Fluid control device

A fluid control device (10) includes a container (13), a pump (11), a solenoid valve (12), and a capacitor. The pump (11) is driven by a main power source, and is capable of pressurizing or depressurizing the inside of the container (13). A suction port and a discharge port of the pump (11) internally communicate with each other. The solenoid valve (12) is connected at both ends thereof to the container (13) and the pump (11). If the voltage of the main power source is reduced or lost, the solenoid valve (12) releases pressure in the container (13) by being driven by the power stored in the capacitor or secondary battery.

FIELD OF THE DISCLOSURE

The present disclosure relates to a fluid control device that controls fluid in a container.

DESCRIPTION OF THE RELATED ART

Examples of conventional fluid control devices include one disclosed in Patent Document 1. This fluid control device includes a cuff having a fluid bag, a pump unit configured to supply air into the fluid bag, a valve configured to open and close for discharging air from or introducing air into the fluid bag, and a CPU configured to control the drive of the pump unit and the valve. The fluid control device controls pressure in the fluid bag by driving the pump unit and the valve.

FIG. 13Ais a schematic block diagram of a fluid control device140having a conventional configuration. In the fluid control device140, a container13is connected to a pump11having a suction port and a discharge port internally communicating with each other. The pump11can transfer a fluid by being driven. By stopping the drive of the pump11, the pump11can reverse the flow of the fluid in accordance with a differential pressure between the suction port and the discharge port of the pump11. Therefore, by repeatedly driving and stopping the pump11, the fluid control device140can control the pressure in the container13to a predetermined level. Even if the main power source of the fluid control device140is lost, since the fluid in the container13is discharged to the outside through the inside of the pump11, the pressure in the container13is released. Thus, even when the fluid control device140is used for a human body, the human body can be prevented from being exposed to a hazard by the pressure maintained in the container13.

FIG. 13Bis a schematic block diagram of a fluid control device150having a conventional configuration. In the fluid control device150, a solenoid valve152is connected between the pump11and the container13. The solenoid valve152has a first port and a second port isolated in the energized state and communicating with each other in the non-energized state. The first port of the solenoid valve152is connected to the pump11, and the second port of the solenoid valve152is connected to the container13. When controlling or releasing pressure in the container13, the fluid control device150opens the solenoid valve152by not energizing it. When maintaining the pressure in the container13, the fluid control device150closes the solenoid valve152by energizing it. If the main power source of the fluid control device150is lost, since the solenoid valve152is opened, the pressure in the container13is released through the pump11and the solenoid valve152.

FIG. 13Cis a schematic block diagram of a fluid control device160having a conventional configuration. In the fluid control device160, the first port of the solenoid valve152is connected between a pump61and the container13, and the second port of the solenoid valve152is connected to the outside. The pump61prevents the backflow of the fluid in the non-energized state. When controlling or maintaining the pressure in the container13, the fluid control device160closes the solenoid valve152by energizing it. When releasing the pressure in the container13to the outside, the fluid control device160opens the solenoid valve152by not energizing it. If the main power source of the fluid control device160is lost, since the solenoid valve152is opened, the pressure in the container13is released through the solenoid valve152.Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-220187

BRIEF SUMMARY OF THE DISCLOSURE

Studies done by the present inventors will now be described.

When keeping the pressure in the container13constant, the fluid control device140needs to continuously drive the pump11, and this increases the power consumption. Inserting a check valve between the pump11and the container13makes it possible to keep the pressure in the container13constant without driving the pump11. However, this makes it unable to release the pressure in the container13.

When keeping the pressure in the container13constant, the fluid control device150needs to continuously energize the solenoid valve152to close it, and this increases the power consumption. When controlling or maintaining the pressure in the container13, the fluid control device160also needs to continuously energize the solenoid valve152to close it, and this increases the power consumption.

An object of the present disclosure is to provide a fluid control device that is capable of releasing the pressure in the container when the power is shut off while reducing the power consumption.

A fluid control device according to the present disclosure includes a container, a pump, a valve, and a capacitor or secondary battery. The pump is driven by a main power source, and is capable of pressurizing or depressurizing an inside of the container. A suction port and a discharge port of the pump internally communicate with each other. The valve connects to or communicates with the container and the pump at one or both ends thereof. If a voltage of the main power source is reduced or lost, the valve releases the pressure in the container by being driven by the power stored in the capacitor or secondary battery.

With this configuration, if the voltage of the main power source is reduced or lost, the pressure in the container is released. The container can thus be prevented from remaining pressurized.

The fluid control device according to the present disclosure may be configured in the following manner. The valve has a first port connected to the pump and a second port connected to the container, allows the first port and the second port to communicate with each other in an energized state, and isolates the first port and the second port in a non-energized state. If the voltage of the main power source is reduced or lost, the valve is energized by the power stored in the capacitor or secondary battery.

The fluid control device according to the present disclosure may be configured in the following manner. The valve has a first port connected to an outside and a second port connected to the pump, allows the first port and the second port to communicate with each other in an energized state, and isolates the first port and the second port in a non-energized state. If the voltage of the main power source is reduced or lost, the valve is energized by the power stored in the capacitor or secondary battery.

With the configurations described above, the pressure in the container is maintained by isolating the first port and the second port of the valve. Since the valve is not energized when the pressure in the container is maintained, it is possible to reduce the power consumption. If the voltage of the main power source is reduced or lost, the valve is energized by the power stored in the capacitor or secondary battery. Since this allows the first port and the second port to communicate with each other, the pressure in the container is released.

In the fluid control device according to the present disclosure, the capacitor or secondary battery is preferably supplied with the power from the main power source.

In the fluid control device according to the present disclosure, the pump may pressurize the inside of the container. The fluid control device according to the present disclosure may measure a blood pressure on the basis of the pressure in the container.

With this configuration, the inside of the container is pressurized by driving the pump and isolating the first port and the second port of the valve. Since the valve is not energized when the inside of the container is pressurized, it is possible to reduce the power consumption. Also, since the pressure in the container is released when the main power source is shut off or the voltage of the main power source drops, the safety of a person to be measured can be ensured.

In the fluid control device according to the present disclosure, the container may be a cuff.

The fluid control device according to the present disclosure may be configured in the following manner. The fluid control device according to the present disclosure includes a drive circuit configured to energize the valve. The drive circuit includes the capacitor or secondary battery connected to a direct-current power source via a diode, and a coil for driving the valve. The drive circuit further includes a switch for applying the power stored in the capacitor or secondary battery to the coil if the voltage of the main power source is reduced or lost.

With this configuration, if the main power source is shut off or the voltage of the main power source drops, a voltage is applied to the coil for driving the valve by switching the switch. Since this allows the first port and the second port of the valve to communicate with each other, the pressure in the container is released.

According to the present disclosure, it is possible not only to reduce the power consumption, but also to release the pressure in the container when the power is shut off.

DETAILED DESCRIPTION OF THE DISCLOSURE

First Embodiment

A fluid control device10according to a first embodiment of the present disclosure will be described. For example, the fluid control device10is used as a pressure massaging device that repeatedly compresses a body with an air bag.FIG. 1Ais a schematic block diagram of the fluid control device10. The fluid control device10includes a pump11, a solenoid valve12, a container13, and a drive circuit14(seeFIG. 3). The solenoid valve12corresponds to “valve” of the present disclosure. The pump11is connected via a tube to the solenoid valve12. The solenoid valve12is connected via a tube to the container13. The pump11and the solenoid valve12are driven by the drive circuit14. In the fluid control device10, the pressure in the container13is controlled by the operation of the pump11. The pump11, the solenoid valve12, and the container13may be directly connected without tubes.

The pump11has a structure in which a suction port and a discharge port thereof internally communicate with each other. In the non-energized state, the fluid can be transferred inside the pump11in accordance with a differential pressure between the suction port and the discharge port. The pump11is driven by a piezoelectric element. The solenoid valve12is opened and closed by movement of a plunger caused by magnetic force produced by energizing a coil. The solenoid valve12has a first port and a second port communicating with each other in the energized state and isolated (not communicating with each other) in the non-energized state. The container13has an inner space for storing the fluid therein, and an opening communicating with the inner space.

The suction port of the pump11communicates with the outside via a flow passage in a tube. The discharge port of the pump11communicates with the first port of the solenoid valve12via a flow passage in the tube. The second port of the solenoid valve12communicates with the opening of the container13via a flow passage in the tube. That is, the pump11is connected to the container13to pressurize the inside of the container13.

FIG. 1Bis a schematic block diagram of a fluid control device according to a modification of the first embodiment. The solenoid valve12is connected via a tube to the pump11. The pump11is connected via a tube to the container13. The first port of the solenoid valve12communicates with the outside via a flow passage in a tube. The second port of the solenoid valve12communicates with the suction port of the pump11via a flow passage in the tube. The discharge port of the pump11communicates with the opening of the container13via a flow passage in the tube. This fluid control device operates in the same manner as the fluid control device10.

FIG. 2Ais a schematic cross-sectional view of a piezoelectric pump21. The piezoelectric pump21is an example of the pump11. The piezoelectric pump21is constructed by stacking a cover plate22, a flow passage plate23, a counter plate24, an adhesive layer25, a vibrating plate26, a piezoelectric element27, an insulating plate28, a feeding plate29, a spacer plate30, and a lid plate31in this order. The piezoelectric pump21is thin in the stacking direction and rectangular in plan view (as viewed from the stacking direction). The piezoelectric pump21has suction ports33on the side of the cover plate22. The piezoelectric pump21has a discharge port34on the side of the lid plate31. The discharge port34of the piezoelectric pump21is connected via a tube to the first port of the solenoid valve12as described above.

The cover plate22has circular flow passage holes37. The flow passage plate23has circular cavities38. The cavities38communicate with the respective flow passage holes37. The cavities38are greater in diameter than the flow passage holes37. The counter plate24is made of metal. The counter plate24has an external connection terminal35protruding outward, and the suction ports33circular in shape. The suction ports33communicate with the respective cavities38. The suction ports33are smaller in diameter than the cavities38. Thus, bendable movable portions39are formed around the respective suction ports33in the counter plate24.

The adhesive layer25is formed in the shape of a frame to coincide with a frame portion44of the vibrating plate26. The adhesive layer25is made of a thermosetting resin, such as an epoxy resin, containing a plurality of conductive particles with a substantially uniform diameter. This makes it possible to achieve a uniform thickness of the adhesive layer25over the entire circumference by making the thickness substantially the same as the diameter of the conductive particles. Also, the counter plate24and the vibrating plate26can be electrically connected, with the conductive particles of the adhesive layer25interposed therebetween.

The vibrating plate26is made of metal, such as SUS301. The vibrating plate26faces the counter plate24at a given distance therefrom. The space between the counter plate24and the vibrating plate26forms a pump chamber40. The vibrating plate26has a center portion41, striking portions42, connecting portions43, and the frame portion44. The center portion41is circular in plan view, and is positioned in the center of the vibrating plate26. The frame portion44has a frame shape in plan view, and is positioned in the outer region of the vibrating plate26. The connecting portions43have a beam-like shape and connect the center portion41to the frame portion44. The striking portions42are circular in plan view and are each positioned around the boundary between the center portion41and the corresponding connecting portion43. The striking portions42are each positioned to face the corresponding suction port33in the center thereof. The striking portions42are greater in diameter than the suction ports33. The striking portions42and the frame portion44are thicker than the center portion41and the connecting portions43. The vibrating plate26has a cavity (not shown) surrounded by the components thereof described above. The pump chamber40communicates with the pump chamber46, with the cavity interposed therebetween.

The piezoelectric element27is formed by placing electrodes on both principal surfaces of a thin plate made of a piezoelectric material. The piezoelectric element27has piezoelectricity that allows the piezoelectric element27to expand or contract in area in the in-plane direction by being subjected to an electric field in the thickness direction. The piezoelectric element27has a disk shape and is affixed to the upper surface of the center portion41of the vibrating plate26. The electrode on the lower surface of the piezoelectric element27is electrically connected to the external connection terminal35via the vibrating plate26, the adhesive layer25, and the counter plate24.

The insulating plate28is made of an insulating resin. The insulating plate28has a cavity which is rectangular in plan view. The feeding plate29is made of metal. The feeding plate29has a cavity which is rectangular in plan view, an internal connection terminal45protruding toward the cavity of the feeding plate29, and an external connection terminal36protruding outward. An end portion of the internal connection terminal45is soldered to the electrode on the upper surface of the piezoelectric element27. The spacer plate30is made of resin. The spacer plate30has a cavity which is rectangular in plan view. The cavities of the insulating plate28, feeding plate29, and spacer plate30communicate with one another to form the pump chamber46. The lid plate31has the discharge port34which is circular in plan view. The discharge port34communicates with the pump chamber46and the outside.

FIG. 2Bis a schematic diagram illustrating an operation of the piezoelectric pump21. In the piezoelectric pump21, when an alternating drive voltage is applied to the external connection terminals35and36, the piezoelectric element27tries to isotropically expand and contract in the in-plane direction. This produces concentric bending vibration of a multilayer body composed of the piezoelectric element27and the vibrating plate26in the thickness direction. This bending vibration is in higher-order resonant mode. The frame portion44serves as a fixed portion, the center of the center portion41corresponds to a first vibration antinode, and the center of each striking portion42corresponds to a second vibration antinode.

Vibration of the striking portions42is transmitted to the movable portions39via fluid facing the striking portions42. The vibration of the striking portions42and the vibration of the movable portions39are coupled to each other, and cause the fluid in the pump chamber40to flow from the vicinity of the suction ports33toward the outer side of the movable portions39. Thus, in the pump chamber40, a negative pressure is produced around the suction ports33, from which the fluid is suctioned into the pump chamber46. Additionally, a positive pressure is produced inside the pump chamber46and released from the discharge port34in the lid plate31. Thus, the fluid suctioned via the suction ports33into the pump chambers40and46flows out of the pump chambers40and46via the discharge port34.

FIG. 3is a circuit configuration diagram of the drive circuit14. The drive circuit14includes a capacitor C1, a diode D1, transistors Q1to Q4, resistors R1, R2, and R7, a switch SW1, a boosting circuit15, an oscillation circuit16, and a microcontroller17. The capacitor C1is, for example, an electric double layer capacitor. A secondary battery may be used instead of the capacitor C1. Examples of the secondary battery include a lithium-ion battery and a nickel-metal-hydride battery. The transistors Q1to Q4are, for example, MOSFETs. The transistor Q2corresponds to “switch” of the present disclosure. The drive circuit14is connected to a main power source P. The main power source P is a direct-current power source, such as a battery. The drive circuit14and the main power source P are connected and disconnected by a switch SW1. Instead of using a direct-current power source as the main power source, the output of an alternating-current power source may be converted by an AC/DC converter.

The capacitor C1is connected between the main power source P and the ground. The diode D1is connected between the main power source P and the capacitor C1. The anode of the diode D1is connected to the main power source P, and the cathode of the diode D1is connected to the capacitor C1. A node N1between the diode D1and the capacitor C1is connected via the solenoid valve12to the drains of the transistor Q2and transistor Q3. The sources of the transistor Q2and transistor Q3are connected to the ground. A node N2between the diode D1and the node N1is connected via the resistor R2to the drain of the transistor Q1. The source of the transistor Q1is connected to the ground. A node between the resistor R2and the transistor Q1is connected to the gate of the transistor Q2. A node N3between the main power source P and the diode D1is connected via the resistor R1to the ground, and is also connected to the gate of the transistor Q1.

The boosting circuit15is connected to the main power source P, and is also connected to the drain of the transistor Q4. The oscillation circuit16is connected to the pump11and the boosting circuit15, and is also connected to the drain of the transistor Q4. The source of the transistor Q4is connected to the ground. The microcontroller17includes terminals P1to P4. The terminal P1is a power terminal connected to the main power source P. The terminal P2is a ground terminal connected to the ground. The terminal P3is connected to the gate of the transistor Q3. The terminal P4is connected to the gate of the transistor Q4. The microcontroller17outputs a solenoid valve drive signal from the terminal P3, and outputs a pump drive signal from the terminal P4. A node between the gate of the transistor Q4and the terminal P4is connected via the resistor R7to the ground.

When the fluid control device10is used, the switch SW1is turned on. This turns on the main power source P in the drive circuit14, and causes the electric charge to be stored in the capacitor C1. That is, the power is stored in the capacitor C1while the main power source P is on.

When the pressure in the container13is controlled by the operation of the pump11, the switch SW1is on, the solenoid valve drive signal goes high, and the pump drive signal is output in a predetermined waveform. When the pump drive signal goes high, the transistor Q4turns on and a voltage from the main power source P is applied to the boosting circuit15. The boosting circuit15boosts the voltage from the main power source P and outputs it. Since the transistor Q4turns on, the voltage output from the boosting circuit15is supplied to the oscillation circuit16. The oscillation circuit generates a drive voltage for driving the pump11. The pump11is driven by the drive voltage. When the pump drive signal goes low, the transistor Q4turns off. Accordingly, no drive voltage is applied to the pump11and the pump11is stopped. The output of the pump11is controlled by repeatedly driving and stopping the pump11in accordance with the pump drive signal. Since the solenoid valve drive signal goes high, the transistor Q3turns on. Thus, since the solenoid valve12is energized by the main power source P, the solenoid valve12is opened to allow the pump11to communicate with the inside of the container13. The pressure in the container13is thus controlled in accordance with the operation of the pump11.

When the pressure in the container13is maintained, the switch SW1is on and the solenoid valve drive signal and the pump drive signal go low. Since the switch SW1is on, the transistor Q1turns on and the transistor Q2turns off. Since the solenoid valve drive signal goes low, the transistor Q3turns off. Thus, since the solenoid valve12is not energized, the solenoid valve12is closed to isolate the pump11and the inside of the container13. This makes it possible to maintain the pressure in the container13. When the pump drive signal goes low, the transistor Q4turns off. The pump11is thus stopped since no drive voltage is applied thereto.

When the use of the fluid control device10is terminated or the main power source P is lost for some reasons, the main power source P is isolated from the drive circuit14(or the main power source P is shut off). Shutting off the main power source P corresponds to turning off the switch SW1. On the other hand, the power stored in the capacitor C1while the main power source P is on is supplied to the drive circuit14. Since a voltage from the capacitor C1is not applied to the gate of the transistor Q1because of the rectifying action of the diode D1, the transistor Q1turns off and the transistor Q2turns on. Thus, since the solenoid valve12is energized by the power stored in the capacitor C1, the solenoid valve12is opened to allow the pump11to communicate with the inside of the container13. As described above, the suction port and the discharge port of the pump11internally communicate with each other. This allows the inside of the container13to communicate with the outside of the fluid control device10. Also, since the power stored in the capacitor C1is not supplied to the pump11and the microcontroller17because of the rectifying action of the diode D1, the pump11is not driven. Therefore, in accordance with a differential pressure between the inside of the container13and the outside of the fluid control device10, the fluid in the container13is discharged to the outside and the pressure in the container13is released to the outside. When the amount of electric charge stored in the capacitor C1becomes insufficient, the solenoid valve12cannot be easily energized and is closed. That is, during several seconds after the main power source P is shut off and before the amount of electric charge stored in the capacitor C1becomes insufficient, the pressure in the container13is released to the outside.

In the first embodiment, when the pressure in the container13is maintained, since the solenoid valve12is not energized, the power is not consumed by the solenoid valve12and is consumed only by the resistors in the drive circuit14. Therefore, the power consumption during the use of the fluid control device10can be reduced. When the main power source P is shut down, since the solenoid valve12is opened for several seconds by the power stored in the capacitor C1, the pressure in the container13can be released to the outside.

Using an electric double layer capacitor as the capacitor C1, or using a secondary battery instead of the capacitor C1, makes it possible to store a larger amount of power. Thus, when the main power source P is shut down, since the solenoid valve12is opened for a certain length of time, it is possible to reliably release the pressure in the container13.

Second Embodiment

A fluid control device according to a second embodiment of the present disclosure will be described. The fluid control device of the second embodiment is configured in the same manner as the fluid control device10of the first embodiment (seeFIG. 1A), except for a drive circuit54of the second embodiment.FIG. 4is a circuit configuration diagram of the drive circuit54. A node between the main power source P and the node N3is connected to the ground via resistors R3and R4connected in series. A node between the resistor R3and the resistor R4is connected to a terminal P5of a microcontroller57. The terminal P5is an input terminal of an A/D converter. The other configuration of the drive circuit54is the same as that of the drive circuit14.

The voltage of the main power source P divided by the resistors R3and R4is applied to the terminal P5of the microcontroller57. The microcontroller57converts the voltage applied to the terminal P5into a digital value. If the digital value is greater than a threshold, the microcontroller57determines that the voltage of the main power source P is within a normal range, whereas if the digital value is smaller than the threshold, the microcontroller57determines that the voltage of the main power source P has dropped. A voltage drop in the main power source P is thus detected. The threshold is set such that normal operation of the fluid control device is secured at around or above the threshold.

If a voltage drop in the main power source P is detected, the solenoid valve drive signal goes high and the pump drive signal goes low. Since the pump drive signal goes low, the pump11is stopped. Since the solenoid valve drive signal goes high, the solenoid valve12is opened to allow the inside of the container13to communicate with the outside of the fluid control device. Thus, the fluid in the container13is discharged to the outside, and the pressure in the container13is released to the outside. The pump drive signal is not output until the voltage of the main power source P returns to a normal value. That is, the operation of the pump11is prohibited until the fluid control device is restarted after battery replacement or the like. Note that the operations that the fluid control device performs when pressure is controlled, the pressure is maintained, and the power is shut off are the same as those in the first embodiment.

When the voltage of the main power source P drops, the fluid control device may not operate properly. For example, due to a voltage drop in the main power source P, the transistor Q2may not properly turn on and off, and thus, the solenoid valve12may not be opened and closed. In the second embodiment, if a voltage drop in the main power source P is detected, the solenoid valve12is opened and the fluid in the container13is discharged to the outside. Therefore, even when the voltage of the main power source P gradually decreases, the pressure in the container13can be released to the outside. Also, since the pump11is not driven until the fluid control device is restarted, it is possible to prevent a malfunction of the fluid control device. The same effect as that of the first embodiment can also be achieved.

Third Embodiment

A fluid control device60according to a third embodiment of the present disclosure will be described.FIG. 5is a schematic block diagram of the fluid control device60. The fluid control device60includes the pump61, the solenoid valve12, the container13, and a drive circuit64(seeFIG. 7). The suction port of the pump61communicates with the outside via a flow passage in a tube. The discharge port of the pump61communicates with the opening of the container13via a flow passage in a tube. The first port of the solenoid valve12communicates with the flow passage in the tube positioned between the pump61and the container13. The second port of the solenoid valve12communicates with the outside via a flow passage in a tube. That is, the pump61is connected to the container13to pressurize the inside of the container13. The pump61prevents the backflow of the fluid in the non-energized state. That is, when the pump61is not energized, no fluid flows through the inside of the pump61from the discharge port to the suction port of the pump61. The pump61is driven by a direct-current motor.

FIG. 6is a schematic cross-sectional view of a diaphragm pump71. The diaphragm pump71is an example of the pump61. The diaphragm pump71has suction ports72and a discharge port73. The discharge port73of the diaphragm pump71is connected, via the tube, to the first port of the solenoid valve12and the opening of the container13as described above.

A case74has a substantially cylindrical shape with a bottom. A motor75driven by a direct-current voltage is attached to the bottom of the case74. An output shaft76of the motor75is inserted into the case74from an opening in the bottom of the case74. A crank base77is secured to the output shaft76. A drive shaft78is mounted at an angle to the crank base77. A drive body79is mounted on the drive shaft78. The drive body79is composed of a bearing80and a pair of drive units81. The drive shaft78is rotatably inserted into the bearing80. The pair of drive units81protrudes in opposite directions from the bearing80. A lid82is attached to the upper part of the case74. The lid82has the suction ports72and the discharge port73. The suction ports72in the lid82are provided with suction valves83. The suction valves83are formed of an elastic material. The suction valves83allow flow only from the suction ports72to pump chambers84.

The pump chambers84are defined by a diaphragm85which partitions off part of the inner space of the case74. The diaphragm85is formed of an elastic material. The diaphragm85has a diaphragm portion86, piston portions87, and discharge valves88. The diaphragm portion86is formed in the shape of a thin film. The piston portions87extend downward from the diaphragm portion86and are attached to the respective drive units81. The discharge valves88extend from the diaphragm portion86along the inner wall of the discharge port73. The discharge valves88allow the flow only from the pump chambers84to the discharge port73.

When the motor75is driven by a drive voltage, the output shaft76and the crank base77rotate to periodically change the direction of the inclination of the drive shaft78. As the direction of the inclination of the drive shaft78changes, the inclination of the drive units81of the drive body79periodically changes, the piston portions87reciprocate, and the volume of the pump chambers84periodically changes. When the volume of the pump chambers84increases, the pump chambers84are depressurized, the discharge valves88are closed, the suction valves83are opened, and the fluid is suctioned from the suction ports72into the pump chambers84. When the volume of the pump chambers84decreases, the pump chambers84are pressurized, the suction valves83are closed, the discharge valves88are opened, and the fluid is discharged from the pump chambers84to the discharge port73. Thus, the fluid suctioned from the suction ports72is discharged from the discharge port73. Since the suction valves83and the discharge valves88of the diaphragm pump71are check valves, no backflow occurs even in the non-energized state.

FIG. 7is a circuit configuration diagram of the drive circuit64. The drain of the transistor Q4is directly connected to the pump61. The drive circuit64does not include the transistor Q3of the first embodiment. A microcontroller67does not include the terminal P3of the first embodiment. The other configuration of the drive circuit64is the same as that of the drive circuit14.

When the pressure in the container13is controlled by the operation of the pump61, the switch SW1is on and the pump drive signal is outputted in a predetermined waveform. When the pump drive signal goes high, the transistor Q4turns on. Accordingly, a direct-current drive voltage is applied to the pump61and the pump61is driven. When the pump drive signal goes low, the transistor Q4turns off. Accordingly, no drive voltage is applied to the pump61and the pump61is stopped. The output of the pump61is controlled by repeatedly driving and stopping the pump61in accordance with the pump drive signal. Since the switch SW1is on, the transistor Q1turns on and the transistor Q2turns off. Thus, since the solenoid valve12is not energized, the solenoid valve12is closed. The pressure in the container13is thus controlled in accordance with the operation of the pump61.

When the pressure in the container13is maintained, the switch SW1is on and the pump drive signal goes low. Since the switch SW1is on, the solenoid valve12is closed as is the case with above. Also, since the pump drive signal goes low, the transistor Q4turns off and the pump61is not energized. Therefore, as described above, the fluid does not flow backward in the pump61. Since the inside of the container13and the outside of the fluid control device60are thus isolated, the pressure in the container13is maintained. Since the pump61is not energized, the pump61is not driven.

When the main power source P is isolated from the drive circuit64, the solenoid valve12is opened for several seconds and the pump61is stopped as in the case of the first embodiment. Therefore, the fluid in the container13is discharged through the solenoid valve12to the outside in accordance with a differential pressure between the inside of the container13and the outside of the fluid control device60. As a result, the pressure in the container13is released to the outside.

In the third embodiment, the same effect as that of the first embodiment can be achieved by using the pump61having a structure which does not cause backflow in the non-energized state. Since a direct-current motor is used to drive the pump61, the pump61can be driven by a low direct-current voltage. Therefore, the drive circuit64does not require a boosting circuit or an oscillation circuit. This simplifies the configuration of the drive circuit64. Also, the solenoid valve12does not need to be controlled by the microcontroller67.

Fourth Embodiment

A fluid control device according to a fourth embodiment of the present disclosure will be described. The fluid control device of the fourth embodiment is configured in the same manner as the fluid control device60of the third embodiment (seeFIG. 5), except for a drive circuit94of the fourth embodiment.FIG. 8is a circuit configuration diagram of the drive circuit94. The node between the main power source P and the node N3is connected to the ground via the resistors R3and R4connected in series. The node between the resistor R3and the resistor R4is connected to the terminal P5of a microcontroller97. The terminal P5is an input terminal of an A/D converter. A node between the solenoid valve12and the drain of the transistor Q2is connected to the drain of the transistor Q3. The source of the transistor Q3is connected to the ground. The gate of the transistor Q3is connected to the terminal P3of the microcontroller97. The microcontroller97outputs a solenoid valve drive signal from the terminal P3. The other configuration of the drive circuit94is the same as that of the drive circuit64.

When pressure in the container13is controlled by the operation of the pump61, the switch SW1is on, the solenoid valve drive signal goes low, and the pump drive signal is outputted in a predetermined waveform. The pump61operates in accordance with the pump drive signal. Since the switch SW1is on, the transistor Q1turns on and the transistor Q2turns off. Since the solenoid valve drive signal goes low, the transistor Q3also turns off. Thus, since the solenoid valve12is not energized, the solenoid valve12is closed. Pressure in the container13is thus controlled in accordance with the operation of the pump61.

When pressure in the container13is maintained, the switch SW1is on, and the solenoid valve drive signal and the pump drive signal go low. Since the switch SW1is on and the solenoid valve drive signal goes low, the solenoid valve12is closed as is the case with above. Also, since the pump drive signal goes low, the pump61is not energized. Therefore, the fluid does not flow backward in the pump61. Since the inside of the container13and the outside of the fluid control device are thus isolated, the pressure in the container13is maintained.

As in the second embodiment, the microcontroller97detects a voltage drop in the main power source P on the basis of a voltage applied to the terminal P5. When a voltage drop in the main power source P is detected, the solenoid valve drive signal goes high and the pump drive signal goes low. Since the pump drive signal goes low, the pump61is stopped. Since the solenoid valve drive signal goes high, the solenoid valve12is opened to allow the inside of the container13to communicate with the outside of the fluid control device. Thus, the fluid in the container13is discharged to the outside, and pressure in the container13is released to the outside. The pump drive signal is not output until the voltage of the main power source P returns to a normal value. That is, the operation of the pump61is prohibited until the fluid control device is restarted after battery replacement or the like. Note that the operation that the fluid control device performs when the power is shut off is the same as that in the third embodiment.

In the fourth embodiment, the same effect as that of the second embodiment can be achieved by using the pump61having a structure which does not cause backflow in the non-energized state.

Fifth Embodiment

A fluid control device according to a fifth embodiment of the present disclosure will be described. The fluid control device of the fifth embodiment is configured in the same manner as the fluid control device10of the first embodiment (seeFIG. 1A), except for a drive circuit104of the fifth embodiment.FIG. 9is a circuit configuration diagram of the drive circuit104. A node between the resistor R2and the gate of the transistor Q2is connected to the terminal P3of the microcontroller107. The microcontroller107outputs a solenoid valve drive signal from the terminal P3. The source of the transistor Q2is connected via the resistor R5to the ground. The diode D2is connected in parallel to the solenoid valve12. The transistors Q1and Q3and the resistor R1of the first embodiment (seeFIG. 3) are not provided. The other configuration of the drive circuit104is the same as that of the drive circuit14. The diode D1may not be provided if the drive circuit is configured not to allow an electric charge stored in the capacitor C1to flow to the pump11and the microcontroller107. The diode D2is provided to protect the solenoid valve12from overvoltage.

When the pressure in the container13is controlled by the operation of the pump11, the switch SW1is on, the solenoid valve drive signal goes high, and the pump drive signal is outputted in a predetermined waveform. The pump11operates in accordance with the pump drive signal. Since the solenoid valve drive signal goes high, the transistor Q2turns on, and the solenoid valve12is energized by the main power source P and opened. The pressure in the container13is thus controlled in accordance with the operation of the pump11.

When the pressure in the container13is maintained, the switch SW1is on, and the solenoid valve drive signal and the pump drive signal go low. Since the solenoid valve drive signal goes low, the transistor Q2turns off. Therefore, since the solenoid valve12is not energized and is closed, the pressure in the container13is maintained. Also, since the pump drive signal goes low, the transistor Q4turns off and the pump11is stopped.

When the main power source P is isolated from the drive circuit104, the terminal P3of the microcontroller107is brought into a high impedance state. The power stored in the capacitor C1while the main power source P is on is supplied to the drive circuit104. Therefore, the transistor Q2turns on and the solenoid valve12is energized. As a result, during several seconds after the main power source P is shut off and before the amount of electric charge stored in the capacitor C1becomes insufficient, the solenoid valve12is opened and the pressure in the container13is released to the outside. As described above, the pump11is not driven because the power stored in the capacitor C1is not supplied to the pump11and the microcontroller107.

When the voltage of the main power source P drops, the terminal P3of the microcontroller107is also brought into a high impedance state. Thus, the transistor Q2turns on, and the solenoid valve12is energized and opened. Therefore, the fluid in the container13is discharged to the outside and the pressure in the container13is released to the outside. When the voltage of the main power source P drops, the terminal P4of the microcontroller107is also brought into a high impedance state. Thus, since the transistor Q4turns off, the pump11is not driven.

In the fifth embodiment, the circuit configuration of the drive circuit104is simplified by using the fact that if the main power source P is shut off or the voltage of the main power source P drops, an input and output terminal of the microcontroller is brought into a high impedance state. Specifically, the number of transistors included in the drive circuit104is reduced to one, and the need for a circuit configuration for detecting a voltage drop in the main power source P is eliminated. That is, in the fifth embodiment, it is possible to achieve the same effect as that of the embodiments described above while simplifying the circuit configuration of the drive circuit104.

Sixth Embodiment

A fluid control device according to a sixth embodiment of the present disclosure will be described. The fluid control device of the sixth embodiment is configured in the same manner as the fluid control device60of the third embodiment (seeFIG. 5), except for a drive circuit114of the sixth embodiment.FIG. 10is a circuit configuration diagram of the drive circuit114. The drive circuit114is configured in the same manner as the drive circuit104of the fifth embodiment (seeFIG. 9), except that the drain of the transistor Q4is directly connected to the pump61.

When the pressure in the container13is controlled by the operation of the pump61, the switch SW1is on, the solenoid valve drive signal goes low, and the pump drive signal is outputted in a predetermined waveform. The pump61operates in accordance with the pump drive signal. Since the solenoid valve drive signal goes low, the transistor Q2turns off and the solenoid valve12is not energized and is closed. The pressure in the container13is thus controlled in accordance with the operation of the pump61.

When the pressure in the container13is maintained, the switch SW1is on, and the solenoid valve drive signal and the pump drive signal go low. Since the solenoid valve drive signal goes low, the transistor Q2turns off. Therefore, the solenoid valve12is not energized and is closed. Also, since the pump drive signal goes low, the transistor Q4turns off and the pump61is not energized. Therefore, as described above, the fluid does not flow backward in the pump61. Since the inside of the container13and the outside of the fluid control device are thus isolated, the pressure in the container13is maintained.

When the main power source P is isolated from the drive circuit114or the voltage of the main power source P drops, the solenoid valve12is opened and the pressure in the container13is released to the outside, as in the case of the fifth embodiment. The pump61is not driven as in the case of the fifth embodiment.

In the sixth embodiment, the same effect as that of the fifth embodiment can be achieved by using the pump61having a structure which does not cause the backflow in the non-energized state.

Seventh Embodiment

A fluid control device120according to a seventh embodiment of the present disclosure will be described. The fluid control device120is used as a sphygmomanometer.FIG. 11is a schematic block diagram of the fluid control device120. The fluid control device120has a configuration similar to that of the fluid control device of the sixth embodiment, and includes a cuff123as the container13of the sixth embodiment. The fluid control device120also has a configuration (not shown), such as a pressure sensor, required for the measurement of blood pressure.

When measuring blood pressure, the user turns on the main power source of the fluid control device120and performs a predetermined operation. By the same operation as that in the sixth embodiment, the fluid control device120closes the solenoid valve12and drives the pump61to pressurize the inside of the cuff123. The fluid control device120measures blood pressure by detecting a pulse wave with the pressure sensor while pressurizing the inside of the cuff123. That is, the fluid control device120measures blood pressure on the basis of the pressure in the cuff123.

Upon completion of the measurement of blood pressure, the pump drive signal goes low, the transistor Q4(seeFIG. 10) turns off, and the pump61is stopped. The solenoid valve drive signal goes high, the transistor Q2turns on, and the solenoid valve12is energized by the main power source P and opened. The solenoid valve12is opened for several seconds, and this allows air in the cuff123to be discharged to the outside.

When the main power source P is isolated from the drive circuit114or the voltage of the main power source P drops, the solenoid valve12is opened as in the case of the fifth embodiment, and air in the cuff123is discharged to the outside. The pump61is not driven as in the case of the fifth embodiment.

FIG. 14is a schematic block diagram of a fluid control device170having a conventional configuration. The fluid control device170is used as a sphygmomanometer. The fluid control device170has a configuration similar to the conventional configuration of the fluid control device160(seeFIG. 13C), and includes the cuff123as the container13of the fluid control device160. The fluid control device170also has a configuration (not shown), such as a pressure sensor, required for measurement of blood pressure.

When measuring blood pressure, the fluid control device170energizes the solenoid valve152to close it, and drives the pump61to pressurize the cuff123at a predetermined rate. The fluid control device170measures blood pressure by detecting a pulse wave with the pressure sensor while pressurizing the inside of the cuff123. To end the measurement of blood pressure, the fluid control device170stops the pump61and opens the solenoid valve152by not energizing it, thereby allowing air inside the cuff123to be discharged to the outside.

In the fluid control device170, the solenoid valve152is opened when not being energized. Therefore, in the fluid control device170, the solenoid valve152is opened when the main power source is shut off. Thus, when the power is shut off, a person to be measured can be prevented from being exposed to a hazard by the unreleased pressure in the cuff123. However, in the fluid control device170, the solenoid valve152needs to be continuously energized during the measurement of blood pressure so that the solenoid valve152is closed.

On the other hand, in the fluid control device120, when the power is shut off, the solenoid valve12is opened for several seconds to release the pressure in the cuff123. This makes it possible to ensure safety. Also, in the fluid control device120, since the solenoid valve12is closed in the non-energized state, the solenoid valve12does not need to be energized for the measurement of blood pressure. That is, the fluid control device120consumes less power than the fluid control device170having a conventional configuration, and can ensure safety.

Eighth Embodiment

A fluid control device according to an eighth embodiment of the present disclosure will be described. The fluid control device of the eighth embodiment is configured in the same manner as the fluid control device10of the first embodiment (seeFIG. 1A), except for a drive circuit134of the eighth embodiment.FIG. 12is a circuit configuration diagram of the drive circuit134. The drive circuit of the pump11and the microcontroller are not shown inFIG. 12.

The capacitor C1is connected between the main power source P and the ground. The node N1between the main power source P and the capacitor C1is connected via the solenoid valve12to the drain of the transistor Q2. The source of the transistor Q2is connected to the ground. The node N2between the main power source P and the node N1is connected via the resistor R2to the gate of the transistor Q2and also to the drain of the transistor Q5. The source of the transistor Q5is connected to the ground. The gate of the transistor Q5is connected to the terminal P3of the microcontroller. The microcontroller outputs a solenoid valve drive signal from the terminal P3. A node between the gate of the transistor Q5and the terminal P3of the microcontroller is connected via a resistor R6to the ground. A diode may be inserted between the main power source P and the node N2.

When the pressure in the container13is controlled by the operation of the pump11, the switch SW1is on and the solenoid valve drive signal goes low. Thus, the transistor Q5turns off and the transistor Q2turns on. Therefore, the solenoid valve12is energized by the main power source P and is opened. The pressure in the container13is thus controlled in accordance with the operation of the pump11.

When the pressure in the container13is maintained, the switch SW1is on and the solenoid valve drive signal goes high. Thus, the transistor Q5turns on and the transistor Q2turns off. Therefore, since the solenoid valve12is not energized and is closed, the pressure in the container13is maintained. The pump11is not driven at this point.

If the main power source P is shut off or the voltage of the main power source P drops, the solenoid valve drive signal goes low because a supply voltage to the microcontroller also drops. Thus, the transistor Q5turns off and the transistor Q2turns on. Therefore, since the solenoid valve12is energized and opened, the pressure in the container13is released to the outside. The pump11is not driven at this point.

In the eighth embodiment, if the main power source P is shut off or the voltage of the main power source P drops, the pressure in the container13can be released to the outside regardless of the impedance state of the terminal P3of the microcontroller. Also, when the pressure in the container13is maintained, the power consumption can be reduced.

Ninth Embodiment

A fluid control device according to a ninth embodiment of the present disclosure will be described. The fluid control device of the ninth embodiment is configured in the same manner as the fluid control device60of the third embodiment (seeFIG. 5), except for a drive circuit. The drive circuit of the ninth embodiment is configured in the same manner as the drive circuit134of the eighth embodiment (seeFIG. 12).

When the pressure in the container13is controlled by the operation of the pump61, the switch SW1is on and the solenoid valve drive signal goes high. Accordingly, the transistor Q5turns on and the transistor Q2turns off. Therefore, the solenoid valve12is not energized and is closed. The pressure in the container13is thus controlled in accordance with the operation of the pump61.

When the pressure in the container13is maintained, the switch SW1is on and the solenoid valve drive signal goes high. Thus, as is the case with above, the solenoid valve12is not energized and is closed. Since the pump61is not energized, the fluid does not flow backward in the pump61. Since the inside of the container13and the outside of the fluid control device are thus isolated, the pressure in the container13is maintained.

If the main power source P is shut off or the voltage of the main power source P drops, the solenoid valve12is opened and the pressure in the container13is released to the outside, as in the case of the eighth embodiment. In this case, the pump61is not driven, as in the case of the eighth embodiment.

In the ninth embodiment, the same effect as that of the eighth embodiment can be achieved by using the pump61having a structure which does not cause backflow in the non-energized state.

Although the inside of the container is pressurized from the outside of the fluid control device in the embodiments described above, the inside of the container may be depressurized from the outside of the fluid control device. In this case, the suction port of the pump is connected to the container side, and the discharge port of the pump is connected to the outside.

Although the pump11is driven by a piezoelectric element in the embodiments described above, the present disclosure is not limited to this. The present disclosure is applicable as long as a pump having a structure which allows a suction port and a discharge port to internally communicate with each other is appropriately positioned with other components.

Although the pump61is driven by a direct-current motor in the embodiments described above, the present disclosure is not limited to this. The present disclosure is applicable as long as a pump that prevents the backflow of the fluid in the non-energized state is appropriately positioned with other components. For example, instead of the pump61, the pump11having a check valve attached to the suction port or discharge port thereof may be used.

Although the output of the pump is controlled by repeatedly driving and stopping the pump in the embodiments described above, the present disclosure is not limited to this. In the present invention, the output of the pump may be controlled by varying the magnitude of the drive voltage of the pump.C1: capacitorD1, D2: diodeN1to N3: nodeP: main power sourceP1to P5: terminalQ1, Q3to Q5: transistorQ2: transistor (switch)R1to R7: resistorSW1: switch10,60,120,140,150,160,170: fluid control device11,61: pump12,152: solenoid valve (valve)13: container14,54,64,94,104,114,134: drive circuit15: boosting circuit16: oscillation circuit17,57,67,97,107: microcontroller21: piezoelectric pump22: cover plate23: flow passage plate24: counter plate25: adhesive layer26: vibrating plate27: piezoelectric element28: insulating plate29: feeding plate30: spacer plate31: lid plate33: suction port34: discharge port35,36: external connection terminal37: flow passage hole38: cavity39: movable portion40,46: pump chamber41: center portion42: striking portion43: connecting portion44: frame portion45: internal connection terminal71: diaphragm pump72: suction port73: discharge port74: case75: motor76: output shaft77: crank base78: drive shaft79: drive body80: bearing81: drive unit82: lid83: suction valve84: pump chamber85: diaphragm86: diaphragm portion87: piston portion88: discharge valve123: cuff