JP2006229068A - Manufacturing method of laminated piezo-electric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a laminated piezo-electric element which is capable of forming a groove unit for mitigating stress generated upon the displacement operation of a laminate on the side surface of a piezo-electric body simply, in a short period of time without giving an unfavorable affection to the piezo-electric body. <P>SOLUTION: When the laminated piezo-electric element is manufactured, a green sheet 9 containing a binder or the like is prepared, and electrode patterns 10A, 10B are formed on surfaces of individual green sheets 9. Subsequently, these green sheets 9 are laminated in a predetermined order to manufacture the green laminate 11. Thereafter, a cutter edge 12a is pushed into the green laminate 11 in a state that the cutter edge 12a is pushed against the side surface of the green laminate 11 whereby a slit 5 is formed on the side surface of the green laminate 11. In this case, it is preferable that the cutter edge 12a is pushed into the green laminate 11 under a condition that the same is heated. Subsequently, the degreasing and calcination of the green laminate 11 are effected. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a laminated piezoelectric element having a groove on a side surface of a laminated body in which piezoelectric bodies and internal electrodes are alternately laminated.

For example, a multilayer piezoelectric element for an injector includes a laminated body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and an external body provided on a side surface of the laminated body and electrically connected to the internal electrodes. And an electrode. In such a laminated piezoelectric element, in order to relieve stress applied to the laminated body during the displacement operation of the laminated body, the side surface of the laminated body extends in a direction crossing the lamination direction of the laminated body. Some have grooves. As a method for forming a groove on the side surface of a laminate, it is known that cutting processing with a blade is performed on a laminate in a green state as described in Patent Document 1, for example.
JP 2004-288794 A

  However, the following problems exist in the prior art. In other words, since cutting with a blade requires a spindle that rotates at a high speed, an apparatus for forming a groove becomes large. In addition, since shavings are generated by cutting, it is necessary to clean the side surface of the laminate, and it takes time to form the groove. Furthermore, there is a possibility that the cutting fluid used at the time of cutting adversely affects the piezoelectric body.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a laminated piezoelectric element capable of easily forming a groove for relaxing stress generated during a displacement operation of a laminated body on a side surface of the laminated body in a short time without adversely affecting the piezoelectric body. It is providing the manufacturing method of an element.

  The present invention relates to a multilayer piezoelectric element having a groove extending in a direction intersecting with a stacking direction of a multilayer body on a side surface of the multilayer body formed by alternately laminating a plurality of piezoelectric bodies and a plurality of internal electrodes. A manufacturing method comprising preparing a green sheet containing a binder and forming a piezoelectric body, forming an internal electrode on the surface of the green sheet, and a plurality of green sheets including the green sheet on which the internal electrode is formed Laminating and producing a laminate, forming a groove on the side of the laminate by pressing a cutter blade against the side of the laminate, and firing the laminate on which the groove is formed It is characterized by including.

  In the multilayer piezoelectric element according to the present invention, a groove extending in a direction intersecting the stacking direction of the multilayer body is formed on the side surface of the multilayer body, so that a voltage is applied to the internal electrode to displace the multilayer body. When operated, the stress applied to the laminate is relaxed, and cracks are less likely to occur in the laminate. In the present invention, such a groove is formed by pressing a cutter blade against the side surface of the laminate before firing. Since the green sheet has flexibility due to the binder, the cutter blade can be easily and reliably placed in the green sheet. For this reason, it becomes possible to form a desired groove part only by pressing the cutter blade against the side surface of the laminate. Therefore, unlike the case of cutting with a blade, it is not necessary to use a large-scale apparatus. Moreover, since the shavings do not come out, it is not necessary to clean the side surfaces of the laminated body. Thereby, formation of the groove part with respect to the side surface of a laminated body can be performed easily and in a short time. Furthermore, since no cutting fluid is used, it can be avoided that the cutting fluid adversely affects the piezoelectric body.

  Preferably, in the step of forming the groove, the cutter blade is pressed against the side surface of the laminated body and pressed in a state where the cutter blade is heated. Thereby, when pushing a cutter blade into the side surface of a laminated body, since the softness | flexibility of the part which the cutter blade contacts in a green sheet becomes still higher, it becomes easy to put a cutter blade in a green sheet. For the same reason, it becomes easy to remove the cutter blade from the green sheet. Therefore, the groove portion can be formed on the side surface of the laminate more easily and in a short time.

  At this time, in the step of forming the groove, it is preferable to heat the cutter blade at a temperature equal to or higher than the glass transition point of the binder. In this case, the portion of the green sheet that contacts the cutter blade is sufficiently softened, so that the cutter blade can be more easily placed in the green sheet and the cutter blade can be more easily removed from the green sheet.

  According to the present invention, the cutter blade is applied to the side surface of the laminated body and pushed in, so that the groove portion for relaxing the stress generated during the displacement operation of the laminated body can be easily performed in a short time without adversely affecting the piezoelectric body, It can be formed on the side surface of the laminate. As a result, it is possible to efficiently manufacture a multilayer piezoelectric element in which cracks are unlikely to occur.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a method for producing a multilayer piezoelectric element according to the present invention will be described in detail with reference to the drawings. In the drawings, elements having the same or equivalent functions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective view showing a multilayer piezoelectric element manufactured by an embodiment of a method for manufacturing a multilayer piezoelectric element according to the present invention, and FIG. 2 is a side view of the multilayer piezoelectric element. In each figure, the laminated piezoelectric element 1 is used for an injector (fuel injection device) of an internal combustion engine mounted on an automobile, for example.

  The multilayer piezoelectric element 1 includes a multilayer body 2 having a polygonal column shape (in this case, a quadrangular column shape). The multilayer body 2 has a structure in which a plurality of internal electrodes 4A and a plurality of internal electrodes 4B are alternately stacked via piezoelectric bodies 3. The piezoelectric body 3 is made of, for example, a piezoelectric ceramic material mainly composed of PZT (lead zirconate titanate). The internal electrodes 4A and 4B are made of a conductive material containing Ag and Pd as main components, for example. The dimension of the multilayer piezoelectric element 1 is, for example, about 10 mm × 10 mm × 35 mm. The thickness of the piezoelectric body 3 is, for example, about 80 to 100 μm per layer. The thickness of the internal electrodes 4A and 4B is, for example, about 0.5 to 5 μm.

  The internal electrode 4A is formed so as to be exposed from the inside of the side surface 2b of the multilayer body 2 to the opposite side surface 2a, and the internal electrode 4B is formed so as to be exposed from the inside of the side surface 2a of the multilayer body 2 to the side surface 2b. ing. Thereby, a part of the internal electrodes 4 </ b> A and 4 </ b> B is overlapped in the stacking direction of the stacked body 2. In the piezoelectric body 3, a portion sandwiched between adjacent internal electrodes 4A and 4B having different polarities is an active portion that expands and contracts (displaces) when a voltage is applied between the internal electrodes 4A and 4B. This is an inactive portion that does not displace even when a voltage is applied between the internal electrodes 4A and 4B.

  Slits (grooves) 5 extending in a direction orthogonal (crossing) to the stacking direction of the stacked body 2 are provided on the side surfaces 2 a and 2 b of the stacked body 2 for each fixed number of layers. These slits 5 are formed to relieve stress applied to the laminate 2 when a voltage is applied between the internal electrodes 4A and 4B to cause the laminate 2 to be displaced. Each slit 5 is formed from one edge to the other edge of the side surfaces 2 a and 2 b of the laminate 2. The length of the slit 5 (the length from the side surfaces 2a and 2b to the bottom of the slit 5) is, for example, about 0.2 to 0.5 mm, and the opening width of the slit 5 is, for example, about 10 to 80 μm.

  An external electrode 6A electrically connected to each internal electrode 4A is provided on the side surface 2a of the multilayer body 2, and an external electrode 6B electrically connected to each internal electrode 4B is provided on the side surface 2b of the multilayer body 2. Is provided.

  The external electrodes 6A and 6B are arranged on the outer side of the electrode portion 7 and the electrode portion 7 extending in the stacking direction of the stack 2 so as to cover a part of the side surfaces 2a and 2b of the stack 2, respectively. The electrode portion 8 extends in a wave shape in the stacking direction of the body 2. The electrode portion 8 is spot-bonded to the electrode portion 7 so as to be stretchable (flexible) in the stacking direction of the stacked body 2. The electrode part 7 is made of a conductive material containing, for example, one of Ag, Au, and Cu as a main component. The electrode portion 8 is made of, for example, Cu and its alloy, Ni and its alloy, a flexible substrate, or the like.

  In such a laminated piezoelectric element 1, when a voltage is applied between the external electrodes 6A and 6B, a voltage is applied between the internal electrodes 4A and 4B connected to the external electrodes 6A and 6B. As a result, an electric field is generated in the piezoelectric body 3 (active portion) sandwiched between the different polar internal electrodes 4A and 4B, and the piezoelectric body 3 expands and contracts in the stacking direction of the stacked body 2, and accordingly, the stacked body 2 Displace. Here, since the slits 5 are formed on the side surfaces 2 a and 2 b of the multilayer body 2, stress applied to the multilayer body 2 is relieved by the slits 5. As a result, cracks are less likely to occur in the multilayer body 2, so that an electrical short circuit between the internal electrodes 4 </ b> A and 4 </ b> B is prevented, and dielectric breakdown of the multilayer piezoelectric element 1 can be avoided.

  Next, a method of manufacturing the multilayer piezoelectric element 1 described above will be described with reference to the flowchart shown in FIG.

  First, a paste is prepared by mixing an organic binder resin, an organic solvent, and the like with ceramic powder containing PZT as a main component. Then, for example, by applying the paste on a carrier film by a doctor blade method, a plurality of ceramic green sheets 9 to be the piezoelectric bodies 3 are formed as shown in FIG. 4 (procedure 101).

  Subsequently, for example, a paste is prepared by mixing an organic binder resin, an organic solvent, and the like with a conductive material having a ratio of Ag: Pd = 85: 15. Then, by screen printing the paste, as shown in FIG. 4, the electrode pattern 10A corresponding to the internal electrode 4A and the electrode pattern 10B corresponding to the internal electrode 4B are formed on the surfaces of the separate green sheets 9. (Procedure 102).

  Subsequently, a predetermined number of green sheets 9 on which the electrode patterns 10A are printed, green sheets 9 on which the electrode patterns 10B are printed, and green sheets 9 on which the electrode patterns 10A and 10B are not printed are shown in FIG. Only in a predetermined order, the green laminate 11 is produced (procedure 103).

  Subsequently, the green laminate 11 is pressed in the stacking direction at a predetermined pressure (for example, about 100 MPa) while being heated at a predetermined temperature (for example, about 60 ° C.) (procedure 104). Then, the green laminated body 11 is cut into a predetermined dimension by, for example, a diamond blade (procedure 105). As a result, as shown in FIG. 4, the electrode patterns 10 </ b> A and 10 </ b> B are exposed on the side surface of the green laminate 11.

  Subsequently, the slits (grooves) 5 are formed at predetermined intervals on the side surface of the green laminate 11 (procedure 106). Specifically, as shown in FIG. 5, the slit is formed using a plate cutter 12 having a V-shaped cutter blade 12a as follows.

  That is, first, the green laminate 11 is placed horizontally so that the side surfaces 11a and 11b of the green laminate 11 are positioned vertically. Then, the cutter blade 12a is pressed against the slit forming position on the side surface 11a or the side surface 11b of the green laminate 11 so that the cutter blade 12a of the plate cutter 12 extends in a direction orthogonal to the lamination direction of the green laminate 11. . The slit forming position is, for example, an intermediate portion between the electrode patterns 10A and 10B in which two green sheets 9 are interposed in order to ensure a sufficient insulation distance between the electrode patterns 10A and 10B having different polarities. Is desirable.

  Then, with the cutter blade 12a applied to the side surface 11a or the side surface 11b of the green laminate 11, as shown in FIG. 6, the cutter blade 12a is pushed into the green laminate 11 along the opposing direction of the side surfaces 11a and 11b. Go. Here, since the green sheet 9 contains an organic binder resin, the green sheet 9 is in a relatively soft state. For this reason, when the cutter blade 12 a is pushed into the green laminate 11, the cutter blade 12 a smoothly enters the green sheet 9. Thereby, the slit 5 having the opening width corresponding to the blade width of the cutter blade 12a can be easily and reliably formed on the side surfaces 11a and 11b of the green laminate 11. Thereafter, when the slit 5 having a predetermined length is formed, the cutter blade 12 a is extracted from the green laminated body 11.

  At this time, when the cutter blade 12a is pressed against the green laminate 11 in a state where the cutter blade 12a is heated by a heater (not shown), the flexibility of the portion of the green sheet 9 touched by the cutter blade 12a is further increased. Get higher. For this reason, the cutter blade 12 a can easily enter the green sheet 9 and the cutter blade 12 a can be easily pulled out from the green sheet 9. The heating temperature of the cutter blade 12a is preferably a temperature equal to or higher than the glass transition point (for example, about 60 ° C.) of the organic binder resin contained in the green sheet 9.

  Further, as a method of forming the slits 5 on the side surfaces 11a and 11b of the green laminate 11, a wire-like cutter blade 13 may be used as shown in FIG. In this case, for example, the cutter blade 13 is heated on the side surface of the green laminated body 11 in a state where the cutter blade 13 is heated by passing a current through the wire-like cutter blade 13 stretched at a predetermined tension between two support points. 11a or side surface 11b is pushed in. Thereby, the slit 5 having an opening width corresponding to the outer diameter of the cutter blade 13 can be easily and reliably formed on the side surfaces 11 a and 11 b of the green laminate 11.

  Returning to FIG. 3, after performing the slit processing step of the above procedure 106, the green laminate 11 is placed on a setter (not shown), and the green laminate 11 is degreased (debinder) at about 350 to 400 ° C., for example. (Procedure 107). Thereafter, the setter on which the degreased green laminate 11 is placed is placed in a closed slag furnace (not shown), and the green laminate 11 is baked at a temperature of about 1000 ° C. for about 2 hours (procedure 108). ). Thereby, the green laminated body 11 is shrink-sintered, and said laminated body 2 is obtained as a sintered compact.

  Subsequently, the external electrode 6A is formed on the side surface 2a of the multilayer body 2 and the external electrode 6B is formed on the side surface 2b of the multilayer body 2 (procedure 109). Specifically, first, for example, a conductive paste containing Ag as a main component is screen-printed on the side surfaces 2a and 2b of the laminate 2, and then subjected to a baking treatment at a temperature of about 700 ° C., for example. Part 7 is formed. In addition, as a formation method of this electrode part 7, you may use sputtering method, an electroless plating method, etc. instead of baking. And the electrode part 8 extended in a wave shape is joined with the electrode part 7 in a several location, for example by soldering.

  Finally, for example, under a temperature of 120 ° C., a polarization process is performed by applying a predetermined voltage, for example, for 3 minutes so that the electric field strength with respect to the thickness of the piezoelectric body 3 becomes 2 kV / mm (procedure 110). Thus, the multilayer piezoelectric element 1 is completed.

  As described above, in the present embodiment, before the green laminate 11 is fired, the cutter blade 12a or the cutter blade 13 is applied to the side surface of the green laminate 11 and pressed to form the slit 5. The slit 5 can be formed very easily compared to the case where the slit is formed by cutting with a blade. Further, since no cutting waste is generated unlike the cutting process, the cleaning process of the green laminate 11 and the subsequent drying process are unnecessary, and the time required for forming the slit 5 can be shortened. Furthermore, unlike the case of cutting, an apparatus such as a spindle that rotates at high speed is not required, so that the apparatus used for forming the slit 5 is simplified, and the manufacturing cost can be reduced. In addition, the cutting fluid used in the cutting process may adversely affect the green sheet 9, but since this method does not use the cutting fluid, such a problem can be surely avoided.

  Accordingly, it is possible to efficiently and inexpensively manufacture a high-quality multilayer piezoelectric element having the slits 5 for relaxing the stress generated during the displacement operation of the multilayer body 2.

  In addition, the manufacturing method of the lamination type piezoelectric element concerning this invention is not limited to the said embodiment.

  For example, in the above-described embodiment, the slit 5 is provided between the adjacent different-polarity internal electrodes 4A and 4B in the stacked body 2, but as shown in FIG. The laminated body 2 may be manufactured, and the slits 5 may be formed between the internal electrodes 4A and 4A and between the internal electrodes 4B and 4B in the laminated body 2.

  In the laminated body 2 having such a structure, portions between the internal electrodes 4A and 4A and between the internal electrodes 4B and 4B in the piezoelectric body 3 become inactive portions that do not expand and contract even when a voltage is applied. Therefore, as shown in FIG. 9, when the slit 5 is formed by pressing the cutter blade 12 a against the side surface 11 a or the side surface 11 b of the green laminated body 11 in the same manner as described above, the position is shifted from the predetermined slit forming position. Even if the cutter blade 12a is pushed into the position, the slit 5 does not affect the insulating properties of the electrode patterns 10A and 10B within the range of the inactive portion. Therefore, the slit 5 can be formed without worrying about the insulation distance between the electrode patterns 10A and 10B.

  Moreover, in the said embodiment, although the slit 5 was formed in the green laminated body 11 using the V-shaped cutter blade 12a or the wire-shaped cutter blade 13, as a cutter blade to be used, it is not restricted especially, Anything can be used as long as the slit 5 can be formed simply by pushing into the green laminate 11.

It is a perspective view which shows the lamination type piezoelectric element manufactured by one Embodiment of the manufacturing method of the lamination type piezoelectric element concerning this invention. FIG. 2 is a side view of the multilayer piezoelectric element shown in FIG. 1. It is a flowchart which shows the process of manufacturing the lamination type piezoelectric element shown in FIG. It is a disassembled perspective view which shows the state after the cutting | disconnection of the green laminated body produced when manufacturing the lamination type piezoelectric element shown in FIG. It is a perspective view which shows the method of forming a slit in the side surface of the green laminated body shown in FIG. It is sectional drawing which shows a mode that a slit is formed in the side surface of a green laminated body with the V-shaped cutter blade shown in FIG. It is sectional drawing which shows a mode that a slit is formed in the side surface of a green laminated body with a wire-shaped cutter blade as another method of implementing the slit processing process shown in FIG. It is a side view which shows the modification of the lamination type piezoelectric element manufactured by one Embodiment of the manufacturing method of the lamination type piezoelectric element concerning this invention. It is a perspective view which shows the method of forming a slit in the side surface of the green laminated body used as the laminated body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric element, 2 ... Laminated body, 3 ... Piezoelectric body, 4A, 4B ... Internal electrode, 5 ... Slit (groove part), 9 ... Ceramic green sheet, 10A, 10B ... Electrode pattern, 11 ... Green laminated body, 12a ... cutter blade, 13 ... cutter blade.

Claims (3)

A method of manufacturing a multilayer piezoelectric element having a groove extending in a direction intersecting a stacking direction of the multilayer body on a side surface of the multilayer body formed by alternately laminating a plurality of piezoelectric bodies and a plurality of internal electrodes. There,
Preparing a green sheet containing a binder to form the piezoelectric body, and forming the internal electrode on a surface of the green sheet;
Laminating a plurality of green sheets including a green sheet on which the internal electrodes are formed, and producing the laminate;
A step of forming the groove on the side surface of the laminate by pressing a cutter blade against the side of the laminate,
And a step of firing the laminated body in which the groove is formed.   2. The method of manufacturing a multilayer piezoelectric element according to claim 1, wherein in the step of forming the groove, the cutter blade is pressed against a side surface of the multilayer body in a state where the cutter blade is heated.   3. The method for manufacturing a multilayer piezoelectric element according to claim 2, wherein, in the step of forming the groove, the cutter blade is heated at a temperature equal to or higher than a glass transition point of the binder.

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