Patent Description:
In a known structure such as a piezoelectric micro blower described in Patent Literature <NUM>, a piezoelectric device attached to a diaphragm is driven to vibrate the diaphragm.

The piezoelectric device vibrates the diaphragm with a known technique. This pump thus has the same characteristics as a diaphragm pump. Further, the pump may operate unstably when a piezoelectric vibrating plate including the piezoelectric device and the diaphragm vibrates out of synchronization with the entire pump chamber. Piezoelectric pumps are to have improved pump characteristics such as operational stability.

Patent Literature <NUM>: <CIT>
Further, <CIT> discloses a piezoelectric pump, <CIT> discloses a piezoelectric blower, and <CIT> discloses a mini throttling refrigeration system.

The present invention provides a piezoelectric pump as defined in claim <NUM> and a piezoelectric pump as defined in claim <NUM>.

Further, the present invention provides a pump unit as defined in claim <NUM>.

The objects, features, and advantages of the present invention will become more apparent from the following detailed description and the drawings.

Example piezoelectric pumps will now be described in detail with reference to the accompanying drawings. The embodiments described below do not limit the present invention. <FIG> is a schematic perspective view of a pump unit, and <FIG> is a cross-sectional view taken along line A-A in <FIG>. <FIG> is a schematic perspective view of a piezoelectric pump. <FIG> and <FIG> each are a schematic cross-sectional view of a piezoelectric pump according to a first embodiment in an operating state.

A pump unit <NUM> includes a piezoelectric pump <NUM> and a housing <NUM> accommodating the piezoelectric pump <NUM>. The piezoelectric pump <NUM> includes a piezoelectric device <NUM> having a through-hole 10a, a first elastic plate <NUM> covering one end of the through-hole 10a, and a second elastic plate <NUM> covering the other end of the through-hole 10a. The first elastic plate <NUM> includes a communication hole 11a communicating with the through-hole 10a of the piezoelectric device <NUM>.

The piezoelectric device <NUM> includes, for example, a piezoelectric member having the through-hole 10a and surface electrodes mounted on a pair of main surfaces of the piezoelectric member opposite to each other. The piezoelectric member included in the piezoelectric device <NUM> may be formed from piezoelectric ceramics based on lead zirconate titanate, barium titanate, or potassium sodium niobate or a piezoelectric single crystal such as quartz or lithium tantalate. The surface electrodes included in the piezoelectric device <NUM> may be formed from, for example, silver, nickel, copper, or a silver-palladium alloy.

The piezoelectric device <NUM> may have any shape that has the through-hole 10a. The piezoelectric device <NUM> may be a plate or a column. The piezoelectric device <NUM> being a plate may be circular or polygonal. The piezoelectric device <NUM> being columnar may be circular or polygonal. The through-hole 10a may be at any position. For the plate-like or columnar piezoelectric device <NUM>, the through-hole 10a is coaxial with the piezoelectric member. In the present embodiment, the piezoelectric device <NUM> is a circular plate and the through-hole 10a is coaxial with the piezoelectric member.

As shown in <FIG>, the piezoelectric device <NUM> is connected with an external circuit with, for example, a wiring member <NUM>. The piezoelectric pump <NUM> can be driven by controlling an applied voltage and vibrating the piezoelectric device <NUM>. The piezoelectric device <NUM> may have the surface electrodes on the pair of surfaces of the piezoelectric member opposite to each other mounted in the manner described below.

The piezoelectric device <NUM> may be separately excited and may include surface electrodes (a pair of surface electrodes) that are separately mounted on the respective two surfaces to spread in the planar direction on the surfaces.

The piezoelectric device <NUM> may also be self-excited and may include, on one surface, a surface electrode including a main surface electrode and a sub-surface electrode separated from the main surface electrode. This structure can drive, for example, multiple piezoelectric pumps <NUM> with optimum frequencies and thus can reduce differences in the fluid flow rate between the individual piezoelectric pumps <NUM>. This structure also reduces changes in the fluid flow rate resulting from varying environmental temperatures of, for example, -<NUM> to +<NUM>.

The first elastic plate <NUM> is formed from an elastically deformable material and may have any shape that covers one end of the through-hole 10a. In the same manner, the second elastic plate <NUM> is formed from an elastically deformable material and may have any shape that covers the other end of the through-hole 10a. The first elastic plate <NUM> includes the communication hole 11a communicating with the through-hole 10a of the piezoelectric device <NUM>.

The first elastic plate <NUM> and the second elastic plate <NUM> elastically deform to follow deformation (vibration) of the piezoelectric device <NUM>. For example, when the piezoelectric device <NUM> deforms and extends in the radial direction as shown schematically in <FIG> and <FIG>, the first elastic plate <NUM> and the second elastic plate <NUM> may also deform elastically to extend in the radial direction. When the piezoelectric device <NUM> deforms and shrinks in the radial direction, the first elastic plate <NUM> and the second elastic plate <NUM> may also deform elastically to shrink in the radial direction. More specifically, when the piezoelectric device <NUM> deforms and shrinks in the radial direction, the piezoelectric device <NUM> may deform and extend in the thickness direction. When the piezoelectric device <NUM> deforms and extends in the radial direction, the piezoelectric device <NUM> may deform and shrink in the thickness direction.

Upon receiving an applied voltage, the piezoelectric device <NUM> deforms and repeatedly changes between the states shown in <FIG> and <FIG>. As the volume of an internal space defined by the piezoelectric device <NUM>, the first elastic plate <NUM>, and the second elastic plate <NUM> changes, the fluid in the internal space is repeatedly drawn in and out through the communication hole 11a to function as pump.

In the example shown in <FIG> and <FIG>, the piezoelectric device <NUM> in the state shown in <FIG> (second state) deforms more outward in the radial direction to have a larger volume in the internal space than in the state shown in <FIG> (first state). The deformation from the first state to the second state causes external fluid to be drawn in. The deformation from the second state to the first state reduces the volume of the internal space and causes the fluid inside to be out.

The first elastic plate <NUM> and the second elastic plate <NUM> may be formed from a metal material such as stainless steel (SUS), brass, or alloy <NUM> or a resin material such as polybutylene terephthalate (PBT) or a liquid crystal polymer. The use of alloy <NUM> reduces the difference in thermal expansion from the piezoelectric device <NUM>, effectively reducing changes in the fluid flow rate resulting from changes in environmental temperature.

The first elastic plate <NUM> and the second elastic plate <NUM> may have any thickness that allows the plates to deform to follow the deformation of the piezoelectric device <NUM>. The first elastic plate <NUM> and the second elastic plate may have a thickness of <NUM> to <NUM>. The first elastic plate <NUM> may have one communication hole 11a as in the present embodiment or multiple communication holes 11a.

The piezoelectric pump <NUM> in one or more embodiments of the present disclosure repeatedly draws fluid in and out in accordance with changes in the volume of the through-hole 10a as the piezoelectric device <NUM> deforms. The characteristics of the piezoelectric device <NUM> directly affect the operation of the piezoelectric pump <NUM>, allowing the piezoelectric pump <NUM> to operate stably. Further, controlling the changes in the volume allows precise control of the flow rate. In this manner, the characteristics of the piezoelectric pump <NUM> can be improved.

The housing <NUM> accommodates the piezoelectric pump <NUM> described above and has an outlet 2a facing the communication hole 11a in the first elastic plate <NUM>. The housing <NUM> in the present embodiment includes a top plate <NUM> facing the first elastic plate <NUM> and a cylindrical frame <NUM> supporting the top plate <NUM> and surrounding the piezoelectric pump <NUM>. The housing <NUM> in the present embodiment covers and accommodates the piezoelectric pump <NUM> placed on, for example, a platform. The housing <NUM> may additionally include a bottom plate to entirely cover and accommodate the piezoelectric pump <NUM>.

The gap between the accommodated piezoelectric pump <NUM> and the housing <NUM> in the internal space of the housing <NUM> serves as a fluid channel <NUM>, through which fluid flows in and out of the housing <NUM> with the piezoelectric pump <NUM>. When the piezoelectric pump <NUM> is driven and deforms from the first state to the second state as described above, the fluid in the fluid channel <NUM> is drawn in through the communication hole 11a. When the piezoelectric pump <NUM> deforms from the second state to the first state, the fluid drawn in is discharged through the communication hole 11a. At the same time, the fluid is discharged out of the housing <NUM> through the outlet 2a facing the communication hole 11a.

The pump unit <NUM> may discharge any fluid. Fluid to be discharged may be, for example, air or a functional fluid containing an aromatic agent, a disinfectant agent, or an antibacterial agent. The pump unit <NUM> is, for example, installed inside an electronic device to cool electronic components, or may be installed in a vehicle such as an automobile, in a house, or in a living space such as in a theater or other entertainment facilities to discharge a functional fluid.

The housing <NUM> may be formed from a metal material such as stainless steel (SUS), brass, or alloy <NUM> or a resin material such as PBT or a liquid crystal polymer. The frame <NUM> is bonded to the outer periphery of the top plate <NUM> and supports the top plate <NUM>. The frame <NUM> has a step on the inner surface in the example shown in <FIG>. In some embodiments, the frame <NUM> may have an axially constant thickness and support the top plate <NUM> on its end face, or may have, on the inner surface, a grooved portion engaged with the periphery of the top plate <NUM> to support the top plate <NUM>. Although the wiring member <NUM> extends outside through insertion ports in the frame <NUM> in the example shown in <FIG>, the wiring member <NUM> may extend outside in any other manner.

<FIG> each are a schematic cross-sectional view of a piezoelectric pump according to a second embodiment in an operating state. A piezoelectric pump 1A in the present embodiment includes the same components as the piezoelectric pump <NUM> in the first embodiment except a first elastic plate 11A and a second elastic plate 12A. The components that are the same as those of the piezoelectric pump <NUM> in the first embodiment are given the same reference numerals and will not be described in detail. In the present embodiment, the first elastic plate 11A includes a protrusion <NUM>, and the second elastic plate 12A includes a protrusion <NUM>. The protrusions <NUM> and <NUM> protrude outward in the axial direction of the through-hole 10a of the piezoelectric device <NUM>. Each of the protrusions <NUM> and <NUM> in the present embodiment has a shape with a peak (highest point) at the center of the first elastic plate 11A or the second elastic plate 12A, which may be, for example, a cone, a truncated cone, or a hemisphere.

The piezoelectric pump 1A in the second embodiment operates in the same manner as the piezoelectric pump <NUM> in the first embodiment. Upon receiving an applied voltage, the piezoelectric device <NUM> deforms and repeatedly changes between a first state shown in <FIG> and a second state shown in <FIG>. In the first state, the internal space defined by the piezoelectric device <NUM>, the first elastic plate 11A, and the second elastic plate 12A has a larger volume due to the protrusions <NUM> and <NUM> than in the first embodiment. In the second embodiment, the volume of the internal space changes between the first state and the second state more largely than in the first embodiment. This structure can increase the fluid flow rate while precisely controlling the flow rate.

The first elastic plate 11A including the protrusion <NUM> and the second elastic plate 12A including the protrusion <NUM> with the shape as described in the present embodiment may be formed from a metal material with, for example, a known processing method such as pressing. For a resin material, a known processing method such as molding may be used.

<FIG> each are a schematic cross-sectional view of a piezoelectric pump according to a third embodiment in an operating state. A piezoelectric pump 1B in the present embodiment includes the same components as the piezoelectric pump 1A in the second embodiment except a first elastic plate 11B and a second elastic plate 12B. The components that are the same as those of the piezoelectric pump 1A in the second embodiment are given the same reference numerals and will not be described in detail. In the present embodiment, the first elastic plate 11B includes a protrusion 13A and the second elastic plate 12B includes a protrusion 14A. The protrusions 13A and 14A are circular and concentric with the first elastic plate 11B and the second elastic plate 12B.

The piezoelectric pump 1B in the third embodiment operates in the same manner as the piezoelectric pump 1A in the second embodiment. Upon receiving an applied voltage, the piezoelectric device <NUM> deforms to a first state shown in <FIG>, a second state shown in <FIG>, or a third state shown in <FIG>. In the second state, the piezoelectric device <NUM> deforms and extends more outward in the radial direction than in the first state. In the third state, the piezoelectric device <NUM> deforms and shrinks more inward in the radial direction than in the first state. The state of the piezoelectric device <NUM> changes to change the volume of the internal space in response to a change in the voltage applied to the piezoelectric device <NUM>. The piezoelectric pump 1B repeatedly draws fluid in and out of the internal space through the communication hole 11a to function as a pump. Although the piezoelectric device <NUM> can change between the three states in the present embodiment, the piezoelectric device <NUM> in operation may switch between two of the states repeatedly, or may switch between the three states repeatedly. The volume of the internal space differs depending on the state of the piezoelectric device <NUM>. The state is thus selected from the three states to control the fluid flow rate.

The first elastic plate 11B including the protrusion 13A and the second elastic plate 12B including the protrusion 14A with the shape as described in the present embodiment may be formed from a metal material with, for example, a known processing method such as pressing. For a resin material, a known processing method such as molding may be used.

<FIG> each are a schematic cross-sectional view of a piezoelectric pump according to a fourth embodiment in an operating state. A piezoelectric pump 1C in the present embodiment includes the same components as the piezoelectric pump <NUM> in the first embodiment except a first elastic plate 11C and a second elastic plate 12C. The components that are the same as those of the piezoelectric pump <NUM> in the first embodiment are given the same reference numerals and will not be described in detail. In the present embodiment, the first elastic plate 11C includes a recess <NUM>, and the second elastic plate 12C includes a recess <NUM>. The recesses <NUM> and <NUM> are inward in the axial direction of the through-hole 10a of the piezoelectric device <NUM>. Each of the recesses <NUM> and <NUM> in the present embodiment may have a shape with a peak (lowest point) at the center of the first elastic plate 11C or the second elastic plate 12C, which may be, for example, a cone, a truncated cone, or a hemisphere.

The piezoelectric pump 1C in the fourth embodiment operates in the same manner as the piezoelectric pump <NUM> in the first embodiment. Upon receiving an applied voltage, the piezoelectric device <NUM> repeatedly deforms between a first state shown in <FIG> and a second state shown in <FIG>. In the first state, the volume of the internal space defined by the piezoelectric device <NUM>, the first elastic plate 11C, and the second elastic plate 12C is smaller than in the first embodiment due to the recesses <NUM> and <NUM> inward in the through-hole 10a. In the fourth embodiment, the volume of the internal space changes between the first state and the second state more largely than in the first embodiment. This structure can increase the fluid flow rate while precisely controlling the flow rate.

The first elastic plate 11C including the recess <NUM> and the second elastic plate 12C including the recess <NUM> may be formed from a metal material with, for example, a known processing method such as pressing. For a resin material, a known processing method such as molding may be used.

<FIG> each are a schematic cross-sectional view of a piezoelectric pump according to a fifth embodiment in an operating state. A piezoelectric pump 1D in the present embodiment includes the same components as the piezoelectric pump 1C in the fourth embodiment except a first elastic plate 11D and a second elastic plate 12D. The components that are the same as those of the piezoelectric pump 1C in the fourth embodiment are given the same reference numerals and will not be described in detail. In the present embodiment, the first elastic plate 11D includes a recess 15A, and the second elastic plate 12D includes a recess 16A. The recesses 15A and 16A are cylindrical and coaxial with the first elastic plate 11D and the second elastic plate 12D.

The piezoelectric pump 1D in the fifth embodiment operates in the same manner as the piezoelectric pump 1C in the fourth embodiment. Upon receiving an applied voltage, the piezoelectric device <NUM> deforms to a first state shown in <FIG>, a second state shown in <FIG>, or a third state shown in <FIG>. In the second state, the piezoelectric device <NUM> deforms and extends more outward in the radial direction than in the first state. In the third state, the piezoelectric device <NUM> deforms and shrinks more inward in the radial direction than in the first state. The state of the piezoelectric device <NUM> changes to change the volume of the internal space in response to a change in the voltage applied to the piezoelectric device <NUM>. The piezoelectric pump 1D repeatedly draws the fluid in and out of the internal space through the communication hole 11a to function as a pump. Although the piezoelectric device <NUM> can change between the three states as the piezoelectric pump 1B in the third embodiment, the piezoelectric device <NUM> in operation may switch between two of the states repeatedly, or may switch between the three states repeatedly. The volume of the internal space differs depending on the state of the piezoelectric device <NUM>. The state is thus selected from the three states to control the fluid flow rate.

The first elastic plate 11D including the recess 15A and the second elastic plate 12D including the recess 16A with the shape as described in the present embodiment may be formed from a metal material with, for example, a known processing method such as pressing. For a resin material, a known processing method such as molding may be used.

<FIG> and <FIG> each are a schematic cross-sectional view of a piezoelectric pump according to a sixth embodiment in an operating state. A piezoelectric pump 1E in the present embodiment includes the same components as the piezoelectric pump 1A in the second embodiment except a first elastic plate 11E and a second elastic plate 12E. The components that are the same as those of the piezoelectric pump 1A in the second embodiment are given the same reference numerals and will not be described in detail. In the present embodiment, the first elastic plate 11E includes the protrusion <NUM>, a flat portion <NUM>, and a groove G. The second elastic plate 12E includes the protrusion <NUM>, a flat portion <NUM>, and a groove G. The protrusions <NUM> and <NUM> protrude outward in the axial direction of the through-hole 10a of the piezoelectric device <NUM>. The flat portions <NUM> and <NUM> surround the protrusions <NUM> and <NUM>. The grooves G are located between the protrusion <NUM> and the flat portion <NUM> and between the protrusion <NUM> and the flat portion <NUM>.

The piezoelectric pump 1E in the sixth embodiment operates in the same manner as the piezoelectric pump 1A in the second embodiment. Upon receiving an applied voltage, the piezoelectric device <NUM> repeatedly deforms between a first state shown in <FIG> and a second state shown in <FIG>. In the sixth embodiment, the volume of the internal space changes between the first state and the second state in the same manner as in the second embodiment. The first elastic plate 11E and the second elastic plate 12E including the grooves G may deform with a smaller force than the structure in the second embodiment with no grooves G. In other words, a lower voltage applied to the piezoelectric device <NUM> than in the second embodiment can deform the first elastic plate 11E and the second elastic plate 12E in the same manner as in the second embodiment to control the fluid flow rate in the same manner.

The first elastic plate 11E and the second elastic plate 12E including the grooves G may be formed from a metal material with, for example, a known processing method such as pressing. For a resin material, a known processing method such as molding may be used.

<FIG> each are a schematic cross-sectional view of a piezoelectric pump according to a seventh embodiment in an operating state. A piezoelectric pump 1F in the present embodiment includes the same components as the piezoelectric pump 1C in the fourth embodiment except a first elastic plate 11F and a second elastic plate 12F. The components that are the same as those of the piezoelectric pump 1C in the fourth embodiment are given the same reference numerals and will not be described in detail. In the present embodiment, the first elastic plate 11F includes the recess <NUM>, a flat portion <NUM>, and a groove G. The second elastic plate 12F includes the recess <NUM>, a flat portion <NUM>, and a groove G. The recesses <NUM> and <NUM> are inward in the axial direction of the through-hole 10a of the piezoelectric device <NUM>. The flat portions <NUM> and <NUM> surround the recesses <NUM> and <NUM>. The grooves G are located between the recess <NUM> and the flat portion <NUM> and between the recess <NUM> and the flat portion <NUM>.

The piezoelectric pump 1F in the seventh embodiment operates in the same manner as the piezoelectric pump 1C in the fourth embodiment. Upon receiving an applied voltage, the piezoelectric device <NUM> repeatedly deforms between a first state shown in <FIG> and a second state shown in <FIG>. In the seventh embodiment, the volume of the internal space changes between the first state and the second state in the same manner as in the fourth embodiment. The first elastic plate 11F and the second elastic plate 12F including the grooves G may deform with a smaller force than the structure in the fourth embodiment with no grooves G. In other words, a lower voltage applied to the piezoelectric device <NUM> than in the fourth embodiment can deform the first elastic plate 11F and the second elastic plate 12F in the same manner as in the fourth embodiment to control the fluid flow rate in the same manner.

The first elastic plate 11F and the second elastic plate 12F including the grooves G may be formed from a metal material with, for example, a known processing method such as pressing. For a resin material, a known processing method such as molding may be used.

An example method for manufacturing a piezoelectric pump will now be described.

Materials for forming the piezoelectric device <NUM>, such as lead zirconate titanate, are mixed with, for example, a ball mill. The resultant mixture is then calcinated at <NUM> to <NUM>. The calcinated material is milled with, for example, a ball mill, mixed with a forming binder, and then granulated with a spray dryer.

The resultant granules are pressed with a mold having an axis pin around the center to form a compact with a through-hole. The compact is degreased and then fired to form a piezoelectric member. The resultant piezoelectric member is processed with, for example, lapping to an intended shape. After a paste for surface electrodes is printed, the piezoelectric member is baked at <NUM> to <NUM> to form surface electrodes. A voltage of about <NUM> kV/mm is then applied to form the piezoelectric device <NUM> with intended piezoelectric characteristics.

Subsequently, plates of alloy <NUM> are, for example, pressed to an intended shape to form the first elastic plate <NUM> and the second elastic plate <NUM>. For example, a thermosetting epoxy adhesive is then printed onto the first elastic plate <NUM> and the second elastic plate <NUM>. The printed portion of the adhesive is then heated at <NUM> to <NUM> while being in contact with the piezoelectric device <NUM>. This bonds the first elastic plate <NUM> and the second elastic plate <NUM> to the piezoelectric device <NUM>.

The wiring member <NUM> is prepared for inputting an external electric signal into the piezoelectric device <NUM>, such as a lead wire with its side surface coated with resin. The wiring member <NUM> is electrically and mechanically bonded to the surface electrodes of the piezoelectric device <NUM> with a bond material such as solder. This completes the piezoelectric pump <NUM>.

In another embodiment, the housing <NUM> formed from alloy <NUM> may be prepared. The piezoelectric pump <NUM> may be accommodated in the housing <NUM>. The piezoelectric pump <NUM> and the housing <NUM> may then be bonded with each other as appropriate. This completes the pump unit <NUM>.

The piezoelectric pump according to embodiments of the present disclosure repeatedly draws fluid in and out in accordance with changes in the volume of the through-hole as the piezoelectric device deforms. The characteristics of the piezoelectric device directly affect the operation of the piezoelectric pump, allowing the piezoelectric pump to operate stably. Further, the flow rate can be controlled precisely by controlling the changes in the volume. In other words, the characteristics of the piezoelectric pump may be improved.

The pump unit according to embodiments of the present disclosure includes any of the piezoelectric pumps described above, and may have improved characteristics.

Claim 1:
A piezoelectric pump (1F), comprising:
a piezoelectric device (<NUM>) having a through-hole (10a);
a first elastic plate (11F) covering an end of the through-hole (10a) and having a communication hole (11a) communicating with the through-hole (10a); and
a second elastic plate (12F) covering another end of the through-hole (10a),
characterized in that
at least one of the first elastic plate (11F) or the second elastic plate (12F) includes a recess (<NUM>, <NUM>) inward in an axial direction of the through-hole (10a), wherein the at least one of the first elastic plate (11F) or the second elastic plate (12F) including the recess (<NUM>, <NUM>) includes a flat portion (<NUM>, <NUM>) surrounding the recess (<NUM>, <NUM>) and a groove (G) located between the recess (<NUM>, <NUM>) and the flat portion (<NUM>, <NUM>).