JP6190131B2 - Fluid pump - Google Patents

Description

  Embodiments of the present invention relate to a fluid pump.

  In general, in a fluid pump (for example, a compressor) for compressing, discharging or transferring a fluid, the fluid is transferred using a rotational motion of a motor or a reciprocating motion obtained by converting the rotational motion of the motor by a crankshaft or the like. As described above, in a fluid pump including a drive mechanism such as a motor or a crankshaft or a transmission mechanism, the size of the device becomes large.

JP 2005-282541 A

Journal of the Japan Society of Mechanical Engineering, 111 (1074), 420-423, 2008

  A fluid pump capable of being miniaturized is provided.

The fluid pump of the embodiment has a hollow container having a hole on the surface, a vibration surface that is movable toward the hole, and is larger than the hole located opposite to the hole, an ultrasonic transducer to vibrate towards the vibration surface to the hole, when the vibration surface is vibrating, and pressing the pressing mechanism with a predetermined pressing force towards the vibration surface to the hole, Is provided. Further, the surface is greater than the vibrating surface, when the vibration surface is vibrating, the vibration surface is proximate with said surface.

The figure which shows the fluid pump which concerns on 1st Embodiment. The figure explaining the acoustic radiation pressure which concerns on 1st Embodiment. The figure which shows the experimental result which concerns on 1st Embodiment. The figure which shows the fluid pump which concerns on the modification of 1st Embodiment. The figure which shows the fluid pump which concerns on 2nd Embodiment. The figure which shows the fluid pump which concerns on 3rd Embodiment. The figure which shows the fluid pump which concerns on 4th Embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically illustrating a fluid pump 100 according to the first embodiment. In the example of FIG. 1, the fluid pump 100 is used as a compressor that compresses fluid. The fluid is air, for example. The air compressed by the fluid pump 100 can be used for, for example, a small actuator, a cylinder or the like driven by air pressure.

  A fluid pump 100 shown in FIG. 1 includes a container 10 containing air therein. The container 10 has a hole 20 in a part thereof. A check valve 30 is provided in the hole 20 so that air from the inside of the container 10 does not leak. In addition, the fluid pump 100 includes the ultrasonic transducer 40 with a vibration surface 45 facing the hole 20 of the container 10 and a predetermined distance from the container 10. The fluid pump 100 of FIG. 1 further includes a pressing mechanism 50 that presses the vibration surface 45 of the ultrasonic transducer 40 against the hole 20 with a constant pressing force F in a direction toward the hole 20.

  In the fluid pump 100, when the ultrasonic transducer 40 vibrates the vibration surface 45 at a certain distance from the container 10, the pressure of the air between the vibration surface 45 of the ultrasonic transducer 40 and the container 10 by acoustic radiation pressure. Will increase. Thereby, air is sent into the container 10 through the hole 20, and the air is compressed inside the container 10. Further, the pressure of the air inside the container 10 can be adjusted by the pressing force F of the pressing mechanism 50.

  The container 10 is a hermetic container that can store air therein. In the example of FIG. 1, the container 10 has a rectangular parallelepiped shape. The container 10 has a substantially circular hole 20 that communicates the inside of the container 10 with the outside of the container 10 in a part of the wall surface. Air flows into the container 10 from the outside through the hole 20. A check valve 30 is provided at the opening of the hole 20 inside the container 10 so as to close the opening. The container 10 is preferably made of a material having high rigidity so that the shape does not change as air flows in and out, and for example, an aluminum-based or iron-based metal material can be used.

  The ultrasonic vibrator 40 is a vibrator having a vibration surface 45 that vibrates ultrasonically. For example, a vibrator that vibrates at a natural frequency of an object such as a bolted Langevin vibrator or a bimorph vibrator can be used. The ultrasonic transducer 40 is provided with a certain distance h between the vibration surface 45 and the container 10 and the vibration surface 45 facing the hole 20 of the container 10. The distance h is preferably 100 μm or less, and more preferably about the amplitude ξ of the vibration surface 45. The vibration surface 45 of the ultrasonic transducer 40 has, for example, a substantially circular shape, and the center of the vibration surface 45 and the center of the hole 20 coincide with each other. At this time, the surface of the vibration surface 45 of the ultrasonic transducer 40 is wider than the surface of the opening of the hole 20 on the outside of the container 10, and the vibration surface 45 covers the entire hole 20 and faces it.

  The pressing mechanism 50 is a slider-like mechanism capable of parallel movement along a line 110 (X-axis direction in FIG. 1) connecting the vibration surface 45 of the ultrasonic transducer 40 and the opening of the hole 20 of the container 10. In a state where the pressing mechanism 50 holds the ultrasonic transducer 40, the ultrasonic transducer 40 is vibrated by applying a certain pressing force F for parallel translation in the X-axis direction to the ultrasonic transducer 40. The surface 45 is pressed against the hole 20 of the container 10. The pressing force F can be set in advance according to the target pressure in the container 10 as will be described later.

  Hereinafter, the operation of the fluid pump 100 will be described with reference to FIGS. 2 and 3.

  When the vibration surface 45 of the ultrasonic transducer 40 is ultrasonically vibrated along the line 110, the pressure P of air between the vibration surface 45 and the container 10 (just below the vibration surface 45) increases due to the acoustic radiation pressure. Here, the acoustic radiation pressure is a pressure generated on the surface of an object when the propagation of ultrasonic waves is blocked by the object. At this time, the pressure P becomes maximum at the center of the vibration surface 45, and the pressure P decreases as the distance from the center of the vibration surface 45 increases in the y-axis direction. In the vicinity of the end of the vibration surface 45 in the y-axis direction, the pressure P becomes equal to the pressure P0 of air outside the vibration surface 45 and the container 10 (outside the vibration surface 45). FIG. 2 shows the pressure distribution in the y-axis direction immediately below the vibration surface 45. Note that the pressure distribution shown in FIG. 2 shows a typical case where the diameter of the vibrator is small compared to the wavelength of the sound wave, and the pressure distribution does not necessarily have an inflection point as shown in the figure and has a convex distribution. It doesn't mean.

The ultrasonic transducer 40 is superposed at a position where the pressing force in the positive direction of the X-axis by the pressing mechanism 50 and the repulsive force in the negative direction of the X-axis due to the pressure difference P-P0 caused by the acoustic radiation pressure are balanced. Sonic levitating. That is, when the pressing force is constant, the distance (levitation distance) h between the vibration surface 45 of the ultrasonic transducer 40 and the container 10 is kept constant. Here, the relationship between the pressing force F and the levitation distance h is given by the following equation (Non-Patent Document 1).

  Here, F is the pressing force [kg · m / s2], S is the vibration surface area [m2], ξ is the vibration amplitude of the vibration surface [m], h is the levitation distance [m], and ρ is the fluid density [ kg / m3], c is the speed of sound [m / s], and the left side F / S corresponds to the acoustic radiation pressure.

  (Equation 1) shows that the levitation distance h decreases as the pressing force F increases. Therefore, when the levitation distance h becomes smaller than the vibration amplitude ξ, the vibration surface 45 and the container 10 come into contact with the vibration of the vibration surface 45 of the ultrasonic transducer 40. For this reason, it is preferable to investigate the relationship between the pressing force F and the levitation distance h in advance, and to determine the upper limit value of the pressing force F within a range satisfying ξ <h. Thereby, abrasion and noise of the vibration surface 45 or the container 10 due to the contact between the vibration surface 45 and the container 10 can be suppressed.

  In the example of FIG. 2, when the pressure Pr in the container 10 is Pr <Pu compared to the pressure Pu above the hole 20, such as immediately after the fluid pump 100 is started, the vibration surface 45 of the ultrasonic transducer 40 is super As the sound wave vibrates, the air above the hole 20 flows into the container 10 through the hole 20 due to the pressure difference Pu−Pr between the pressure Pu above the hole 20 and the pressure Pr inside the container 10. At this time, the air flows into the container 10 until the pressure Pr in the container 10 becomes equal to the pressure Pu above the hole 20. Thereby, compressed air accumulates in the container 10.

  It has been confirmed that the pressure Pr in the container 10 when the pressure in the container 10 becomes equal to the pressure above the hole 20 depends on the pressing force F and the opening area (diameter of the circle) of the hole 20 in the container 10. .

  FIG. 3 is a diagram showing experimental results. In this experiment, an aluminum container (volume 56 ml) was used as the container 10. Further, an ultrasonic vibrator 40 having a vibration amplitude ξ = 12 μm of the vibration surface 45 was used. FIG. 3 is a result of measuring the pressure in the container 10 when the pressing force (pressing pressure) is changed with respect to two patterns of the diameters Φ = 0.1 mm and Φ = 0.3 mm of the hole 20 of the container 10. . In this experiment, noise was generated due to contact between the contact surface 45 and the container 10 when the pressing pressure exceeded 55 kPa.

  As shown in FIG. 3, when the pressing force is equal, the pressure (saturation pressure) that finally reaches (saturates) in the container 10 increases as the diameter of the hole 20 decreases. When the diameters of the holes 20 are equal, the saturation pressure increases as the pressing force increases. In particular, when the diameter of the hole 20 is 0.1 mm, it can be seen that the saturation pressure is sufficiently higher than the pressing pressure within a range where noise is not generated. Therefore, in order to adjust the pressure Pr in the container 10 by the pressing force, the diameter of the hole 20 included in the container 10 is preferably set to 0.1 mm or less.

  Note that the shape of the vibration surface 45 of the ultrasonic transducer 40 may not be circular. For example, the rectangular vibration surface 45 can be used. At this time, it is preferable that the position of the center of gravity (centroid) of the hole 20 coincides with the position of the center of gravity (centroid) of the vibration surface 45. Alternatively, it is preferable that the position where the displacement is greatest in the vibration surface 45 coincide with the position of the center of gravity (centroid) of the hole 20. The container 10 may have a plurality of holes 20. At this time, by providing the ultrasonic transducer 40 facing each hole 20, the pressure in the container 10 can reach the saturation pressure in a shorter time.

  Further, as the pressing mechanism 50, the dead weight of the ultrasonic transducer 40 can be used. For example, the ultrasonic transducer 40 and a counter load are connected via a wire, and a pressing force is generated based on a difference between the counter load and its own weight. At this time, a predetermined pressing force can be obtained by adjusting the counter load. An actuator such as a linear motor or a solenoid can also be used.

  The fluid may be a liquid such as water or oil.

  According to the fluid pump 100 of this embodiment, it is not necessary to include a drive mechanism or a transmission mechanism such as a motor or a crankshaft, and the apparatus can be miniaturized by using an ultrasonic vibrator. Further, since the ultrasonic vibrator vibrates in an ultrasonic region that cannot be heard by humans, noise associated with the operation of the apparatus can be reduced. Further, since there is no contact sliding portion such as a drive mechanism or a transmission mechanism, deterioration due to wear or the like can be reduced, and the life of the apparatus can be improved.

(Modification)
FIG. 4 is a view showing a modification of the fluid pump 100.

  In the fluid pump 100 shown in FIG. 4, the vibration surface 45 of the ultrasonic transducer 40 has an arc shape having a convex curved surface (first curved surface). Further, the container 10 has a concave curved surface (second curved surface) in a part of the wall surface, and has a hole 20 in a part of the second curved surface. At this time, the area of the vibration surface 45 in the projection plane perpendicular to the axis in the X-axis direction is wider than the area of the opening of the hole 20 in the projection plane. The opening of the hole 20 is preferably circular with a diameter of 0.1 mm or less on a projection plane perpendicular to the axis in the X-axis direction. Thereby, even if the attitude | position of the ultrasonic transducer | vibrator 40 inclines slightly, it can prevent that the vibrating surface 45 and the container 10 contact. Further, even when the posture of the ultrasonic transducer 40 is slightly inclined, the distance between the hole 20 and the vibration surface 45 can be kept close. Since the acoustic radiation pressure increases as h is smaller than Equation 1, a higher acoustic radiation pressure can be generated as the distance between the upper surface of the hole 20 and the vibration surface 45 becomes closer.

(Second Embodiment)
FIG. 5 is a diagram schematically illustrating a fluid pump 200 according to the second embodiment. In addition, about the structure same as the fluid pump 100 shown in FIG. 1, description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  The fluid pump 200 illustrated in FIG. 5 further includes an adjustment unit 60 that adjusts the pressing force of the pressing mechanism 50.

  The adjustment unit 60 adjusts the pressing force of the pressing mechanism 50 to be smaller than the final pressing force (target pressing force) when starting to drive the ultrasonic transducer 40, and increases it with time. Adjustment is made so that the target pressing force is reached when a predetermined time set in advance elapses. In this way, immediately after the start of driving of the ultrasonic transducer 40, the ultrasonic transducer 40 is pressed with a relatively small pressing force, so that even if a sufficient acoustic radiation pressure is not generated, the vibrating surface 45 And the container 10 can be prevented from contacting each other. Thereby, the noise by abrasion of the vibration surface 45 or the container 10 and a contact can be reduced.

  The adjustment unit 60 further adjusts the pressing force so that the vibration surface 45 of the ultrasonic transducer 40 and the container 10 are in contact with each other so as to close the hole 20 when the ultrasonic transducer 40 is not in operation. Thereby, the pressure change in the container 10 by air passing the hole 20 at the time of non-operation can be prevented.

(Third embodiment)
FIG. 6 is a diagram schematically illustrating a fluid pump 300 according to the third embodiment. In addition, about the structure same as the fluid pump 100 shown in FIG. 1, description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  A fluid pump 300 shown in FIG. 6 uses a bimorph type ultrasonic transducer 40. Further, a regulating member 70 that suppresses the floating of the ultrasonic transducer 40 is provided. The distance H between the regulating member 70 and the container 10 is determined so that the flying height of the ultrasonic transducer 40 becomes h when the ultrasonic transducer 40 comes into contact with the regulating member 70. At this time, the flying height h of the ultrasonic transducer 40 is determined in advance so that a desired acoustic radiation pressure can be obtained. The distance H is determined to be the sum of the thickness of the ultrasonic transducer 40 and h. The distance h is preferably about 100 μm or less, and more preferably about the amplitude ξ of the vibration surface 45.

  The regulating member 70 suppresses the rise of the ultrasonic transducer 40 that floats due to the acoustic radiation pressure, and keeps the distance between the vibrating surface 45 and the hole 20 below a certain level. By using the regulating member 70, the rise of the ultrasonic transducer 40 can be suppressed without using an actuator or a counter load, and the apparatus can be further downsized.

  The regulating member 70 may be integrated with the container 10 or may be fixed to another member. The regulating member 70 is preferably made of a highly rigid material such as aluminum or iron so that the flying of the ultrasonic transducer can be reliably regulated.

(Fourth embodiment)
FIG. 7 is a diagram showing an outline of a fluid pump 400 according to the third embodiment. In addition, about the structure same as the fluid pump 100 shown in FIG. 1, description is abbreviate | omitted by attaching | subjecting the same code | symbol. In the example of FIG. 6, the fluid pump 400 illustrated in FIG. 6 is used as a decompressor that decompresses the inside of the container 10.

  In the fluid pump 400 shown in FIG. 7, the ultrasonic transducer 40 and the pressing mechanism 50 are provided inside the container 10. When the vibration surface 45 of the ultrasonic transducer 40 is vibrated, the pressure of air between the vibration surface 45 of the ultrasonic transducer 40 and the container 10 is improved by the acoustic radiation pressure. At this time, air is discharged from the inside of the container 10 to the outside of the container 10 through the hole 20 due to a pressure difference from the external pressure, and the pressure inside the container 10 is reduced.

  According to the fluid pump according to at least one of the embodiments described above, the apparatus can be reduced in size.

  These embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention and are also included in the invention described in the claims and the equivalents thereof.

100, 200, 300, 400 ... Fluid pump 10 ... Container 20 ... Hole 30 ... Check valve 40 ... Ultrasonic vibrator 45 ... Vibrating surface 50 ... Pushing mechanism 60 ... Adjustment unit 70 ... Regulating member 110 ... Line

Claims (8)

A hollow container having a hole on the surface ;
An ultrasonic transducer that is movable toward the hole and has a vibration surface that is larger than the hole located opposite the hole, and vibrates the vibration surface toward the hole;
A pressing mechanism that presses the vibrating surface toward the hole portion with a predetermined pressing force when the vibrating surface vibrates;
Fluid pump wherein the surface is greater than the vibrating surface, when the vibration surface is vibrating, the vibration surface is proximate with said surface.   The fluid pump according to claim 1, further comprising an adjusting unit that adjusts a pressing force of the pressing mechanism.   The fluid pump according to claim 1, wherein the hole has a circular shape with a diameter of 0.1 mm or less. The vibrating surface has a convex first curved surface, the container has a concave second curved surface in a part of the surface, and the hole in a part of the second curved surface;
The projection area of the said vibration surface in the projection surface perpendicular | vertical to the line which connects the said vibration surface and the said hole part is wider than the projection area of the said hole part in the said projection surface. Fluid pump.   The fluid pump according to claim 4, wherein the hole has a circular shape with a diameter of 0.1 mm or less on the projection surface.   The fluid pump according to any one of claims 1 to 5, wherein a check valve is provided in the hole. The fluid pump according to any one of claims 1 to 6, wherein the container has a plurality of the hole portions, and has a plurality of the ultrasonic transducers provided with the vibration surfaces facing each hole portion. . The fluid pump according to claim 1, further comprising a regulating member that regulates the floating of the ultrasonic transducer.