JP2004307182A - Piezoelectric oscillating feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric oscillating feeder capable of rapidly performing measurement and supply with high accuracy. <P>SOLUTION: The piezoelectric vibration feeder comprises (a) a piezoelectric element 4 to convert an electric signal into a mechanical displacement, (b) an operation unit 5 which is oscillated in the horizontal direction by the mechanical displacement of the piezoelectric element 4 with an outgoing motion and an incoming motion asymmetric, (c) a load cell 2 to be connected to the operation unit 5, (d) a trough 3 which is connected to a load receiving unit 26 of the load cell 2 and disposed parallel to the oscillating direction of the operation unit 5, and (e) a control unit which applies a voltage signal to the piezoelectric element 4 to feedback-control the voltage signal by the received load data of the load cell 2. The acceleration of the ongoing motion and the incoming motion in the oscillation of the operation unit 5 is preferably asymmetric. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric vibratory feeder capable of accurately and quickly metering a conveyed object such as a powder.
[0002]
[Prior art]
Today, in a manufacturing process of various products, a piezoelectric vibratory feeder that continuously conveys and supplies powders such as metals, additives, and samples is used. As shown in FIG. 5, a conventional piezoelectric vibration feeder includes a base 50 installed horizontally, a trough 51 disposed substantially horizontally above the base 50, and a base 50 and a trough 51. And a plurality of piezoelectric actuators 52 disposed therebetween. The piezoelectric vibration feeder having such a structure is disclosed in, for example, JP-A-2001-171823 and JP-A-2000-77734.
[0003]
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 controller 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.
[0004]
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 the voltage signal by the control 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 oblique direction m. As a result, a conveyed object such as powder on the trough 51 can be conveyed in a certain direction.
[0005]
[Patent Document 1]
JP 2001-171823 A [Patent Document 2]
JP 2000-77734 A
[Problems to be solved by the invention]
According to the above-described conventional piezoelectric vibration feeder, the vibration in the oblique direction m (perpendicular to the plate surface of the piezoelectric element 55) is applied to the trough 51, and the conveyed object such as powder is continuously and obliquely upward. Jump and transport. In such a jump type piezoelectric vibratory feeder, there is a certain limitation in improving the transfer accuracy due to the jump of the transferred object, and specifically, it is difficult to supply a small amount of powder or the like and adjust the supply amount. However, it is impossible to transport the transported object in the reverse direction.
[0007]
Further, in the above-described conventional piezoelectric vibration feeder, since the piezoelectric actuator 52 and the trough 51 vibrate in the vertical direction, a load cell for measuring the supply amount of the object to be conveyed requires a vertical actuator which has little vertical vibration to affect the measurement. It must be installed below the base 52 or below the base 50. Therefore, according to the conventional piezoelectric vibration feeder, it is necessary to measure the entire transport system, and it is difficult to use a load cell with high resolution, and it is necessary to correct the measured value. Further, according to the above-described conventional piezoelectric vibration feeder, since the supply amount cannot be accurately measured during operation due to vertical vibration, it is necessary to stop the vibration and measure the supply amount. That is, according to the above-mentioned conventional piezoelectric vibration feeder, it is difficult to perform high-precision and quick metering.
[0008]
The present invention has been made in view of these inconveniences, and has as its object to provide a piezoelectric vibratory feeder capable of quickly and accurately metering and supplying.
[0009]
[Means for Solving the Problems]
The invention made to solve the above-mentioned problems includes (a) a piezoelectric element for converting a voltage signal into a mechanical displacement, and (b) a horizontal movement and a forward movement and a backward movement due to the mechanical displacement of the piezoelectric element. An operating part that vibrates asymmetrically; (c) a load cell connected to the operating part; (d) a trough connected to the load receiving part of the load cell and disposed in parallel with the vibration direction of the operating part; A) a piezoelectric vibration feeder including a control unit that applies a voltage signal to the piezoelectric element and performs feedback control of the voltage signal based on the received load data of the load cell.
[0010]
The piezoelectric vibratory feeder is capable of transporting the transported object without jumping in one direction of the vibration direction by the vibration of the trough in the forward and backward movements which are asymmetrical and horizontal, thereby enabling highly accurate transport and supply. is there. Further, the piezoelectric vibration feeder can control the supply amount with high accuracy by further adjusting the voltage applied to the piezoelectric element, the shape of the rising portion in the voltage signal waveform, and the frequency of the voltage signal. Further, the piezoelectric vibration feeder conveys the object to be conveyed in the reverse direction by reversing the asymmetry of the forward movement and the backward movement in the vibration of the operating part by simple means such as electrical switching of the control part. For example, the transported object is backed before the transport is stopped, so that unintended spilling of the transported object from the tip of the trough can be prevented.
[0011]
Further, in the piezoelectric vibration feeder, since the vibration supplied to the transport supply is in the horizontal direction and there is no vertical component affecting the measurement of the load cell, the load cell is connected between the operation unit and the trough, and the trough and the trough are connected. Only the transferred object can be weighed. Therefore, the piezoelectric vibrating feeder can measure the supply amount in real time at the time of transport and supply, can use a load cell with high resolution, and can eliminate the need to correct the measurement value. Further, the piezoelectric vibration feeder performs feedback control of the voltage signal using the real-time load data, thereby enabling more accurate and prompt conveyance and supply.
[0012]
It is preferable that the acceleration of the forward movement and the backward movement in the vibration of the operating portion be asymmetric. By providing the trough with asymmetrical vibration in which the acceleration of the reciprocating motion is applied, the object can be slid and conveyed quickly and reliably during the motion in which the acceleration of the vibration is large.
[0013]
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 speed at which a piezoelectric vibratory feeder using the piezoelectric element is fed can be improved.
[0014]
The voltage signal applied by the control unit may alternately repeat a positive voltage and a negative voltage, and make the positive and negative waveforms asymmetrical. 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.
[0015]
It is preferable that the load cell is reciprocally mounted on a rail provided in parallel with the vibration direction of the operating section. By placing the load cell on the rail in this way, the load on the piezoelectric element due to receiving the load of the load cell on the rail and connecting the load cell to the operating portion can be reduced.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a perspective view showing a piezoelectric vibration feeder according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of the piezoelectric vibration feeder of FIG. 1, and FIG. FIG. 4 is a schematic configuration diagram showing a piezoelectric element and a control unit provided in the piezoelectric actuator of FIG. 1.
[0017]
The piezoelectric vibration feeder shown in FIG. 1 is for transporting and supplying a conveyed object (eg, a metal, an additive, a sample, etc.) such as a powder or a granular material in a horizontal direction. Specifically, the piezoelectric actuator 1 and the load cell 2 , A trough 3 and a control unit (not shown).
[0018]
As shown in FIGS. 1 to 3, the piezoelectric actuator 1 includes a piezoelectric element 4 that converts a voltage signal into bending vibration, an operating unit 5 that vibrates in a horizontal direction due to bending vibration of the piezoelectric element 4, and a piezoelectric element 4. And a housing 6 for supporting and storing and slidably supporting the operating portion 5.
[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 piezoelectric vibration feeder. The pair of pillars 8 are vertically protruded from the base 7 at a predetermined interval, and are screwed with bolts screwed from the bottom side of the base 7. The pair of side walls 9 are fixed to both side surfaces of the pair of columns 8 by screws or the like, and are arranged in parallel 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 4 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 4 having the above structure, a lead wire 10 extending from a control unit is connected to a pair of electrodes 15 and a shim plate 11 provided on the outer surface side. The control unit applies a positive voltage and a negative voltage alternately to both outer electrodes 15 via the lead wires. When a positive voltage is applied in this manner, one piezoelectric body 14 expands and the other piezoelectric body 14 contracts, and as a result, the piezoelectric element 4 is curved to the left or right with respect to the plate surface. 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 4 bends to the left or right side (opposite to the above case). Therefore, by alternately applying the positive voltage and the negative voltage to the piezoelectric element 4, the piezoelectric element 4 bends and vibrates to the left and right sides.
[0025]
The front end portion 18 and the rear end portion 19 of the piezoelectric element 4 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 flexibility against the bending motion of No. 4 is preferable. Further, the synthetic resin coating of the rear end portion 19 is tapered so as to be thinner toward the front end side, so that resistance to the bending motion of the piezoelectric element 4 and breakage of the piezoelectric element 4 are reduced.
[0026]
In the piezoelectric actuator 1, a plurality of (ten in the figure) piezoelectric elements 4 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 4 are erected vertically and are arranged in parallel and at equal intervals. At the rear end 19 of each piezoelectric element 4, two upper and lower pins 20 and 21, which are vertically extended between a pair of side walls 9, are inserted, and the plate surface is directed vertically to the side walls 9, and , And the tip 18 is supported upward. Therefore, when a voltage signal is applied by the control unit as described above to cause the piezoelectric element 4 to bend and vibrate, the distal end portion 18 vibrates in parallel with the side wall 9 along a substantially circular orbit.
[0027]
The operating portion 5 is a substantially rectangular plate-like body, and is slidably supported on the upper end surfaces of the pair of columns 8 of the housing 6. A number of concave grooves 22 corresponding to the number of the piezoelectric elements 4 are formed in the lower surface of the operating portion 5 in a direction perpendicular to the side wall 9. The distal end portion 18 of the piezoelectric element 4 is fitted into the concave groove 22 with play in the vertical direction. Therefore, when the tip portion 18 of the piezoelectric element 4 vibrates along a substantially circular orbit, the operating portion 5 vibrates in the horizontal direction n in parallel with the side wall 9.
[0028]
The load cell 2 is a load measuring device using a flexure element that converts strain into a resistance change. The load cell 2 is connected to the operating portion 5 of the piezoelectric actuator 1 via a connecting plate 23 having an L-shaped cross section, and is mounted on a rail 24 so as to be able to reciprocate. The rail 24 is provided on the base 7 in parallel with the side wall 9. Accordingly, the load cell 2 vibrates in the horizontal direction n in parallel with the side wall 9 as in the case of the operating portion 5 of the piezoelectric actuator 1. As described above, the load cell 2 is connected to the operating unit 5 and oscillates at the time of transport and supply. However, since the load cell 2 oscillates in the horizontal direction and does not vibrate in the vertical direction, it does not affect the weighing. Further, the load applied to the vibration of the piezoelectric actuator 1 is reduced by being mounted on the rail 24. The load data detected by the load cell 2 is transmitted to the control unit via the lead wire 25.
[0029]
The trough 3 is in the shape of a toy, which is a transport path of an object to be transported, and is fixed to the load receiving portion 26 of the load cell 2. The trough 3 has its longitudinal direction oriented parallel to the side wall 9 and in the horizontal direction n. Therefore, the trough 3 vibrates in the horizontal direction n (that is, in the longitudinal direction) in parallel to the side wall 9 and asymmetrically in the forward movement and the backward movement, similarly to the operating part 5 and the load cell 2.
[0030]
The control unit applies a voltage signal to the piezoelectric element 4 via the lead wire 10 and performs feedback control of the voltage signal based on the load data of the load cell 2 received via the lead wire 25. 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. The specific contents of the voltage signal that is 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 shape of the voltage waveform curve is defined as the positive side and the negative side. It is good to make it different. By applying such asymmetrical voltage signals on the positive side and the negative side to the piezoelectric element 4, the speed, acceleration, and the like of the forward movement and the backward movement in the flexural vibration of the piezoelectric element 4 become asymmetric, and thus the operating part 5 and The forward movement and the backward movement in the vibration of the trough 3 also have asymmetric speed, acceleration, and the like. In the control section, a means for generating such asymmetrical voltage signal on the positive side and the negative side is not particularly limited, and a known means is employed. For example, a circuit for applying a positive voltage and a negative There is a means for connecting a pair of resistors to a circuit for applying a voltage, and making the pair of resistors have different sizes.
[0031]
Therefore, according to the piezoelectric vibration feeder, the transported object can be transported in one longitudinal direction by the asymmetrical vibration of the trough 3 in the longitudinal direction without jumping the transported object unlike the conventional feeder. it can. For example, among the vibrations of the trough 3, the acceleration of the forward movement is made smaller than μ * G (μ: coefficient of friction between the trough 3 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 piezoelectric vibration feeder, the conveyance accuracy is remarkably improved.
[0032]
Further, according to the piezoelectric vibration feeder, the amplitude of the trough 3 is determined by the magnitude of the voltage in the voltage signal applied to the piezoelectric element 4 by the control unit, and the acceleration and frequency of the vibration of the trough 3 are determined by the shape of the rising portion of the voltage waveform. The frequency can be controlled, and as a result, the transported supply amount can be controlled with high accuracy, and a small amount can be supplied.
[0033]
Further, according to the piezoelectric vibration feeder, since the vibration supplied to the conveyance supply is in the horizontal direction and there is no vertical vibration affecting the measurement of the load cell 2, the trough 3 ) Is measured in real time during transport and supply, and the voltage signal can be feedback-controlled based on the real-time load data. In addition to the horizontal and asymmetrical vibration of the piezoelectric actuator 1, higher accuracy and speed are achieved. Transport and supply are possible. Since the load cell 2 can be directly connected to the trough 3 in this manner, it is possible to use the load cell 2 having a higher resolution than a conventional jump type piezoelectric vibratory feeder which needs to measure the entire transport system, and to measure the measured value. Can be dispensed with.
[0034]
Further, according to the piezoelectric vibration feeder, the positive and negative asymmetries (for example, the acceleration) of the voltage signal applied by the control unit are reversed, so that the forward movement and the backward movement of the vibration of the trough 3 are performed. Can be easily reversed, and the transport direction can be reversed (back). Therefore, according to the piezoelectric vibration feeder, the transported object can be backed before the transport is stopped, and the unintended discharge of the transported object from the tip of the trough 3 can be prevented.
[0035]
Note that the piezoelectric actuator of the present invention is not limited to the above-described embodiment. For example, the side wall may be configured to cover the entire internal space for housing the piezoelectric element 4, and may be configured with a plurality of sheets. Is also possible. The piezoelectric element is not limited to the piezoelectric element 4 in which the two piezoelectric members 14 are bonded, and may be in any form as long as the forward movement and the backward movement can extract asymmetric vibration. 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 control unit is asymmetric on the positive side and the negative side, and for example, means for utilizing the characteristic itself of the piezoelectric effect of the piezoelectric body may be used. It is possible.
[0036]
In addition, a transfer line for an object to be transferred is constituted by a piezoelectric vibration feeder having no load cell and not having a weighing function, and the piezoelectric vibration feeder is provided in a part of the transfer line (particularly preferably on the supply end side). Good. By sequentially supplying the trough 3 (secondary trough) of the piezoelectric vibratory feeder from the trough (primary trough) of the piezoelectric vibratory feeder having no measuring function, the load cell 2 of the piezoelectric vibratory feeder measures the trough 3 and The load of the transported object is further reduced, so that transport with higher precision can be performed. As the piezoelectric vibratory feeder constituting this transport line, a horizontal vibratory feeder similar to the piezoelectric vibratory feeder of the present invention is preferable, and more precise transport / supply control is possible.
[0037]
【The invention's effect】
As described above, according to the piezoelectric vibration feeder of the present invention, since the forward movement and the backward movement are asymmetric and the conveyed object is conveyed and supplied by the vibration of the horizontal trough, the load cell directly connected to the trough is used in real time. High-precision weighing can be performed, and the object to be transported can be transported and supplied with high accuracy and speed, in combination with good controllability of the horizontal vibration type transport supply.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a piezoelectric vibration feeder according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line AA of the piezoelectric vibration feeder of FIG.
FIG. 3 is a sectional view of the piezoelectric vibration feeder taken along line BB of FIG. 1;
FIG. 4 is a schematic configuration diagram showing a piezoelectric element and a control unit provided in the piezoelectric vibration feeder of FIG. 1;
FIG. 5 is a schematic configuration diagram showing a conventional piezoelectric vibration feeder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator 2 Load cell 3 Trough 4 Piezoelectric element 5 Actuator 6 Housing 7 Base 8 Post 9 Side wall 10 Lead wire 11 Shim plate 12 Conductive adhesive layer 13 Square piezoelectric plate 14 Piezoelectric member 15 Electrode 16 Conductor 17 Adhesive 18 Tip Part 19 rear end part 20 pin 21 pin 22 concave groove 23 connecting plate 24 rail 25 lead wire 26 load receiving part

Claims (5)

A piezoelectric element that converts a voltage signal into a mechanical displacement,
An actuating section in which the forward movement and the backward movement vibrate asymmetrically in the horizontal direction due to the mechanical displacement of the piezoelectric element;
A load cell connected to the operating part;
A trough connected to the load receiving portion of the load cell and disposed in parallel with the vibration direction of the operating portion;
A control unit that applies a voltage signal to the piezoelectric element and performs feedback control of the voltage signal based on the received load data of the load cell. 2. The piezoelectric vibration feeder according to claim 1, wherein the acceleration of the forward movement and the backward movement in the vibration of the operating portion is 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 vibration feeder according to claim 1, wherein the mechanical displacement of the piezoelectric element is bending vibration. 4. The piezoelectric type according to claim 1, wherein the voltage signal applied by the control unit alternately repeats a positive voltage and a negative voltage, and a positive waveform and a negative waveform are asymmetric. Vibrating feeder. The piezoelectric vibratory feeder according to any one of claims 1 to 4, wherein the load cell is reciprocally mounted on a rail provided in parallel with a vibration direction of the operating portion.

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