JP4354549B2 - Transport device drive element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive element of a transport device used as a drive source of a parts feeder, for example.
[0002]
[Problems to be solved by the invention]
For example, in various automatic assembly processes, there is a piezoelectric part feeder that uses a piezoelectric ceramic vibrator as a drive element as a part feeder that conveys relatively small parts such as electronic parts, resin molded parts, and machine parts. Such piezoelectric parts feeders are widely used because they have features such as smoother article transportation and lower power consumption than conventional electromagnetic parts feeders.
[0003]
8 and 9 show the basic configuration of this type of piezoelectric part feeder (linear drive system). Here, a trough 2 extending in a substantially horizontal direction is arranged above the base 1, and at this time, a horizontal frame piece 3 attached on the base 1, and the trough 2 The horizontal frame piece 4 attached to the lower surface is connected at both left and right ends by a piezoelectric ceramic vibrator 5 that extends obliquely in the vertical direction and a displacement expansion spring 6 that is screwed and fixed to the upper part.
[0004]
As shown in FIG. 10, the piezoelectric ceramic vibrator 5 is formed by, for example, quenching SK steel at the center of both sides of a metal shim plate 7 having a considerably large thickness compared to a general leaf spring material. The piezoelectric ceramic elements 8 and 8 are attached. In this case, although not shown, a conductive paste such as silver is printed and baked on both surfaces of the piezoelectric ceramic element 8 so as to be electrodes. A plurality of screw holes 9 (see FIG. 10) are formed at both upper and lower ends of the metal shim plate 7.
[0005]
Adhesion between the piezoelectric ceramic element 8 and the metal shim plate 7 is performed by, for example, an adhesive mixed with conductive powder, and electrical connection between the back side electrode of the piezoelectric ceramic element 8 and the metal shim plate 7 is achieved. It is supposed to be. As another method of bonding between the piezoelectric ceramic element 8 and the metal shim plate 7, the convex portion of the surface unevenness of the electrode on the back surface of the piezoelectric ceramic element 8 contacts the metal shim plate 7 in a point shape. In some cases, some were adhered by an adhesive. At this time, in order to achieve reliable conduction, the thickness of the adhesive layer was set to be as thin as 20 μm or less.
[0006]
As shown in FIG. 8, a lead wire 11 connected to one power supply terminal 10 is connected to the metal shim plate 7 and a lead wire 13 connected to the other power supply terminal 12 is connected to each piezoelectric ceramic. It is connected to the surface portion of the element 8 by soldering (soldering portion 14). As a result, an AC voltage generated by a power supply device (not shown) is applied via the lead wires 11 and 13, whereby the piezoelectric ceramic vibrator 5 is flexibly vibrated, and the component 15 on the trough 2 is moved to, for example, an arrow. It is designed to move in the A direction.
[0007]
However, in the piezoelectric ceramic vibrator 5 described above, the soldered portion 14 of the lead wire 13 on the surface side of the piezoelectric ceramic element 8 is harder than the other portions. The stress at the time is concentrated, and a crack C (see FIG. 10) that passes through the soldered portion 14 is likely to occur, and there is a problem that the life of the piezoelectric ceramic vibrator 5 is shortened.
[0008]
In addition to the cracks in the soldered portion 14 of the piezoelectric ceramic element 8, fatigue is generated particularly in the lower side portion of the piezoelectric ceramic element 8 due to a moment load generated by the inertial force of the trough 2 with long-term use. There is a problem in that the piezoelectric ceramic element 8 is peeled off from the metal shim plate 7 due to the above, and cracks are generated.
[0009]
On the other hand, in such a piezoelectric parts feeder, in recent years, there has been a demand for downsizing of the entire apparatus accompanying the downsizing of the transporting part A and high speed transporting, and the amplitude of the piezoelectric ceramic vibrator 5 is increased. There is a demand for the development of a piezoelectric ceramic vibrator that can withstand use under even more severe conditions such as increasing the size of the piezoelectric ceramic vibrator and has excellent durability and reliability.
[0010]
The present invention has been made in view of the above circumstances, purpose of that is by improving the adhesion structure of a metal shim plate and the piezoelectric ceramic element, in the adhesive surface between the metal shim plate and the piezoelectric ceramic element An object of the present invention is to provide a driving element for a conveying apparatus that can effectively prevent the occurrence of peeling of an adhesive or a crack , and thereby improve the durability.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a drive device for a conveying device in which a piezoelectric ceramic element is attached to one side or both sides of a metal shim plate and an AC voltage is applied between the metal shim plate and the piezoelectric ceramic element. In a state in which the conductive resin is arranged in a linear or dot shape between the metal shim plate and the piezoelectric ceramic element, both of them are bonded by an adhesive at the non-coated portion of the conductive resin. It has the characteristics.
According to this, the metal shim plate and the piezoelectric ceramic element are bonded to each other by an adhesive, but at this time, a reliable electrical connection between the two is achieved by the conductive resin arranged in a linear or dot shape. Conductivity can be achieved, and nevertheless, the stress acting on the piezoelectric ceramic element can be reduced by the adhesive layer. In this case, there is no need to use a conductive adhesive, so the type of adhesive can be freely selected, and conduction is achieved by the conductive resin, so the thickness of the adhesive layer can also be set arbitrarily. Is possible.
[0013]
At this time, a conductive foil is attached to the surface portion of the piezoelectric ceramic element via a conductive adhesive to constitute an electrode, and a lead wire for applying an AC voltage is soldered to the conductive foil. Can do.
According to this, since the conductive adhesive is interposed between the conductive foil to which the lead wire is soldered and the surface portion of the piezoelectric ceramic element, the soldered portion on the surface side of the piezoelectric ceramic element during vibration The stress acting on the conductive adhesive is absorbed by the conductive adhesive. As the conductive foil, various materials such as a copper foil can be employed, and a copper adhesive tape or the like obtained by applying a conductive adhesive in advance to the back surface of the copper foil is also commercially available.
[0016]
By the way, when the metal shim plate and the piezoelectric ceramic element are bonded as described above, the ease of peeling and the likelihood of cracking differ depending on the hardness of the adhesive after curing. According to the inventor's experiment and research, if the hardness of the adhesive after curing is 80 to 85 in Shore D code (the invention of claim 3), it is most effective in preventing peeling and cracking. It was confirmed that there was. When the hardness is less than 80, cracks are relatively likely to occur in the piezoelectric ceramic element, and when the hardness is more than 85, adhesion peeling is relatively likely to occur.
[0017]
Furthermore, the ease of peeling of the piezoelectric ceramic element and the likelihood of cracking also vary depending on the thickness dimension of the adhesive layer. According to the experiment and research of the present inventor, it is most desirable that the thickness dimension of the adhesive layer is in the range of 30 to 50 μm (the invention of claim 4), and cracks are relatively generated beyond that range. It becomes easy to do.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a piezoelectric ceramic vibrator used as a drive source of a parts feeder will be described. First, a first embodiment of the present invention (corresponding to claims 1 to 4) will be described with reference to FIGS. The basic configuration of the parts feeder (the portion excluding the piezoelectric ceramic vibrator) is a well-known configuration similar to that described in the conventional example, and thus illustration and description thereof will be omitted.
[0019]
1 and 2 show the configuration of a piezoelectric ceramic vibrator 21 (corresponding to Example 1 to be described later) as a drive element according to the present embodiment. As shown in FIG. 3, the piezoelectric ceramic vibrator 21 is configured by pasting piezoelectric ceramic elements 23, 23 on both surfaces of a metal shim plate 22 in this case. The metal shim plate 22 has a rectangular plate shape and is formed by quenching SK steel, for example. The specific dimensions of the metal shim plate 22 are, for example, a width of 50 mm, a length of 86 mm, and a thickness of 6 mm. As shown in FIG. 2, a plurality of screw holes 24 are formed at both upper and lower ends of the metal shim plate 22.
[0020]
On the other hand, the piezoelectric ceramic element 23 has a rectangular thin plate shape, for example, a soft material having a dielectric constant of about 2000 having lead titanate and lead zirconate as main components and having a polarity by polarization treatment. . As shown in FIG. 4, surface electrodes 25 are provided on both surfaces of the piezoelectric ceramic element 23 so as to be located on almost the entire surface excluding only the peripheral edge. The surface electrode 25 is formed, for example, by printing a silver paste and baking it. The specific dimensions of the piezoelectric ceramic element 23 are, for example, 45 mm in width, 47 mm in length, and 0.75 mm in thickness.
[0021]
Now, the piezoelectric ceramic element 23 is affixed to the central portion of the metal shim plate 22 at one adhesive surface (this surface is the back surface). At this time, as shown in FIGS. In addition, a linear conductor 26 made of a conductive resin is provided between the metal shim plate 22 and the piezoelectric ceramic element 23 so as to be electrically connected between the two. The non-formed portion is bonded by the adhesive 27.
[0022]
The linear conductor 26 is provided by printing a conductive resin such as a carbon resin paste on the back surface of the piezoelectric ceramic element 23 by a screen printing method, and drying and curing at 100 to 140 ° C. for 20 minutes. In this case, as shown in FIG. 4, the linear conductors 26 extend in a straight line in the longitudinal direction (length direction) of the piezoelectric ceramic element 23, and, for example, nine wires are formed at approximately equal intervals in parallel. It has become. The specific dimensions of the linear conductor 26 are 1.0 to 1.5 mm in width, slightly shorter than the length of the piezoelectric ceramic element 23, and 35 to 40 μm in thickness.
[0023]
The adhesive 27 is, for example, an epoxy adhesive having a hardness after curing of 83 in Shore D code, and is applied to the non-formation portion of the linear conductor 26 on the back surface of the piezoelectric ceramic element 23. The For bonding, the piezoelectric ceramic elements 23 coated with the adhesive 27 are attached to predetermined positions on both surfaces of the metal shim plate 22 and dried at, for example, 100 to 120 ° C. with the pressure applied thereto. This is done by curing.
[0024]
As shown in FIG. 3, the piezoelectric ceramic elements 23 are attached to both surfaces of the metal shim plate 22, and the metal shim plate 22 and the surface electrode 25 on the back side of the piezoelectric ceramic element 23 are connected to the linear conductor 26. Is brought into an electrically conductive state. At this time, the thickness of the adhesive 27 layer can be controlled by the linear conductor 26, and the thickness dimension of the adhesive 27 layer is set to 35 to 40 μm in this case. Furthermore, the thickness of the adhesive 27 layer can be made uniform by the linear conductor 26. As shown in FIG. 1, a lead wire 29 connected to one output terminal of an AC power supply device 28 is connected to the metal shim plate 22.
[0025]
As shown in FIG. 1, the lead wire 30 connected to the other output terminal of the AC power supply device 28 is connected to the surface side of each piezoelectric ceramic element 23. At this time, as shown in FIG. As shown, a copper foil 31 as a conductive foil is affixed to the central portion of the surface electrode 25 on the surface portion of the piezoelectric ceramic element 23, and the lead wire 30 is soldered to the surface of the copper foil 31 (the soldering portion is indicated by a symbol). 32). The copper foil 31 has, for example, a rectangular shape with a thickness dimension of 70 μm, and a conductive adhesive is applied to the back side thereof, and the copper foil 31 is attached in a state in which conduction is ensured by the conductive adhesive. Yes.
[0026]
Although not shown, the piezoelectric ceramic vibrator 21 configured as described above is incorporated in a parts feeder as a drive source, and an AC voltage from an AC power supply device 28 is supplied to each piezoelectric ceramic element via lead wires 29 and 30. When applied to 23, the piezoelectric ceramic element 23 flexes and vibrates due to expansion and contraction, thereby moving parts on the trough.
[0027]
Thus, in such a piezoelectric ceramic vibrator 21, there is a situation in which stress during vibration concentrates on the soldered portion 32 portion of the lead wire 30 on the surface side of the piezoelectric ceramic element 23. However, in this embodiment, the lead wire 30 is not directly soldered to the piezoelectric ceramic element 23, but the lead wire 30 is soldered to the copper foil 31 attached to the piezoelectric ceramic element 23 via a conductive adhesive. Thus, the stress acting on the soldering portion 32 of the piezoelectric ceramic element 23 during vibration can be absorbed by the conductive adhesive.
[0028]
On the other hand, due to the moment load generated by the trough inertia force, etc., due to the long-term use, the piezoelectric ceramic element 23 is peeled off from the metal shim plate 22 at the lower portion of the piezoelectric ceramic element 23, or the piezoelectric ceramic element. There is a problem of occurrence of cracks due to fatigue 23, and there is also a risk of causing discharge breakdown of the piezoelectric ceramic element 23 due to them. However, in this embodiment, unlike the case of using an adhesive mixed with conductive powder, the linear conductor 26 is used to ensure reliable electrical continuity between the metal shim plate 22 and the piezoelectric ceramic element 23. The thick layer of the adhesive 27 can relieve stress acting on the piezoelectric ceramic element 23 while firmly bonding the piezoelectric ceramic element 23.
[0029]
In this case, as will be described later in the description of the test results, particularly in this embodiment, the hardness of the adhesive 27 after curing is set in the range of 80 to 85 in the Shore D code, here 83. An extremely high effect can be obtained for preventing peeling of the element 23 and preventing occurrence of cracks. Furthermore, since the thickness of the layer of the adhesive 27 is in the range of 30 to 50 μm, here 35 to 40 μm, it is also a piezoelectric ceramic. An extremely high effect can be obtained for prevention of peeling of the element 23 and prevention of occurrence of cracks.
[0030]
Therefore, according to the piezoelectric ceramic vibrator 21 of the present embodiment, it is possible to effectively prevent the occurrence of cracks due to the stress concentration in the soldering portion 32, and the metal shim plate 22 and the piezoelectric ceramic element 23. It is possible to effectively prevent the occurrence of adhesion peeling and cracks on the adhesive surface. As a result, in order to increase vibration acceleration and achieve high-speed conveyance, even if there are circumstances where it is used under severe conditions, sufficient durability can be obtained and a long life can be achieved. It is possible to improve the property.
[0031]
Figure 5 shows a second according to the shape condition of the exemplary drive elements serving the piezoelectric ceramic resonator 41 of the present invention (corresponding to Example 2 to be described later). The ceramic vibrator 41 is different from the ceramic vibrator 21 of the first embodiment in that the lead wire 30 is directly attached to the surface portion (surface electrode 25) of the piezoelectric ceramic element 23 without providing the copper foil 31. It is in the place where it soldered.
[0032]
Even in such a configuration, in a state where the linear conductor 26 is provided between the metal shim plate 22 and the piezoelectric ceramic element 23, the hardness after curing is 83 by Shore D code, and the layer thickness is 35-40 μm. By adhering with the adhesive 27, it is possible to obtain excellent effects in preventing the piezoelectric ceramic element 23 from peeling off and preventing the occurrence of cracks.
[0033]
FIG. 6 shows the conditions (a) and results (b) of the accelerated life test of the piezoelectric ceramic vibrator conducted by the present inventors. Here, the test was performed using seven samples of Examples 1 to 6 and Comparative Example 1 as shown in FIG. These are the presence / absence of a linear conductor 26 between the metal shim plate 22 and the piezoelectric ceramic element 23, the thickness of the adhesive 27 layer (whether it falls within the range of 30 to 50 μm), and after the adhesive 27 is cured. The four conditions of hardness (whether the Shore D code falls within the range of 80 to 85) and whether or not the copper foil 31 is provided on the surface portion of the piezoelectric ceramic element 23 are different.
[0034]
Specifically, Example 1, Ri piezoelectric ceramic resonator 21 der according to the first embodiment, second embodiment, Ru piezoelectric ceramic resonator 41 der according to the second embodiment . Example 3, although the copper foil 31 is provided on the surface portion of the piezoelectric element 23, Ru der not to have provided a line-shaped conductor 26. In Example 4, the copper foil 31 and the linear conductor 26 were provided, but the thickness of the adhesive 27 layer (the thickness of the linear conductor 26) deviated from the above range to the larger one. der Ru.
[0035]
Example 5, is provided with the a formed and linear conductors 26 copper foil 31 state, and are not hardness after curing of the adhesive was deviated to the higher of the above range, Example 6, copper foil 31 is a provided and providing the linear conductor 26, but Ru der those hardness after curing of the adhesive is outside the lower the above range. And the comparative example 1 has deviated from the claim , the copper foil 31 and the linear conductor 26 do not exist, and the thickness and hardness of the adhesive are also out of the above ranges.
[0036]
In the test, two piezoelectric ceramic vibrators of the current product and two piezoelectric ceramic vibrators of each sample were incorporated in the drive part of a bowl-type parts feeder having a transport bowl with a diameter of 230 mm, and four piezoelectrics were installed. The ceramic vibrator was driven simultaneously. In this case, continuous driving is performed under the conditions where the resonant vibration frequency is 170 Hz and the maximum driving voltage is 250 Vrms, and the time until abnormalities such as cracks, adhesion peeling, and discharge breakdown occur in the piezoelectric ceramic element of the sample is examined. The number of vibrations was calculated from This test was performed several times for each sample, and the results are shown in FIG. In FIG. 6B, for each sample, the average number of vibrations up to the time of occurrence of an abnormality is indicated by a thick line, and the range of variation in test results is indicated by a broken double arrow.
[0037]
In this test result, in Comparative Example 1, various abnormalities such as adhesion peeling and cracks occurred, and the variation in durability was the largest. On the other hand, in Example 1, the durability was the best and the variation was small. In Example 2 in which the copper foil 31 was not provided, cracks were observed in the soldered portion, and the durability was inferior to that in Example 1. In Examples 3 and 4 in which the thickness of the adhesive layer was too small or too large, the occurrence of cracks in the lower portion of the piezoelectric ceramic element 23 was observed. In Example 5 where the hardness of the adhesive was large, adhesion peeling was observed at the lower portion of the piezoelectric ceramic element 23, and in Example 6 where the hardness of the adhesive was small, occurrence of cracks was observed at the lower portion of the piezoelectric ceramic element 23. About these Examples 2-6, the dispersion | variation in the test result was small.
[0038]
As is clear from this result, by providing the copper foil 31, it is possible to effectively prevent the occurrence of cracks in the soldering portion 32. On the other hand, by providing a linear conductor 26 between the metal shim plate 22 and the piezoelectric ceramic element 23 and adhering with an appropriate hardness and thickness dimension of the adhesive 27, the adhesion peeling at the lower part of the piezoelectric ceramic element 23 is achieved. And the occurrence of cracks can be effectively prevented.
[0039]
At this time, setting the hardness of the adhesive 27 after curing to 80 to 85 with Shore D code is most effective in preventing peeling and preventing cracks. If the hardness is less than 80, the piezoelectric ceramic element Cracks are relatively likely to occur at the bottom of 23, and if the hardness exceeds 85, peeling of the adhesive is relatively likely to occur. The thickness of the adhesive 27 layer is most preferably in the range of 30 to 50 μm, and cracks are relatively likely to occur in the lower portion of the piezoelectric ceramic element 23 no matter which direction is exceeded. It will end up.
[0040]
In the above-described embodiment, the linear conductor 26 extending linearly is provided between the metal shim plate 22 and the piezoelectric ceramic element 23. For example, as shown in FIG. A conductive resin may be applied in the form of spots to form a dotted conductor 42, or as shown in FIG. 7B, a linear conductor 43 having a part of a broken line may be used. Or a combination of these. Moreover, in the said embodiment, although the piezoelectric ceramic element 23 was provided on both surfaces of the metal shim board 22, this invention is applicable also to what provides a piezoelectric ceramic element on the single side | surface of a metal shim board.
[0041]
In addition, the desired effect can be obtained by soldering the lead wire through the conductive foil even if the piezoelectric ceramic element is attached to the leaf spring material instead of the metal shim plate. The foil is not limited to the copper foil 31 and can be made of various materials. Furthermore, the present invention is merely an example of the material and shape of the piezoelectric ceramic element, specific dimensions of each part, etc. Can be implemented with appropriate modifications within the scope not departing from the gist.
[0042]
【The invention's effect】
As apparent in the above description, according to the driving element of the conveyance device of the present invention, between the metal shim plate and the piezoelectric ceramic element, in a state of disposing a conductive resin in a linear or point-like, Since it is made to adhere with an adhesive at the non-coated portion of the conductive resin, it is possible to effectively prevent the occurrence of adhesion peeling and cracks on the adhesive surface between them, and to improve durability. Excellent effect.
[Brief description of the drawings]
FIG. 1 shows a first embodiment of the present invention, and is a cross-sectional view of a piezoelectric ceramic vibrator. FIG. 2 is a perspective view of a piezoelectric ceramic vibrator. FIG. FIG. 4 is a diagram showing a state in which a linear conductor is provided on the back surface of the piezoelectric ceramic element. FIG. 5 is a diagram corresponding to FIG. 1 showing a second embodiment of the present invention. FIG. 7 is a diagram showing conditions (a) and test results (b). FIG. 7 is a diagram equivalent to FIG. 4 showing two modifications of the conductor form. FIG. 8 is a schematic front view of a parts feeder showing a conventional example. FIG. 9 is a schematic perspective view of a parts feeder. FIG. 10 is a view corresponding to FIG.
In the drawings, 21 and 41 are piezoelectric ceramic vibrators (drive elements), 22 is a metal shim plate, 23 is a piezoelectric ceramic element, 26 and 43 are linear conductors (conductive resin), 27 is an adhesive, and 30 is a lead. Reference numeral 31 denotes a copper foil (conductive foil), 32 denotes a soldering portion, and 42 denotes a dotted conductor (conductive resin).

Claims (4)

A piezoelectric ceramic element is attached to one or both sides of a metal shim plate, and an alternating voltage is applied between the metal shim plate and the piezoelectric ceramic element,
Between the metal shim plate and the piezoelectric ceramic element, the conductive resin is arranged in a linear or dot shape, and both of them are bonded with an adhesive at an uncoated portion of the conductive resin. A drive element for a conveying device. Claims wherein the surface portion of the piezoelectric element, the electrodes constitute a pasted onto the conductive foil via the conductive adhesive composition, characterized in that the lead wires for applying an AC voltage is soldered to said conductive foil 2. A drive element of the transfer apparatus according to 1 . The drive element of the conveying apparatus according to claim 1 or 2, wherein the hardness of the adhesive after curing is 80 to 85 in Shore D code. 4. The driving element of the transport device according to claim 1 , wherein a thickness dimension of the adhesive layer is 30 to 50 μm. 5.

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