JP2002243571A - Plug with built-in pressure sensor and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a pressure sensor with water resistance and air tightness by forming a welded portion for fixing a sensor case to a metal shell without forming welding defects due to gap formation. Provided is a plug with a built-in pressure sensor having excellent durability and a method of manufacturing the same. The outer surface of a case support portion formed on a second bulging portion has a reduced diameter surface that continuously decreases in diameter in a forward direction in the axial direction.
The bottom 2 of the sensor case 21 is
An engaging portion 21c protruding from the inner peripheral front end side of 1b is swaged from the outside. Along the circumferential direction of the sensor case 21, the front end edge of the engaging portion 21c and the reduced diameter surface 11t of the case supporting portion 11s
Is applied over the entire circumference to form a welded portion W1 on the reduced diameter surface 11t over the entire circumference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plug with a built-in pressure sensor mounted on an internal combustion engine and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, by measuring the pressure (in-cylinder pressure) of a combustion chamber of an internal combustion engine, for example, knocking detection,
It detects the peak position of the combustion pressure, detects misfire, and the like, and is useful for controlling the operation of the internal combustion engine. In some cases, a pressure sensor provided with a piezoelectric element such as an annular piezoelectric ceramic is used for measuring the in-cylinder pressure. Such a pressure sensor is disposed, for example, on a metal shell of a spark plug, which is an embodiment of a plug, and is mounted by screwing a male thread formed on the metal shell and a female thread of a cylinder head.
The spark plug is pushed up by the combustion pressure, and the tightening load on the cylinder head of the spark plug fluctuates. The electrical output generated by the piezoelectric element in response to the fluctuation of the load is taken out to the outside via a lead wire. Is measured.

As an example of a spark plug with a pressure sensor as described above, Japanese Patent Application Laid-Open No. 6-52967 and Japanese Patent Application Laid-Open
There is a type with a built-in pressure sensor as shown in JP-A-290853. In this type, a pressure sensor containing an insulating plate, a piezoelectric element, an electrode plate, and the like in a sensor case is integrally mounted on a mounting seat of a metal shell, and a pressure is applied between the mounting seat and a seat surface of a plug hole. In this method, the sensor is pressed and held. In such a pressure sensor built-in type, in order to integrally mount the pressure sensor to the mounting seat of the metal shell, the side surface and the front end surface side of the piezoelectric element and the like are respectively covered by a cylindrical portion and a bottom portion. Is generally joined to the mounting seat by laser welding or the like.

Conventionally, a bottom portion of a sensor case covering a front end face of a piezoelectric element or the like and a mounting seat portion of a metal shell are joined as shown in FIG. 7, for example. The spark plug 100 with a built-in pressure sensor shown in FIG. 7 has a front end side in the axial direction (below the figure).
Is attached to a plug hole (not shown) of the internal combustion engine, and has a metallic shell 111.
And an annular pressure sensor 120. And
The metal shell 111 has a first bulging portion 11 bulging in the radial direction.
1c1 and a second bulging portion 111c2 bulging in the radial direction with an outer diameter smaller than that of the first bulging portion 111c1 so as to follow the front end side of the first bulging portion 111c1. .
Further, the pressure sensor 120 includes a piezoelectric element 123 that generates an electrical output based on the pressure of the combustion chamber, and a side surface and a front end surface side of the piezoelectric element 123 outside the piezoelectric element 123, each of which has a cylindrical portion 121a and a bottom portion. And a sensor case 121 that surrounds the sensor case 121b so as to cover it in a half-section L-shape.
Further, the pressure sensor 120 is configured such that the second bulging portion 111c2 is inserted inward along the axial direction, and that the seating surface (not shown) of the plug hole and the first bulging portion 1 facing the same are provided.
It is sandwiched between the end face 111f of 11c1 and held at a predetermined pressing force in the axial direction.

[0005]

The second bulge 1
A front end outer peripheral surface of 11c2 and an inner edge tip (inner peripheral surface) of bottom 121b of sensor case 121 are arranged in abutting manner, and laser beam LB from laser welding machine LW is applied along the circumferential direction of sensor case 121. By irradiating and performing laser welding (seam welding), a welded portion W1 that extends over the inner edge tip (inner peripheral surface) of the bottom portion 121b and the outer peripheral surface of the front end portion of the second bulging portion 111c2 is formed all around.

Since the sensor case 121 needs to be covered from the side of the mounting screw portion 111a (front side) formed on the metallic shell 111 in a manner following the front end side of the second bulging portion 111c2, the inner diameter of the bottom portion 121b is required. Is the mounting screw 11
The gap S1 is larger than the radius 1a (the thread radius of the external thread 111a ') R0. Since the radius of the internal thread formed in the plug hole is set in advance, the thread radius R0 of the external thread 111a 'to be screwed therewith is constant, so that the inner edge tip of the bottom 121b in the radial direction (inside The position of the peripheral surface) is substantially determined.

On the other hand, in order to increase the surface area of the end face of the piezoelectric element 123 and the like to reduce the supporting load per unit area (the pressing force in the axial direction) and to improve the durability of the piezoelectric element 123 and the like, Since there is a demand to make the radius R2 of the bulging portion 111c2 as small as possible,
A gap S2 tends to be formed between the inner edge tip (inner peripheral surface) of b and the outer peripheral surface of the second bulging portion 111c2. At this time, the welded portion W1 may not completely fill the gap S2 and may cause a defect such as a hole, and the water resistance and airtightness of the pressure sensor 120 may not be secured. Durability (lifetime) of built-in spark plug 100
May be impaired.

Accordingly, an object of the present invention is to provide a pressure sensor with water resistance and airtightness in which a welded portion for fixing a sensor case to a metal shell is formed all around without causing welding defects due to gap formation. Accordingly, an object of the present invention is to provide a plug with a built-in pressure sensor having excellent durability and a method of manufacturing the same.

[0009]

In order to solve the above-mentioned problems, a plug with a built-in pressure sensor according to the present invention is intended to be mounted on a plug hole of an internal combustion engine at a front end side in an axial direction, and to expand radially. A first bulging portion that protrudes, and a second bulging portion that bulges in a radial direction with an outer diameter smaller than the first bulging portion in a form following the front end side of the first bulging portion. A plug body having the metal shell formed therein, a piezoelectric element that generates an electrical output based on the pressure of the combustion chamber, and a side surface side and a front end surface side of the piezoelectric element outside the piezoelectric element, each of which is a cylindrical portion. And a sensor case that surrounds the sensor case so as to be covered with the bottom portion. The second bulging portion is inserted inside along the axial direction, and the seating surface of the plug hole and the first bulging portion facing the plug hole. Between the end face of the protrusion and the predetermined pressing force in the axial direction. An annular pressure sensor that is held, a case supporting portion formed in the second bulging portion, and a welded portion that spans an inner edge bent toward the axial front end of the bottom of the sensor case, It is characterized in that it is formed all around the sensor case in the circumferential direction.

That is, in the present invention, the case supporting portion formed in the second bulging portion and the welded portion extending over the inner edge bent toward the front end in the axial direction of the bottom portion of the sensor case are formed as follows.
Since the sensor case is formed all around the circumferential direction, welding defects due to the formation of a gap between the welding members (that is, between the case supporting portion and the inner edge bent toward the front end in the axial direction of the bottom portion) are less likely to occur. . Therefore, since the welded portion for fixing the sensor case to the metal shell is formed without generating welding defects due to the formation of the gap, the water resistance and airtightness of the pressure sensor can be sufficiently ensured, and the pressure sensor having excellent durability can be obtained. A plug with a built-in sensor can be easily obtained.

Further, the welded portion is formed all around the case supporting portion of the second bulging portion and the inner edge of the bottom portion of the sensor case bent toward the front end in the axial direction, and the tip of the sensor case is located closer to the tip than the welded portion. Since it does not protrude to the front end side, for example, a mounting screw part (male screw) formed on the metal shell in a form following the front end side of the second bulging part is a screw part (female screw) formed on the cylinder head of the internal combustion engine. There is no possibility that the bottom or the welded portion of the sensor case will interfere with the metallic shell when mounting the sensor case.

At this time, if the welded portion is positioned axially forward of the bottom outer surface of the sensor case, the welded portion can be formed all around while pressing the bottom outer surface of the sensor case from the outside. This is advantageous in securing an arrangement space for the pressing tool.

The case supporting portion formed in the second bulging portion has a diameter-reducing surface that continuously reduces in diameter in the forward direction in the axial direction, and the welded portion is formed on the diameter-reducing surface. Is desirable. Accordingly, the welded portion extending between the reduced diameter surface of the case support portion that continuously reduces in diameter in the forward direction in the axial direction and the inner edge bent toward the axial front end of the bottom of the sensor case is formed in the circumferential direction of the sensor case. Along the entire circumference. Therefore, a welding defect due to the formation of a gap is unlikely to occur between the two welding members (that is, between the reduced-diameter surface of the case support portion and the inner edge bent toward the front end in the axial direction of the bottom portion). Airtightness is more reliably ensured.

At this time, the outer edge diameter D4 of the welded portion is formed to be smaller than the thread diameter D0 of the mounting screw portion formed on the metal shell so as to follow the front end side of the second bulging portion. When the mounting screw portion of the metal shell is screwed into the screw portion of the cylinder head, the welding portion can be smoothly mounted without interfering with the cylinder head side. Further, even if the welded portion is broken due to poor welding or the like, the sensor case does not slip through the mounting screw portion and fall off.

The attachment of the sensor case to the metallic shell is performed, for example, by engaging an engagement portion projecting toward the inner front end of the bottom of the sensor case with respect to a case support formed at the second bulging portion. This is realized by caulking from the outside.

Therefore, when the inner edge diameter D3 of the bottom of the sensor case is formed to be larger than the outer diameter D2 of the second bulging portion, the above-described engagement of the sensor case is carried out by the case supporting portion having the reduced diameter surface. When caulking the joint portion, the engaging portion is easily bent along the reduced diameter surface. Therefore, a gap is not easily formed between the reduced-diameter surface of the case supporting portion and the inner surface of the engaging portion, so that welding defects are less likely to occur.

Next, in order to solve the above-mentioned problems, a method for manufacturing a plug with a built-in pressure sensor according to the present invention is provided in which the front end side in the axial direction is scheduled to be attached to a plug hole of an internal combustion engine, and A first bulging portion that bulges out,
A plug body having a metal shell formed with a second bulging portion bulging in a radial direction with an outer diameter smaller than that of the first bulging portion in a form following the front end side of the first bulging portion. On the other hand, outside the piezoelectric element that generates an electrical output based on the pressure of the combustion chamber, the side surface and the front end surface of the piezoelectric element are surrounded by a cylindrical portion and a bottom portion of the sensor case, respectively. An annular pressure sensor is assembled so that the second bulging portion is inserted inward along the axial direction, and the bottom portion of the sensor case is formed with respect to a case supporting portion formed in the second bulging portion. The outer circumferential end of the sensor case is swaged along the circumferential direction of the sensor case and spans the front end edge of the engaging portion and the outer peripheral surface of the case supporting portion. It is characterized by doing.

According to the present invention, when the plug body is assembled so that the second bulge portion of the plug body is inserted inside the pressure sensor along the axial direction, the case support formed on the second bulge portion is provided. The pressure sensor can be easily set with respect to the plug body by crimping an engaging portion projecting from the inner peripheral front end side of the bottom of the sensor case to the plug body. As a result, the next step, a weld forming step,
In other words, the process of welding the entire circumference along the circumferential direction of the sensor case and across the front end edge of the engaging portion and the outer peripheral surface of the case supporting portion can be quickly performed, and the manufacturing process can be simplified.

The front end inner edge diameter D of the engaging portion before caulking.
A step of fitting and fixing the cylindrical portion of the sensor case, which is formed larger than the thread diameter D0 of the mounting screw portion of the metallic shell, to the first bulging portion of the plug body; The process of caulking the engagement part of the sensor case to the part, and the step of welding the entire circumference on the reduced diameter surface in sequence, assembling the plug with built-in pressure sensor without the need for advanced skills and expensive jigs etc. Efficiency can be improved.

[0020]

Embodiments of the present invention will now be described with reference to the embodiments shown in the drawings. FIG. 1 is a half sectional front view of a spark plug with a built-in pressure sensor according to one embodiment of the present invention, and FIG. 2 is a partially cutaway front view showing an enlarged main part thereof. The spark plug with a built-in pressure sensor 1 (plug with a built-in pressure sensor) has a spark plug body 10 (a plug body) and a pressure sensor 20 integrally attached to a metal shell 11 of the spark plug body 10.
In the following description, the side toward the plug hole PH of the spark plug 1 with a built-in pressure sensor, that is, the side toward the combustion chamber CR is referred to as “front side” (or “front end side”), and the side toward the opposite direction is referred to as “rear side”. (Or “rear end side”).

In FIG. 1, the front end of the spark plug 1 with a built-in pressure sensor is formed at the innermost part (forwardmost part) of a plug hole PH formed in the cylinder head of the internal combustion engine, and is formed to communicate with the combustion chamber CR. It is inserted into the insertion hole 111, and is disposed in the plug hole PH such that the tip thereof enters the combustion chamber CR of the internal combustion engine. When a high voltage generated in the ignition coil unit is applied to the spark plug body 10 via the high voltage supply unit, a spark discharge is generated in the combustion chamber CR to burn the air-fuel mixture. The pressure (in-cylinder pressure) of the combustion chamber CR at this time is measured by the pressure sensor 20 to perform, for example, knocking detection, combustion pressure peak position detection, misfire detection, and the like, which is used for operation control of the internal combustion engine.

In the spark plug body 10 shown in FIG. 1, an insulator 12 made of a ceramic sintered body such as alumina or aluminum nitride is fitted inside a metallic shell 11 formed in a cylindrical shape. A leg long portion 12b formed on the distal end side projects forward from the metal shell 11. On the other hand, a rear portion of the insulator 12 extends from a rear end of the metal shell 11 to form a corrugation portion 12a on the rear end side, and a terminal electrode 13 projects rearward from the rear end of the corrugation portion 12a. A center electrode 14 electrically connected to the terminal electrode 13 projects forward from the tip of the leg portion 12b. The other end of the ground electrode 15, one end of which is joined to the tip of the metal shell 11, is bent laterally, and its side faces the tip of the center electrode 14, and the spark discharge gap g
Is formed.

The metal shell 11 is formed at the bottom of the cylinder head of the internal combustion engine from the front side, and is formed in the insertion hole 111 communicating with the combustion chamber.
A mounting screw portion 11a having a cylindrical shape formed with 1a ', a gasket 11b for sealing leakage of combustion gas, a mounting seat portion 11c for fixing the pressure sensor 20 to a seat surface, and a male screw formed on the mounting screw portion 11a. A tool engaging portion 11 with which a tool such as a plug wrench is engaged to advance the screw 11a '
d. As shown in FIG. 4A, the mounting seat 11c includes a first bulging portion 11c1 bulging in a radial direction,
A second bulging portion 11c2 bulging in the radial direction with an outer diameter smaller than that of the first bulging portion 11c1 in a form following the plug hole mounting side (front side) of the first bulging portion 11c1. It is formed in stages.

The second bulging portion 11 of the mounting seat 11c
c2 is inserted along the axial direction on the inner peripheral surface side of the pressure sensor 20, and the pressure sensor 20 is connected to the seat surface S of the plug hole PH (in FIG. 1, the gasket 11b is directly in contact; In some cases) and the sensor supporting end face 11 of the first bulging portion 11c1 opposed thereto.
f, and is pressed and held in the axial direction. The inner peripheral surface of the cylindrical portion 21a of the sensor case 21 is fitted and fixed to the outer peripheral surface of the first bulging portion 11c1 of the mounting seat portion 11c by interference fit, and a temporary fixing portion T is formed on the cylindrical portion 21a. Have been.

As shown in FIG. 2, the cylindrical portion 21a and the bottom 2
1b is lower (front) on the bottom 21b in the inner space of the annular sensor case 21 formed in a half-section L-shape.
The packing 22, the piezoelectric element 23, the electrode plate 24, and the insulating plate 25, each of which is formed in an annular shape so as to be sequentially stacked from one another, are housed to form a pressure sensor 20. A lead wire 27 extends rearward from a terminal 24a formed on the outer peripheral edge of the annular electrode plate 24, and takes out the electrical output of the piezoelectric element 23 based on the pressure in the combustion chamber CR to the outside.
The insulating tube 29 of the pressure sensor 20 is placed on the second bulging portion 11c2 so as to be located inside the piezoelectric element 23.

The outer surface of the case supporting portion 11s formed at the front end of the second bulging portion 11c1 is formed with a reduced diameter surface 11t which continuously reduces its diameter as it goes forward in the axial direction. The inner surface of an engaging portion 21c formed to project from the inner peripheral front end of the bottom 21b of the sensor case 21 is in contact with the reduced diameter surface 11t so as to overlap from the outside. Along the circumferential direction of the sensor case 21, the entire circumference is welded over the front end edge of the engaging portion 21 c and the reduced diameter surface 11 t of the case supporting portion 11 s, so that the reduced diameter surface 1 is formed.
Above 1t, a first welded portion W1 (welded portion) which is immovable in the axial direction and fixed in a closed state is formed in the engaging portion 21c.

As described above, the reduced-diameter surface 11t of the case supporting portion 11s and the inner surface of the engaging portion 21c abut on each other so as to overlap with each other, and the front end edge of the engaging portion 21c and the reduced-diameter surface 11t of the case supporting portion 11s contact each other. Since the laser welding is performed all around, welding defects due to the formation of a gap between the case supporting portion 11s and the engaging portion 21c are unlikely to occur. The weld W1 is
Because it is located on the axially forward side of the outer surface of the bottom 21b of the sensor case 21, the bottom 21b of the sensor case 21
When forming the welded portion W1 while pressing the outer surface from the outside,
This is advantageous in securing an arrangement space for the pressing tool (see P in FIG. 6A).

Further, the cylindrical portion 21a is overlapped with a part of the temporary fixing portion T at the axially intermediate portion of the cylindrical portion 21a.
By performing laser welding along the entire circumference of the cylindrical portion 21a, a second welded portion W2 that is immovable in the axial direction and fixed in a sealed state is formed in the cylindrical portion 21a.

As shown in FIG. 2, the outer edge diameter D4 of the welded portion W1 is obtained.
In a shape following the front end side of the second bulging portion 11c2.
Is smaller than the thread diameter D0 of the mounting screw portion 11a. Thereby, when screwing the mounting screw portion 11a of the metal shell 11 to the screw portion of the cylinder head,
The welded portion W1 does not interfere with the cylinder head side.

The inner diameter D3 of the bottom 21b of the sensor case 21 is larger than the outer diameter D2 of the second bulging portion 11c2. Accordingly, when the engaging portion 21c of the sensor case 21 is swaged to the case supporting portion 11s having the reduced diameter surface 11t, the inner edge of the bottom portion 21b is formed by the second bulging portion 11c2.
Is not in contact with the outer peripheral surface from the beginning, it is easy to bend the engaging portion 21c along the reduced diameter surface 11t. The inner edge diameter D3 of the bottom portion 21b is, specifically,
The bottom portion 21b and the engagement portion 21
Represented by the intersection K of the extension of each inner edge of c.

As shown in FIG. 3, a slit-shaped opening 11 is formed in the outer peripheral edge of the first bulging portion 11c1 of the metal shell 11 and the tool engaging portion 11d in order to arrange the lead wire 27.
j, and a tool engaging portion side receiving portion 11 also having a slit-like opening 11k on the outer peripheral edge.
h are formed along the axial direction. The slit-like opening 11j of the first bulging portion 11c1 and the slit-like opening 11k of the tool engaging portion 11d are arranged at positions substantially corresponding to each other in the circumferential direction.

Therefore, the terminals 24 of the annular electrode plate 24
The lead wire 27 drawn rearward from FIG. 1a passes through the mounting seat side receiving portion 11g (slit-shaped opening 11j) of the first bulging portion 11c1, and furthermore, the tool engaging portion 11d receives the tool engaging portion 11d. The plug hole PH extends rearward through a portion 11h (slit-like opening 11k), and is drawn out from the rear end opening of the plug hole PH. At this time, two slit-shaped openings 1
1j and 11k to connect the lead wire 27 to the first bulging portion 11.
lead wire accommodating portion 11g, 1 between c1 and tool engaging portion 11d
It can be stored almost simultaneously in 1h, and held almost linearly.

In the first bulging portion 11c1, the slit-like opening 11j of the mounting seat side receiving portion 11g is closed by the rear inner surface of the cylindrical portion 21a of the sensor case 21,
The rear end edge of the cylindrical portion 21a of the sensor case 21 is connected to the rear end face 11e of the first bulging portion 11c1 (the mounting seat side housing portion 1).
1g). At least the inner surface of the sensor case 21 and the mounting seat-side housing portion 11g
Between the lead wire 27 and the first bulging portion 11
A filling layer 26 of a polymer material (for example, silicone rubber, fluorosilicone rubber, epoxy resin, etc.) is formed in the internal space of the sensor case 21 behind the rear end face 11e of c1. Further, in the internal space of the sensor case 21, for example, the inner peripheral surface of the sensor case 21 and the piezoelectric element 23
Of the polymer material filled layer 2
6 may be sealed. As described above, since the pressure sensor 20 is formed integrally with the mounting seat 11c of the metal shell 11, the water resistance and airtightness are sufficiently maintained by the sensor case 21 and the filling layer 26.

Next, FIGS. 4 to 6 show a process of assembling the spark plug 1 with a built-in pressure sensor of FIG. In the inner space of the cylindrical portion 21a of the sensor case 21, a plate packing 22, a piezoelectric element 23, and an electrode
Then, the pressure sensor 20 is assembled by housing the insulating plate 25 on the bottom portion 21b in a sequentially stacked manner from below (front). On the inner peripheral surface side of the pressure sensor 20 assembled in this manner, the mounting seat portion 11c covering the insulating tube 29 is provided.
When the second bulging portion 11c2 is relatively moved along the axial direction and inserted therethrough, the pressure sensor 20 detects the first bulging portion 11c1.
Is pressed and held in the axial direction by a predetermined pressing force on the sensor supporting end face 11f side (FIG. 4A). At this time, the electrode plate 2
The lead wire 27 connected to the fourth terminal 24a is accommodated in the mounting seat side accommodating portion 11g and the tool engaging portion side accommodating portion 11h from the outside in the radial direction through the two slit-shaped openings 11j and 11k almost simultaneously. Further, the inner peripheral surface of the cylindrical portion 21a is fitted and fixed to the outer peripheral surface of the first bulging portion 11c1 by interference fit, and a temporary fixing portion T is formed in the cylindrical portion 21a. At this time, the rear end edge of the cylindrical portion 21a of the sensor case 21 is pushed down to a state protruding rearward from the rear end surface 11e of the first bulging portion 11c1 (FIG. 4B).

On the other hand, focusing on the front end side of the sensor case 21, the front end inner edge diameter D of the engaging portion 21c formed on the inner peripheral front end side of the bottom portion 21b of the sensor case 21 before caulking is formed.
1 'is the thread diameter D0 of the mounting screw portion 11a of the metal shell 11.
The mounting screw portion 11a of the metal shell 11 is provided with the engaging portion 21 of the sensor case 21 from the rear side.
c and protrudes from the front side (FIG. 5).
(A)). Next, a case supporting portion 11s having a diameter-reduced surface 11t whose diameter is continuously reduced toward the front in the axial direction.
By crimping the engaging portion 21c,
The inner surface of the engaging portion 21c abuts on t such that it overlaps from the outside. As a result, the front end inner edge diameter D of the engagement portion 21c
1 is formed smaller than the thread diameter D0 of the mounting screw portion 11a (FIG. 5B).

Spark plug body 10 and pressure sensor 20
And the sensor case 21 is moved to the bottom 21
When the pressing tool P is pressed from the outside of the sensor case 2b, the sensor case 2
The pressure sensor 2 moves in the axial direction until the inner peripheral surface of the bottom 21b comes into contact with the outer surface of the lower end of the second bulging portion 11c2.
0 is pressed and held in the axial direction by a predetermined pressing force on the sensor supporting end face 11f side of the first bulging portion 11c1. In this state, the laser welding machine LW is moved along the lower peripheral edge of the bottom 21b.
Irradiates the laser beam LB from above to perform laser welding all around, thereby forming a first welded portion W1 that is immovable in the axial direction and fixed in a closed state on the bottom portion 21b. Furthermore, the laser beam LB is irradiated from the laser welding machine LW along the entire circumference of the cylindrical portion 21a so as to be superimposed on a part of the temporary fixing portion T, and laser welding is performed. A second welded portion W2 is formed that is immovable in the axial direction and fixed in a sealed state.
(A)).

The spark plug body 10 and the pressure sensor 20 are turned upside down again, and the polymer material PM is injected into the internal space of the sensor case 21 by the polymer material injector RI to solidify the polymer material PM. The sensor case 21 is sealed by the filling layer 26. At this time, the first bulging portion 11c
1, the cylindrical portion 21a of the sensor case 21
Is used as a container (liquid reservoir) for injecting the polymer material PM, and the liquid polymer material PM is naturally dropped (vacuum is drawn from the front side of the sensor case 21). In some cases) and the capillary phenomenon, a gap in the sensor case 21 is filled with the polymer material PM. As described above, the spark plug 1 with a built-in pressure sensor
Is completed (FIG. 6B). FIG.
If the circumscribed circle diameter (maximum outer diameter) of the hexagonal tool engaging portion 11d is set smaller than the outer diameter of the first bulging portion 11c1 as shown in FIG. The installation space can be easily secured, and the injection work of the polymer material PM can be easily performed.

Although the above description has been given only of the embodiment of the spark plug with a built-in pressure sensor, the present invention can also be applied to a glow plug with a built-in pressure sensor. In the embodiment of the present invention, the spark plug with the built-in pressure sensor is fixed to the cylinder head by screwing a male screw formed in the mounting screw portion of the metal shell into the insertion hole of the plug hole and screwing it into the screw. However, a mode in which the mounting seat of the metal shell is pressed and fixed to the seating surface of the plug hole by other means is also applicable.

[Brief description of the drawings]

FIG. 1 is a half sectional front view of a spark plug with a built-in pressure sensor according to an embodiment of the present invention.

FIG. 2 is an enlarged partial cutaway front view of a main part of FIG. 1;

FIG. 3 is a partially enlarged perspective view of FIG. 1;

FIG. 4 is a perspective view and a partially broken front view showing an assembling process of the spark plug with a built-in pressure sensor of FIG. 1;

FIG. 5 is a partially cutaway front view showing an assembling step following FIG. 4;

FIG. 6 is a partially cutaway front view showing an assembling step following FIG. 5;

FIG. 7 is a partially cutaway front view showing a conventional structure for mounting a spark plug body and a pressure sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Spark plug with built-in pressure sensor (plug with built-in pressure sensor) 10 Spark plug main body (plug main body) 11 Metal shell 11a Mounting screw part 11c Mounting seat part 11c1 First bulging part 11c2 Second bulging part 11f Sensor supporting end face 11s Case support Part 11t Reduced diameter surface 20 Pressure sensor 21 Sensor case 21a Cylindrical part 21b Bottom part 21c Engaging part 23 Piezoelectric element CR Combustion chamber PH Plug hole S Seat surface W1 First welded part (welded part)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01T 13/40 H01T 13/40 21/02 21/02 (72) Inventor Takahiro Suzuki Mizuho-ku, Nagoya-shi, Aichi 14-18, Takatsuji-cho F-term (reference) 2F055 AA23 BB12 CC11 DD20 EE23 FF38 GG01 GG12 GG25 3G019 KA01 KA11 KA28 5G059 AA10 CC01 KK03

Claims (7)

[Claims] An axially front end is to be attached to a plug hole of an internal combustion engine, and has a first bulging portion bulging in a radial direction and a shape following the front end of the first bulging portion. A plug body having a metal shell formed with a second bulging portion bulging radially with an outer diameter smaller than the first bulging portion; and an electric output based on a pressure of the combustion chamber. A piezoelectric element to be generated, and a sensor case surrounding the piezoelectric element on the outer side of the piezoelectric element so as to cover a side surface and a front end surface of the piezoelectric element with a cylindrical portion and a bottom portion, respectively, and the second bulging portion. Is inserted inward along the axial direction, and is held between the seating surface of the plug hole and the end surface of the first bulging portion facing the plug hole at a predetermined pressing force in the axial direction. And a case support formed in the second bulging portion. A pressure sensor built-in pressure sensor, wherein a welded portion extending over a portion and an inner edge of the bottom of the sensor case bent toward the front end in the axial direction is formed all around the sensor case in a circumferential direction. . 2. The pressure sensor built-in plug according to claim 1, wherein the welding portion is located on the axial front side of the bottom outer surface of the sensor case. 3. The case support portion has a diameter-reducing surface that continuously reduces in diameter as it goes forward in the axial direction,
3. The plug with a built-in pressure sensor according to claim 1, wherein the welded portion is formed on the reduced diameter surface. 4. An outer edge diameter D4 of the welded portion is formed to be smaller than a thread diameter D0 of a mounting screw portion formed on the metal shell in a shape following the front end side of the second bulging portion. The plug with a built-in pressure sensor according to claim 1. 5. An inner edge diameter D of the bottom of the sensor case.
The pressure sensor built-in plug according to any one of claims 1 to 4, wherein 3 is formed to be larger than an outer diameter D2 of the second bulging portion. 6. A first bulging portion which is supposed to be attached to a plug hole of an internal combustion engine at a front end side in an axial direction and bulges in a radial direction, and which is connected to a front end side of the first bulging portion. A plug body having a metal shell formed with a second bulging portion bulging in the radial direction with an outer diameter smaller than the first bulging portion is electrically connected to the plug main body based on the pressure of the combustion chamber. Outside the piezoelectric element that generates an output, an annular pressure sensor that surrounds a side surface and a front end surface side of the piezoelectric element with a cylindrical portion and a bottom portion of the sensor case, respectively, wherein the second bulging portion Is engaged so as to be inserted inward along the axial direction, and engages with a case supporting portion formed on the second bulging portion so as to protrude from an inner peripheral front end side of the bottom portion of the sensor case. Caulking the part from the outside, along the circumferential direction of the sensor case, Pressure sensor internal plug manufacturing method characterized by circumferential welding across the front edge and the outer peripheral surface of the case supporting portion of the engaging portion. 7. A front end inner edge diameter D of the engaging portion before swaging.
1 ′, the cylindrical portion of the sensor case formed to be larger than the thread diameter D0 of the mounting screw portion formed in the metal shell in a form following the front end side of the second bulging portion, After being fitted and fixed to the first bulging portion of the plug body, the engaging portion is swaged to the case supporting portion having a diameter-reducing surface that continuously decreases in diameter in the axial direction. The method for manufacturing a plug with a built-in pressure sensor according to claim 6, wherein the entire circumference is welded on the reduced diameter surface.