JP5527545B2 - Piezoelectric element and pressure sensor - Google Patents

Description

  The present invention relates to a piezoelectric element, a pressure sensor including the piezoelectric element, and a method for manufacturing the piezoelectric element.

  Conventionally, a piezoelectric element has been used as an element for pressure detection of a pressure sensor. For example, Patent Document 1 discloses a pressure sensor equipped with a piezoelectric element. Such a piezoelectric element utilizes a piezoelectric effect in which, when a pressure is applied, a charge corresponding to the pressure is generated.

  Patent Document 2 discloses a pressure sensor in which a plurality of electrode plates are formed by a single plate. According to this pressure sensor, it is said that soldering for electrically connecting the electrodes is unnecessary, and the number of manufacturing steps can be reduced.

JP-A-5-164463 Japanese Unexamined Patent Publication No. 4-132919

  Incidentally, in recent years, in the field of piezoelectric elements, miniaturization is required and further long-term reliability is required. Accordingly, an object of the present invention is to provide a piezoelectric element that can be miniaturized and has excellent long-term reliability, a method for manufacturing the same, and a pressure sensor.

The first piezoelectric element according to the present invention is disposed between a pair of first conductive substrates arranged in parallel and the pair of first conductive substrates, and has a pole different from that of the first conductive substrate. A second conductive substrate to be connected; and two conductive substrates provided between the first conductive substrate and the second conductive substrate, respectively, and in contact with the first conductive substrate and the second conductive substrate, respectively. The piezoelectric layer and the pair of first conductive substrates are electrically connected, and are bridged from one side of the first conductive substrate to the side of the other first conductive substrate. And a first insulating layer formed on a surface of the first connecting portion , wherein the first insulating layer is made of the same material as the piezoelectric layer. To do.

A second piezoelectric element according to the present invention includes a plurality of first conductive substrates opposed to each other with an interval, and a first connecting portion that connects adjacent first conductive substrates, and the first conductive element includes A first polar structure formed by folding back one conductive substrate in which the substrate and the first connection portion are alternately arranged at the first connection portion so that the adjacent first conductive substrate faces each other; ,
A plurality of second conductive substrates provided between the adjacent first conductive substrates and facing each other at an interval, and a second connecting portion connecting the adjacent second conductive substrates. The second conductive substrate and the second connecting portion are alternately folded at the second connecting portion so that the adjacent second conductive substrates face each other. A second pole structure;
A piezoelectric element comprising two piezoelectric layers provided between the first conductive substrate and the second conductive substrate and in contact with the first conductive substrate and the second conductive substrate, respectively. Because
A first insulating layer is provided on the surface of the first connecting portion, a second insulating layer is provided on the surface of the second connecting portion, and the second insulating layer is made of the same material as the piezoelectric layer. It is characterized by this.

The third piezoelectric element according to the present invention is disposed between a pair of first conductive substrates arranged in parallel and the pair of first conductive substrates, and has a pole different from that of the first conductive substrate. A second conductive substrate to be connected; and two conductive substrates provided between the first conductive substrate and the second conductive substrate, respectively, and in contact with the first conductive substrate and the second conductive substrate, respectively. The piezoelectric layer and the pair of first conductive substrates are electrically connected, and are bridged from one side of the first conductive substrate to the side of the other first conductive substrate. And a first connecting portion having a thickness smaller than that of the first conductive substrate , wherein the first connecting portion has a thickness that gradually decreases from both ends toward the center. It is.

A fourth piezoelectric element according to the present invention includes a plurality of first conductive substrates facing each other at intervals and a first connecting portion that connects between the adjacent first conductive substrates, and the first conductive element is provided. A first polar structure formed by folding back one conductive substrate in which the substrate and the first connection portion are alternately arranged at the first connection portion so that the adjacent first conductive substrate faces each other; ,
A plurality of second conductive substrates provided between the adjacent first conductive substrates and facing each other at an interval, and a second connecting portion connecting the adjacent second conductive substrates. The second conductive substrate and the second connecting portion are alternately folded at the second connecting portion so that the adjacent second conductive substrates face each other. A second pole structure;
A piezoelectric element comprising two piezoelectric layers provided between the first conductive substrate and the second conductive substrate and in contact with the first conductive substrate and the second conductive substrate, respectively. Because
The thickness of the first connecting portion is thinner than the thickness of the first conductive substrate, the thickness of the second connection part, the rather thin than the thickness of the second conductive substrate, wherein the second connecting portion, The thickness is gradually reduced from both ends toward the center .

  The pressure sensor according to the present invention includes any one of the first to fourth piezoelectric elements, and a housing in which the piezoelectric element is disposed.

  According to the first or second piezoelectric element of the present invention, since the first insulating layer and the second insulating layer are formed on the surfaces of the first connecting portion and the second connecting portion, the piezoelectric element can be reduced in size. Even when different substrates are close to each other, high insulation can be maintained in the first connecting portion and the second connecting portion. Thereby, since it can suppress over a long period that the sensitivity of a piezoelectric element falls, durability of a piezoelectric element can be improved.

  In addition, according to the third or fourth piezoelectric element according to the present invention, the thickness of the first connecting portion and the second connecting portion is thinner than that of the first conductive substrate and the second conductive substrate. Even when the radius of curvature of the connecting portion is small, it is possible to suppress the occurrence of problems such as cracks in the first connecting portion and the second connecting portion. Thereby, since it can suppress over a long period that the sensitivity of a piezoelectric element falls, durability of a piezoelectric element can be improved.

1 is a plan view showing a piezoelectric element according to a first embodiment of the present invention. It is sectional drawing in the AA line of FIG. 1A. It is a top view which shows the 1st member which comprises the piezoelectric element which concerns on 1st Embodiment. It is sectional drawing in the BB line of FIG. 2A. It is a top view which shows the 2nd member which comprises the piezoelectric element which concerns on 1st Embodiment. It is sectional drawing in the CC line of FIG. 2C. It is a 1st process drawing in the manufacturing method of the piezoelectric element concerning a 1st embodiment. It is a 2nd process figure in the manufacturing method of the piezoelectric element concerning a 1st embodiment. It is a 3rd process figure in the manufacturing method of the piezoelectric element which concerns on 1st Embodiment. It is a 4th process figure in the manufacturing method of the piezoelectric element concerning a 1st embodiment. It is sectional drawing which shows the piezoelectric element which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the piezoelectric element which concerns on the 3rd Embodiment of this invention. It is a top view which shows the piezoelectric element which concerns on the 4th Embodiment of this invention. It is a front view which shows the piezoelectric element which concerns on 4th Embodiment. It is sectional drawing in the DD line of FIG. 5A. It is sectional drawing in the EE line | wire of FIG. 5A. It is a top view which shows the 1st member which comprises the piezoelectric element which concerns on 4th Embodiment. It is a side view which shows the 1st member which comprises the piezoelectric element which concerns on 4th Embodiment. It is a top view which shows the 2nd member which comprises the piezoelectric element which concerns on 4th Embodiment. It is a side view which shows the 2nd member which comprises the piezoelectric element which concerns on 4th Embodiment. It is a 1st process drawing in the manufacturing method of the piezoelectric element concerning a 4th embodiment. It is a 2nd process figure in the manufacturing method of the piezoelectric element which concerns on 4th Embodiment. It is a 3rd process figure in the manufacturing method of the piezoelectric element which concerns on 4th Embodiment. It is a 4th process figure in the manufacturing method of the piezoelectric element concerning a 4th embodiment. It is a top view which shows the piezoelectric element which concerns on the 5th Embodiment of this invention. It is sectional drawing in the FF line of FIG. 8A. It is a top view which shows the 1st member which comprises the piezoelectric element which concerns on 5th Embodiment. It is sectional drawing in the GG line of FIG. 9A. It is a top view which shows the 2nd member which comprises the piezoelectric element which concerns on 5th Embodiment. It is sectional drawing in the HH line of FIG. 9C. It is a 1st process drawing in the manufacturing method of the piezoelectric element concerning a 5th embodiment. It is a 2nd process figure in the manufacturing method of the piezoelectric element which concerns on 5th Embodiment. It is a 3rd process figure in the manufacturing method of the piezoelectric element which concerns on 5th Embodiment. It is a 4th process drawing in the manufacturing method of the piezoelectric element concerning a 5th embodiment. It is sectional drawing which shows the piezoelectric element which concerns on the 6th Embodiment of this invention. It is a top view which shows the piezoelectric element which concerns on the 7th Embodiment of this invention. It is a front view which shows the piezoelectric element which concerns on 7th Embodiment. It is sectional drawing in the II line | wire of FIG. 12A. It is sectional drawing in the JJ line of FIG. 12A. It is a top view which shows the 1st member which comprises the piezoelectric element which concerns on 7th Embodiment. It is a side view which shows the 1st member which comprises the piezoelectric element which concerns on 7th Embodiment. It is a top view which shows the 2nd member which comprises the piezoelectric element which concerns on 7th Embodiment. It is a side view which shows the 2nd member which comprises the piezoelectric element which concerns on 7th Embodiment. It is a 1st process drawing in the manufacturing method of the piezoelectric element concerning a 7th embodiment. It is a 2nd process figure in the manufacturing method of the piezoelectric element which concerns on 7th Embodiment. It is a 3rd process figure in the manufacturing method of the piezoelectric element which concerns on 7th Embodiment. It is a 4th process figure in the manufacturing method of the piezoelectric element concerning a 7th embodiment. It is a side view which shows a part of 1st member in the piezoelectric element which concerns on the 8th Embodiment of this invention. It is a side view which shows a part of 1st member in the piezoelectric element which concerns on the 9th Embodiment of this invention. It is sectional drawing which shows the pressure sensor which concerns on one Embodiment of this invention.

Explanation of symbols

1, 31, 201, 301, 501, 601, 701 Piezoelectric element 13 First conductive substrate 13a, 13b Side portion 15 of first conductive substrate Second conductive substrate 15a, 15b Side portion 17 of second conductive substrate 27, 35, 37 Piezoelectric layers 19, 29, 190, 290 First insulating layers 43, 49, 430, 490 Second insulating layers 21, 51, 53, 210 First connecting portion 33 of the first conductive substrate, 330 Second connecting portion 25, 45 of second conductive substrate First member 39, 47 Second member 101 Housing 103 Pressure receiving surface 105 Pressure transmitting member 107 Fixing screw

  A piezoelectric element according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition, each embodiment shown below illustrates this invention, Comprising: This invention is not limited to these. Moreover, in each figure, about the common part and member, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

(First embodiment)
A piezoelectric element according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1A is a plan view showing the piezoelectric element 1 according to the present embodiment, and FIG. 1B is a cross-sectional view taken along the line AA. As shown in these drawings, the piezoelectric element 1 according to this embodiment is arranged between a pair of first conductive substrates 13 and 13 arranged in parallel and the pair of first conductive substrates 13 and 13. And a second conductive substrate 15 connected to a pole different from that of the first conductive substrate 13. A piezoelectric layer 17 is disposed between the first conductive substrate 13 and the second conductive substrate 15. The side portions 13 a and 13 b of the two first conductive substrates 13 adjacent to both sides in the stacking direction via the second conductive substrate 15 are electrically connected by the first connecting portion 21. The first connecting portion 21 has an arch shape extending from one side portion 13a to the other side portion 13b.

  A first insulating layer 19 is formed on the inner surface of the surface of the first connecting portion 21 facing the side surface of the piezoelectric element 1. Thus, since the 1st insulating layer 19 is formed in the inner surface of the 1st connection part 21, it can suppress that the 1st conductive substrate 13 and the 2nd conductive substrate 15 short-circuit. As a result, the sensitivity of the piezoelectric element 1 can be suppressed over a long period of time, so that durability is improved. Further, as shown in FIG. 1B, the inner surface of the first connecting portion 21 is preferably separated from the side portion of the second conductive substrate 15 via the first insulating layer 19 and the space 23, and the space 23 Thus, the short-circuit suppressing effect between the first conductive substrate 13 and the second conductive substrate 15 can be further improved. For the same reason, the second connecting portion 33 (FIG. 5D) is also separated from the side portion of the first conductive substrate 13 disposed between the second conductive substrates 15 to which the second connecting portion 33 is connected. It is preferable to be formed.

  Moreover, it is preferable that the thickness of the first insulating layer 19 is thinner than the thickness of the first connecting portion 21, and in this way, even if the first connecting portion 21 is folded as shown in FIG. The occurrence of cracks in 19 can be suppressed. This effect becomes remarkable when the first insulating layer 19 is made of ceramics. For the same reason, the thickness of the second insulating layer 49 (FIG. 5D) is preferably thinner than the thickness of the second connecting portion 33. The first insulating layer 19 is preferably made of the same piezoelectric ceramic as the piezoelectric layer 17. Thereby, since the first insulating layer 19 can be formed in the same process as the piezoelectric layer 17, the manufacturing process described later can be simplified and the cost can be reduced. For the same reason, the second insulating layer 49 is preferably made of the same piezoelectric ceramic as the piezoelectric layer 37.

  3A to 3D are process diagrams showing an example of a method for manufacturing the piezoelectric element 1. As shown in FIG. 3A, in this manufacturing method, first, from the first member 25 in which the two first conductive substrates 13 and 13 are connected via the first connecting portion 21 and the second conductive substrate 15. A second member 39 is produced.

  Next, as shown in FIG. 3B, the piezoelectric layer 17 is formed on the surface of the first conductive substrate 13, and the first insulating layer 19 is formed on the surface of the first connecting portion 21. Examples of the method for forming the piezoelectric layer 17 on the surface of the first conductive substrate 13 and the method for forming the first insulating layer 19 on the surface of the first connecting portion 21 include vapor deposition, CVD, sol-gel, and screen printing. A known film such as a method can be used to form a required film, and then fired or the like.

  Next, the first member 25 is folded back at the first connecting portion 21 (FIG. 3C), and the two first conductive substrates 13 and 13 are arranged substantially in parallel so as to face each other. The second conductive substrate 15 is disposed between the conductive substrates 13 and 13, and the first conductive substrate 13 and the second conductive substrate 15 are alternately stacked (FIG. 3D). When the piezoelectric layer 17 is formed by a sol-gel method or a screen printing method, a firing step may be performed thereafter. In the case where the piezoelectric layer 17 is a polycrystalline body, a step of polarizing the piezoelectric layer 17 by applying a predetermined voltage between the first conductive substrate 13 and the second conductive substrate 15 after the firing step. May be applied.

  The first conductive substrate 13 and the second conductive substrate 15 are not particularly limited as long as they have conductivity. For example, a metal such as silver, copper, nickel, iron, or an alloy containing at least one of these is used. Can do. As the alloy, for example, brass, stainless steel, silver-palladium alloy, an alloy mainly composed of Ni, Fe, or the like can be used. As the alloy mainly composed of Ni and Fe, it is more preferable to use an alloy such as 52Fe-31Ni-17Co (Kovar (registered trademark)) or 58Fe-42Ni (42 alloy) which has a thermal expansion coefficient close to that of the piezoelectric layer. . Although the thickness of the 1st conductive substrate 13 and the 2nd conductive substrate 15 is not specifically limited, Preferably it is about 0.02-1.0 mm. Since the thickness of the first conductive substrate 13 and the second conductive substrate 15 is 0.02 mm or more, the rigidity of the substrate is increased, and handling in the formation process of the piezoelectric layer 17 and the subsequent lamination process becomes easy. . When the thicknesses of the first conductive substrate 13 and the second conductive substrate 15 are 1.0 mm or less, the adhesion when the two are laminated and integrated is improved, and the linearity of the output with respect to pressure is improved.

  The piezoelectric layer 17 is made of a known piezoelectric material such as a piezoelectric ceramic material mainly composed of lead zirconate titanate, barium titanate, aluminum nitride, lithium niobate, or the like. As the first insulating layer 19, for example, various insulating ceramics can be used, and among them, it is preferable to use the same material as the piezoelectric layer 17 described above. The thickness of the piezoelectric layer 17 and the thickness of the first insulating layer 19 are not particularly limited, but preferably about 0.001 to 0.1 mm. When the thickness of the piezoelectric layer 17 and the thickness of the first insulating layer 19 are 0.001 mm or more, the insulation resistance is improved, the leakage charge is reduced, and the sensitivity characteristics are improved. Further, when the thickness of the piezoelectric layer 17 is 0.1 mm or less, the adhesion with the first conductive substrate 13 is enhanced, and the linearity of the output with respect to the pressure is improved. When the thickness of the first insulating layer 19 is 0.1 mm or less, the flexibility of the first insulating layer 19 is increased, and the first insulating layer 19 is cracked or broken with respect to the deformation of the first connecting portion 21. Can be suppressed.

(Second Embodiment)
As shown in FIG. 4A, the piezoelectric element 201 according to the second embodiment of the present invention is the same as the first embodiment in terms of the shape between the first connecting portion 21 and the second conductive substrate 15. It differs from the piezoelectric element 1 which concerns. That is, in the piezoelectric element 201 according to the present embodiment, the inner surface of the first connecting portion 21 facing the side surface of the second conductive substrate 15 is not separated from the side surface of the second conductive substrate 15, and the first The side surface of the second conductive substrate 15 is in contact with the insulating layer 19. In the case of this form, the excessive movement of the 1st connection part 21 can be suppressed, and since the 1st connection part 21 becomes difficult to deform | transform, the durability of the 1st connection part 21 improves.

(Third embodiment)
As shown in FIG. 4B, the piezoelectric element 301 according to the third embodiment of the present invention is related to the first embodiment in that the piezoelectric layer 27 is also formed on the surface of the first conductive substrate 13. Different from the piezoelectric element 1. In the piezoelectric element 301 according to the present embodiment, the first insulating layer 19 is formed on the inner surface of the first connecting portion 21, and the first insulating layer 29 is also formed on the outer surface of the first connecting portion 21. Is formed. Preferably, the first insulating layer 19 is integrated with the piezoelectric layer 17. Thereby, while being able to improve the insulation with the other member of the outer surface side in the 1st electroconductive board | substrate 13, durability of the 1st connection part 21 with respect to corrosion, the impact from another member, etc. improves. Further, since the piezoelectric layers 301 and 27 are formed on the front and back surfaces of the piezoelectric element 301, the durability against impact and corrosion is improved in the same manner as described above. For the same reason, the second insulating layer 49 (FIG. 5D) is also preferably formed on the inner surface facing the first conductive substrate 13 in the surface of the second connecting portion 33. It is preferable that the second connecting portion 33 is formed on the outer surface. The second insulating layer 49 is preferably formed on the inner surface facing the first conductive substrate 13 and integrated with the piezoelectric layer 37.

(Fourth embodiment)
As shown in FIGS. 5A to 5D and FIGS. 6A to 6D, the piezoelectric element 401 according to the fourth embodiment includes a plurality of first conductive substrates 13 and second conductive substrates 15 alternately diffracted. Is formed. That is, the pair of first conductive substrates 13 and 13 and the first connecting portion 21 are alternately arranged to form a single conductive substrate, and the pair of first conductive substrates 13 and 13. Are folded at the first connecting portion 21 so as to face each other. The piezoelectric element 401 according to the fourth embodiment is different from the piezoelectric element 1 according to the first embodiment in the number of times of stacking. In the fourth embodiment, seven layers of the first conductive substrate 13 and six layers of the second conductive substrate 15 are used and are alternately stacked.

  As shown in FIGS. 5A to 5D and FIGS. 6A to 6D, the piezoelectric element 401 according to the fourth embodiment includes seven first conductive substrates 13 and these first conductive substrates 13 alternately. And six second conductive substrates 15 arranged and connected to poles different from the first conductive substrate 13. Piezoelectric layers 17, 27, 35, and 37 are disposed between the first conductive substrate 13 and the second conductive substrate 15.

  Two first conductive substrates 13, 13 adjacent in the stacking direction via the second conductive substrate 15 are connected by a first connecting portion 21 that electrically connects the side portions 13 a, 13 b ( FIG. 5B). Similarly, two second conductive substrates 15 and 15 that are adjacent to each other in the stacking direction via the first conductive substrate 13 are connected by a second connection portion 33 that electrically connects the side portions 15a and 15b. (FIG. 5D).

As described above, the piezoelectric element 401 according to the fourth embodiment has constituent members shown in the following (1) to (4).
(1) The 1st polar structure provided with the 1st connection part 21 which connects between the several 1st electroconductive board | substrate 13 which opposes at intervals, and the 1st electroconductive board | substrate 13 adjacent.
In this first polar structure, one conductive substrate (first member) 45 (FIG. 6A, FIG. 6B) in which the first conductive substrate 13 and the first connecting portion 21 are alternately arranged is adjacent. The first conductive portion 13 is folded back at the first connecting portion 21 so as to face each other.
(2) A second connecting portion that is provided between adjacent first conductive substrates and that connects a plurality of second conductive substrates 15 that are opposed to each other at an interval from each other and adjacent second conductive substrates 15. And a second polar structure.
In this second polar structure, one conductive substrate (second member) 47 (FIG. 6C, FIG. 6D) in which the second conductive substrate 15 and the second connecting portion 33 are alternately arranged is adjacent. The second conductive substrate 15 is folded back at the second connecting portion 33 so as to face each other. Thereby, it arrange | positions sequentially so that one of the 2nd conductive substrates 15 of a 2nd polar structure may enter between the 1st conductive substrates 13 which a 1st polar structure mutually opposes.
Further, the first and second polar structures are combined so that the first conductive substrate 13 and the second conductive substrate 15 are alternately arranged.
(3) Two piezoelectric layers provided so as to overlap between the first conductive substrate 13 and the second conductive substrate 15.
One of the two piezoelectric layers 17 and 27 is in contact with the first conductive substrate 13, and the other piezoelectric layers 35 and 37 are in contact with the second conductive substrate 15.
(4) First insulating layers 19 and 29 provided on the surface of the first connecting portion 21 and second insulating layers 43 and 49 provided on the surface of the second connecting portion 33.
Specifically, the first insulating layer 19 or the first insulating layer 29 is formed on the inner surface of the first connecting portion 21, and the first insulating layer 29 or the first insulating layer 29 is formed on the outer surface of the first connecting portion 21. An insulating layer 19 is formed. The second insulating layer 43 or the second insulating layer 49 is formed on the inner surface of the second connecting portion 33, and the second insulating layer 49 or the second insulating layer 43 is formed on the outer surface of the second connecting portion 33. Has been.
Here, the first insulating layer 19 or the first insulating layer 29 may be formed on either the inner surface or the outer surface of the first connecting portion 21, and the second insulating layer 43 or the second insulating layer 49. May be formed on either the inner surface or the outer surface of the second connecting portion 33.

  7A to 7D are process diagrams illustrating an example of a method for manufacturing the piezoelectric element 401. As shown in FIG. 7A, in this manufacturing method, first, the first member 45 in which the seven first conductive substrates 13 are connected in series via the first connecting portion 21 is manufactured. Next, the second member 47 in which the six second conductive substrates 15 are connected in series via the second connecting portion 33 is produced.

  Next, as shown in FIG. 7B, the piezoelectric layer 17 and the piezoelectric layer 27 are formed on both main surfaces of the first conductive substrate 13, respectively. Further, the first insulating layer 19 and the first insulating layer 29 are also formed on the front and back surfaces of the first connecting portion 21, respectively. Similarly, the piezoelectric layer 35 and the piezoelectric layer 37 are respectively formed on both main surfaces of the second conductive substrate 15. Further, the second insulating layer 43 and the second insulating layer 49 are also formed on the front and back surfaces of the second connecting portion 33.

  Next, as shown in FIG. 7C, the first members 45 are folded at the plurality of first connecting portions 21 to arrange the plurality of first conductive substrates 13 so as to overlap substantially in parallel, and the second member 47. Are folded at the second connecting portion 33 and the plurality of second conductive substrates 15 are arranged so as to be substantially parallel to each other. As shown in FIG. 7C, the first conductive substrate 13 and the second conductive substrate 15 are combined with the piezoelectric layers 17, 27, 35, and 37 by combining the first member 45 and the second member 47. Are stacked alternately.

(Fifth embodiment)
The piezoelectric element 501 according to the fifth embodiment of the present invention is configured in the same manner as the piezoelectric element 1 according to the first embodiment, except that the structure of the connecting portion is different from that of the piezoelectric element 1 according to the first embodiment. ing. In the drawings referred to in the following description, the same members as those of the piezoelectric element 1 of the first embodiment are denoted by the same reference numerals, and are the same as the members of the first embodiment unless otherwise specified. It is a configuration.
That is, as shown in FIGS. 8A and 8B, the piezoelectric element 501 of the fifth embodiment is formed in place of the first connecting portion 21, the first insulating layer 19 and the space 23 of the first embodiment. Are provided with different first connecting portions 210, first insulating layers 190, and spaces 230, respectively.
And each side part 13a, 13b of the 1st electroconductive board | substrate 13 is electrically connected by the 1st connection part 210, The 1st connection part 210 is changed from one side part 13a to the other side part 13b. Although it is an arch-like one that is stretched over, the shape is different from that of the first connecting portion 21.

  Specifically, in the fifth embodiment, the outer periphery and the inner periphery of the first connecting portion 210 have an arc shape, and the center angle with respect to the inner arc is larger than the center angle with respect to the outer arc. . In other words, the radius of curvature of the outer circumferential arc is larger than the radius of curvature of the inner circumferential arc. With this configuration, the thickness of the first connection part 210 can be made thinner than the thickness of the first conductive substrate 13, and the first connection part 210 gradually increases from both ends of the first connection part 210 toward the center. The thickness can be reduced. In addition, the outer and inner peripheries of the second connecting portion 330 are arc-shaped, and the center angle with respect to the inner arc can be made larger than the center angle with respect to the outer arc. Thus, the thickness can be gradually reduced from both ends toward the center.

  In addition, a first insulating layer 190 is formed on the inner surface of the surface of the first connecting portion 210 facing the side surface of the second conductive substrate 15. Thus, since the 1st insulating layer 190 is formed in the inner surface of the 1st connection part 210, it can suppress that the 1st conductive substrate 13 and the 2nd conductive substrate 15 short-circuit. As a result, the sensitivity of the piezoelectric element 501 can be suppressed over a long period of time, so that the durability is improved. In addition, since the inner surface of the first connecting portion 210 is separated from the side surface of the piezoelectric element 501 via the first insulating layer 190 and the space 230, the short circuit between the first conductive substrate 13 and the second conductive substrate 15 is suppressed. The effect can be further improved.

  Further, as described above, as shown in FIGS. 8B and 9B, the thickness of the first connecting portion 210 is thinner than the thickness of the first conductive substrate 13. Specifically, the inner surface on the side facing the side surface of the piezoelectric element 501 when the first connecting portion 210 is folded back has an arc-shaped cross section, and the thickness near the center is the thinnest. The thickness in the vicinity of the boundary with the conductive substrate 13 is the largest and is approximately the same as the thickness of the first conductive substrate 13. As described above, the thickness of the first connecting portion 210 gradually decreases from the both end sides toward the center side, so that it is possible to suppress local concentration of stress.

  In addition, by reducing the thickness of the inner surface side of the first connecting portion 210, the stress is reduced at the portion where the first connecting portion 210 is turned and becomes compressive stress as shown in FIG. 8B. can do. As a result, even when the first insulating layer 190 is formed on the inner surface, it is possible to suppress problems such as the occurrence of cracks in the first insulating layer 190. This effect is remarkable when the first insulating layer 190 is made of ceramics. The first insulating layer 190 is preferably made of the same piezoelectric ceramic as the piezoelectric layer 17. Thereby, since the first insulating layer 190 can be formed in the same process as the piezoelectric layer 17, the manufacturing process described later can be simplified and the cost can be reduced.

  Further, it is preferable that the thickness of the first insulating layer 190 is smaller than the thickness of the first connecting portion 210. Accordingly, even when the first connecting portion 210 is folded back as shown in FIG. The generation of cracks can be suppressed. This effect is remarkable when the first insulating layer 190 is made of ceramics. The first insulating layer 190 is preferably made of the same piezoelectric ceramic as the piezoelectric layer 17. Thereby, since the first insulating layer 190 can be formed in the same process as the piezoelectric layer 17, the manufacturing process described later can be simplified and the cost can be reduced.

10A to 10D are process diagrams showing an example of a method for manufacturing the piezoelectric element 501. As shown in FIG. 10A, in this manufacturing method, first, a first member 250 in which two first conductive substrates 13 are connected via a first connecting portion 210 and a second conductive substrate 15 is used. 2 member 39 is produced.
Next, a recess having an arcuate cross section is formed in the first connecting portion 210 of the first member 250.
A method such as etching, grinding, pressing, or forging may be used to form a recess having an arcuate cross section in the first connecting portion 210 of the first member 250.

  Next, as shown in FIG. 10B, the piezoelectric layer 17 is formed on the surface of the first conductive substrate 13, and the first insulating layer 190 is formed on the surface of the first connecting portion 210. Examples of the method for forming the piezoelectric layer 17 on the surface of the first conductive substrate 13 and the method for forming the first insulating layer 190 on the surface of the first connecting portion 210 include vapor deposition, CVD, sol-gel, and screen printing. Using a known means such as a method, a required film can be formed and then formed by a treatment such as firing.

  Next, the first member 250 is folded back at the first connecting portion 210 so that the two first conductive substrates 13 and 13 are arranged substantially in parallel. The conductive substrate 15 is disposed (FIG. 10C), and the first conductive substrate 13 and the second conductive substrate 15 are alternately stacked (FIG. 10D). When the piezoelectric layer 17 is formed by a sol-gel method or a screen printing method, a firing step may be performed thereafter. When the piezoelectric layer 17 is a polycrystalline body, a step of polarizing the piezoelectric layer 17 by applying a predetermined voltage between the first conductive substrate 13 and the second conductive substrate 15 is then performed. There is.

(Sixth embodiment)
As shown in FIG. 11, the piezoelectric element according to the sixth embodiment differs from the piezoelectric element 501 according to the fifth embodiment in terms of the formation position of the piezoelectric layer. That is, in the piezoelectric element 601 according to the present embodiment, the first insulating layer 190 is formed on the inner surface of the first connecting portion 210, and the first insulating layer 290 is also formed on the outer surface of the first connecting portion 210. Is formed. Thereby, while being able to improve the insulation with the other member of the outer surface side in the 1st conductive substrate 13, durability of the 1st connection part 210 with respect to corrosion, the impact from another member, etc. improves. Since the piezoelectric layers 27 are formed on the front and back surfaces of the piezoelectric element 601, durability against impact and corrosion is improved in the same manner as described above.

(Seventh embodiment)
The piezoelectric element 701 of the seventh embodiment according to the present invention is configured in the same manner as the piezoelectric element 401 of the fourth embodiment, except that the structure of the connecting portion is different from the piezoelectric element 401 of the fourth embodiment. ing. In the drawings referred to in the following description, the same members as those of the piezoelectric element 1 of the first embodiment are denoted by the same reference numerals, and are the same as the members of the fourth embodiment unless otherwise specified. It is a configuration.
That is, as shown in FIGS. 12A to 12D, the piezoelectric element 701 of the seventh embodiment is shaped in place of the first connecting portion 21, the first insulating layer 19, and the space 23 of the fourth embodiment. Are provided with different first connecting portions 210, first insulating layers 190 and spaces 230, and instead of the second connecting portions 33 and the second insulating layers 43, 49 of the fourth embodiment, the shapes thereof are different from each other. 2 connection part 330 and 2nd insulating layers 430 and 490 are provided.
Here, in the piezoelectric element 701 of the seventh embodiment, the first connecting portion 210, the first insulating layer 190, and the space 230 are configured in the same manner as in the fifth embodiment.
In addition, the second connecting portion 330 and the second insulating layers 430 and 490 are configured similarly to the first connecting portion 210 and the first insulating layer 190 in the fifth embodiment.

  As shown in FIGS. 12A to 12D and FIGS. 13A to 13D, the piezoelectric element 701 of the seventh embodiment configured as described above includes seven first conductive substrates 13 and their first conductive properties. Six second conductive substrates 15 that are alternately arranged with the substrates 13 and are connected to poles different from those of the first conductive substrate 13 are provided. Piezoelectric layers 17, 27, 35, and 37 are disposed between the first conductive substrate 13 and the second conductive substrate 15.

  Further, the two first conductive substrates 13 and 13 adjacent in the stacking direction via the second conductive substrate 15 are connected by the first connecting portion 210 that electrically connects the side portions 13a and 13b. Yes. Similarly, two second conductive substrates 15 and 15 that are adjacent to each other in the stacking direction via the first conductive substrate 13 are coupled by a second coupling unit 330 that electrically connects the side portions 15a and 15b. ing.

  A first insulating layer 190 is formed on the inner surface of the first connecting portion 210, and a first insulating layer 290 is formed on the outer surface of the connecting portion 19. A second insulating layer 430 is formed on the inner surface of the second connecting part 330, and a second insulating layer 490 is formed on the outer surface of the second connecting part 330.

  14A to 14D are process diagrams showing an example of a method for manufacturing the piezoelectric element 701. As shown in FIG. 14A, in this manufacturing method, first, a first member 450 in which seven first conductive substrates 13 are connected in series via a first connecting portion 210 is manufactured. Next, the second member 470 in which the six second conductive substrates 15 are connected in series via the second connecting portion 330 is produced.

  Next, as shown in FIG. 14B, the piezoelectric layer 17 and the piezoelectric layer 27 are formed on both main surfaces of the first conductive substrate 13, respectively. Also, the first insulating layer 190 and the first insulating layer 290 are formed on the front and back surfaces of the first connecting part 210, respectively. Similarly, the piezoelectric layer 35 and the piezoelectric layer 37 are respectively formed on both main surfaces of the second conductive substrate 15. Further, the second insulating layer 430 and the second insulating layer 490 are also formed on the front and back surfaces of the second connection part 330.

  Next, the first member 450 is folded back at the plurality of first connecting portions 210 to arrange the plurality of first conductive substrates 13 substantially in parallel, and the second member 470 is folded back at the second connecting portion 330. A plurality of second conductive substrates 15 are arranged substantially in parallel. By combining the first member 450 and the second member 470, the first conductive substrate 13 and the second conductive substrate 15 are alternately stacked.

(Eighth embodiment)
As shown in FIG. 15A, in the piezoelectric element according to the eighth embodiment, both main surfaces of the first connecting portion 51 are formed with recesses, and the cross section of the first connecting portion 51 is both main surfaces. Is arcuate. Thereby, the stress relaxation effect when folded in the 1st connection part 51 can be heightened more.

(Ninth embodiment)
As shown in FIG. 15B, the thickness of the first coupling portion 53 may be made substantially constant while being thinner than the thickness of the first conductive substrate 13. In this case, there is an advantage that processing is easy.

(Pressure sensor)
As shown in FIG. 16, this pressure sensor has a piezoelectric element 701 mounted in a housing 101 made of metal or the like. A diaphragm-shaped pressure receiving surface 103 is provided at the front end (lower end in the figure) of the housing 101. The pressure receiving surface 103 is disposed, for example, in a cylinder of the internal combustion engine. The pressure received by the pressure receiving surface 103 is transmitted to the piezoelectric element 701 via the pressure transmitting member 105 in the housing 101. The pressure can be detected by detecting the charge generated according to the pressure applied to the piezoelectric element 701 by a known means. One end of the pressure transmission member 105 is in contact with the pressure receiving surface 103, and the other end is in contact with the piezoelectric element 701. The piezoelectric element 701 and the pressure transmission member 105 are pressed against the pressure receiving surface 103 by a fixing screw 107 that presses the upper surface of the piezoelectric element 701.

  In the above pressure sensor, the piezoelectric element 701 according to the seventh embodiment of the present invention is used. However, for example, the piezoelectric element 401 according to the fourth embodiment of the present invention is used in other embodiments according to the present invention. You may comprise using a piezoelectric element.

Claims (31)

A pair of first conductive substrates arranged in parallel;
A second conductive substrate disposed between the pair of first conductive substrates and connected to a pole different from the first conductive substrate;
Two piezoelectric layers respectively provided between the first conductive substrate and the second conductive substrate and in contact with the first conductive substrate and the second conductive substrate;
A first connection that electrically connects the pair of first conductive substrates and spans from a side of one of the first conductive substrates to a side of the other first conductive substrate. And
A first insulating layer formed on a surface of the first connecting portion ,
The piezoelectric element, wherein the first insulating layer is made of the same material as the piezoelectric layer .   The pair of first conductive substrates and the first connecting portion are alternately arranged to form a single conductive substrate, and the pair of first conductive substrates are opposed to each other. The piezoelectric element according to claim 1, wherein the piezoelectric element is folded at the first connecting portion. A plurality of first conductive substrates facing each other at intervals and a first connecting portion connecting adjacent first conductive substrates, wherein the first conductive substrate and the first connecting portion are alternately arranged. A first polar structure formed by folding back one conductive substrate at the first connecting portion so that the adjacent first conductive substrates face each other;
A plurality of second conductive substrates provided between the adjacent first conductive substrates and facing each other at an interval, and a second connecting portion connecting the adjacent second conductive substrates. The second conductive substrate and the second connecting portion are alternately folded at the second connecting portion so that the adjacent second conductive substrates face each other. A second pole structure;
A piezoelectric element comprising two piezoelectric layers provided between the first conductive substrate and the second conductive substrate and in contact with the first conductive substrate and the second conductive substrate, respectively. Because
A first insulating layer is provided on a surface of the first connecting portion, and a second insulating layer is provided on a surface of the second connecting portion ;
The piezoelectric element, wherein the second insulating layer is made of the same material as the piezoelectric layer .   The second connection part is formed apart from a side part of the first conductive substrate disposed between the second conductive substrates to which the second connection part is connected. The piezoelectric element according to claim 3.   5. The piezoelectric element according to claim 3, wherein the second insulating layer is formed on an inner surface of the surface of the second coupling portion that faces the first conductive substrate. 6.   6. The piezoelectric element according to claim 3, wherein the second insulating layer is formed on an outer surface of the second coupling portion.   7. The piezoelectric element according to claim 3, wherein a thickness of the second insulating layer is thinner than a thickness of the second coupling portion. 4. The piezoelectric element according to claim 3 , wherein the second insulating layer is formed on an inner surface facing the first conductive substrate, and is integrated with the piezoelectric layer. 5. The first connection part is formed apart from a side part of the second conductive substrate disposed between the pair of first conductive substrates to which the first connection part is connected. The piezoelectric element according to any one of claims 1 to 8 . The first insulating layer is formed on an inner surface of the surface of the first connecting portion facing the second conductive substrate, according to any one of claims 1 to 9. The piezoelectric element described in 1. The first insulating layer, the piezoelectric element according to any one of claims 1-9, characterized in that formed on the outer surface of the first connection part. The thickness of the first insulating layer, a piezoelectric element according to any one of claims 1 to 11, characterized in that thinner than the thickness of the first connection part. 2. The piezoelectric element according to claim 1 , wherein the first insulating layer is formed on an inner surface facing the second conductive substrate, and is integrated with the piezoelectric layer. A pair of first conductive substrates arranged in parallel;
A second conductive substrate disposed between the pair of first conductive substrates and connected to a pole different from the first conductive substrate;
Two piezoelectric layers respectively provided between the first conductive substrate and the second conductive substrate and in contact with the first conductive substrate and the second conductive substrate;
The pair of first conductive substrates are electrically connected to each other, spanned from one side of the first conductive substrate to the side of the other first conductive substrate, A first connecting portion having a thickness smaller than that of the conductive substrate;
Equipped with a,
The piezoelectric element according to claim 1, wherein the first connecting portion has a thickness that gradually decreases from both ends toward the center . The pair of first conductive substrates and the first connecting portion are formed of a single conductive substrate, and the pair of first conductive substrates are folded back at the first connecting portion so as to face each other. The piezoelectric element according to claim 14 . A plurality of first conductive substrates facing each other at intervals and a first connecting portion connecting adjacent first conductive substrates, wherein the first conductive substrate and the first connecting portion are alternately arranged. A first polar structure formed by folding back one conductive substrate at the first connecting portion so that the adjacent first conductive substrates face each other;
A plurality of second conductive substrates provided between the adjacent first conductive substrates and facing each other at an interval, and a second connecting portion connecting the adjacent second conductive substrates. The second conductive substrate and the second connecting portion are alternately folded at the second connecting portion so that the adjacent second conductive substrates face each other. A second pole structure;
A piezoelectric element comprising two piezoelectric layers provided between the first conductive substrate and the second conductive substrate and in contact with the first conductive substrate and the second conductive substrate, respectively. Because
The thickness of the first connecting portion is thinner than the thickness of the first conductive substrate, the thickness of the second connecting portion, rather thin than the thickness of said second conductive substrate,
The piezoelectric element is characterized in that the second connecting portion has a thickness that gradually decreases from both ends toward the center . 17. The piezoelectric element according to claim 16 , wherein the second connecting portion has an arc shape on the outer periphery and the inner periphery, and the central angle of the inner periphery is larger than the central angle of the outer periphery. The second connection part is formed apart from a side part of the first conductive substrate disposed between the pair of second conductive substrates to which the second connection part is connected. The piezoelectric element according to claim 16 or 17 . The piezoelectric element according to any one of claims 16 to 18 , wherein a second insulating layer is formed on a surface of the second connecting portion. The piezoelectric element according to claim 19 , wherein the second insulating layer is formed on an inner surface of the surface of the second coupling portion that faces the first conductive substrate. The piezoelectric element according to claim 19 or 20 , wherein the second insulating layer is formed on an outer surface of the second connecting portion. The piezoelectric element according to any one of claims 16 to 21 , wherein a thickness of the second insulating layer is thinner than a thickness of the second connecting portion. The piezoelectric element according to any one of claims 16 to 22 , wherein the second insulating layer is made of the same material as that of the piezoelectric layer. The first connection part, the outer periphery and the inner periphery an arc shape, according to any one of claims 14 to 23, characterized in that the larger inner circumference of the central angle than the central angle of the outer periphery Piezoelectric element. The first connection part is formed apart from a side part of the second conductive substrate disposed between the first conductive substrates to which the first connection part is connected. The piezoelectric element according to any one of claims 14 to 24 . The piezoelectric element according to any one of claims 14 to 25 , wherein a first insulating layer is formed on a surface of the first connecting portion. 27. The piezoelectric element according to claim 26 , wherein the first insulating layer is formed on an inner surface of the surface of the first connecting portion facing the second conductive substrate. The first insulating layer, piezoelectric element according to claim 26 or 27, characterized in that formed on the outer surface of the first connection part. The piezoelectric element according to any one of claims 14 to 28 , wherein a thickness of the first insulating layer is thinner than a thickness of the first connecting portion. 30. The piezoelectric element according to any one of claims 26 to 29 , wherein the first insulating layer is made of the same material as the piezoelectric layer. Pressure sensor comprising: the piezoelectric element according, and a housing which the piezoelectric element is disposed within any one of claims 1 to 30.

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