JP2004067360A - Piezoelectric actuator, feeder, and precipitation preventing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator for use as a drive source of a feeder or the like, capable of conveying objects with high precision during high attitude controlling without making the conveying objects jump and conveying the conveying objects in a reverse direction (back) with an easy operation, and to provide a feeder equipped with the piezoelectric actuator and a precipitation preventing device. <P>SOLUTION: The feeder is equipped with the piezoelectric actuator 1 and a trough 2. The piezoelectric actuator 1 is equipped with a piezoelectric element 3 for converting a voltage signal to a mechanical displacement (flexural vibration), a drive part 4 for impressing the voltage signal to the piezoelectric element 3, and an operating part 5 vibrating in the left and right directions by the mechanical displacement of the piezoelectric element 3. The piezoelectric actuator 1 is characterized in that the speed and the acceleration speed of the vibration of the back and forth movements of the operating part 5 is asymmetrical. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric actuator used as a drive source of, for example, a parts feeder, and a feeder and a settling prevention device including the piezoelectric actuator.
[0002]
[Prior art]
Nowadays, in various automatic assembling processes and molding processes, a part feeder for continuously transporting small parts such as particulates such as metal powders, electronic parts, resin molded parts, and mechanical parts is used. Conventionally, this type of parts feeder includes an electromagnetic type parts feeder that uses an electromagnet as a driving source and a piezoelectric type parts feeder that uses a piezoelectric element as a driving source. In addition, it is widely used because of its features such as smooth transportation of articles and low power consumption.
[0003]
As shown in FIG. 5, the conventional piezoelectric parts feeder includes a base 50 installed horizontally, a trough 51 disposed substantially horizontally above the base 50, a base 50 and the trough 51. And a plurality of piezoelectric actuators 52 disposed between the two. The piezoelectric parts feeder having such a structure is disclosed in, for example, JP-A-2001-171823 and JP-A-2000-77734.
[0004]
The piezoelectric actuator 52 includes a flat supporting frame 53 fixed on the base 50, a flat operating portion 54 fixed to the lower surface of the trough 51 so as to mate with the supporting frame 53, A rectangular plate-shaped piezoelectric element 55 projecting obliquely upward from the frame piece 53; a rectangular plate-shaped displacement expanding spring 56 bridged between an upper end portion of the piezoelectric element 55 and the operating portion 54; 55 is provided with a driving unit 57 for applying a voltage signal. Therefore, the base 50 and the trough 51 are connected at a plurality of locations by a piezoelectric element 55 and a displacement expanding spring 56 extending in a predetermined direction obliquely upward.
[0005]
The piezoelectric element 55 includes a square metal shim plate 58 made of spring steel or the like, and a pair of piezoelectric bodies 59 laminated on both surfaces of the metal shim plate 58. A pair of electrodes are laminated on both surfaces of the piezoelectric body 59. The piezoelectric element 55 having such a structure bends and vibrates due to the application of a voltage signal by the driving unit 57, and the bending vibration is expanded by the displacement expanding spring 56, and the operating unit 54 and the trough 51 vibrate in a predetermined direction. As a result, an object to be conveyed such as a granular object or a small component on the trough 51 can be conveyed in a certain direction.
[0006]
[Problems to be solved by the invention]
According to the above-described conventional piezoelectric parts feeder, the vibration in the oblique direction A (perpendicular to the plate surface of the piezoelectric element 55) is applied to the trough 51, and the conveyed objects such as small parts are continuously obliquely upward. Jump and transport. In such a jump type piezoelectric parts feeder, there is a certain limitation in improving the transfer accuracy due to the jump of the transferred object. Specifically, on the trough 51 of the piezoelectric type part feeder, an upper holding plate for controlling the posture of the transported object is usually provided. Is necessary, there is a risk of falling over and the like, and it is difficult to control the posture of the transferred object. Further, as the distance from the piezoelectric actuator 52 increases, the vibration in the vertical direction of the trough 51 increases, making smooth transport more difficult. In particular, when the transported object is a granular material, a powder, or the like, the transported object may fall out of the trough 51 after the transport is stopped.
[0007]
Further, in the above-described conventional piezoelectric parts feeder, the piezoelectric element 55 is provided to project obliquely upward in a predetermined direction as described above, and a vibration is applied to the trough 51 in an oblique direction to convey an object. It is impossible to transport an object in the reverse direction or to separate an object to be transported continuously. Therefore, when picking up an object to be conveyed by the above-mentioned conventional piezoelectric type part feeder, a cutting-out mechanism in a right angle direction is used to prevent the adjacent objects from rising together and to pick up only one piece. Further, it is necessary to additionally provide the transfer equipment, which results in complication of the transport equipment and an increase in equipment cost.
[0008]
The present invention has been made in view of these inconveniences, and is used as a drive source of a feeder or the like, and can perform high-accuracy conveyance with high attitude control without jumping a conveyed object, and can perform simple operation. It is an object of the present invention to provide a piezoelectric actuator capable of conveying (back) an object to be conveyed in the opposite direction, and a feeder and a settling prevention device including the piezoelectric actuator.
[0009]
[Means for Solving the Problems]
An invention made to solve the above-mentioned problem is a piezoelectric element that converts a voltage signal into a mechanical displacement, a driving unit that applies a voltage signal to the piezoelectric element, and an operation that vibrates due to the mechanical displacement of the piezoelectric element. And a forward movement and a backward movement in the vibration of the operating part are asymmetric.
[0010]
Therefore, the feeder includes the piezoelectric actuator and a trough connected to an operating portion of the piezoelectric actuator, and the feeder vibrates in the longitudinal direction by the piezoelectric actuator. The object can be transported in one direction without jumping. Therefore, according to the feeder, high-accuracy conveyance with high attitude control is possible. In addition, the feeder reverses the asymmetry between the forward movement and the backward movement in the vibration of the operating portion of the piezoelectric actuator by a simple means such as, for example, electrical switching of the driving portion, thereby moving the transported object in the reverse direction. Can be transported. In this way, according to the feeder, since the forward / reverse switching of the transport direction can be easily and reliably performed, the transported object can be backed before the transport is stopped, and the unintended spilling of the transported object from the trough tip can be prevented. Further, if a slope is provided at the tip of the trough such that the transported object cannot be reversely fed, the transported object can be separated by switching the transport direction between forward and reverse. Therefore, in the transfer equipment including the above-mentioned conventional piezoelectric type part feeder, a cutting mechanism in a perpendicular direction provided for picking up the transferred objects one by one becomes unnecessary, which simplifies the transfer equipment and reduces the equipment cost. Reduction can be promoted.
[0011]
Further, the feeder includes a plurality of the piezoelectric actuators and a flat table connected to the operating portions of the piezoelectric actuators. The feeder vibrates in two orthogonal directions parallel to the table surface by the flat tables. By adjusting the asymmetry of the forward movement and the backward movement of the two vibrations in the two directions perpendicular to the plane, the object can be conveyed in any direction on the flat table.
[0012]
Further, the sedimentation preventing device further includes the piezoelectric actuator and a container engaging portion connected to the operating portion of the piezoelectric actuator, and the sedimentation preventing device in which the container engaging portion vibrates in the vertical direction by the piezoelectric actuator. By adjusting the upward movement, the liquid (including the viscous fluid) in the container attached to the container engaging portion is prevented from settling, and the liquid can be stirred.
[0013]
It is preferable that the acceleration of the forward movement and the backward movement in the vibration of the operating portion be asymmetric. By applying an asymmetrical vibration to the trough or the like from the operating portion, the acceleration of the reciprocating motion allows even the longitudinal vibration of the trough or the like to slide the object to be conveyed during the motion in which the acceleration of the vibration is large. can do.
[0014]
The piezoelectric element includes a square shim plate having conductivity and a pair of square piezoelectric plates laminated on both sides of the shim plate while maintaining electrical continuity. The square piezoelectric plate includes a piezoelectric body and the piezoelectric member. It is preferable to provide a pair of electrodes laminated on both surfaces of the body, and wherein the mechanical displacement is bending vibration. Here, “flexural vibration” means flexural vibration to the left and right sides with respect to the center plane (center plane of the shim plate) of the piezoelectric element having a rectangular plate shape. The flexural vibration of such a plate-shaped piezoelectric element in which two piezoelectric bodies are stacked has a relatively large amplitude, and the feed speed of a feeder using the piezoelectric element can be improved.
[0015]
It is preferable that the voltage signal applied by the driving unit alternately repeats a positive voltage and a negative voltage so that the positive waveform and the negative waveform are asymmetric. By applying a voltage signal that alternately repeats a positive voltage and a negative voltage in this way, a bending vibration is applied to the piezoelectric element, and the positive and negative waveforms of the voltage signal are asymmetrical, thereby The acceleration and the like of the forward movement and the backward movement of the bending vibration of the piezoelectric element can be easily and reliably made asymmetric.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. 1 is a perspective view showing a feeder provided with a piezoelectric actuator according to one embodiment of the present invention, FIG. 2 is a cross-sectional view of the feeder of FIG. 1 along AA, FIG. 3 is a cross-sectional view of the feeder of FIG. FIG. 4 is a schematic configuration diagram showing a piezoelectric element and a drive unit provided in the piezoelectric actuator of FIG.
[0017]
The piezoelectric actuator shown in FIGS. 1 to 3 conveys an object to be conveyed substantially horizontally and linearly, such as a granular material such as a metal powder or a small component such as an electronic component, a resin molded component, or a mechanical component. An actuator 1 and a trough 2 are provided.
[0018]
The piezoelectric actuator 1 includes a piezoelectric element 3 that converts a voltage signal into bending vibration, a driving unit 4 that applies a voltage signal to the piezoelectric element 3, an operating unit 5 that vibrates horizontally due to bending vibration of the piezoelectric element 3, A housing 6 for supporting and housing the element 3 and for supporting the operating portion 5 so as to be slidable horizontally.
[0019]
The housing 6 includes a base 7, a pair of columns 8, a pair of side walls 9, and the like. The base 7 is a substantially rectangular disk-shaped body having a predetermined thickness serving as a base for the feeder, and has a ridge 10 formed in the center in the upper surface in the left-right direction (parallel to the long side). The pair of columns 8 are vertically protruded on both left and right sides of the ridge 10 of the base 7, and are screwed with bolts screwed from the bottom side of the base 7. The pair of side walls 9 are screwed to both side surfaces of the protruding ridge portion 10 of the base 7, and are arranged in parallel in the front-rear direction (in a direction parallel to the short side of the base 7) at a predetermined interval.
[0020]
The material of the base 7, the support 8 and the side wall 9 is not particularly limited as long as the strength and the like required for each member can be secured. For example, metals such as aluminum alloy, copper alloy, steel, and engineering plastics are used. A synthetic resin or the like is used.
[0021]
The piezoelectric element 3 is a rectangular plate having a multilayer structure including a piezoelectric body. Specifically, as shown in FIG. 4, a square shim plate 11 and conductive adhesive layers 12 on both sides of the shim plate 11 are provided. And a pair of rectangular piezoelectric plates 13 laminated through the same. The shim plate 11 is a reinforcing material having conductivity at least on its surface, and a material obtained by, for example, quenching SK steel is preferably used.
[0022]
The rectangular piezoelectric plate 13 includes a piezoelectric body 14 and a pair of electrodes 15 stacked on both surfaces of the piezoelectric body 14. The piezoelectric member 14 is not particularly limited as long as it is a material having a piezo effect in which distortion is generated by application of a voltage. For example, a piezoelectric ceramic, a polymer piezoelectric member, a single crystal piezoelectric member, or the like can be used. Among them, a piezoelectric titanate / lead zirconate piezoelectric ceramic (PZT) having a large piezoelectric effect and good durability is preferable. The electrode 15 is laminated on almost the entire surface of the piezoelectric body 14 excluding the outer edge, and is formed by, for example, printing and baking a silver paste. The directionality of the piezoelectric effect of the pair of rectangular piezoelectric plates 13 having such a structure is uniform.
[0023]
The conductive adhesive layer 12 has a conductor 16 laminated in a line shape, a scattered point shape, and the like, and an adhesive 17 filled in portions other than the conductor 16. The electrical conductivity of the shim plate 11 and the rectangular piezoelectric plate 13 is imparted by the conductor 16, the stress acting on the rectangular piezoelectric plate 13 is reduced by the adhesive 17, and the occurrence of delamination and cracks is reduced. As the conductor 16, for example, a conductive resin such as a carbon resin paste is used, and is formed by printing and curing on the surface of the rectangular piezoelectric plate 13 or the shim plate 11. As the adhesive 17, for example, an epoxy-based adhesive is used, and is formed by coating the conductor 16 on the laminated surface.
[0024]
In the piezoelectric element 3 having the above structure, a lead wire extending from the drive unit 4 is connected to a pair of electrodes 15 and the shim plate 11 provided on the outer surface side. The driving unit 4 alternately applies a positive voltage and a negative voltage to both outer electrodes 15 via the lead wires. When a positive voltage is applied as described above, one piezoelectric body 14 expands and the other piezoelectric body 14 contracts, and as a result, the piezoelectric element 3 bends to the left or right. Conversely, when a negative voltage is applied, one piezoelectric body 14 contracts and the other piezoelectric body 14 expands, and as a result, the piezoelectric element 3 bends to the left or right side (opposite to the above case). Therefore, by alternately applying a positive voltage and a negative voltage to the piezoelectric element 3, the piezoelectric element 3 bends and vibrates to the left and right sides.
[0025]
The front end 18 and the rear end 19 of the piezoelectric element 3 are covered with a synthetic resin by means such as insert molding. The synthetic resin used for the front end portion 18 and the rear end portion 19 is not particularly limited, and examples thereof include thermoplastic elastomer resins such as urethane-based resins, ester-based resins, amide-based resins, and ionomer-based resins. Polyester thermoplastic elastomer resin which does not lose its flexibility with respect to the bending motion of No. 3 is preferable. Further, the synthetic resin coating of the rear end portion 19 is formed to be tapered so as to become thinner toward the front end side, so that resistance to the bending motion of the piezoelectric element 3 and damage to the piezoelectric element 3 are reduced.
[0026]
In the piezoelectric actuator 1, a plurality of (six in the figure) piezoelectric elements 3 are housed and supported in an internal space surrounded by a base 7, a pair of columns 8, and a pair of side walls 9. These piezoelectric elements 3 are erected vertically and are arranged at equal intervals. At the rear end 19 of each piezoelectric element 3, two upper and lower pins 20 and 21 vertically extending between a pair of paired side walls 9 are inserted, and the plate surface is turned in the left-right direction and the front end is formed. 18 is supported upward. Therefore, when a voltage signal is applied by the drive unit 4 to cause the piezoelectric element 3 to bend and vibrate as described above, the distal end portion 18 vibrates in the left-right direction along a substantially circular orbit.
[0027]
The operating portion 5 is a substantially rectangular plate-like body, and is supported on upper end surfaces of a pair of columns 8 of the housing 6. The operating portion 5 is engaged with a shaft portion and a head portion of a bolt 23 driven into an upper portion of the support column 8 so as to be slidable only in a small range in the left-right direction and to suppress upward jump. . A number of concave grooves 22 corresponding to the number of the piezoelectric elements 3 are formed in the lower surface of the operating portion 5 along the front-rear direction. The distal end portion 18 of the piezoelectric element 3 is fitted into the concave groove 22 with play in the vertical direction. Accordingly, when the distal end portion 18 of the piezoelectric element 3 vibrates in the left-right direction along a substantially circular orbit, the operating portion 5 vibrates in the left-right direction n.
[0028]
The driving section 4 applies a voltage signal to the piezoelectric element 3 via the lead wire as described above. This voltage signal alternately repeats a positive voltage and a negative voltage, and is characterized in that the waveform on the positive side and the waveform on the negative side are asymmetric. Although the specific contents of the voltage signal asymmetric on the positive side and the negative side are not particularly limited, for example, the voltage increasing speed and the voltage increasing acceleration, that is, the slope shape of the voltage increasing curve is changed to the positive side and the negative side. It is good to make it different. By applying such asymmetrical voltage signals to the piezoelectric element 3 on the positive side and the negative side, the speed, acceleration, and the like of the forward movement and the backward movement in the bending vibration of the piezoelectric element 3 become asymmetric. The forward movement and the backward movement in the vibration in the left-right direction also have asymmetric speed, acceleration, and the like. In the driving unit 4, as means for generating such an asymmetrical voltage signal on the positive side and the negative side, a known means is not particularly limited. For example, a circuit for applying a positive voltage may be used. There is a means for connecting a pair of resistors to a circuit for applying a negative voltage, for example, to make the sizes of the pair of resistors different.
[0029]
The trough 2 is a toy-shaped one that is a transfer path for a transferred object such as a granular part such as a metal powder or a small part such as an electronic part. The trough 2 is disposed substantially horizontally and horizontally on the upper surface of the operating part 5 of the piezoelectric actuator 1. Fixed towards. Therefore, the trough 2 vibrates in the left-right direction n (that is, the longitudinal direction), and the speed, acceleration, and the like of the forward motion and the backward motion are asymmetrical, similarly to the operation portion 5.
[0030]
Therefore, according to the feeder, the transported object can be transported in one lateral direction by the asymmetrical vibration of the trough 2 in the horizontal direction without jumping the transported object unlike the conventional feeder. For example, among the vibrations of the trough 2, the acceleration of the forward movement is made smaller than μ * G (μ: coefficient of friction between the trough 2 and the transferred object, G: the gravitational acceleration), and the acceleration of the backward movement is made smaller than μ * G. By increasing the size, it is possible to move the transported object without slipping during the forward movement, slide the transported object during the backward movement and leave it in place, and repeatedly transport the transported object in the forward movement direction. it can. Therefore, according to the feeder, a high attitude control is possible, and the transfer accuracy such as the transfer speed is remarkably improved.
[0031]
Further, according to the feeder, the asymmetry (for example, the acceleration) on the positive side and the negative side of the voltage signal applied by the driving section 4 is reversed, so that the vibration of the piezoelectric element 3, the operating section 5, and the trough 2 is achieved. The asymmetry of the forward movement and the backward movement can be easily reversed, and the transport direction can be reversed (back). Therefore, according to the feeder, the transported object can be backed before the transport is stopped to prevent the transported object from being unintentionally discharged from the front end of the trough 2, and the transported object cannot return to the front end of the trough 2. If a gradient is provided, the transported object can be separated by the forward / reverse switching operation of the transport direction.
[0032]
The piezoelectric actuator of the present invention is not limited to the above embodiment. For example, the side wall may be configured to cover the entire inner space for housing the piezoelectric element 3, and may be configured by a plurality of sheets. Is also possible. The piezoelectric element is not limited to the two-lead type piezoelectric element 3 in which the two piezoelectric members 14 are bonded, and any form can be used as long as the forward movement and the backward movement can extract asymmetric vibration. is there. The means for obtaining the asymmetry of the vibration is not limited to the means of the present embodiment in which the voltage signal by the driving unit 4 is asymmetric on the positive side and the negative side. For example, means for utilizing the characteristic itself of the piezoelectric effect of the piezoelectric body Is also possible.
[0033]
Further, the feeder includes two piezoelectric actuators 1 and a flat table, and these piezoelectric actuators 1 are installed so that the directions of vibration of the operating portions 5 are orthogonal to each other, and the flat table is fixed to these operating portions 5. Is also possible. According to this feeder, by adjusting the asymmetry of the forward movement and the backward movement of the vibration in the two orthogonal directions in the piezoelectric actuator 1, it is possible to convey the object in any direction on the flat table.
[0034]
Further, the piezoelectric actuator 1 and the container engaging portion are provided, and the piezoelectric actuator 1 is installed with the vibration direction of the operating portion 5 oriented vertically, and the container engaging portion is connected to the operating portion 5 to prevent sedimentation. Devices are also possible. According to this sedimentation prevention device, by adjusting the asymmetry of the upward vibration and making the downward movement an acceleration greater than 1 G, sedimentation of the liquid in the container attached to the container engaging portion is prevented. Thus, the liquid can be agitated.
[0035]
【The invention's effect】
As described above, according to the piezoelectric actuator of the present invention, the forward movement and the backward movement can be used as a driving source of a high-precision feeder or a settling prevention device due to asymmetric vibration. Further, according to the feeder provided with the piezoelectric actuator, it is possible to carry the conveyance with good conveyance accuracy and attitude control without jumping the object, and to carry the object in the reverse direction by a simple operation ( Back) is possible. Furthermore, according to the settling prevention device provided with the piezoelectric actuator, by attaching to the container, the settling prevention and stirring of the liquid mixed with the metal fine particles and the like can be performed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a feeder including a piezoelectric actuator according to an embodiment of the present invention.
FIG. 2 is a sectional view of the feeder taken along line AA of FIG.
FIG. 3 is a sectional view taken along line BB of the feeder of FIG. 1;
FIG. 4 is a schematic configuration diagram illustrating a piezoelectric element and a drive unit provided in the piezoelectric actuator of FIG. 1;
FIG. 5 is a schematic configuration diagram showing a conventional piezoelectric parts feeder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator 2 Trough 3 Piezoelectric element 4 Actuator 5 Actuator 6 Housing 7 Base 8 Post 9 Side wall 10 Convex ridge 11 Shim plate 12 Conductive adhesive layer 13 Square piezoelectric plate 14 Piezoelectric body 15 Electrode 16 Conductor 17 Adhesive 18 Front end 19 Rear end 20 Pin 21 Pin 20
22 Concave groove 23 Bolt

Claims (7)

A piezoelectric element that converts a voltage signal into a mechanical displacement, a driving unit that applies a voltage signal to the piezoelectric element, and a piezoelectric actuator that includes an operating unit that vibrates due to mechanical displacement of the piezoelectric element,
A piezoelectric actuator characterized in that the forward movement and the backward movement of the vibration of the operating part are asymmetric. 2. The piezoelectric actuator according to claim 1, wherein accelerations of the forward movement and the backward movement in the vibration of the operating portion are asymmetric. The piezoelectric element includes a square shim plate having conductivity, and a pair of square piezoelectric plates stacked while having electrical conduction on both surfaces of the shim plate,
The square piezoelectric plate includes a piezoelectric body and a pair of electrodes stacked on both surfaces of the piezoelectric body,
3. The piezoelectric actuator according to claim 1, wherein the mechanical displacement of the piezoelectric element is bending vibration. 4. The piezoelectric actuator according to claim 1, wherein the voltage signal applied by the drive unit alternately repeats a positive voltage and a negative voltage, and a positive waveform and a negative waveform are asymmetric. 5. . A piezo-electric actuator according to any one of claims 1 to 4, and a trough connected to an operating part of the piezo-electric actuator,
This trough is a feeder that vibrates in the longitudinal direction by a piezoelectric actuator. A plurality of piezoelectric actuators according to any one of claims 1 to 4, and a flat table connected to an operation unit of the piezoelectric actuators,
A feeder in which this flat table vibrates in two orthogonal directions parallel to the table surface by these piezoelectric actuators. A piezoelectric actuator according to any one of claims 1 to 4, and a container engaging part connected to an operating part of the piezoelectric actuator,
A sedimentation prevention device in which the container engaging portion vibrates vertically by a piezoelectric actuator.

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