JP2019111037A - Sphygmomanometer and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sphygmomanometer and its control method capable of accurately controlling an exhaust flow rate even when an electromagnetic valve having a hysteresis in a relation between an opening degree and a magnitude of a drive current is used as an exhaust valve. A sphygmomanometer having a solenoid valve for reducing the internal pressure of an airbag, and a drive circuit for controlling the opening degree of the solenoid valve. The drive circuit drives the solenoid valve using a pulse signal having a frequency lower than the frequency corresponding to the time constant of the solenoid valve, and controls the opening degree of the solenoid valve. [Selection diagram] Figure 1

Description

  The present invention relates to a sphygmomanometer and its control method, and more particularly to a sphygmomanometer that measures blood pressure using an air bag and its control method.

  As a sphygmomanometer for measuring a pulse wave and a blood pressure, what measures the blood pressure by an oscillometric method is known using the strip | belt-shaped cuff which incorporated an airbag. The blood pressure measurement by the oscillometric method is performed by attaching a cuff to the measurement site of the person to be measured and supplying blood to the air bag with a pump to pressurize the measurement site to ankle and then measure the amplitude of the pulse wave measured while depressurizing Determine the blood pressure value based on

  In such a sphygmomanometer, an exhaust valve is provided in the gas flow path connected to the inside of the air bag, the exhaust valve is closed at the time of anemia, and after exhaustion, the exhaust valve is maintained until the blood pressure value is determined (during measurement). Partially open and depressurize the inside of the air bag at a constant rate. Then, when the blood pressure value is determined, the exhaust valve is fully opened to rapidly depressurize the inside of the air bag. When two exhaust valves are provided, only one is partially opened during measurement, and both are fully opened when the blood pressure value is determined.

  As an exhaust valve, a solenoid valve whose opening degree can be adjusted using a solenoid is widely used. The solenoid has a hollow cylindrical coil and a plunger (mover) inserted in the central axis of the coil, and an electric machine which causes the plunger to move linearly along the central axis by the magnetic field generated by the current flowing through the coil. It is a conversion element. Some solenoids can control the position of the plunger only on (full open) and off (full close), and some can control the position of the plunger at any position from full open to full close, and the latter is also a proportional solenoid be called. By controlling the position (movement amount) of the plunger using a proportional solenoid, the size (opening degree) of the gap between the solenoid valve and the exhaust port can be controlled.

  For proportional solenoids, the same drive current is used for controlling the degree of opening of the solenoid valve from 0% (fully closed) to 100% (fully open) and for controlling the degree of opening from 100% to 0%. Some have hysteresis characteristics in which the degree of opening with respect to is different (Patent Document 1).

Unexamined-Japanese-Patent No. 2006-75435 (FIG. 19)

  Since it is desirable that the decompression speed during blood pressure measurement is constant, the pressure is monitored, and if the pressure is higher than the target value or target range, feedback control is performed to increase the opening degree and decrease the opening degree when the pressure is low. May. At this time, if the hysteresis of the solenoid valve is large, the accuracy of the feedback control is lowered, and the measurement accuracy of the blood pressure value is also lowered.

  The present invention has been made in view of the problems of the prior art as described above, and the exhaust flow rate can be accurately controlled even if a solenoid valve having a hysteresis in the relationship between the opening degree and the magnitude of the drive current is used as the exhaust valve. Main object of the present invention is to provide a blood pressure monitor and its control method.

  The above-described object is a sphygmomanometer having an air bag mounted on a measurement site of a subject, a solenoid valve for reducing the internal pressure of the air bag, and a drive circuit for controlling the opening degree of the solenoid valve. The driving circuit is achieved by a sphygmomanometer characterized by driving the solenoid valve using a pulse signal having a frequency lower than the frequency corresponding to the time constant of the solenoid valve to control the opening degree of the solenoid valve. Ru.

  With such a configuration, according to the present invention, a sphygmomanometer capable of accurately controlling the exhaust flow rate and its control even if a solenoid valve having hysteresis in the relationship between the opening degree and the magnitude of the drive current is used as the exhaust valve. We can provide a way.

It is a block diagram showing an example of functional composition of a blood pressure monitor concerning an embodiment of the present invention. It is a flowchart regarding operation | movement of the sphygmomanometer which concerns on embodiment. It is a figure showing an example of composition of a constant displacement valve drive circuit concerning an embodiment. It is a figure for demonstrating the effect of the drive method of the constant discharge valve which concerns on embodiment.

  Hereinafter, the present invention will be described in detail based on the exemplary embodiments with reference to the drawings. In the following, a configuration in which the present invention is applied to a sphygmomanometer will be described. However, the present invention is not limited to the sphygmomanometer, and can be applied to a biological information measurement apparatus that measures biological information using an air bag that is attached to a person to be measured, such as a pulse wave meter or a blood flow meter It is. In addition, a computer apparatus capable of functioning as a sphygmomanometer to which the present invention is applied or a biological information measuring apparatus by executing application software is also included in the sphygmomanometer or biological information measuring apparatus of the present invention.

● (Configuration of sphygmomanometer)
FIG. 1 is a block diagram showing an example of a functional configuration of an automatic blood pressure monitor 150 as an example of the blood pressure monitor according to the embodiment. The automatic sphygmomanometer 150 measures blood pressure by the oscillometric method using the cuff 10.
The cuff 10 incorporates an air bag 11 connected to one end of the air hose H, and is attached to a subject's blood pressure measurement site (for example, one or more of limbs and toes). The cuff 10 is attached to the automatic sphygmomanometer 150 by attaching a connector provided at the other end of the air hose H to the air connector 24 of the automatic sphygmomanometer 150. The air connector 24 is connected to the pressure sensor 12, the constant discharge valve 14, the rapid discharge valve 16, and the pump 18 by a common gas flow path R. Therefore, with the cuff 10 attached to the automatic blood pressure monitor 150, the air bag 11, the air hose H, and the gas flow passage R form one continuous space.

  The pressure sensor 12 is, for example, a pressure-electricity conversion sensor using a piezo element or the like, and outputs an electric signal (sensor output signal) representing the internal pressure of the air bag 11. Since the internal pressure of the air bag 11 changes due to the pulse, the sensor output signal contains a pulse wave component. The sensor output signal is sampled at a predetermined frequency by the AD converter 22 and digitized.

  The constant exhaust valve 14 and the rapid exhaust valve 16 are exhaust valves for reducing the internal pressure of the air bag 11. The constant exhaust valve 14 has a variable opening degree (exhaust gas flow rate), and is used to gradually lower the internal pressure of the air bag 11 from the blood-striking state. On the other hand, the rapid exhaust valve 16 is used to rapidly reduce the internal pressure of the air bag 11, and is opened at the end of measurement. The rapid exhaust valve 16 may be capable of controlling two states of 0% and 100% (fully closed and fully open). The constant discharge valve 14 and the rapid discharge valve 16 can be realized by, for example, a solenoid valve using a solenoid.

The pump 18 is used to supply air to the air bag 11 to increase the internal pressure.
The cuff control unit 20 controls the opening degree of the constant discharge valve 14 and the rapid discharge valve 16 and the start / stop of the pump 18. The cuff control unit 20 operates according to the control of the main control unit 30. For the constant discharge valve 14 having a variable opening degree, the constant discharge valve drive circuit 21 is driven to have an opening degree according to the instruction of the cuff control unit 20. Since the rapid exhaust valve 16 only needs to control two states of 100% (full open) and 0% (full close), the cuff control unit 20 directly drives.

  In the present embodiment, a configuration in which one cuff 10 is connected to the automatic blood pressure monitor 150 is shown for ease of description and understanding, but a plurality of cuffs 10 may be connected. When a plurality of cuffs 10 are connected, the air connectors 24, the pressure sensors 12, the constant discharge valves 14, the quick discharge valves 16, and the pumps 18 are basically provided in the same number as the cuffs 10. On the other hand, the cuff control unit 20 and the AD converter 22 do not necessarily have to be provided in the same number as the cuffs 10.

The sensor output signal digitized by the AD converter 22 is supplied to the pulse wave signal extraction filter 50 and the pressure signal extraction filter 51.
The pulse wave signal extraction filter 50 extracts a volume pulse wave signal component (hereinafter simply referred to as a pulse wave signal component) from the sensor output signal, and outputs it to the main control unit 30 as a pulse wave signal.
The pressure signal extraction filter 51 removes the pump noise component and the pulse wave signal component from the sensor output signal, and outputs the result as a pressure signal to the main control unit 30.

Each of these filters can be realized by a filter having a frequency characteristic that passes the band of the signal component to be extracted and blocks or largely attenuates the other band. For example, the pulse wave signal extraction filter 50 can be realized by a band pass filter that passes a general pulse frequency. In addition, the frequency band differs in the pulse wave measured in the site | part of four limbs, such as an upper arm and an ankle, and the pulse wave measured by a footpad. Therefore, it is possible to switchably provide a band pass filter of a frequency characteristic according to a measurement site (a site to which the cuff 10 is attached) or to change the frequency characteristic of the filter according to the measurement site.
The pressure signal extraction filter 51 can be configured by a low pass filter that removes AC components such as a pump noise component and a pulse wave signal component from the sensor output signal.

  The main control unit 30 includes, for example, one or more programmable processors (MPU) and a memory, and the MPU stores the program stored in the memory and executes the program by the MPU to control the operation of each part of the automatic sphygmomanometer 150. Achieve 150 functions. The memory may also store information (such as various constants and set values) used to execute the program. Although the pulse wave signal extraction filter 50 and the pressure signal extraction filter 51 are shown as separate components from the main control unit 30 in FIG. 1, the functions of these filters are executed by the MPU of the main control unit 30. May be realized.

  The main control unit 30 acquires a pulse wave signal and a pressure signal, and controls the operation of the pump 18, the constant discharge valve 14 and the rapid discharge valve 16 through the cuff control unit 20 based on the pressure signal. Further, the main control unit 30 determines blood pressure values (systolic blood pressure, mean blood pressure, and diastolic blood pressure) based on the value of the pressure signal when the amplitude of the pulse wave signal satisfies a specific condition.

  The operation unit 60 is, for example, a key, a switch, or a button, and receives an instruction or setting from the user. For example, a power button / switch, a switch / button for instructing start of blood pressure measurement, a switch / button for instructing cancellation of blood pressure measurement being performed, and the like are included. When the display unit 70 has a touch panel, the combination of the GUI display on the display unit 70 and the touch panel also constitutes a part of the operation unit 60. The operation of the operation unit 60 is monitored by the main control unit 30, and the main control unit 30 executes an operation according to the detected operation.

  The display unit 70 includes, for example, a dot matrix type display such as an LCD, an LED lamp, and the like, and displays the operation state of the automatic blood pressure monitor 150, measurement results, guidance and the like under control of the main control unit 30. The automatic sphygmomanometer 150 may include another output device such as a speaker or a printer instead of or in addition to the display unit 70.

  The storage unit 80 is a storage device that stores information related to measurement data (such as information of a subject), measurement data, and the like, and may be, for example, a non-volatile memory. The storage unit 80 may be configured to use a recording medium removable from the automatic blood pressure monitor 150, such as a memory card. At least a part of the program executed by the MPU of the main control unit 30 and the information used for executing the program may be stored in the storage unit 80.

  The external interface (I / F) 90 is a wired and / or wireless communication interface for connecting an external device using the measured blood pressure value to the automatic blood pressure monitor 150, for example. The automatic sphygmomanometer 150 can communicate with an external device through an external interface (I / F) 90. Alternatively, power may be supplied from an external device through the external interface (I / F) 90.

● (Operation of automatic sphygmomanometer)
FIG. 2 is a flowchart for explaining the blood pressure measurement process of the automatic blood pressure monitor 150 of the present embodiment. For example, when the start of the blood pressure measurement operation is instructed by pressing the start button or the like of the operation unit 60, the main control unit 30 instructs the cuff control unit 20 to start air supply to the cuff 10 in S101.

  The cuff control unit 20 operates the pump 18 in response to this instruction. Thus, the air supply to the air bag 11 is started. During the air supply, the cuff control unit 20 controls both the constant discharge valve 14 and the rapid discharge valve 16 to a fully closed state. The sensor output signal output from the pressure sensor 12 is a signal representing the static internal pressure (cuff pressure) of the air bag 11, the pressure fluctuation (volume pulsating wave component) due to the pulse at the attachment site of the cuff 10 and the operation noise of the pump 18 (Pump noise component) is an electrical signal superimposed.

  The sensor output signal is digitized by the AD converter 22 and then supplied to the pulse wave signal extraction filter 50 and the pressure signal extraction filter 51. The pulse wave signal extraction filter 50 supplies the pulse wave signal component extracted from the sensor output signal to the main control unit 30 as a pulse wave signal. The pressure signal extraction filter 51 supplies a signal obtained by removing the pump noise component and the pulse wave signal component from the sensor output signal to the main control unit 30 as a pressure signal.

  In S103, the main control unit 30 determines whether or not the cuff pressure represented by the pressure signal has reached a predetermined target value. If it is determined that the pressure has reached, the process proceeds to S105. Proceed with each process.

  In S121, the main control unit 30 determines whether or not an abnormality is detected. If it is not determined, the process returns to S103 to continue the air supply, and when it is determined that it is detected, the process proceeds to S123. For example, the main control unit 30 may not normally pressurize the cuff 10, such as when the elapsed time since the start of the supply of air exceeds the threshold or when the amplitude of the sensor output signal is less than the threshold When it is determined that there is an abnormality in the circuit component, or when stop of the measurement is instructed from the operation unit 60, it can be determined that the abnormality is detected.

At S123, the main control unit 30 forcibly terminates the blood pressure measurement.
Specifically, the main control unit 30 causes the cuff control unit 20 to
・ Operation stop of pump 18 (air supply stop)
・ Instructs full opening of the constant discharge valve 14 and the rapid discharge valve 16.

  In S125, the cuff control unit 20 stops the operation of the pump 18 in accordance with the instruction from the main control unit 30, and makes the constant discharge valve 14 and the rapid discharge valve 16 fully open.

  In S127, for example, the main control unit 30 displays a message on the display unit 70 or outputs an alarm sound to notify of a device abnormality, and ends the blood pressure measurement process. After the main control unit 30 instructs the cuff control unit 20 in S123, the process may proceed to S127 without waiting for the completion of the operation of the cuff control unit 20.

  On the other hand, when it is determined in S103 that the cuff pressure has reached the target value, the main control unit 30 instructs the cuff control unit 20 to stop the air supply in S105. Alternatively, even if it is not determined in S103 that the cuff pressure represented by the pressure signal has reached a predetermined target value, the process proceeds to S105 when it is confirmed that the pulse wave signal continues to disappear for a predetermined time. May be The cuff control unit 20 stops the operation (air supply) of the pump 18 in response to the air supply stop instruction.

  Next, the main control unit 30 starts blood pressure determination processing. The blood pressure determination process can be performed by a method based on a known oscillometric method. First, at S107, the main control unit 30 opens the constant discharge valve 14 to the cuff control unit 20 at an opening degree corresponding to a predetermined target value (for example, 5 mmHg / sec) of the pressure reduction rate. To tell. The cuff control unit 20 notifies the constant discharge valve drive circuit 21 of the opening degree or the flow rate instructed from the main control unit 30. The constant discharge valve drive circuit 21 generates a drive current according to the notified opening degree or flow rate, and drives the constant discharge valve 14. As a result, the opening degree of the constant discharge valve 14 becomes larger than 0 (fully closed), exhausting from the constant discharge valve 14 is started, and the internal pressure of the air bag 11 of the cuff 10 also starts to decrease.

  When the initial opening degree at the time of opening the constant discharge valve 14 is preset in the cuff control unit 20, the main control unit 30 simply opens the constant discharge valve 14 without specifying the opening degree in S107. You may instruct the cuff control unit 20 as follows.

  When instructing the cuff control unit 20 to open the constant discharge valve 14, the main control unit 30 starts the process of determining the blood pressure value based on the pulse wave signal and the pressure signal. For example, before and after the time when the amplitude of the pulse wave signal reaches a maximum, the main control unit 30 systolic blood pressure indicates the pressure value indicated by the pressure signal when the amplitude of the pulse wave signal corresponds to a predetermined ratio of the maximum amplitude. And can be determined as diastolic blood pressure. Alternatively, the main control unit 30 can determine, as systolic blood pressure and diastolic blood pressure, the pressure values indicated by the pressure signal at the time when a significant change occurs in the amplitude of the pulse wave signal. In addition, a temporary blood pressure value may be determined during decompression, and a final blood pressure value may be determined after decompression processing is completed.

  In S109, the main control unit 30 monitors the pressure signal while executing the blood pressure determination process, and determines whether the pressure reduction rate is within the target range. Specifically, the main control unit 30 determines whether the current cuff pressure is within the target range of the current target value ± tolerance obtained from the elapsed time from opening the constant discharge valve 14 and the target pressure reduction rate. judge.

  If it is determined that the pressure reduction rate is within the target range, the main control unit 30 advances the process to S111 and determines whether the blood pressure determination process has ended. If it is determined that the blood pressure determination process is completed, the main control unit 30 proceeds to step S113. If it is not determined that the blood pressure determination process is completed, the process returns to step S109. As described above, in the blood pressure determination process, a provisional blood pressure value may be determined.

In S113, the main control unit 30 instructs the cuff control unit 20 to set both the constant discharge valve 14 and the rapid discharge valve 16 to the fully open state. In response to this, the cuff control unit 20 controls the constant discharge valve 14 and the rapid discharge valve 16 to the fully open state.
In S120, the main control unit 30 presents the measured value such as the blood pressure value determined during decompression or after S113, the reliability of the blood pressure value, and other information obtained during the measurement, and ends the blood pressure measurement process. The presentation of the information may be, for example, a display on the display unit 70, a notification by voice, or a combination thereof. Here, it is assumed that the display unit 70 is displayed.

  On the other hand, when the pressure reduction rate is not determined to be within the target range in S109, the main control unit 30 adjusts the opening degree of the constant discharge valve 14 in S115 to S119. Specifically, in S115, the main control unit 30 determines whether the current cuff pressure) is lower than the target range, and if it is determined to be lower, the process proceeds to S119. If it is not determined to be lower, the process proceeds to S117. Advance.

  In S119, the main control unit 30 instructs the cuff control unit 20 to increase the opening degree of the constant discharge valve 14 in order to increase the exhaust flow rate, and returns the process to S109. Further, in step S117, the main control unit 30 instructs the cuff control unit 20 to reduce the opening degree of the constant discharge valve 14 in order to reduce the exhaust flow rate, and the process returns to step S109. The cuff control unit 20 instructs the constant discharge valve drive circuit 21 to increase or decrease the opening degree of the constant discharge valve 14 by a predetermined ratio in accordance with an instruction from the main control unit 30.

● (fixed exhaust valve drive circuit 21)
FIG. 3 is a view showing a configuration example of the constant discharge valve drive circuit 21. As shown in FIG. In the present embodiment, the constant discharge valve 14 is a solenoid valve using a solenoid, and the constant discharge valve drive circuit 21 is a modulation signal obtained by pulse width modulation (PWM) of a pulse signal (square wave) having a predetermined frequency. Is used to drive the constant discharge valve 14. The PWM circuit 211 can be realized by, for example, an FPGA (Field Programmable Gate Array). The PWM circuit 211 adjusts the frequency of the pulse signal supplied as a clock signal (carrier signal) as necessary, and then performs a pulse so as to have a duty ratio according to the opening degree or the flow rate instructed from the cuff control unit 20. Modulate width and output. Although the clock signal is supplied from the outside of the constant exhaust valve drive circuit 21 here, an oscillator may be provided in the constant exhaust valve drive circuit 21 to generate a clock signal.

  The pulse signal output from the PWM circuit 211 is input to the base of the transistor 212 as a switching element. The transistor 212 is turned on when the pulse signal is high, and turned off when the pulse signal is low. The constant discharge valve 14 is connected between the power source E and the collector of the transistor 212.

  As the duty ratio of the pulse signal output from the PWM circuit 211 becomes higher, the drive current of the constant discharge valve 14 becomes larger. When the notification of the opening degree or flow rate is received from the cuff control unit 20, the PWM circuit 211 stores the duty ratio of the pulse signal according to a table or a relational expression stored in advance indicating the relation between the opening degree or flow rate and the duty ratio. Decide. Then, the PWM circuit 211 generates and outputs a pulse having the determined duty ratio.

  In the present embodiment, the PWM circuit 211 controls the duty ratio of a pulse signal having a frequency such that the drive current of the constant discharge valve 14 becomes a pulsating current or a pulsating current (current whose magnitude changes periodically).

The solenoid can be viewed as an LR series circuit consisting of a coil and parasitic resistance. Therefore, the equation of the drive circuit can be expressed by the following equation (1), where L is the inductance of the coil, Rs is the parasitic resistance, e is the power supply voltage, and i is the current.

The drive current of the constant discharge valve 14 obtained by switching the transistor 212 with the pulse signal output from the PWM circuit 211 follows the voltage with a first-order lag characteristic. Here, when equation (1) is solved with the frequency of the pulse signal (carrier signal) for controlling the duty ratio of the PWM circuit 211 as ω _c , the amplitude current I of the PWM pulse signal component in the drive current of the constant discharge valve is
It becomes. Here, E is the power supply voltage [V].

From equation (2), it can be seen that the amplitude current I becomes smaller as the frequency ω _{c of the} pulse signal is higher. In this embodiment, by making the drive current pulsating by decreasing the frequency ω _{c of the} pulse signal, the plunger is always slightly vibrated, and the hysteresis of the drive amount in the drive direction is suppressed. As described above, since the solenoid can be regarded as an RL series circuit, when the frequency ω _{c of the} pulse signal is higher than the frequency corresponding to the time constant of the solenoid, the magnitude of the drive current becomes substantially constant. Therefore, the frequency ω _{c of the} pulse signal is set to a value lower than the frequency corresponding to the time constant of the solenoid valve used for the constant discharge valve 14. Moreover, in order not to affect blood pressure measurement, the value is set higher than the cutoff frequency (for example, 150 Hz) of a low pass filter used as a pulse wave signal extraction filter.

The frequency ω _c of the pulse signal can define the frequency ω _c of the pulse signal in a range where the hysteresis [%] is less than a predetermined threshold. The threshold may be, for example, about 3%, but it is not limited to this.

  Since the constant discharge valve drive circuit 21 shown in FIG. 3 is configured to directly PWM drive the constant discharge valve 14, for example, the current control parameter of the constant current circuit is periodically varied to pulse the drive current of the constant discharge valve 14. It is simpler than the current configuration.

FIG. 4 is a view showing a specific example of the relationship between the drive current and the exhaust flow rate in the sphygmomanometer using a proportional solenoid as a constant discharge valve. Here, the drive voltage E of the constant discharge valve 14 is 6 [V], and the internal pressure of the air bag 11 detected by the pressure sensor 12 is 300 mmHg, and the direction from fully closed to fully open and from fully open to fully closed The drive current (due ratio) was changed depending on the direction of travel, and the exhaust flow rate was measured. The inductance L of the proportional solenoid was 49 mmH (1 kHz), and the parasitic resistance Rs was 137 Ω. Therefore, the time constant τ = L / R = 3.58 × 10 ⁻⁴ [sec] of the solenoid valve, and the frequency 1 / t = 2795.9 [Hz] corresponding to the time constant τ. The cut-off frequency of the pulse wave signal extraction filter 50 applied to the pulse wave signal is 150 Hz.

The measurement results for the case where the frequency ω _{c of the} pulse signal is higher (ω _c = 32 kHz) and lower (ω _c = 1 kHz and 300 Hz) than the frequency corresponding to the time constant τ are shown in FIG. -It shows in FIG.4 (c).

As shown in FIG. 4, when the frequency ω _c of the pulse signal is higher than the frequency corresponding to the time constant τ, the hysteresis is large, which is suitable for feedback control as implemented in S109 and S115 to S119 of FIG. 2. Absent. On the other hand, when the frequency ω _{c of the} pulse signal is lower than the frequency corresponding to the time constant τ, the hysteresis is largely suppressed, and particularly when ω _c = 300 Hz, the hysteresis is almost eliminated.

  Thus, according to the present invention, even when the solenoid valve used as a constant discharge valve has hysteresis in the relationship between the opening degree and the drive current, it becomes possible to carry out feedback control of the opening degree with high accuracy. As a result, blood pressure measurement accuracy can be improved. Also, in general, solenoid valves with small hysteresis are more expensive than solenoid valves with large hysteresis. According to the present invention, since the influence of hysteresis can be significantly suppressed, accurate blood pressure measurement can be performed even using a solenoid valve with a relatively large hysteresis, which is extremely useful also from the viewpoint of cost reduction of a sphygmomanometer. It is.

  The constant discharge valve driving method according to the present invention may be implemented as a program (application software) that causes one or more programmable processors (computers) of the cuff control unit 20 to execute the same operation as the PWM circuit 211. You can also. Therefore, such a program and a storage medium storing the program (an optical recording medium such as a CD-ROM or a DVD-ROM, a magnetic recording medium such as a magnetic disk, a semiconductor memory card, etc.) also constitute the present invention. .

DESCRIPTION OF SYMBOLS 10 ... Cuff, 11 ... Airbag, 12 ... Pressure sensor, 14 ... Fixed discharge valve, 16 ... Sudden discharge valve, 18 ... Pump, 20 ... Cuff control part, 21 ... Fixed discharge valve drive circuit, 22 ... AD converter, 30 ... main control unit, 51 ... pulse wave extraction filter, 52 ... pressure extraction filter, 150 ... sphygmomanometer

Claims (7)

An air bag attached to the measurement site of the subject;
A solenoid valve for reducing the internal pressure of the air bag;
A sphygmomanometer having a drive circuit for controlling the opening degree of the solenoid valve;
The sphygmomanometer according to claim 1, wherein the drive circuit drives the solenoid valve using a pulse signal having a frequency lower than a frequency corresponding to a time constant of the solenoid valve to control an opening degree of the solenoid valve.   The sphygmomanometer according to claim 1, wherein the frequency is higher than a cut-off frequency of a low pass filter applied to a pulse wave signal detected by using the air bag.   The said frequency is defined in the range from which the hysteresis of the magnitude | size of the drive current of the said solenoid valve and the opening degree of the said solenoid valve becomes less than a predetermined threshold value. Sphygmomanometer.   The sphygmomanometer according to any one of claims 1 to 3, wherein the drive circuit controls an opening degree of the solenoid valve by changing a duty ratio of the pulse signal.   The sphygmomanometer according to any one of claims 1 to 4, wherein the solenoid valve is used as a constant discharge valve.   6. The apparatus according to claim 1, further comprising control means for controlling the degree of opening of said solenoid valve using said drive circuit so that the internal pressure of said air bag becomes a target value during measurement of blood pressure. The sphygmomanometer according to any one of the above. An air bag attached to the measurement site of the subject;
A control method of a sphygmomanometer having a solenoid valve for reducing the internal pressure of the airbag.
Control of a sphygmomanometer comprising a control step of driving the solenoid valve using a pulse signal having a frequency lower than a frequency corresponding to a time constant of the solenoid valve to control an opening degree of the solenoid valve Method.