating a time displacement of the skin, and is a cavity that communicates with the outside and has a flexible bottom surface. Based on the output of the differential pressure sensor, and a differential pressure sensor that outputs a signal related to the differential pressure between the internal pressure and the external pressure of the cavity in a state where the bottom surface of the cavity is in contact with the skin, An arithmetic processing unit for calculating the time displacement of the skin, and the arithmetic processing unit, when the skin pulsates, based on an output signal of the differential pressure sensor, A differential pressure calculation unit that calculates the differential pressure of the cavity, an internal pressure calculation unit that calculates the internal pressure of the cavity based on the differential pressure and external pressure calculated by the differential pressure calculation unit, and the differential pressure calculation unit Based on the calculated differential pressure, The number of moles of air in the cavity is calculated based on the number of moles of air flow that calculates the number of moles of air flowing between the cavities and the number of moles of flow of air calculated by the number of moles of air flow. And a volume calculation unit for calculating the volume in the cavity based on the number of air moles calculated by the air mole number calculation unit and the internal pressure of the cavity calculated by the cavity internal pressure calculation unit, A displacement calculating unit that calculates a time displacement of the skin based on the volume in the cavity calculated by the volume calculating unit.
According to the invention, it is possible to provide a pulse wave measuring device capable of reducing power consumption, improving accuracy, and improving sensitivity.

In addition, a second feature of the present invention is that the arithmetic processing unit has a circulation mole number database section that stores in advance the circulation mole number of the air corresponding to the magnitude of the differential pressure, and the number of moles of air circulation. A calculation part is extracting the said air circulation mole number according to the magnitude | size of the said differential pressure calculated by the said differential pressure calculation part from the said circulation mole number database part.
According to the present invention, after calculating the differential pressure by the differential pressure calculation unit, it is not necessary to repeatedly calculate the number of moles of air flow, and it is possible to obtain the number of moles of air flow in a shorter time. Is possible.

Further, according to a third feature of the present invention, the flow mole number database unit obtains a relationship between a pressure difference at both ends of the cavity and a flow rate of air in advance by numerical calculation, and the relationship and the difference are calculated. It is generated by calculating the number of moles of air flow based on the pressure.
According to the present invention, by performing numerical calculations that require a large amount of calculations in advance and creating a database, arithmetic processing can be performed in a short time during pulse wave measurement.

Moreover, the 4th characteristic of this invention has an air temperature acquisition part which acquires the temperature information of the said air, The said air mole number calculation part is the air in the said cavity based on the said temperature information and the said distribution | circulation mole number. It is to calculate the number of moles.
According to the present invention, even when the air temperature fluctuates at high speed, the number of moles of air is always calculated using an accurate temperature, so that a more accurate and highly accurate pulse wave measuring device can be obtained.

A fifth feature of the present invention is that it has an external air pressure acquisition unit that acquires the external air pressure.
According to the present invention, even when the external air pressure fluctuates at high speed, the pressure in the cavity is always calculated using the accurate external air pressure, so that a more accurate and highly accurate pulse wave measuring device can be obtained. .

According to a sixth aspect of the present invention, there is provided a strain detection unit that detects a displacement amount due to distortion of the side wall of the cavity, and the volume calculation unit uses the displacement amount detected by the strain detection unit. Is to calculate the volume inside.
According to the present invention, even when the cavity inner wall fluctuates at high speed, the accurate cavity cross-sectional area is always calculated, so that a more accurate and highly accurate pulse wave measuring device can be obtained.

According to a seventh aspect of the present invention, the differential pressure sensor is provided so as to close an upper portion of the cavity, and the cantilever is bent and deformed according to the differential pressure between the internal pressure and the external pressure of the cavity. And a displacement measuring unit that measures displacement according to the bending deformation of the cantilever.
According to the present invention, it is possible to obtain a more accurate and highly sensitive pulse wave measuring device by detecting pressure fluctuation due to slight displacement of the skin surface with high sensitivity.

Further, an eighth feature of the present invention is that the cavity covers a side wall and has a frame-shaped sensor frame that has a through-hole over the top and bottom, and the skin that covers the bottom surface in contact with the bottom surface, It is formed by.
According to the present invention, since a slight displacement of the skin surface is detected as a change in the pressure in the cavity, a more sensitive pulse wave measuring device can be obtained.

A ninth feature of the present invention is a pulse wave measurement method for measuring a pulse wave by calculating time displacement of the skin, comprising a cavity communicating with the outside and having a flexible bottom surface, A differential pressure output step that outputs a differential pressure output signal related to the differential pressure between the internal pressure and the external pressure of the cavity with the bottom surface of the skin in contact with the skin, and the differential pressure output signal that is output when the skin pulsates A differential pressure calculating step for calculating the differential pressure between the internal pressure and the external atmospheric pressure of the cavity, and an internal pressure calculation step for calculating the internal pressure of the cavity based on the calculated differential pressure and the external pressure, Based on the calculated differential pressure, the step of calculating the number of moles of air flowing between the outside and the cavity, and the number of moles of air in the cavity based on the calculated number of moles of circulation. Air mode to calculate A volume calculation step for calculating the volume in the cavity based on the calculated number of moles of air and the internal pressure in the cavity, and a displacement calculation for calculating the amount of skin displacement based on the calculated volume in the cavity. And having steps.
According to the present invention, it is possible to provide a pulse wave measuring method capable of reducing power consumption, improving accuracy, and improving sensitivity.

The tenth feature of the present invention is that at least the differential pressure output step, the intracavity pressure calculation step, the air circulation mole number calculation step, the air mole number calculation step, the volume calculation step, and the displacement calculation step, And a repetitive processing step of repeatedly executing.
According to the present invention, a pulse wave can be automatically measured for a predetermined time.

An eleventh feature of the present invention is that the repetitive processing step is executed at predetermined time intervals.
According to the present invention, it is possible to perform arithmetic processing in the shortest time while realizing the required accuracy.

The twelfth feature of the present invention is that the differential pressure calculating step stores each differential pressure output signal for each predetermined time output in the differential pressure output step in a storage device, and stores the differential pressure output signal in the stored differential pressure output signal. Based on this, the differential pressure is determined every predetermined time.
According to the invention, it is possible to perform arithmetic processing even when a large amount of data that cannot be processed at a time occurs.

A thirteenth feature of the present invention is that the differential pressure calculation step continues that the differential pressure output signal output in the differential pressure output step is lower than a predetermined signal strength reference value for a predetermined time. To be executed after.
According to the present invention, it is possible to automatically select an appropriate initial state and perform more accurate pulse wave measurement.

  Therefore, the present invention can provide a pulse wave measuring device and a pulse wave measuring method that are small and have low power consumption and high accuracy and high sensitivity.

It is a mimetic diagram showing a schematic structure of pulse wave measuring device 1 concerning a 1st embodiment of the present invention. It is a block diagram of the pulse wave measuring device 1 of FIG. FIG. 2 shows a cross-sectional view of the differential pressure sensor 5 shown in FIG. 1. It is a flowchart which shows the flow of a function of the pulse-wave measuring apparatus concerning the 1st Embodiment of this invention. It is a "reference table of differential pressure and air inflow" according to the first embodiment of the present invention. The structure of the pulse-wave measuring apparatus 41 which concerns on the 2nd Embodiment of this invention is shown. It is a flowchart which shows the flow of the function of the pulse-wave measuring apparatus 51 concerning the 3rd Embodiment of this invention. It is a flowchart which shows the flow of the function of the pulse-wave measuring apparatus 61 concerning the 4th Embodiment of this invention. It is a flowchart which shows the flow of a function of the pulse-wave measuring apparatus 71 concerning the 5th Embodiment of this invention.

Hereinafter, embodiments of a pulse wave measurement device and a pulse wave measurement method according to the present invention will be described with reference to the drawings.
(First embodiment)
(overall structure)
FIG. 1 shows a configuration of a pulse wave measuring apparatus 1 according to the first embodiment of the present invention. In the present embodiment, the pulse wave measuring device 1 has a form similar to a wristwatch, and includes a device main body 3 and a band 2 fixed to a side surface of the device main body 3.
The band 2 is composed of, for example, an annular elastic material or the like, and the apparatus main body 3 is attached so as to be in close contact with the user's skin 4.

  The apparatus main body 3 has a differential pressure sensor 5 in the lower part (skin 4 side). The differential pressure sensor 5 has a lower part in close contact with the skin 4 and an upper part communicating with the outside air through the opening 6. The structure of the differential pressure sensor 5 will be described in detail later. The apparatus body 3 has a control board 7 on which elements having various functions to be described later are mounted.

FIG. 2 shows a block diagram of the pulse wave measuring apparatus 1. In addition to the differential pressure sensor 5, the pulse wave measurement device 1 includes a control unit 11, a power source 12, a storage unit 13, and an arithmetic processing unit 14 corresponding to the control board 7.
The control unit 11 includes, for example, a CPU, a ROM, and the like, and comprehensively controls driving of the entire apparatus body 3.

The power source 12 is, for example, a power source such as various primary batteries such as a dry battery or a secondary battery such as a battery, and supplies power to each unit included in the apparatus main body 3.
The storage unit 13 includes, for example, various nonvolatile memories and stores a drive program executed by the control unit 11, various data, and a reference table described later.

  The arithmetic processing unit 14 includes a differential pressure calculation unit 15 that calculates a differential pressure based on the output of the differential pressure sensor 5, a cavity internal pressure calculation unit 16 that calculates an atmospheric pressure inside the cavity of the differential pressure sensor 5 described later, An air circulation mole number calculation unit 17 that calculates the number of moles of air flowing through the cavity, an air mole number calculation unit 18 that calculates the number of moles of air in the cavity, and a volume calculation unit that calculates the volume of the cavity. 19 and a displacement calculator 20 that calculates the displacement of the skin due to pulsation. The function of each unit included in the arithmetic processing unit 14 will be described in detail later (on the displacement calculation flow).

(Configuration of differential pressure sensor)
Next, the configuration of the differential pressure sensor 5 will be described. 3A and 3B are cross-sectional views of the differential pressure sensor 5. FIG. 3A shows a cross section at time T0 representing the initial state, and FIG. 3B shows a cross section at time T1 when skin pulsation occurs after time T0. The differential pressure sensor 5 includes, for example, a sensor frame 31 that is a frame having a square shape when viewed from above, and a cantilever 32 that protrudes in a cantilever manner with the upper surface of the sensor frame 31 as a base end. And having. The differential pressure sensor 5 is a space formed by the sensor frame 31 (side wall) and the skin portion 33 (flexible bottom surface) by closely contacting the skin portion 33 that is displaced by pulsation in the user's skin. A cavity 34 is formed.

  Although not shown, the lower portion of the cavity 34 is not necessarily opened in a state of being separated from the user's skin, and a flexible thin film that is in close contact with the skin portion 33 is fixed to the lower surface of the sensor frame 31. You may keep it.

  Here, the volume, pressure, and the number of moles of air inside the cavity 34 are V, Pin, and N, respectively, and V (0), Pin (0), Let N (0), V (1), Pin (1), and N (1).

(Differential pressure sensor structure and operation)
Next, a specific structure of the differential pressure sensor 5 will be described with reference to FIG. The differential pressure sensor 5 has a through hole surrounded by a sensor frame 31, and most of the mouth on the upper side is covered with a cantilever 32. The cantilever 32 is a substantially rectangular plate-like beam made of extremely thin Si of about 300 nm, for example, and one end is fixed to the sensor frame 31. The cantilever 32 has a side of, for example, a size of about 100 microns, and bends due to the differential pressure if there is a slight difference between the upper and lower atmospheric pressures. Since the vicinity of the fixed end of the cantilever 32 functions as a piezoresistor by doping impurities such as P (phosphorus) only in the vicinity of the upper surface, a remarkable piezoresistive effect is exhibited. A small gap of about 1 micron is formed between the side surface of the cantilever 32 and the sensor frame 31, and air flows between the outside air and the cavity 34 through the gap. Since only one end of the cantilever 32 is fixed, the cantilever 32 can be bent even with a slight force as compared with a diaphragm sensor that is fixed at the entire periphery, and functions as a highly sensitive sensor.

  Here, as shown in FIG. 3B, it is assumed that the skin portion 33 is displaced downward due to the pulsation of the lower artery at time T1. Then, the volume V inside the cavity increases and the atmospheric pressure Pin decreases. As a result, the cantilever 32 bends downward due to the differential pressure between the atmospheric pressure Pin and the external atmospheric pressure. Then, since the electrical resistance value of the piezoresistive element built in the cantilever 32 changes, the differential pressure sensor 5 outputs a signal corresponding to the bending amount of the cantilever 32 via a bridge circuit (not shown). .

  Here, the relationship between the amount of bending of the cantilever 32 and the pressure difference (differential pressure) inside and outside the cavity 34 is measured in advance and stored in the storage unit 13 as a “piezoresistance value and differential pressure reference table”. Therefore, the differential pressure calculation unit 15 can calculate the differential pressure from the output signal of the differential pressure sensor 5 and the reference table of the storage unit 13.

  Further, when the pressure Pin in the cavity 34 decreases, air flows from the outside air into the cavity 34. At this time, the amount of the inflow of the air expressed in moles is ΔN. Thus, when the skin part 33 is displaced, V, Pin, and N all change. The relationship between the differential pressure and ΔN is acquired in advance by an experiment in which a flow meter is incorporated in the pulse wave measuring device 1 or a computer simulation in which the relationship between the displacement of the cantilever 32 and the air inflow / outflow is coupled. It is stored in the storage unit 13 as a “pressure and air inflow amount reference table”.

(Displacement calculation flow)
Next, the flow of calculating the displacement of the skin portion 33 by the pulse wave measurement device 1 according to the first embodiment of the present invention will be described with reference to an explanatory diagram (flowchart) shown in FIG.

  First, at time T0 representing the initial state, the volume V (0) in the cavity 34 is known from the design dimensions of the sensor frame 31. The pressure Pin (0) in the cavity 34 is the same as the external pressure. Therefore, the air mole number calculation unit 18 can obtain the mole number N (0) = Pin (0) V (0) / RK from the gas state equation PV = NRK using the temperature K (STEP 1). The temperature K and the external pressure are based on a control signal from the control unit 11 and are connected to the pulse wave measuring device 1 or provided in the pulse wave measuring device 1 or a pressure for measuring absolute pressure. A sensor (not shown) transmits the signal as an electrical signal to the arithmetic processing unit 14 (number-of-air calculating unit 18).

  Next, after the pulse wave measuring device 1 starts measuring the displacement, the skin portion 33 is displaced by the pulsation at time T 1, the cantilever 32 is bent, and a signal related to the piezoresistance value is sent from the differential pressure sensor 5 to the arithmetic processing unit 14. It is output (STEP 2).

  Next, the differential pressure calculation unit 15 refers to the “piezoresistance value and differential pressure reference table” stored in the storage unit 13 and calculates the differential pressure from the piezoresistance value. Further, the cavity internal pressure calculation unit 16 calculates the pressure Pin (1) in the cavity 34 by subtracting the calculated differential pressure from the external pressure assuming that the external air pressure is constant (STEP 3).

  Next, the air circulation mole number calculation unit 17 refers to the “reference table of differential pressure and air inflow amount” stored in the storage unit 13 and calculates the air inflow amount ΔN from the differential pressure calculated in STEP 3. (STEP 4). Here, the “reference table of differential pressure and air inflow amount” is, for example, as shown in FIG. 5, the value of air inflow amount Q per unit time (mol / sec) corresponding to the value (Pa) of differential pressure ΔP. Is tabulated in accordance with the magnitude of the differential pressure ΔP.

  Next, the air mole number calculation unit 18 adds the air inflow amount ΔN calculated in STEP 4 to the air mole number N (0) at the time T0, so that the air mole number N (( 1) is calculated (STEP 5).

  Next, the volume calculation unit 19 substitutes Pin (1) calculated in STEP 3 and N (1) calculated in STEP 5 into the gas state equation again, so that the volume V (1 ) Is calculated (STEP 6).

  Next, assuming that the sensor frame 31 itself is not deformed, the displacement calculation unit 20 does not change the cross-sectional area of the cavity 34, so the volume change (V (1) −V (0)) By dividing, the displacement of the skin portion 33 is calculated (STEP 7).

  Then, the control unit 11 determines whether or not to continue the measurement (STEP 8). If it is determined that the measurement is to be continued (STEP 8; Y), the control unit 11 continuously causes the processing unit 14 to repeatedly execute the processing from step 2 and does not continue. If it is determined (STEP8; N), this process is terminated.

  In STEP 4, the air circulation mole number calculation unit 17 calculates the air inflow amount Q per unit time and the time interval (when the air inflow amount ΔN is calculated from the “reference table of differential pressure and air inflow amount” described above). T1-T0) is integrated. This step time can be set as needed.If the time is shortened, the amount of calculation increases, but a high-accuracy result can be obtained.If the length is shortened, the accuracy is reduced, but it can be calculated in a short time. Set.

  In addition, the arithmetic processing unit 14 replaces the processing procedure of the flowchart shown in FIG. 4 and repeatedly obtains the piezoresistance value (STEP 2) for a predetermined time before storing the result data in the storage unit 13. Alternatively, the piezoresistance value may be sequentially read from the storage unit 13 and the processing after STEP3 may be performed. In addition, when the arithmetic processing unit 14 performs the acquisition of the piezoresistance value (STEP 2) and determines that the state in which the acquired piezoresistance value is less than the predetermined value continues for a predetermined time, the determination time point May be time T0 representing the initial state, and processing after STEP1 may be executed.

  As described above, according to the pulse wave measuring apparatus 1 according to the present embodiment, when the skin portion 33 is slightly displaced by pulsation, it is acquired as a piezoresistance value generated from the bending of the cantilever 32, and between the outside air and the cavity 34. The displacement of the skin portion 33 can be calculated by solving a gas equation of state that takes into account the amount of air flowing in and out. Further, according to the pulse wave measuring device 1, by using the cantilever 32 having only one end fixed, it is possible to detect with high sensitivity which is greatly bent even with a slight differential pressure, and between the cantilever 32 and the sensor frame 31. By calculating the displacement of the skin portion 33 while taking into account the influence of air flowing in and out, highly sensitive and accurate sensing can be realized.

(Second Embodiment)
Next, a pulse wave measuring device 41 according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 6 shows a configuration of a pulse wave measuring device 41 according to the second embodiment of the present invention. The pulse wave measuring device 41 according to this embodiment includes a cuff 43 wound around a user's arm 42, a differential pressure sensor 45 connected to the cuff 43 via an air tube 44, and a pump 47 that presses the cuff 43. And a control board 48 connected to the differential pressure sensor 45 and the pump 47. The pulse wave measuring device 41 is configured to wrap and press the cuff 43 around the user's arm 42 and detect a pressure fluctuation in the cuff 43 by a differential pressure sensor 45 connected by an air tube 44 ( A space that combines the internal spaces of the cuff 43, the air tube 44, and the differential pressure sensor 45 functions as a cavity).

The cuff 43 is a bag-like member wound around the user's arm 42, for example, and can press the arm 42 by enclosing air therein.
The air tube 44 is, for example, a tube-shaped member having a hollow inside for allowing air to flow into and out of the cuff 43.

  The differential pressure sensor 45 has the same configuration as the differential pressure sensor 5 according to the first embodiment except that a flexible thin film is formed on the bottom surface of the sensor frame 31 and communicates with the outside air through the opening 46. . The pump 47 presses the cuff 43 by pushing air into the cuff 43 via the air tube 44.

  The control board 48 includes the control unit 11, the power supply 12, the storage unit 13, and the arithmetic processing unit 14, similarly to the control board 7 of the first embodiment. Here, the displacement calculation processing of the skin portion 33 by the arithmetic processing unit 14 is the same as that in the first embodiment, and thus the description thereof is omitted.

  In the pulse wave measuring device 41 according to the present embodiment, in order to measure the displacement while pressing the arm 42 with the cuff 43, the movement of the blood vessel inside the arm 42 can strongly cause the displacement of the cuff inner wall, Highly sensitive detection is possible. Moreover, since the differential pressure sensor 45 is arrange | positioned in the place different from the arm 42 in the pulse wave measuring device 41 (because the pulse wave measuring device 41 except the cuff 43 is not a structure that is directly attached to the human body), Even if the pulse wave measuring device 41 excluding the cuff 43 is enlarged, there is no burden on the user. Therefore, the pulse wave measuring device 41 can relatively easily realize an increase in size of a cantilever for improving sensitivity.

(Third embodiment)
Next, a pulse wave measurement device 51 according to a third embodiment of the present invention will be described with reference to FIG.
FIG. 7 is a flowchart for explaining the displacement calculation processing of the skin portion 33 by the pulse wave measurement device 51 according to the third embodiment of the present invention. In addition, about the process same as 1st Embodiment, the same name is attached | subjected and description is abbreviate | omitted. Here, the displacement calculation process by the pulse wave measurement device 51 is different from the displacement calculation process in the first embodiment in that the pulse wave can be accurately measured even when the temperature fluctuates over time.

First, the arithmetic processing unit 14 acquires the air temperature K (0) by a temperature sensor or the like connected to the pulse wave measuring device 1 or provided in the pulse wave measuring device 1 (STEP 11). In the initial state, the volume V (0) of the cavity 34 is determined by the design of the sensor frame 31, and the pressure Pin (0) in the cavity 34 is the same as the external pressure. The form is the same. Therefore, the air mole number calculation unit 18 calculates the mole number N (0) by substituting these V (0), Pin (0), and K (0) into the gas state equation (STEP 12).
Thereafter, the steps from obtaining the piezoresistance value (STEP 13) to updating the number of moles (STEP 16) are the same as the displacement calculation process in the first embodiment.

  Next, the arithmetic processing unit 14 acquires the temperature K (1) at time T (1) (STEP 17). And the volume calculation part 19 calculates volume V (1) from the state equation of gas using the K (1) (STEP18). Subsequent processing is the same as in the first embodiment.

  In the pulse wave measuring device 51 according to the present embodiment, even when the air temperature fluctuates during measurement, the pulse wave is always accurate and highly sensitive by continuously measuring it and taking the temperature into account. Measurement becomes possible.

(Fourth embodiment)
Next, a pulse wave measurement device 61 according to a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a flowchart for explaining the displacement calculation processing of the skin portion 33 by the pulse wave measurement device 61 according to the fourth embodiment of the present invention. In addition, about the process same as 1st Embodiment, the same name is attached | subjected and description is abbreviate | omitted. Here, the displacement calculation process by the pulse wave measuring device 61 is different from the displacement calculation process in the first embodiment in that the pulse wave can be accurately measured even when the external air pressure fluctuates over time.

  First, the arithmetic processing unit 14 acquires the external air pressure by a pressure sensor (not shown) that is connected to the pulse wave measuring device 61 or that can measure the absolute pressure provided in the pulse wave measuring device 61 (STEP 21). .

Since the pressure Pin (0) in the cavity 34 is the same as the outside air pressure in the initial state, the air mole number calculating unit 18 uses the outside air pressure measured in STEP 21 as Pin (0) and uses the mole number N (0 ) Is calculated (STEP 22).
Next, the arithmetic processing unit 14 acquires a piezoresistance value from the differential pressure sensor 5 (STEP 23), and acquires an external air pressure at time T (1) by the pressure sensor (STEP 24).

  Then, the arithmetic processing unit 14 updates the pressure in the cavity 34 from the external pressure acquired in STEP 24 and the differential pressure calculated based on the piezoresistance value acquired in STEP 23 to Pin (1). (STEP 25). Subsequent processing is the same as in the first embodiment.

  In the pulse wave measuring device 61 according to the present embodiment, even when the external air pressure fluctuates during measurement, it is always accurate and highly sensitive by continuously measuring it and taking the external air pressure into consideration. Pulse wave measurement becomes possible.

(Fifth embodiment)
Next, a pulse wave measurement device 71 according to a fifth embodiment of the present invention will be described with reference to FIG.
FIG. 9 is a flowchart for explaining the displacement calculation processing of the skin portion 33 by the pulse wave measurement device 71 according to the fifth embodiment of the present invention. Here, the same processing for the displacement calculation processing by the pulse wave measuring device 71 as in the first embodiment is given the same name, and the description is omitted. Here, the displacement calculation process by the pulse wave measuring device 71 is different from the displacement calculation process in the first embodiment in that the pulse wave can be accurately measured even when the side wall of the cavity 34 is displaced in time. .

  First, the arithmetic processing unit 14 acquires displacement information of the side wall of the cavity 34 (the inner peripheral surface of the sensor frame 31) using a strain sensor (not shown) provided in the pulse wave measuring device 71 (STEP 31).

  The air mole number calculation unit 18 calculates the volume V (0) of the cavity 34 using both the displacement information and the design of the sensor frame 31, and the number of moles N in the cavity N based on the volume V and the external air pressure. (0) is obtained (STEP 32). The subsequent processing is the same as that of the first embodiment from the piezoresistance value acquisition (STEP 33) to the volume update (STEP 37).

  Next, the arithmetic processing unit 14 acquires displacement information at time T (1) by the strain sensor (STEP 38), and calculates the displacement amount of the skin surface using the latest cavity cross-sectional area (STEP 39). Subsequent processing is the same as in the first embodiment.

In the present embodiment, even if the side wall of the cavity 34 changes during measurement, it is possible to always measure the pulse wave accurately and with high sensitivity by continuously measuring it and processing it.
In the third embodiment, the fourth embodiment, and the fifth embodiment, the case where the temperature, the external air pressure, and the side wall of the cavity 34 fluctuate has been described. It is possible.

1, 51, 61, 71 Pulse wave measuring device 2 Band 3 Device body 4 Skin 5 Differential pressure sensor 6 Opening 7 Control board 11 Control unit 12 Power supply 13 Storage unit 14 Processing unit 15 Differential pressure calculation unit 16 Intracavity pressure calculation unit 17 Air flow mole number calculation unit 18 Air mole number calculation unit 19 Volume calculation unit 20 Displacement calculation unit 31 Sensor frame 32 Cantilever 33 Skin portion 34 Cavity 41 Pulse wave measuring device 42 Arm 43 Cuff 44 Air tube 45 Differential pressure sensor 46 Opening 47 Pump 48 Control board V Volume inside cavity 34 Pressure N inside cavity 34 Number of moles of air inside cavity 34 STEP1-8 STEPs 11-20 of the pulse wave measuring method according to the first embodiment of the present invention Steps 21 to 30 of the pulse wave measuring method according to the third embodiment of the present invention The fourth embodiment of the present invention Each step of the method of measuring the pulse wave according to a fifth embodiment of the stages STEP31~40 present invention method for measuring a pulse wave according to the

Claims (12)

A pulse wave measuring device that measures a pulse wave by calculating time displacement of the skin,
A frame-shaped sensor frame having a through-hole, a cantilever projecting so as to cover the through-hole of the sensor frame in a cantilever shape with the upper surface of the sensor frame as a base end, and having a gap between the sensor frame and A cavity formed by the opening of the lower surface of the through hole of the sensor frame coming into contact with the skin part,
A differential pressure sensor that outputs a signal relating to a differential pressure between an internal pressure of the cavity and an external pressure that is an external pressure of the cavity ;
An arithmetic processing unit that calculates the time displacement of the skin based on the output of the differential pressure sensor;
With
The arithmetic processing unit
When the skin is pulsed, and the difference based on the output signal of the pressure sensor, differential pressure calculator for calculating a differential pressure between the outer pressure and the inner pressure of the cavity,
Based on the outer pressure and differential pressure calculated by the pressure difference calculating unit, and the intracavity pressure calculation unit for calculating the internal pressure of the cavity,
Based on the differential pressure calculated by the pressure difference calculating unit, and the air flow mole number calculating section for calculating a distribution number of moles of air flowing through the gap between the external and the cavity of the cavity,
Based on the flow mole number calculated by the air flow mole number calculation section, the air mole number calculation section for calculating the air mole number in the cavity;
Based on the number of air moles calculated by the air mole number calculation unit and the internal pressure of the cavity calculated by the cavity internal pressure calculation unit, a volume calculation unit that calculates the volume in the cavity;
A pulse wave measuring device comprising: a displacement calculating unit that calculates time displacement of the skin based on the volume in the cavity calculated by the volume calculating unit. The pulse wave measuring device according to claim 1, wherein the cavity is formed of a flexible thin film fixed to a lower surface of the sensor frame. The arithmetic processing unit has a circulation mole number database unit that stores in advance the circulation mole number of the air corresponding to the magnitude of the differential pressure,
The air flow mole number calculation unit extracts the air flow mole number corresponding to the magnitude of the differential pressure calculated by the differential pressure calculation unit from the flow mole number database unit. Or the pulse wave measuring device according to 2; The circulation number-of-moles database unit obtains, in advance, a relationship between the pressure difference between the internal pressure and the external pressure of the cavity and the flow rate of air by numerical calculation, and based on the relationship and the differential pressure, The pulse wave measuring device according to claim 3 , wherein the pulse wave measuring device is generated by calculating the number of moles of air flow. An air temperature acquisition unit for acquiring temperature information of the air;
The pulse wave measurement according to any one of claims 1 to 4 , wherein the air mole number calculation unit calculates the air mole number in the cavity based on the temperature information and the flow mole number. apparatus. The pulse wave measuring apparatus according to any one of claim 1 to 5, characterized in that with an outer pressure acquisition unit for acquiring the outer pressure. A strain detection unit that detects a displacement amount due to distortion of the side wall of the cavity;
The volume calculation unit, a pulse wave measuring apparatus according to any one of claim 1 to 6, characterized in that to calculate the volume in the cavity by using a displacement detecting the distortion detector. A pulse wave measuring method for measuring a pulse wave by calculating a time displacement of the skin,
A frame-shaped sensor frame having a through-hole, a cantilever projecting so as to cover the through-hole of the sensor frame in a cantilever shape with the upper surface of the sensor frame as a base end, and having a gap between the sensor frame and A differential pressure sensor having a cavity formed by contacting an opening of a lower surface of the through hole of the sensor frame with a skin portion, and an internal pressure of the cavity and an external pressure that is an external pressure of the cavity A differential pressure output step for outputting a differential pressure output signal relating to the differential pressure;
When the skin is pulsating, on the basis of the outputted differential pressure output signal, and the differential pressure calculation step of calculating a differential pressure between the outer pressure and the inner pressure of the cavity,
Based on the outer pressure and the calculated differential pressure, and cavity pressure calculation step of calculating the internal pressure of the cavity,
Based on the calculated differential pressure, the air flow moles calculating step of calculating a distribution number of moles of air flowing through the gap between the external and the cavity of the cavity,
Based on the calculated number of circulation moles, the mole number calculation step of calculating the number of moles of air in the cavity;
Based on the calculated number of moles of air and the internal pressure of the cavity, a volume calculating step for calculating the volume in the cavity;
A displacement calculating step of calculating a displacement amount of the skin based on the calculated volume in the cavity. Repetitively executing at least the differential pressure output step, the cavity internal pressure calculation step, the air circulation mole number calculation step, the air mole number calculation step, the volume calculation step, and the displacement calculation step The pulse wave measuring method according to claim 8 , further comprising a processing step. The pulse wave measuring method according to claim 9 , wherein the repetitive processing step is executed every set predetermined time. The differential pressure calculating step stores each of the differential pressure output signals for each predetermined time output in the differential pressure output step in a storage device, and based on the stored differential pressure output signal, for each predetermined time The pulse wave measuring method according to claim 8 , wherein the differential pressure is obtained. The differential pressure calculating step is executed after the differential pressure output signal output in the differential pressure output step continues for a predetermined time period lower than a predetermined reference value of signal strength. The pulse wave measuring method according to claim 11 .

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