JP4914231B2 - Pressure detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure detector for stably receiving a pressure detection element, and achieving a proper piezoelectric conversion function of the pressure detection element. <P>SOLUTION: An annular thick section 1351 of an annular negative electrode plate 1350 passes through an annular lower opening 1311 between an inner casing member 1320 and an outer casing member 1330, and is coaxially fitted into a cylindrical small diameter section 1323 so as to be protruded in the extended direction of the cylindrical small diameter section 1323. An annular thin section 1352 of the annular negative electrode plate 1350 is fixed on an annular bottom wall section 1332 by laser welding so as to be outwardly and radially extended from the annular thick section 1351. An annular piezoelectric plate 1360 is coaxially fitted into the cylindrical small diameter section 1323 so as to be laminated on the annular negative electrode plate 1350. An annular positive electrode plate 1370 is coaxially fitted into the cylindrical small diameter section 1323, and laminated on the annular piezoelectric plate 1360 so as to be held between an annular intermediate wall section 1322 and the annular negative electrode plate 1350 along with the annular piezoelectric plate 1360. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a pressure detection device.

  Conventionally, as this type of pressure detection device, a pressure detection device unit disclosed in Patent Document 1 below has been proposed. In this pressure detection device unit, a sensor accommodating portion that accommodates the pressure detection device assembly is provided at the lower end of a plug tube that is inserted into the plug hole of the cylinder head together with the spark plug.

  Here, the sensor housing portion includes an inner bulging portion of the inner cylindrical member and an outer cylindrical member facing the inner bulging portion among the inner and outer cylindrical members constituting the unit main body portion of the pressure detecting device unit. It is comprised by the wall part of this and the bottom obstruction | occlusion part.

The sensor housing portion having such a configuration is formed as follows. That is, an inner cylinder projecting from the pressure detection device assembly is formed by forming a circumferential projecting portion on the inner peripheral edge of the end surface of the main body portion (corresponding to the wall portion of the outer cylinder member) formed in a cylindrical shape on the outer cylinder member. The crimped portion is bent so that the leading end portion (corresponding to the above-described bottom closing portion) of the reduced diameter portion (corresponding to the inner bulging portion of the above-described inner cylindrical member) of the member is bent toward the protruding portion side. Apply. Thereafter, the distal end portion of the reduced diameter portion of the inner cylinder member and the protruding portion are welded. The pressure detection device assembly has a structure in which each ring-shaped insulating plate, electrode plate, piezoelectric plate, and plate packing are sequentially stacked from the side opposite to the bottom closing portion, and the sensor housing portion described above. Contained.
Japanese Patent Laid-Open No. 2002-24369

  By the way, in the pressure detecting device unit, when the plug tube is inserted into the plug hole of the cylinder head, the sensor housing portion is seated on the bottom of the plug hole by the bottom closing portion.

  However, in forming the sensor housing portion, the bottom closing portion is formed by caulking the tip portion of the reduced diameter portion of the inner cylinder member as described above. Here, since the above-described process called caulking is equivalent to plastic working, even if the process called caulking is performed, the subsequent bottom closing portion has a very unstable shape. This means that the seat surface shape of the sensor accommodating portion is very unstable.

  For this reason, even if the bottom closing portion of the sensor housing portion is seated on the bottom of the plug hole as described above, the bottom closing portion cannot be properly seated on the bottom of the plug hole and is unstable. In such a situation, the piezoelectric conversion action of the piezoelectric plate cannot be properly exhibited.

  Further, as described above, when the tip portion of the reduced diameter portion of the inner cylinder member and the overhang portion are welded, the welded portion between the tip portion and the overhang portion, that is, the outer peripheral edge portion of the bottom closing portion is annular. It is formed as a weld bead and protrudes to the bottom side of the plug hole from the portion other than the outer peripheral edge portion of the bottom closing portion.

  For this reason, the seat surface shape of the bottom blocking portion becomes more unstable, and as a result, the bottom blocking portion becomes more difficult to sit on the bottom of the plug hole, and the piezoelectric conversion of the piezoelectric plate described above The action cannot be exhibited even more appropriately.

  Therefore, in order to cope with the above, the present invention realizes the seat surface shape of the casing that accommodates the pressure detection element in a stable shape without depending on caulking, and piezoelectric conversion of the pressure detection element. It is an object of the present invention to provide a pressure detection device that can appropriately exert its action.

In solving the above-described problem, the pressure detection device according to the present invention, according to the description of claim 1,
A cylinder (1100), a casing (1310), and a pressure detection element (1340) are provided.

And the casing
A cylindrical large-diameter portion (1321) extending from the tip of the cylindrical body, and an annular intermediate wall portion (1322) extending radially inward from the extended end of the cylindrical large-diameter portion An inner casing member (1320) provided with a cylindrical small-diameter portion (1323) extending in the extending direction of the cylindrical large-diameter portion from the inner peripheral edge of the annular intermediate wall portion,
A cylindrical surrounding portion (1331) surrounding the inner casing member from its periphery, and the cylindrical small diameter extending inward from the cylindrical small diameter portion side end of the cylindrical surrounding portion toward the inside. An outer casing member (1330) provided with an annular bottom wall (1332) having an inner peripheral edge formed by forming an annular opening (1311) between the extended end of the part.

  The pressure detection element includes each annular piezoelectric body (1360) and a pair of electrodes (1350, 1370).

And one of the pair of electrodes is
An annular thick portion disposed coaxially with the cylindrical small-diameter portion so as to protrude through the annular opening in the extending direction of the cylindrical small-diameter portion between the inner and outer casing members. An annular thick part (1351) formed by fixing the extending end of the cylindrical small diameter part of the inner casing member on the inner peripheral surface by welding, and the annular thick part being thinner than the annular thick part. An annular thin part (1352) extending radially outward from the part and secured to the annular bottom wall part of the outer casing member by welding,
The annular piezoelectric body is coaxially disposed on the cylindrical small diameter portion so as to be laminated on the one electrode,
The other electrode of the pair of electrodes is disposed coaxially with the cylindrical small-diameter portion so as to be laminated on the annular piezoelectric body, and the annular intermediate wall portion of the inner casing member and the one of the ones together with the annular piezoelectric body. It is sandwiched between the electrodes.

  Under such a configuration, if the pressure detection device is inserted into the insertion hole formed in the cylinder head of the internal combustion engine from the casing to the cylinder, the casing is seated on the bottom surface of the insertion hole. .

  Here, as described above, one electrode of the pressure detection element protrudes from the annular opening of the casing at the annular thick portion. In other words, the annular thick portion of one of the electrodes protrudes in the extending direction of the cylindrical small diameter portion from the extending end portion of the cylindrical small diameter portion of the inner casing member and the annular bottom wall portion of the outer casing member. Yes.

  Further, the extending end portion of the cylindrical small-diameter portion of the inner casing member is fixed to the inner peripheral surface of the annular thick portion of one electrode by welding without depending on caulking. The bottom wall portion is fixed to the annular thin portion of one electrode from below by welding without depending on caulking. Therefore, no weld bead is formed on the bottom surface of the casing.

  With the configuration as described above, the seating surface shape of the casing that accommodates the pressure detection element can be realized in a stable shape with the annular thick part and the annular thin part of one electrode without depending on caulking. . For this reason, not only the bottom of the casing (the cylindrical small-diameter portion of the inner casing member and the annular bottom wall portion of the outer casing member), only one electrode is on the bottom surface of the insertion hole portion at the annular thick portion. You will be seated.

  Therefore, the pressure detecting device can be stably seated on the bottom surface in the insertion hole of the cylinder head with the annular thick portion of one of the electrodes. As a result, the pressure detection element, and thus the piezoelectric body, can be maintained in a state in which the piezoelectric conversion action is properly exhibited.

  In such a state, the spark plug is inserted into the cylinder, and is fastened to a screw hole formed in a portion of the cylinder head that is coaxially positioned at the center of the bottom of the insertion hole in the mounting screw. Then, the said spark plug clamps a pressure detection element between the bottom face of the said insertion hole part via the annular intermediate wall part of an inner side casing member in the annular collar part of the metal shell.

  At this time, as described above, the pressure detection device is stably seated on the bottom surface in the insertion hole portion of the cylinder head with the annular thick portion of one of the electrodes. The pressure detection element can be properly clamped. Therefore, the pressure detection element can properly exhibit the piezoelectric conversion action.

  According to a second aspect of the present invention, in the pressure detection device according to the first aspect, the annular piezoelectric body is laminated only on the annular thick portion.

  Thereby, the whole piezoelectric body can be firmly clamped between the annular intermediate wall portion of the inner casing member and the bottom surface of the insertion hole portion of the cylinder head only on the annular thick portion of one electrode. As a result, the function and effect described in claim 1 can be further improved.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a pressure detection device 1000 according to the present invention applied to a cylinder head 100 of an internal combustion engine.

  The pressure detection apparatus 1000 includes a metal cylinder 1100, a connector 1200, and a detection body 1300.

  The metal cylinder 1100 is inserted into the insertion hole 110 formed in the cylinder head 100 from the annular opening 111, and the metal cylinder 1100 is connected to the base end 1110 via the connector 1200. The cylinder head 100 is supported by the annular opening 111 of the insertion hole 110 of the cylinder head 100. In this embodiment, the insertion hole 110 described above is formed from the outer surface 120 of the cylinder head 100 toward the combustion chamber 130 of the internal combustion engine as shown in FIG. The annular opening 111 is formed so as to project outward from the outer surface 120 of the cylinder head 100 in an annular shape.

  The connector 1200 includes a connector main body 1210 and a grommet 1220. The connector main body 1210 includes a cylindrical portion 1211, and a flange portion 1212 that extends radially from the central portion in the axial direction of the outer peripheral surface of the cylindrical portion 1211. It is integrally formed of an electrically insulating resin material so as to have a connector portion 1213 extending outward in a radial direction from a part of the flange portion 1212.

  The grommet 1220 is formed by using a rubber material so as to be an annular body having a U-shaped cross section with the inner annular wall portion 1221, the outer annular wall portion 1222, and the annular connecting wall portion 1223. The grommet 1220 is fitted to the cylindrical portion 1211 of the connector main body 1210 from below at the inner annular wall portion 1221, and is seated and fixed to the flange portion 1212 of the connector main body 1210 from below by the annular connecting wall portion 1223. Yes.

  Here, the grommet 1220 attaches the tubular portion 1211 of the connector main body 1210 to the cylinder head 100 so that the annular opening 111 of the insertion hole 110 is sandwiched between the inner annular wall portion 1221 and the outer annular wall portion 1222. The insertion hole 110 is supported substantially coaxially.

  Therefore, the support for the annular opening 111 of the insertion hole 110 of the metal cylinder 1100 described above is specifically performed as follows. That is, the metal cylinder 1100 is coaxially fitted into the cylinder part 1211 of the connector 1200 at the base end part 1110 as shown in FIG. It is supported by the annular opening 111 of the portion 110.

  As shown in FIGS. 1 and 2, the detection body 1300 is coaxially supported by the tip 1120 of the metal cylinder 1100, and this detection body 1300 includes a metal casing 1310, an annular pressure detection, and the like. An element 1340 and both electrical insulating members 1380 and 1390 are configured. In the present embodiment, the cylindrical body 1100 and the casing 1310 are made of metal as described above, so that the strength of the cylindrical body 1100 and the casing 1310 can be ensured.

  The metal casing 1310 has an inner casing member 1320 and an outer casing member 1330. The inner casing member 1320 is formed by pressing so as to have the cross-sectional shape shown in FIGS. 1 and 2, and this inner casing member 1320 has a cylindrical large-diameter portion 1321, an annular intermediate wall portion 1322, and a cylinder. A small-diameter portion 1323 is formed.

  The cylindrical large-diameter portion 1321 is coaxially fitted to the distal end portion 1120 of the metal cylinder 1100 at the upper end portion thereof by laser welding. The annular intermediate wall portion 1322 is annularly extended from the lower end portion of the cylindrical large-diameter portion 1321 to the inside so as to be perpendicular to the axis of the cylindrical large-diameter portion 1321, and the cylindrical small-diameter portion 1323 is The cylindrical intermediate wall 1322 extends in a cylindrical shape downward from the inner peripheral edge.

  The outer casing member 1330 is positioned coaxially with the inner casing member 1320 so as to surround the inner casing member 1320 from the periphery thereof. The outer casing member 1330 includes a cylindrical surrounding portion 1331 and an annular bottom wall portion. 1332. The annular bottom wall portion 1332 extends inward from the lower end portion of the cylindrical surrounding portion 1331 so as to be perpendicular to the axis of the cylindrical surrounding portion 1331, and the inner peripheral edge portion of the annular bottom wall portion 1332 An annular lower opening 1311 as a metal casing 1310 is formed between the extended end portion of the cylindrical small-diameter portion 1323.

  As can be seen from FIG. 2, the annular pressure detection element 1340 is coaxially fitted to the cylindrical small diameter portion 1323 and is accommodated between the inner casing member 1320 and the outer casing member 1330. The detection element 1340 is constituted by an annular negative electrode plate 1350, a piezoelectric plate 1360, and a positive electrode plate 1370.

  The annular negative electrode plate 1350 is configured by an annular thick part 1351 and an annular thin part 1352, and the annular thin part 1352 is concentric with the annular thick part 1351 on the radially outer side of the annular thick part 1351. And integrally formed.

  In the present embodiment, the annular thick portion 1351 has a radial thickness that is equal to or greater than the sum of the radial thickness of the piezoelectric plate 1360 and the radial thickness of the electrical insulating member 1390. Further, the annular thin portion 1352 is formed thinner than the annular thick portion 1351 in the axial thickness thereof, and the upper surface of the annular thin portion 1352 is in the same plane as the upper surface of the annular thick portion 1351. .

  In the annular negative electrode plate 1350 configured in this manner, the annular thick portion 1351 is coaxially formed by laser welding on the inner peripheral surface 1353 to the extending end portion of the cylindrical small diameter portion 1323 of the inner casing member 1320. Is fitted. Further, the annular thin portion 1352 is fixed to the annular bottom wall portion 1332 of the outer casing member 1330 from below by an annular lower surface 1354 by laser welding. Here, the axial thickness of the annular thick portion 1351 is larger than the sum of the axial thickness of the annular thin portion 1352 and the thickness of the annular bottom wall portion 1332 of the outer casing member 1330.

  As a result, the negative electrode plate 1350 projects at the annular thick portion 1351 in the extending direction of the cylindrical small-diameter portion 1323 (downward of the annular bottom wall portion 1332 of the outer casing member 1330). The bottom surface 1355 of the portion 1351 is seated on the bottom surface 112 of the insertion hole 110 of the cylinder head 100. This means that the negative electrode plate 1350, in combination with the inner casing member 1320 and the outer casing member 1330, serves as an annular bottom wall of the metal casing 1310 and is seated on the bottom surface 112 of the insertion hole 110. means.

  The negative electrode plate 1350 serves as the annular bottom wall of the metal casing 1310 as described above. The negative electrode plate 1350 is basically formed on both sides of the piezoelectric plate 1360 together with the positive electrode plate 1370. It plays a role as an electrode. Accordingly, the piezoelectric plate 1360 is stacked on the negative electrode plate 1350 and the positive electrode plate 1370 is stacked on the piezoelectric plate 1360. As a result, the piezoelectric plate 1360 exhibits a piezoelectric conversion action while being sandwiched between the negative electrode plate 1350 and the positive electrode plate 1370.

  However, as described above, the annular thick portion 1351 has a radial thickness equal to or greater than the sum of the radial thickness of the piezoelectric plate 1360 and the radial thickness of the electrical insulating member 1390. Utilizing this, the positive electrode plate 1370 and the piezoelectric plate 1360 are positioned on the thick portion 1351 of the negative electrode plate 1350 together with the electrical insulating member 1380 (see FIG. 2). The piezoelectric plate 1360 is formed of a piezoelectric material.

  The detection body 1300 has a positive-side covered lead wire 1371, and this positive-side covered lead wire 1371 is electrically connected to the positive-side electrode plate 1360 by brazing or resistance welding at its inner end connection portion. Has been. The positive-side covered lead wire 1371 extends in the axial direction along the outer peripheral surface of the metal cylinder 1100 from the annular upper opening 1312 of the metal casing 1310. Thus, by extending the positive-side covered lead wire 1371 along the outer peripheral surface of the metal cylinder 1100 in the axial direction, space saving in the cylinder 1100 can be ensured. Note that the extended tip end portion of the positive-side covered lead wire 1371 is electrically connected to the inner end portion of the terminal 1214 in the connector main body 1210 of the connector 1200.

  In the present embodiment, the negative electrode plate 1350 serves as a ground terminal of the pressure detection device via the metal casing 1310. Note that the extended tip end portion of the positive-side covered lead wire 1371 is covered with an insulating rubber member 1372 (see FIG. 1) fixed to the opening 1110 of the metal cylinder 1100. The terminal 1214 is provided in the connector portion 1213 of the connector 1200 so that it can be connected to an external circuit (not shown).

  The electrically insulating member 1380 is made of an electrically insulating material and is formed in a ring plate shape. The electrically insulating member 1380 is formed on the positive electrode plate 1370 so as to be stacked on the cylindrical small diameter portion 1323 of the inner casing member 1320. And is sandwiched between the annular intermediate wall 1322 of the inner casing member 1320 and the positive electrode plate 1370. As a result, the electrical insulating member 1380 electrically insulates the inner casing member 1320 from the positive electrode plate 1370.

  In addition, the electrical insulation member 1390 is formed in a cylindrical shape with an electrical insulation material, and this electrical insulation member 1390 is coaxially fitted to the cylindrical small-diameter portion 1323 of the inner casing member 1320 to form an inner casing. The member 1320 is electrically insulated from the positive electrode plate 1370.

  Of the annular pressure detecting element 1340, the two electrical insulating members 1380 and 1390, and the positive-side covered lead wire 1371, the portion located between the inner casing member 1320 and the outer casing member 1330 is the inner casing member 1320 and the outer casing member. It is molded by filling a molding member 1301 made of an electrically insulating resin material in between 1330.

  Accordingly, the positions of the piezoelectric plate 1360 and the positive electrode plate 1370 between the inner and outer casing members 1320 and 1330 can be maintained more securely, and the inner casing member of the piezoelectric plate 1360 and the positive electrode plate 1370 can be maintained. The electrical insulation from 1320 can be secured even better in combination with both electrical insulation members 1380 and 1390.

  In the present embodiment, the spark plug 2000 passes through the cylindrical portion 1211 of the connector 1200 and is inserted into the insertion hole 110 of the cylinder head 100. The spark plug 2000 includes a cylindrical insulator 2100, and a terminal fitting 2200 is inserted into the insulator 2100 together with the center electrode 2300 from the base end side of the insulator 2100.

  The metal shell 2400 is fixed to the tip side portion of the insulator 2100, and the metal shell 2400 has a mounting screw portion 2410 at the tip. Further, the metal shell 2400 has an annular flange 2420, and the annular flange 2420 is formed to project outward in a ring shape at a position directly above the attachment screw portion 2410 in the metal shell 2400. The center electrode 2300 protrudes from the mounting screw portion 2410 of the metal shell 2400 and constitutes a discharge portion together with the ground electrode 2430 fixed to the metal shell 2400.

  Thus, the spark plug 2000 is fastened to a screw hole 140 formed in a portion of the cylinder head 100 that is coaxially located at the center of the bottom of the insertion hole 110 at the attachment screw 2424 of the metal shell 2400. ing. Accordingly, the spark plug 2000 is configured such that the pressure detection element 1340 is inserted into the insertion hole 110 via the annular intermediate wall 1322 of the inner casing member 1320 and the electrical insulating member 1380 at the annular flange 2420 of the metal shell 2400. It is sandwiched between the bottom surface 112 and exposed to the combustion chamber 130 of the internal combustion engine at the discharge portion.

  Further, as shown in FIG. 1, a cylindrical member 2500 made of an electrically insulating rubber material is inserted into the insertion hole 110 of the cylinder head 100 through the cylindrical portion 1211 of the connector 1200. At the tip, the insulator 2100 of the spark plug 2000 is fitted from the outside into the upper part of the metal shell 2400.

  Further, the ignition device 3000 is supported by the upper end portion of the cylindrical portion 1211 of the connector 1200 with a grommet 3110 (having the same configuration as the grommet 1220) provided on the bottom wall of the casing 3100. The ignition device 3000 The covered lead wire 3200 passes through the inside of the cylindrical member 2500 and is electrically connected to the base end portion of the terminal fitting 2200 of the spark plug 2000.

  In this embodiment configured as described above, the negative electrode plate 1350 of the pressure detection element 1340 protrudes downward from the annular lower opening 1311 of the casing 1310 at the annular thick portion 1351 as described above. Yes. In other words, the negative electrode plate 1350 protrudes in the extending direction of the cylindrical small diameter portion 1323 from the extending end of the cylindrical small diameter portion 1323 of the inner casing member 1320 and the annular bottom wall portion 1332 of the outer casing member 1330. ing.

  Further, the cylindrical small diameter portion 1323 of the inner casing member 1320 is formed by laser welding without depending on caulking on the inner peripheral surface 1353 of the annular thick portion 1351 of the negative electrode plate 1350 at its extended end. The annular bottom wall portion 1332 of the outer casing member 1330 is fixed to the lower surface 1354 of the annular thin portion 1352 of the negative electrode plate 1350 by laser welding without depending on caulking. Therefore, the weld bead is not formed on the bottom surface side of the casing 1310.

  With the above configuration, the seat surface shape of the casing 1310 can be realized in a stable shape with the annular thick portion 1351 of the negative electrode plate 1350 without depending on caulking. Therefore, only the negative electrode plate 1350 is not the bottom of the casing 1310, in other words, the cylindrical small-diameter portion 1323 of the inner casing member 1320 and the annular bottom wall portion 1332 of the outer casing member 1330. The lower surface 1355 of the cylinder head 100 is seated on the bottom surface 112 of the insertion hole 110 of the cylinder head 100.

  This means that the pressure detecting device 1000 can be stably seated on the bottom surface 112 in the insertion hole 110 of the cylinder head 100 with the annular thick part 1351 of the negative electrode plate 1350. To do. As a result, the pressure detection element 1340, and thus the piezoelectric plate 1360, can be maintained in a state where the piezoelectric conversion action can be properly exhibited.

  Further, the spark plug 2000 is inserted into the cylinder 1100 and fastened to the screw hole 140 of the cylinder head 100 with a mounting screw part 2410. Therefore, the spark plug 2000 is configured such that the pressure detection element 1340 is connected to the insertion hole 110 via the annular intermediate wall 1322 of the inner casing member 1320 and the electrical insulating member 1380 at the annular flange 2420 of the metal shell 2400. It is sandwiched between the bottom surface 112.

  At this time, as described above, the pressure detection device 1000 is stably seated on the bottom surface 112 in the insertion hole 110 of the cylinder head 100 with the annular thick part 1351 of the negative electrode plate 1350. Therefore, the pressure detecting element 1340 can be favorably held by the spark plug 2000 described above. As a result, the pressure detection element 1340 and, in turn, the piezoelectric plate 1360 can appropriately exhibit the piezoelectric conversion action.

  Further, as described above, the annular thick portion 1351 of the negative electrode plate 1350 has a radial thickness equal to or greater than the sum of the radial thickness of the piezoelectric plate 1360 and the radial thickness of the electrical insulating member 1390. Utilizing this, the piezoelectric plate 1360 is laminated only on the annular thick portion 1351.

  Accordingly, the entire piezoelectric plate 1360 can be firmly held between the annular intermediate wall portion 1322 of the inner casing member 1320 and the bottom surface 112 of the insertion hole 110 of the cylinder head 100 on the annular thick portion 1351. As a result, the pressure detection element 1340 and, in turn, the piezoelectric plate 1360 can exhibit the piezoelectric conversion action more appropriately, and the seal between the insertion hole 110 of the cylinder head 100 and the combustion chamber 130. Good maintainability.

In carrying out the present invention, the following various modifications are possible without being limited to the above embodiment.
(1) In the negative electrode plate 1350, the upper surface of the annular thin portion 1352 may not be in the same plane as the upper surface of the annular thick portion 1351.
(2) The cylinder 1100 or the casing 1310 is not limited to being made of metal, and may be made of, for example, a synthetic resin.

1 is a longitudinal sectional view showing a state in which an embodiment of a pressure detection device according to the present invention is attached to a cylinder head of an internal combustion engine together with an ignition device. FIG. 2 is an enlarged partial half sectional view of the detection body and spark plug of FIG. 1.

Explanation of symbols

1100 ... cylinder, 1310 ... casing, 1311 ... annular lower opening,
1320 ... Inner casing member, 1321 ... Cylindrical large diameter portion, 1322 ... An annular intermediate wall portion,
1323 ... cylindrical small diameter part, 1330 ... outer casing member, 1332 ... annular bottom wall part,
1331 ... Cylinder surrounding part, 1340 ... Pressure detection element, 1350 ... Negative electrode plate,
1351 ... An annular thick part, 1352 ... An annular thin part, 1360 ... Piezoelectric plate,
1360: Positive electrode plate, 1380, 1390: Electrical insulating member.

Claims (2)

A cylindrical body, a casing and a pressure detection element are provided.
The casing is
A cylindrical large-diameter portion extending from the tip of the cylindrical body, an annular intermediate wall portion extending radially inward from the extended end of the cylindrical large-diameter portion, and the annular intermediate An inner casing member provided with a cylindrical small diameter portion extending in the extending direction of the cylindrical large diameter portion from the inner peripheral edge of the wall portion;
A cylindrical surrounding portion that surrounds the inner casing member from its periphery, and an extension of the cylindrical small diameter portion that extends radially inward from an end portion on the cylindrical small diameter portion side of the cylindrical surrounding portion. An outer casing member provided with an annular bottom wall portion having an inner peripheral edge portion formed with an annular opening portion between the protruding end portion, and
The pressure detection element includes each annular piezoelectric body and a pair of electrodes,
One electrode of the pair of electrodes is
An annular thick portion disposed coaxially with the cylindrical small-diameter portion so as to protrude through the annular opening in the extending direction of the cylindrical small-diameter portion between the inner and outer casing members. An annular thick portion formed by welding the extended end portion of the cylindrical small-diameter portion of the inner casing member on the inner peripheral surface of the lever, and the annular thick portion is thinner than the annular thick portion. An annular thin-walled portion extending radially outward from the meat portion and secured by welding onto the annular bottom wall portion of the outer casing member;
The annular piezoelectric body is coaxially disposed on the cylindrical small diameter portion so as to be laminated on the one electrode,
The other electrode of the pair of electrodes is coaxially disposed on the cylindrical small diameter portion so as to be laminated on the annular piezoelectric body, and the annular intermediate wall portion of the inner casing member together with the annular piezoelectric body. And a pressure detection device sandwiched between the one electrode.   The pressure detection device according to claim 1, wherein the annular piezoelectric body is laminated only on the annular thick portion.

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