JP2019102474A - Laminated piezoelectric element and actuator - Google Patents

Abstract

To provide a laminated piezoelectric element and an actuator that are not easily affected by a noise when a crack is generated in a scheduled breaking layer, and can perform accurate control.SOLUTION: A laminated piezoelectric element 1 of the present disclosure includes a laminate 13 having piezoelectric layers 11 and internal electrode layers 12 that are laminated in plurality and a scheduled breaking layer 14 that is more easily broken than the other portions. The laminated piezoelectric element 1 includes: an external electrode 16 that is electrically connected to the internal electrode layers 12, and has an area extending along the lamination direction on a side face of the laminate 13; and a lead pin 17 that is electrically connected to the external electrode 16, and is arranged separated from the area extending along the lamination direction of the external electrode 16. The lead pin 17 is provided not to be located on the extension line of the scheduled breaking layer 14.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a laminated piezoelectric element and an actuator, for example, to a laminated piezoelectric element and an actuator used for, for example, a mass flow controller and a precision positioning device for an XY table.

  The multilayer piezoelectric element includes a multilayer body in which a plurality of piezoelectric layers and internal electrode layers are stacked, and is elastically deformed during driving. The laminated piezoelectric element is mainly used for an actuator or a sensor because it is excellent in response speed and deformation accuracy. And, in order to meet the demand for higher durability, the multilayer piezoelectric element adopts a technology that includes in a part of the laminate a planned fracture layer planned in advance for a location where a crack between piezoelectric layers occurs during driving. It is done. This prevents, for example, cracking in the direction in which a short circuit occurs.

  In addition, the laminated piezoelectric element has the external electrode on the side surface of the laminated body, is electrically connected to the external electrode, and is disposed at a distance from the region extending along the laminating direction of the external electrode. And a lead pin. With this configuration, the laminated piezoelectric element is energized through the lead pin connected to the external circuit, and the driving and sensing of the laminated piezoelectric element are controlled.

Patent No. 5322384

  In recent years, high frequency or pulse driving has been used to control with high accuracy. Here, in the existing technology in which the lead pin is located on the extension line of the planned breaking layer, the noise when the planned breaking layer functions and cracks are generated affects the electric signal of the lead pin and is accompanied by it. Control accuracy may be reduced. Specifically, the noise of the radio wave generated when a crack is generated in the planned fracture layer is picked up like an antenna by the lead pin, and this noise may get on the output signal, making it impossible to perform highly accurate control.

  The present disclosure has been made in view of the above circumstances, and it is an object of the present invention to provide a laminated piezoelectric element and an actuator that are less susceptible to noise when a crack occurs in a planned fracture layer and can be controlled with high accuracy. Do.

  The multilayer piezoelectric element according to the present disclosure includes a multilayer body in which a plurality of piezoelectric layers and internal electrode layers are laminated and which has a planned breaking layer that is more easily broken than other portions, the internal electrode layer, and the electricity. And an external electrode having a region extending along the stacking direction on the side surface of the stack, and a region electrically connected to the outer electrode and extending along the stacking direction of the external electrode And are provided with spaced apart lead pins. And, the lead pin is provided so as not to be positioned on the extension line of the predetermined breaking layer.

  In addition, the actuator of the present disclosure includes the above-described stacked piezoelectric element and a case housed inside so as to press the stacked piezoelectric element from above and below, the case includes a cylinder having a bellows portion. The lead pin is disposed so as not to be located to the side of the bellows portion.

  According to the laminated piezoelectric element of the present disclosure, by setting the tip of the lead pin below the extension line of the planned fracture layer, it becomes less susceptible to noise due to the occurrence of cracks in the planned fracture layer, enabling highly accurate control. .

It is a schematic perspective view which shows an example of embodiment of a lamination type piezoelectric element. It is a schematic perspective view which shows the other example of embodiment of a lamination type piezoelectric element. It is a schematic perspective view which shows the other example of embodiment of a lamination type piezoelectric element. It is a schematic perspective view which shows the other example of embodiment of a lamination type piezoelectric element. It is a schematic perspective view showing an example of an embodiment of an actuator. It is the schematic sectional drawing cut | disconnected by the VI-VI line of the actuator shown in FIG.

  Embodiments of a laminated piezoelectric element will be described with reference to the drawings.

  The multilayer piezoelectric element 1 shown in FIGS. 1 to 4 includes a multilayer body 13 in which a plurality of piezoelectric layers 11 and internal electrode layers 12 are stacked.

  The laminated body 13 is, for example, in the form of a square prism (rectangular parallelepiped) having a length of 0.5 mm to 10 mm, a width of 0.5 mm to 10 mm, and a height of 1 mm to 100 mm. The shape of the laminate 13 may be a hexagonal prism shape, an octagonal prism shape, a cylindrical shape, or the like.

The piezoelectric layer 11 is made of a ceramic having piezoelectric characteristics. As such ceramics, for example, lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ) or the like can be used. The thickness of the piezoelectric layer 11 is, for example, 3 μm to 250 μm.

  The internal electrode layer 12 is formed, for example, by simultaneous firing with the piezoelectric layer 11. The internal electrode layer 12 includes a first internal electrode layer 121 and a second internal electrode layer 122. For example, with the first internal electrode layer 121 as a positive electrode and the second internal electrode layer 122 as a negative electrode or a ground electrode, a driving voltage can be applied to the piezoelectric layer 11 sandwiched therebetween. Here, the first internal electrode layer 121 is drawn out to one side surface of the laminate 13, and the second internal electrode layer 122 is drawn out to the other side surface. As such a material, for example, a conductor containing silver, silver-palladium, silver-platinum, copper or the like as a main component can be used. The thickness of the first internal electrode layer 121 and the second internal electrode layer 122 is, for example, 0.1 μm to 5 μm.

  The laminate 13 has a predetermined breaking layer 14 which is more susceptible to cracking than other portions. Here, the planned breaking layer 14 is a layer for reducing a stress generated by driving the laminated piezoelectric element 1 by causing a crack at this portion. As the planned fracture layer 14, for example, a porous metal layer which does not function as the internal electrode layer 12, a metal layer which is cracked in advance, and the like can be mentioned.

  Moreover, the conductor layer 15 is each provided in the pair of side surface from which the end surface of any one of the 1st internal electrode layer 121 and the 2nd internal electrode layer 122 was pulled out. The conductor layer 15 is electrically connected to the end face of the first internal electrode layer 121 or the end face of the second internal electrode layer 122 which has been pulled out.

The conductor layer 15 can be produced, for example, by baking a conductive paste containing metal such as Ag or Cu and glass. Here, when the conductor layer 15 is viewed in a cross section perpendicular to the side surface of the laminate 13, the thickness of the conductor layer 15 is, for example, 5 μm to 70 μm.

  The multilayer piezoelectric element 1 includes an external electrode 16 electrically connected to the internal electrode layer 12. The external electrode 16 has a region extending along the stacking direction on the side surface of the stacked body 13. For example, the external electrode 16 is attached on the surface of the conductor layer 15 using a conductive bonding material made of an epoxy resin or a polyimide resin containing a conductive metal powder such as Ag powder or Cu powder. In addition, although the external electrode 16 can be attached after the conductor layer 15 is provided, as long as conduction between the external electrode 16 and the first internal electrode layer 121 or the second internal electrode layer 122 can be sufficiently taken. The conductor layer 15 may not be provided, and the external electrode 16 may be directly attached to the side surface of the laminate 13.

  The external electrode 16 is made of metal such as copper, iron, stainless steel, phosphor bronze, etc., and is formed to have a width of 0.5 mm to 10 mm and a thickness of 0.01 mm to 1.0 mm, for example. The outer electrode 16 may be plated with tin, silver, or the like to improve electrical conductivity and thermal conductivity. Here, the external electrode 16 may be bent in a direction away from the side surface of the laminate 13 as shown in FIGS. 1 and 2, and as shown in FIGS. 3 and 4, one side surface of the laminate 13 It may be bent so as to wrap around to the next side. Although not shown in the figure, an external electrode 16 is provided on the side surface opposite to the one side surface of the laminate 13.

  The multilayer piezoelectric element 1 is electrically connected to the external electrode 16 and includes lead pins 17 arranged at an interval from a region extending along the stacking direction of the external electrode 16. For example, the end of the external electrode 16 is bent at a bend and separated from the side surface of the laminate 13 and has a hole or a slit at the end of the external electrode 16 and the lead pin 17 is in the hole or the slit. It is inserted and joined by the joining material. Here, FIG. 1 shows a mode in which the end of the external electrode 16 has a hole, and FIG. 2 shows a mode in which a slit is at the end of the external electrode 16. As the bonding material, in addition to solder, conductive resins such as silver polyimide and silver epoxy can be mentioned.

  The end of the external electrode 16 is bent at a bending portion and is separated from the side surface of the laminated body 13, and a hole or a slit is provided at the end of the external electrode 16, and the lead pin 17 is inserted into the hole or the slit By being bonded to the upper side, the lead pin 17 can be fixed more firmly than the flat surface of the external electrode 16 and can not be easily peeled off. Moreover, vibration can be absorbed at the bent portion, and the displacement amount of the laminate 13 is stabilized for a long time.

  In addition, the end face of both the first internal electrode layer 121 and the second internal electrode layer 122 reaches, for example, the other side face of the laminate 13, and a covering layer made of resin, insulating ceramic, etc. It may be provided.

  The lead pin 17 is provided so as not to be located on the extension of the planned breaking layer 14.

  When a crack occurs in the planned fracture layer 14, noise is emitted mainly toward the extension line. When the lead pin 17 functions and receives the radiated noise like an antenna, the input signal for driving and expanding the laminated piezoelectric element 1 may be disturbed, and high precision control may not be possible. Furthermore, by continuing to use the laminated piezoelectric element 1 in which the crack is generated, the piezoelectric layer 11 in the vicinity of the planned fracture layer 14 may be rubbed, and noise may continue to be generated.

On the other hand, by providing the lead pins 17 so as not to be located on the extension of the planned breaking layer 14, it becomes less susceptible to noise at the time of the occurrence of a crack in the planned breaking layer 14. Further, even after the crack is generated in the planned fracture layer 14, it is possible to make it difficult for the noise to directly interfere. Therefore, highly accurate control of the laminated piezoelectric element 1 is possible.

  Here, as shown in FIGS. 1 to 4, the stacking direction of the stacked body 13 and the axial direction of the lead pin 17 may be parallel. In general, the antenna receives radio waves from the vertical direction with high sensitivity. On the other hand, when the lamination direction of the laminated body 13 and the axial direction of the lead pin 17 are parallel, the radiation direction of the noise generated in the planned fracture layer 14 and the lead pin 17 do not intersect perpendicularly. Therefore, even if the generated noise is received like the antenna by the lead pin 17, it is not received in the vertical direction, so that it is less susceptible to the noise and highly accurate control becomes possible.

  Further, as shown in FIG. 3, in the configuration in which the laminated body 13 is a polygonal columnar body having the joined surface of the external electrode 16 and the non-joined surface of the external electrode 16, the lead pins 17 join the external electrode 16. It may be arranged facing the side which is not done.

  For example, the external electrode 16 shown in FIG. 3 has a plurality of bent portions between the bonding region joined to the laminate 13 and the end, and the side surface of the laminate 13 to which the external electrode 16 is joined. It is bent and drawn towards the side next to. Then, a hole or a slit is provided at the drawn end of the external electrode 16, and the lead pin 17 is inserted into the hole or the slit and is joined by a bonding material. The presence of the plurality of bent portions from the region of the external electrode 16 joined to the laminate 13 to the junction with the lead pin 17 can reduce the vibration transmitted through the external electrode 16. In addition, it is also effective to reduce vibration that the distance from the region of the external electrode 16 joined to the laminate 13 to the junction with the lead pin 17 is long.

  Further, as shown in FIG. 4, the external electrode 16 is not joined to the side surface of the laminate 13 to which the end faces of both the first internal electrode layer 121 and the second internal electrode layer 122 reach. A ceramic covering layer may be provided as the covering layer 18 on the non-bonded surface of the electrode 16. By providing a ceramic coating layer as the coating layer 18, it is possible to delay the speed of fracture due to cracks of the planned fracture layer 14 to reduce noise, and to absorb or block noise emitted from the planned fracture layer 14 to reduce It can be done. The ceramic coating layer is set, for example, to a thickness of 5 μm to 15 μm.

  Next, embodiments of the actuator will be described with reference to the drawings.

  The piezoelectric actuator 10 shown in FIG. 5 and FIG. 6 includes a laminated piezoelectric element 1 and a case 2 accommodated therein so as to press the laminated piezoelectric element 1 from above and below.

  The case 2 includes a base 21, a cylindrical body 22 whose lower end is joined to the upper surface of the base 21, and a lid 23 joined to the upper end of the cylindrical body 22. The lower end surface of the laminated piezoelectric element 1 is in contact with the upper surface of the base 21, and the upper end surface of the laminated piezoelectric element 1 is in contact with the lower surface of the lid 23.

  The base 21, the cylindrical body 22 and the lid 23 are made of, for example, a metal such as SUS304 or SUS316L.

The cylindrical body 22 has a cylindrical portion 221 extending in the vertical direction, and a collar portion 222 connected to the lower end of the cylindrical portion 221. The tubular portion 221 has a bellows 220. The bellows 220 can be formed, for example, by rolling or hydrostatic pressing after producing a seamless tube with a predetermined shape. The cylindrical body 22 has a predetermined spring constant so that it can follow the expansion and contraction of the laminated piezoelectric element 1 when a voltage is applied to the laminated piezoelectric element 1, and the spring depending on the thickness, groove shape and number of grooves. I'm adjusting the constant. For example, the thickness of the cylindrical body 22 is, for example, 0.1 mm to 0.5 mm. The cylindrical portion 221 extending up and down from the cylindrical body 22 to the one end side opening (upper end side opening) is cylindrical, but the other end side opening (lower end side opening) of the cylindrical body 22 is radially outward It has a so-called wrapper shape that spreads out. As described above, the other end side opening of the cylindrical body 22 has a trumpet shape, so that the cylindrical body 22 has a flange portion 222.

  Further, the base 21 is in the form of a disk, and the peripheral portion is thinner than the other portions. The peripheral portion of the base 21 and the flange portion 222 of the cylindrical body 22 are welded, for example, in a state in which a compressive load is applied to the laminated piezoelectric element 1. Two through holes 211 through which the lead pins 17 can be inserted are formed in the base 21, and the lead pins 17 are inserted through the through holes 211. And the soft glass 212 is filled with the clearance gap of the through-hole 211, for example. Then, the lead pin 17 is electrically connected to an external circuit, and a driving voltage is applied to the laminated piezoelectric element 1.

  The lid 23 has an outer diameter that is substantially the same as the inner diameter of the opening at one end of the cylinder 22. The lid 23 is fitted from one end side opening of the cylindrical body 22, and the side surface is welded to the inner wall in the vicinity of the one end side opening (near the upper end) of the cylindrical body 22, for example. At this time, the flange portion 222 of the cylindrical body 22 and the base 21 are welded in a state where a compressive load is applied to the laminated piezoelectric element 1.

  And, the lead pin 17 is disposed so as not to be located to the side of the bellows part 220.

  When the lead pin 17 is positioned to the side of the bellows portion 220, the echo of noise due to the bellows shape may reach the lead pin 17 at an angle close to vertical. On the other hand, by arranging the lead pin 17 not to be located to the side of the bellows portion 220, even if the echo of the noise reaches the lead pin 17, it can be transmitted at a small incident angle, so high precision control can be achieved. Can be maintained.

  Next, a method of manufacturing the actuator of the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 11 is manufactured. Specifically, a ceramic slurry is prepared by mixing a calcined powder of a piezoelectric ceramic, a binder made of an organic polymer such as acrylic and butyral, and a plasticizer. Then, a ceramic green sheet is produced using this ceramic slurry by using a tape forming method such as a doctor blade method or a calender roll method. Any piezoelectric ceramic may be used as long as it has piezoelectric characteristics, and, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) can be used. Further, as a plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP) or the like can be used.

  Next, a conductive paste to be the internal electrode layer 12 is produced. Specifically, a conductive paste is produced, for example, by adding and mixing a binder and a plasticizer to metal powder of a silver-palladium alloy. This conductive paste is applied on the above-mentioned ceramic green sheet in the pattern of the internal electrode layer 12 using a screen printing method. Furthermore, a plurality of ceramic green sheets on which the conductive paste is printed are laminated.

  In addition, a conductive paste to be the planned breaking layer 14 is produced. The conductive paste may be, for example, silver-palladium different in silver ratio from the internal electrode layer 12 and may contain a filler which is burnt out by firing.

Next, the ceramic slurry used as the coating layer 18 is apply | coated to the side surface of the green sheet laminated body by which multiple ceramic green sheets were laminated | stacked as needed. The application of the ceramic slurry is controlled to a predetermined thickness by printing or dispensing.

  Thereafter, the binder removal process is performed at a predetermined temperature, and then firing is performed at a temperature of 900 to 1200 ° C., and the laminate 13 is manufactured by performing a grinding process so as to have a predetermined shape using a surface grinder or the like.

  Next, the conductor layer 15 is formed on the side surface of the laminate 13. Specifically, a conductive paste containing a metal such as Ag or Cu is used. This is baked in a region where one end face of the first internal electrode layer 121 and the second internal electrode layer 122 on the side surface of the laminated body 13 is drawn out, for example, the conductor layer 15 having a thickness of 5 to 70 μm. Form. It can be formed to be controlled to a predetermined thickness or width by screen printing or a dispensing method. For example, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer and a solvent to a mixture of conductive particles containing silver as a main component and glass is used. Then, after printing by screen printing on the side surface of the laminate 13 with the pattern of the conductor layer 15 and drying, printing is performed at a temperature of 650 to 750 ° C.

  Next, the external electrode 16 is manufactured. For example, a thin plate of SUS304 is plated and then etched to form a flat electrode plate. Here, in order to provide a hole or a slit in the external electrode 16, it may be processed by, for example, etching, laser, or punching. Further, in order to provide the outer electrode 16 with a bent portion, bending may be performed on a flat electrode plate.

  Then, the bent outer electrode 16 is attached onto the conductor layer 15 through a conductive bonding material such as conductive resin, and the lead pin 17 is bonded to the end of the outer electrode 16 by a bonding material such as solder or conductive resin. .

  Further, the base 21 having the through holes 211 formed by drilling is prepared. The lead pins 17 are respectively inserted into the two through holes 211 formed in the base 21 and soft glass 212 is filled and fixed in the gap, and the lower end of the multilayer piezoelectric element 1 is bonded to the upper surface of the base 21 with a bonding material. Glue.

  Next, a bellows shape is formed on the seamless cylindrical tube 22 made of SUS304 by rolling. By changing the shape of the mold at the time of rolling, the thickness of the groove and the radius of curvature can be changed. The lid body 23 made of SUS304 is welded by laser welding so as to close the opening at one end side (upper end side) of the cylindrical body 22. In addition, the collar part 222 is formed in the other end side (lower end side) of the cylindrical part 221 of the cylindrical body 22. As shown in FIG.

  Next, the cylindrical body 22 is covered on the laminated piezoelectric element 1 bonded to the base body 21, the cylindrical body 22 is pulled with a predetermined load, and a load is applied to the laminated piezoelectric element 1. In this state, the flange portion 222 of the cylindrical body 22 and the base 21 are welded by, for example, resistance welding.

  Finally, a DC electric field of 0.1 to 3 kV / mm is applied to the lead pin 17 to polarize the piezoelectric layer 11 constituting the laminate 13.

  The piezoelectric actuator 10 of the present embodiment can be obtained by the above manufacturing method.

DESCRIPTION OF SYMBOLS 1 ..... lamination type piezoelectric element 11 .... piezoelectric material layer 12 ... internal electrode layer 121 ... 1st internal electrode layer 122 ... 2nd internal electrode layer 13 ... laminated body 14 ... -Predetermined fracture layer 15-Conductor layer 16-External electrode 17-Lead pin 18-Coating layer 2-Case 21-Substrate 211-Through hole 212-Soft glass 22 ... cylindrical body 221 ... cylindrical portion 222 ... collar portion 220 ... bellows portion 23 ... lid

Claims (5)

  A multilayer body in which a plurality of piezoelectric layers and internal electrode layers are stacked and which has a planned breaking layer that is more likely to break than other portions, and the internal electrode layer are electrically connected, An external electrode having a region extending along the stacking direction on the side surface, and a region electrically connected to the external electrode and spaced from the region extending along the stacking direction of the external electrode And a lead pin, wherein the lead pin is provided so as not to be located on the extension of the predetermined breaking layer.   The stacked piezoelectric device according to claim 1, wherein a stacking direction of the stacked body and an axial direction of the lead pin are parallel.   The laminated body is formed of a polygonal columnar body having a joined surface of the external electrode and a non-joined surface of the external electrode, and the lead pin is disposed facing the non-joined surface of the external electrode The laminated piezoelectric element according to claim 1 or 2.   The laminated piezoelectric element according to claim 3, wherein a ceramic covering layer is provided on the non-bonded surface of the external electrode.   A laminated piezoelectric element according to any one of claims 1 to 4 and a case accommodated therein so as to press the laminated piezoelectric element from above and below, the case is a cylinder having a bellows portion. An actuator comprising a body, wherein the lead pin is not located laterally of the bellows.

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