WO2009087714A1

WO2009087714A1 - Diaphragm air pump

Info

Publication number: WO2009087714A1
Application number: PCT/JP2008/003535
Authority: WO
Inventors: Katsushi Yuguchi; Kazushige Tajima
Original assignee: Star Micronics Co., Ltd.
Priority date: 2008-01-09
Filing date: 2008-12-01
Publication date: 2009-07-16
Also published as: JP2009185800A

Abstract

A simply constructed space saving diaphragm air pump in which air suction noise is effectively reduced. A diaphragm (3) to which a piezoelectric element (9) is bonded is supported by a housing (2) to form a pump chamber (5) between the housing (2) and the diaphragm (3). The diaphragm (3) has a vibration area located on the opposite side of the pump chamber (5), and the vibration area is covered with a cover (4) to form a sound muffling chamber (6). The diaphragm (3) and a vibration body (7) including the piezoelectric element (9) are resonated to flexurally vibrate, and air sucked from an air inlet opening (45) formed in the cover (4) is compressed by the pump chamber (5) to be discharged from a discharge opening (23). Air suction noise produced by air when it passes through a communication hole (31) leading from the sound muffling chamber (6) to the pump chamber (5) is reduced by the sound muffling effect of the sound muffling chamber (6).

Description

Diaphragm air pump

The present invention relates to a diaphragm type air pump that pressure-feeds air by bending and vibrating a thin plate-like diaphragm by a piezoelectric element.

An air pump that generates compressed air by bending and vibrating a diaphragm is suitable as, for example, a micropump that quantitatively pumps a relatively small amount of fluid with high accuracy, and is widely provided. In this type of pump, a part of the wall portion forming the pump chamber is composed of a flexible thin plate-like vibrating body called a diaphragm, and the diaphragm is flexibly vibrated by a driving means such as a piezoelectric element. The fluid sucked into the pump chamber is discharged out of the pump chamber (see Patent Document 1, etc.). In addition, recently, a diaphragm pump is known in which a diaphragm is ultrasonically vibrated to generate a resonance phenomenon in the pump chamber, and a fluid is conveyed from a pressure difference obtained thereby (Patent Document 4, etc.).

In such a diaphragm type air pump, reduction of wind noise generated at the intake port when air is inhaled is a problem. Especially when the air intake is made small due to material or design restrictions, or when the flow rate is high, or when the diaphragm resonates at a relatively high frequency, the wind noise causes dissatisfaction as noise. is there. Therefore, in order to reduce the intake noise, there has been known a countermeasure provided by providing a silencing chamber or a silencing tank (see Patent Document 2.3, etc.).

JP 2004-60632 A Japanese Utility Model Publication No. 61-101679 Japanese Utility Model Publication No. 3-87985 WO2006 / 111775

Providing a silencing chamber or a silencing tank that performs silencing action increases space and complicates the structure, and is not suitable for a micropump that requires a compact structure.
Accordingly, an object of the present invention is to provide a diaphragm type air pump capable of effectively reducing intake noise while having a simple structure and saving space.

The present invention includes a diaphragm having a thin plate shape and a piezoelectric element attached to the diaphragm, and a vibrating body that bends and vibrates when driven by the piezoelectric element, and is disposed on one surface side of the vibrating body. A housing that supports the vibrating body and forms a pump chamber between the vibrating body, a discharge port that is formed in the housing and communicates between the pump chamber and the outside of the housing, and disposed on the other surface side of the vibrating body And a cover member that forms a silencing chamber with the vibrator, an intake port that is formed in the cover member and communicates with the outside of the silencing chamber and the cover member, and a pump chamber and the silencing chamber. And a communication path.

In the air pump of the present invention, the vibrating body repeatedly reciprocates and vibrates, so that the fluid is sucked into the sound deadening chamber inside the cover member from the inlet of the cover member, and further enters the pump chamber through the communication path. When the chamber is compressed, a suction and compression pump action is generated such that the chamber is discharged from the discharge port of the housing. A vibrating body including a diaphragm that bends and vibrates reciprocally vibrates across a space on the pump chamber side that is the one surface side and a space on the other surface side opposite to the pump chamber.

Here, in the present invention, the space opposite to the pump chamber is covered with a cover member, and the inside of the cover member is used as a muffler chamber. For this reason, the intake sound (wind noise) generated when air is sucked into the pump chamber from the communication passage is reduced by the noise reduction chamber, and the noise reduction effect is exhibited. In the present invention, the vibration space of the vibrating body is effectively used as a muffler chamber, so that space saving is achieved. Moreover, since the sound deadening chamber can be formed by providing a cover member, it can be realized with a simple structure.

The communication path that connects the pump chamber and the muffler chamber is configured by a hole formed in a vibrating body such as a diaphragm that partitions the pump chamber and the muffler chamber. In the air pump of the present invention, the vibrating body can be driven to vibrate, that is, to resonate at a frequency (resonance frequency) that matches the natural frequency of the vibrating body itself. In the case where a communicating path is formed in the vibrating body and the vibrating body is resonated, a form in which the communicating path is arranged at or near the circumferential node portion generated in the vibrating body when resonating is preferable. The node portion is a circular vibration node that is concentrically generated near the outer periphery when the vibrating body resonates and does not vibrate. Therefore, when the communication path is formed in such a node part or in the vicinity of the node part, the communication path has little influence on the vibration of the vibrating body, and as a result, the designed vibration characteristics can be obtained.

According to the present invention, the vibration region of the vibrating body supported by the housing is covered with the cover member to form the muffler chamber, so that the intake noise can be effectively reduced with a simple structure and space saving. There is an effect that can be.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a diaphragm type air pump (hereinafter abbreviated as “air pump”) 1 according to an embodiment. The entire air pump 1 has a disk shape, and includes a housing 2, a diaphragm 3, and a cover 4. The housing 2 is composed of an upper housing 10 and a lower housing 20 that are arranged vertically in FIG. The upper and

lower housings

10 and 20 have a disk shape with the same outer diameter, and the lower housing 20 is concentrically joined to the lower surface of the upper housing 10 to constitute the housing 2.

An annular thick part 11 is formed concentrically on the upper surface of the upper housing 10. A flange 12 is formed on the outer peripheral side of the thick portion 11, and a recess inside the thick portion 11 is a pump chamber recess 13. The thickness of the bottom plate portion 14 and the flange portion 12 in the pump chamber recess 13 is equal to or less than half the thickness of the thick portion 11. That is, the depth of the pump chamber recess 13 is set to be not less than half the thickness of the upper housing 10, that is, the thickness of the thick portion 11. These dimensional relationships are merely examples and do not limit the present invention.

At the center of the lower housing 20, a discharge pipe portion 21 that protrudes downward is formed. A discharge flow path 22 is formed in the discharge pipe portion 21, and a front end opening of the discharge flow path 22 is a discharge port 23. A tube (not shown) for leading out air is connected to the discharge pipe portion 21.

A valve housing recess 24 is formed at a location corresponding to the discharge pipe portion 21 on the upper surface of the lower housing 20 (joint surface to the upper housing 10). The discharge passage 22 communicates with the valve housing recess 24. Further, a discharge hole 15 is formed at a position corresponding to the valve housing recess 24 of the bottom plate portion 14 in the upper housing 10 so as to communicate the valve housing recess 24 with the pump chamber recess 13.

In the valve accommodating recess 24, a check valve 25 is accommodated. The check valve 25 is formed in a tongue shape by an elastic material such as rubber or resin. The check valve 25 covers the discharge hole 15 of the upper housing 10, and one end is fixed to the lower surface of the upper housing 10. The check valve 25 can swing in the direction of the lower housing 20 with the fixed end portion as a fulcrum. When the check valve 25 swings in that direction, the pump chamber recess 13 communicates with the discharge flow path 22.

The diaphragm 3 is formed in a disc shape using a metal thin plate having elasticity as a material, and has a diameter equivalent to the outer diameter of the thick portion 11 of the upper housing 10. A disk-shaped piezoelectric element 9 is concentrically arranged on one surface (upper surface) of the diaphragm 3 and is fixed by means such as adhesion with an adhesive. The diameter of the piezoelectric element 9 is smaller than the diameter of the diaphragm 3 and smaller than the inner diameter of the pump chamber recess 13.

The diaphragm 3 is concentrically fixed to the upper surface of the thick part 11 of the upper housing 10 by means of adhesion or the like with the piezoelectric element 9 facing upward. The diaphragm 3 covers the pump chamber recess 13 and is airtightly fixed to the upper housing 10, and the pump chamber recess 13 is formed as the pump chamber 5.

The cover 4 has a disk shape whose outer diameter is equal to the outer diameter of the housing 20, and annular step portions 41 and 42 that are thicker toward the outer peripheral side are formed on the inner surface, that is, the outer peripheral portion of the lower surface. Yes. The central circular recess is a muffler chamber recess 43. The inner diameter of the silencing chamber recess 43 is substantially the same as the inner diameter of the pump chamber recess 13 of the upper housing 10, and the depth is also equal. A circular intake port 45 that communicates between the silencing chamber recess 43 and the outside is formed through the center of the upper plate portion 44 of the cover 4 that forms the silencing chamber recess 43.

In the cover 4, the lower surface of the step portion 41 is joined to the upper surface of the flange portion 12 by means of adhesion or the like in a state where the outer step portion 41 is fitted to the thick portion 11 of the upper housing 10 from the outside. In this joined state, the lower surface of the inner stepped portion 42 is in close contact with the peripheral edge of the diaphragm 4 fixed to the thick portion 11, and the diaphragm 3 is sandwiched between the cover 4 and the housing 2. The diaphragm 3 covers the silencing chamber recess 43 and is airtightly fixed to the cover 4, and the silencing chamber recess 43 is formed as the silencing chamber 6.

The diaphragm 3 and the cover 4 are joined to the housing 2 in such a manner that the diaphragm 3 is placed without being particularly fixed to the thick portion 11, and then the cover 4 is put on, and the step portion 41 of the cover 4 and the flange portion of the upper housing 10 are placed. 12 and the lower housing 20 are fastened with bolts penetrating the peripheral portion thereof, and the peripheral portion of the diaphragm 3 is tightly and tightly sandwiched between the step portion 42 and the thick portion 11. Also good.

A driving signal such as an AC signal is applied to the piezoelectric element 9 fixed to the diaphragm 3. When a drive signal is applied to the piezoelectric element 9, the piezoelectric element 9 contracts and vibrates in the radial direction, and the vibration causes the diaphragm 3 to bend and vibrate integrally with the piezoelectric element 9. In this case, not only the diaphragm 3 but also the piezoelectric element 9 vibrates integrally when a voltage is applied to the piezoelectric element 9, and furthermore, the piezoelectric element 9 is integrally fixed to the diaphragm 3 other than the piezoelectric element 9. Other attachments (for example, wiring of the piezoelectric element 9) are also included. These vibrating areas are the entire inner side of the peripheral edge where the diaphragm 3 is sandwiched and fixed by the upper housing 10 and the cover 4 and are sandwiched between the pump chamber 5 and the muffler chamber 6. is there. Here, the vibration region is referred to as a vibrating body 7.

In the present embodiment, the driving signal applied to the piezoelectric element 9 is such that the vibrating body 7 vibrates, that is, resonates at a frequency (resonance frequency) that matches the natural frequency of the vibrating body 7 itself. When the vibrating body 7 resonates, circumferential nodes that do not vibrate, that is, node portions, are formed concentrically at a fixed position. In this case, the node portion 8 is generated at the position of the diaphragm 3 alone where the piezoelectric element 9 is not fixed to the outer peripheral portion of the vibrating body 7 and just inside the region sandwiched between the upper housing 10 and the cover 4. A plurality of communication holes (communication passages) 31 that communicate between the pump chamber 5 and the muffler chamber 6 are formed at positions corresponding to the node portions 8 of the diaphragm 3. These communication holes 31 are formed at equal intervals in the circumferential direction of the diaphragm 3.

Each communication hole 31 is provided with a check valve that allows air to flow from the muffler chamber 6 to the pump chamber 5 through the communication hole 31 but prevents backflow of air from the pump chamber 5 to the muffler chamber 6. (Not shown). As the check valve, for example, a tongue-like one that opens and closes naturally in response to air pressure is used, similar to the check valve 25. In the case of such a tongue-like one, the diaphragm 3 The lower surface is provided so as to cover the communication hole 31.

The above is the configuration of the air pump 1 of the embodiment, and the air pump 1 operates as follows.
By applying a voltage to the piezoelectric element 9 and continuously applying a predetermined drive signal, the entire vibrator 7 including the diaphragm 3 bends and vibrates in a vertical direction at a relatively high frequency (for example, about 20 kHz) and resonates. FIG. 2 shows a state in which the vibrating body 7 bends and vibrates. When the vibrating body 7 bends upward as shown in FIG. 2A, the volume of the pump chamber 5 increases, as shown in FIG. 2B. When the vibrating body 7 bends downward, the volume of the pump chamber 5 decreases. The arrows in FIG. 2 indicate the flow of air.

When the vibrating body 7 bends upward and the volume of the pump chamber 5 increases, the inside of the pump chamber 5 becomes negative pressure. As a result, the check valve 25 swings in the direction of the upper housing 10 and enters a closed state in which the discharge hole 15 is closed. External air enters the muffler chamber 6 from the air inlet 45, and the air flows into the pump chamber 5 through the communication hole 31. The check valve provided in the communication hole 31 is opened by the flow of air that is about to flow into the pump chamber 5 from the muffler chamber 6. Therefore, air can flow from the muffler chamber 6 into the pump chamber 5 through the communication hole 31.

Next, when the vibrating body 7 bends downward and the volume of the pump chamber 5 decreases, the inside of the pump chamber 5 is compressed to a positive pressure. As a result, the check valve 25 swings in the direction toward the lower housing 20 and is opened, so that the air in the pump chamber 5 passes through the discharge hole 15, the valve housing recess 24, and the discharge flow path 22 to the discharge port 23. It is discharged from. At this time, the check valve provided in the communication hole 31 is closed by the positive air in the pump chamber 5. Therefore, air is prevented from flowing from the pump chamber 5 through the communication hole 31 into the muffler chamber 6.
In this manner, the intake / discharge operation is repeated at a high speed, whereby a pump action is continuously generated, and air is pumped from the discharge port 23.

In the air pump 1 of the above-described embodiment, the vibrating body 7 including the diaphragm 3 that bends and vibrates reciprocally vibrates between the pump chamber 5 on the lower surface side and the muffler chamber 6 on the upper surface side. Here, when air is sucked into the pump chamber 5 through the communication hole 31, if the silencer chamber 6 is not formed by the cover 4, an intake sound (wind noise) is generated from the communication hole 31. However, in the present embodiment, since the communication hole 31 communicates with the sound deadening chamber 6 and is covered with the cover 4, the intake sound is reduced and the sound deadening effect is exhibited.

The communication hole 31 is preferably smaller in consideration of the influence of vibration on the diaphragm 3, but there has been a conventional problem that if the communication hole 31 is made smaller, the intake sound becomes louder. However, in the present embodiment, since the intake sound generated in the communication hole 31 is reduced by the muffler chamber 6, the communication hole 31 can be made smaller. Moreover, in the present embodiment, the communication hole 31 that communicates the pump chamber 5 and the muffler chamber 6 is formed at a location corresponding to the node portion 8 that does not vibrate even when the vibrating body 7 resonates. As a result, the influence of vibration on the diaphragm 3 can be suppressed. In addition, although the volume of the generated intake sound is increased by resonating the diaphragm 3 at a relatively high frequency, the intake sound is reduced even if the diaphragm 3 is resonated due to the silencing effect of the noise reduction chamber 6.

The space of the silencer chamber 6 is originally a vibration space of the vibrating body 7, and therefore, it can be said that the vibration space of the vibrating body 7 on the opposite side (upper side) from the pump chamber 5 is effectively used as the silencer chamber 6. Therefore, a significant space saving can be achieved as compared with a case where a silencing chamber having only a silencing function is separately formed in another location. Further, since the sound deadening chamber 6 can be formed by covering the housing 4 with the housing 2, it can be realized with a simple structure.

Further, as shown in FIG. 2 (b), the maximum amplitude point of the vibrating body 7 is at the center of the vibrating body 7. The discharge hole 15 communicating with the discharge port 23 of the housing 2 is formed at a position concentric with a line passing through the center of the vibrating body 7 and orthogonal to the surface direction of the diaphragm 3 (this coincides with the axis of the air pump). Has been.

In the above embodiment, the communication passage of the present invention that leads from the muffler chamber 6 to the pump chamber 5 is constituted by the communication hole 31 formed in the diaphragm 3, and the communication passage 32 shown in FIG. It may be. The communication passage 32 is pierced radially outward from the inner peripheral surface of the step portion 42 inside the cover 4, then bent at right angles to the direction of the diaphragm 3, penetrates the diaphragm 3, and is a thick portion of the upper housing 10. 11, and then bent at a right angle to the inner peripheral surface direction of the thick portion 11, and is formed in a U shape that opens to the inner peripheral surface of the thick portion 11. A plurality of communication paths 32 are formed at equal intervals in the circumferential direction. Like the communication hole 31, each communication passage 32 allows air to flow from the muffler chamber 6 to the pump chamber 5 through the communication passage 32, but backflow of air from the pump chamber 5 to the muffler chamber 6 does not occur. A check valve for blocking is provided (not shown). This check valve is provided in the middle of the communication path 32 or at the opening of the communication path 32 in the upper housing 10.

In the above embodiment, the diaphragm 3 is resonated. However, the present invention is not limited to resonating the diaphragm, and the diaphragm is vibrated at a relatively low frequency (for example, about several tens to several hundreds Hz). The vibration conditions of the diaphragm are arbitrary.

In addition, the present invention is not limited to a pump that pumps fluid by changing the volume of the pump chamber due to the oscillation of the diaphragm, but generates a resonance phenomenon in the pump chamber by ultrasonically oscillating the diaphragm, and the pressure difference obtained thereby The present invention can also be applied to a pump that conveys the gas.

It is sectional drawing of the air pump which concerns on one Embodiment of this invention. It is sectional drawing which shows operation | movement of the air pump which concerns on one Embodiment, Comprising: (a) is at the time of intake, (b) is at the time of discharge. It is sectional drawing which shows the example of a change of one Embodiment, Comprising: (a) is at the time of inhalation, (b) is at the time of discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diaphragm type air pump, 2 ... Housing, 3 ... Diaphragm, 4 ... Cover, 5 ... Pump chamber, 6 ... Silencer chamber, 7 ... Vibrating body, 8 ... Node part, 9 ... Piezoelectric element, 10 ... Upper housing, 20 ... Lower housing, 23 ... discharge port, 31 ... communication hole (communication passage), 32 ... communication passage, 45 ... intake port.

Claims

Including a thin plate-like diaphragm and a piezoelectric element attached to the diaphragm, and a vibrating body that bends and vibrates when driven by the piezoelectric element;
A housing which is disposed on one surface side of the vibrating body to support the vibrating body and forms a pump chamber with the vibrating body;
A discharge port formed in the housing and communicating between the pump chamber and the outside of the housing;
A cover member disposed on the other surface side of the vibrating body, and forming a silencing chamber with the vibrating body;
An air inlet that is formed in the cover member and communicates with the silencer chamber and the outside of the cover member;
A diaphragm type air pump comprising a communication passage communicating the pump chamber and the muffler chamber.
The diaphragm type air pump according to claim 1, wherein the communication path is formed in the vibrating body.
2. The communication path according to claim 2, wherein the communication path is arranged at or near a circumferential node portion generated in the vibrating body when the vibrating body vibrates at a natural frequency. The diaphragm type air pump as described in the item.