FLUID CONTROL DEVICE AND SPHYGMOMANOMETER

• US 20190331101A1
• Filed: 07/11/2019
• Published: 10/31/2019
• Est. Priority Date: 01/20/2017
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: OKAGUTI, Kenjiro
• Granted Patent: US 11,773,835 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2560/0214 of power generation or supply
• CPC Class Codes: A61B 5/02141 Details of apparatus construction, e.g. pump units or housings therefor, cuff pressurising systems, arrangements of fluid conduits or circuits A61B5/02233, A61B5/0235 take precedence
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds
• CPC Class Codes: F04B 17/003 driven by piezoelectric means F04B43/046 and F04B43/095 take precedence
• CPC Class Codes: F04B 17/03 driven by electric motors
• CPC Class Codes: F04B 43/095 Piezoelectric drive
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: F04B 49/08 Regulating by delivery pressure

Abstract

Provided are a fluid control device capable of operating a piezoelectric pump even in a case where a low discharge pressure or a slow pressurization speed is required and a sphygmomanometer including the fluid control device. A fluid control device includes a piezoelectric pump that includes a piezoelectric element, a self-excited circuit that performs, upon application of a driving power source voltage thereto, self-excited oscillation to drive the piezoelectric element, a switch that interrupts the driving power source voltage for the self-excited circuit, and a control circuit that changes an on duty ratio of the self-excited circuit by switching between states of the switch at a predetermined switching frequency and a predetermined on duty ratio.

Claims

1. A fluid control device comprising:

a piezoelectric pump comprising a piezoelectric element;

a self-excited circuit configured to, upon application of a driving power source voltage, self-excitedly oscillate and apply a driving voltage to the piezoelectric element, thereby driving the piezoelectric element; and

a control circuit configured to determine an on-time duty ratio for driving the piezoelectric element.

2. The fluid control device according to claim 1, further comprising:

a switch configured to selectively apply or interrupt the application of the driving power source voltage to the self-excited circuit.

3. The fluid control device according to claim 2, wherein the control circuit is further configured to change a state of the switch according to the on-time duty ratio.

4. The fluid control device according to claim 1, further comprising:

a switch configured to selectively apply or interrupt the application of the driving voltage to the piezoelectric element.

5. The fluid control device according to claim 4, wherein the control circuit is further configured to change a state of the switch according to the on-time duty ratio.

6. The fluid control device according to claim 1, wherein the on-time duty ratio is predetermined.

7. The fluid control device according to claim 2, wherein the switch comprises:

a field-effect transistor (FET), and

a circuit configured to drive the FET according to the on-time duty ratio.

8. The fluid control device according to claim 4, wherein the switch comprises:

a field-effect transistor (FET), and

a circuit configured to drive the FET according to the on-time duty ratio.

9. The fluid control device according to claim 1, further comprising:

a DC/DC converter configured to convert a DC input power source voltage to the driving power source voltage.

10. The fluid control device according to claim 9, wherein the control circuit is further configured to selectively control output of the driving power source voltage from the DC/DC converter according to the on-time duty ratio.

11. The fluid control device according to claim 1, wherein:

when a desired operating pressure of the piezoelectric pump is below a predetermined value, the on-time duty ratio corresponds to a ratio at which the applied driving power source voltage is the lowest voltage at which the self-excited circuit is operable, and

when the desired operating pressure of the piezoelectric pump is greater than or equal to the predetermined value, the driving power source voltage is greater than a lowest voltage corresponding to an on-time duty ratio of 100%.

12. The fluid control device according to claim 2, wherein:

when a desired operating pressure of the piezoelectric pump is below a predetermined value, the on-time duty ratio corresponds to a ratio at which the applied driving power source voltage is the lowest voltage at which the self-excited circuit is operable, and

when the desired operating pressure of the piezoelectric pump is greater than or equal to the predetermined value, the driving power source voltage is greater than a lowest voltage corresponding to an on-time duty ratio of 100%.

13. The fluid control device according to claim 10, wherein:

when a desired operating pressure of the piezoelectric pump is below a predetermined value, the on-time duty ratio corresponds to a ratio at which the applied driving power source voltage is the lowest voltage at which the self-excited circuit is operable, and

when the desired operating pressure of the piezoelectric pump is greater than or equal to the predetermined value, the driving power source voltage is greater than a lowest voltage corresponding to an on-time duty ratio of 100%.

14. The fluid control device according to claim 1, wherein the control circuit comprises a microcontroller including a pulse width modulation (PWM) signal generation circuit configured to generate a PWM signal, wherein the on-time duty ratio corresponds to the PWM signal.

15. A sphygmomanometer comprising:

a cuff;

the fluid control device of claim 1 configured to pressurize the cuff by an output of the piezoelectric pump;

a valve configured to adjust pressure inside the cuff by controlling a supply of the output of the piezoelectric pump; and

a controller and a sensor together configured to measure a blood pressure of a subject based on the pressure of the cuff.

16. The sphygmomanometer according to claim 15, wherein the sensor is configured to measure the blood pressure of the subject based further on a pulse wave of the subject or Korotkoff sounds.

17. A sphygmomanometer comprising:

a cuff;

the fluid control device of claim 3 configured to pressurize the cuff by an output of the piezoelectric pump;

a valve configured to adjust pressure inside the cuff by controlling a supply of the output of the piezoelectric pump; and

a controller and a sensor together configured to measure a blood pressure of a subject based on the pressure of the cuff,

wherein the control circuit is further configured to change a state of the switch at a predetermined frequency.

18. The sphygmomanometer according to claim 17, wherein the frequency is greater than or equal to ten times the reciprocal of a measurement period of the controller and sensor, and is less than or equal to one tenth a driving frequency of the piezoelectric element.