JP2001249105A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calking structure for hermetically sealing and supporting against a main metal fitting an element for detecting a gas to be detected within exhaust gas. SOLUTION: This gas sensor has an element 2 disposed in the hollow section 105 of the main metal fitting 1. A gap between the element 2 and the main metal fitting 1 is filled with filling members 3, 4 and 6 so that the element 2 is integrated with and supported by the main metal fitting 1 and attached to an exhaust pipe. A bent section 102 formed at the upper end of the main metal fitting is thermally caulked whereby the filling members 3, 4 and 6 are pressurized to maintain good airtightness. A curved section 101 is provided at the root of the bent section and is formed with a stepped part 116 such that its thickness varies in steps, reducing variations in position of the bent section 101 formed when the curved section is bent by calking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor having a characteristic shape of a metal shell for fixing an element inside. In particular, the present invention relates to a gas sensor for detecting a detected gas concentration in a gas to be measured such as an exhaust gas discharged from an internal combustion engine or the like.

Conventionally, as a gas sensor for measuring a detected gas concentration in a gas to be measured, for example, an oxygen sensor having a cylindrical element described in JP-A-9-184822 or JP-A-11-295263 is used. Some are known, and the applicant has already filed an application in Japanese Patent Application No. 11-228322. Alternatively, as an oxygen sensor having a plate-like element, one described in Japanese Patent Application Laid-Open No. H11-271254 is known.

[0003]

In the above-mentioned conventional gas sensor, as a means for arranging the element 2 for detecting the detection gas in the flow path through which the gas to be measured flows, as shown in FIG. Element 2 with metal shell 1 having
And filling the gap between the metal shell 1 and the element 2 with filling members 3, 4, 6 made of a heat-resistant material such as talc or ceramic, and filling these filling materials 3, 4, 6 with the lower end of the inner space 105. The shoulder surface 111 formed in the opening 110 and the upper end opening 107
In the above, the metal shell 1 is sandwiched between bent portions 102 formed by bending the metal shell 1 inward, and the filling elements 3, 4, 6
And the gap between the element 2 and the metal shell 1 is hermetically sealed. The process of assembling such a gas sensor will be described with reference to FIGS. Bent part 1
FIG. 2 (a) shows a state before 02 is bent inward.
As described above, the vicinity of the upper end opening 107 of the metal shell 1 has a cylindrical shape extending straight upward. In this state, the SUS lower packing 7, the alumina holder 6, the SUS plate packing 8, the element 2, the talc seal ring 4, the alumina sleeve 3, the SU
The caulking packings 5 made of S are arranged one after another. Thereafter, the crimping die P is pressed and pressed from above, and the bent portion 1 is pressed.
2 was bent inward, and furthermore, pressure was applied in a heated state to squeeze and heat, and pressure was applied to the filling members 3, 4, and 6, and FIG.
As shown in (b), the gap between the element 2 and the metal shell 1 is hermetically sealed. However, in the gas sensor having such a structure, when the swaged portion A is shown in an enlarged manner, FIG.
As shown in (a), since the position where the bent portion 102 is bent inward cannot be specified, the dimensions of the bent portion 102 vary, and as a result, the caulking dimensions are different and the filling members 3, 4, There was a problem that the stress acting on No. 6 varied. As shown in FIG. 3A, when the metal shell 1 has a heat crimping portion 112 that is deformed while being heated at the time of crimping below the bent portion 102, the heat crimping portion 112 is pressurized. Therefore, the variation in the caulking dimensions of the heat caulking portion 112 has a significant effect on the pressing force applied to the filling members 3, 4, and 6. Further, even when the bent portion 102 is bent in a different size even in the case where there is no heat crimping portion as in FIG. 3B, the crimping size varies, and as a result, the same as in FIG. In addition, there is a problem that the pressure applied to the filling members 3, 4, and 6 varies.

The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a gas sensor of a type in which an element 2 is disposed in a metal shell 1, in which a gas-tight space is provided between the element 2 and the metal shell 1. An object of the present invention is to supply a gas sensor having good airtightness while suppressing variations in the pressure applied to the filling members 3, 4, and 6 to be sealed.

[0005]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the inventor filled filling members 3, 4, and 6 between the element 2 and the metal shell 1 into the inner space 105 of the metal shell 1. Then, at a position where the bent portion 102 is bent at the upper end opening 107 of the metal shell 1, that is, at a position near the bent portion 101 where the bent portion 102 is bent from the metal shell 1, the step portion 116 whose wall thickness is changed in a stepwise manner is formed. By providing the bent portion 102, it has been invented that when the bent portion 102 is pressurized from above, the bent portion is accurately bent at a predetermined position.

In the conventional oxygen sensor, the bent portion 1
It is presumed that the variation in the bending position of 02 occurs because the bending strength changes almost continuously near the bent portion 101 where the bent portion 102 bends from the metal shell 1. Then, after many trials, the inventor forms a portion where the bending strength changes relatively sharply compared to the surroundings near the bent portion 101, so that the deformation energy is concentrated at that point, and the bending with high accuracy is performed. We have invented that accuracy can be obtained. Then, as one of the means, the thickness was reduced stepwise in the vicinity of the bent portion 101, and a sharp change in bending strength occurred before and after that. For example, as shown in FIGS. 4 and 6, the thickness of the bent portion 102 is reduced near the bent portion 101, and the thickness of the metal shell 1 is increased, as shown in FIGS. The shape in which the thickness is changed to form the step portion 116 is the mode that most easily realizes the configuration of the present application. That is, when the inner space of the metal shell 1 is formed, a counterbore hole is formed up to the bent portion 101 by using a drill or a lathe having a diameter larger than that of the lower portion, so that the metal shell having such a shape can be manufactured.

As a method of reducing the thickness of the bent portion and increasing the thickness of the metal shell 1, the inner wall 106 of the metal shell 1 is used.
Instead, the outer wall 104 may be processed. FIG. 7 (a)
In the example, the outer wall 104 of the metal shell 1 is shaved at the bent portion 102 above the bent portion 101 to reduce the thickness, thereby forming a step-shaped step 117. However, the bent portion 10
In the case where a step-like step is formed near 1, the inner wall 106 of the metal shell is formed rather than the outer wall 104 of the metal shell is cut.
Is more convenient because the bent portion 102 can be bent with high accuracy.

In order to achieve the object of the present invention, as a means for causing a sudden change in bending strength, there is a method in which grooves 113 and 114 are formed near the bent portion 101 in addition to a stepwise change. . Even if a portion where the wall thickness changes rapidly is formed in the metal shell 1 by forming the groove 113 in the bent portion 101 as shown in FIG. 5, the bent dimension of the bent portion 102 is stable, so that caulking can be performed with high accuracy. . Such a groove 113
Can be easily formed by lathing. In FIG. 7B, the metal shell 1 at the bent portion 101 is shown.
A groove 114 is formed in the outer wall 104 of the first embodiment to cause a sudden change in bending strength.

In order to achieve the object of the present application, it is easiest to realize a mode in which a shape that causes a sudden change in bending strength is formed in the bent portion 101. Points can be formed. As one means, there is a mode in which the hardness of the bent portion 102 is weakened to cause a change in bending strength in terms of physical properties.
For example, as shown in FIG. 7C, annealing is performed by irradiating a laser over the entire outer wall 104 of the metal shell 1 at the bent portion 101 before bending and temporarily raising the temperature in the vicinity of the bent portion to cause annealing. Thus, the soft portion 109 can be locally formed in the bent portion 101 as compared with the surrounding portion. According to this method, since shape processing is not performed, crimping with high dimensional accuracy can be realized while maintaining the mechanical strength of the crimped portion unchanged from the conventional one. As shown in FIG. 7D, the soft portion 115 can be formed by irradiating the inner wall 106 of the bent portion 101 with a laser.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described with reference to an example. FIG. 1 shows a gas sensor that measures the oxygen concentration in the gas to be measured. This gas sensor is the same as the conventional sensor shown in FIG. 10 except for the caulked portion of the metallic shell. The metal shell 1 has an inner space 105 for accommodating the element, and the inner space has a large diameter at an upper end opening 107 as shown in FIG. 8 when the bent portion 102 is not bent, and is tapered downward. 4 through the part
A small diameter portion of the step is formed and reaches the lower end opening 110. The diameter D1 at the top is φ13.2 mm, and the diameter D2 at the second is φ1
2.8 mm, the diameter D3 of the third stage is φ11.6 mm, and the diameter D4 of the lowermost stage is φ7.5 mm. The metal shell has a hexagonal part having a hexagonal opposite side D7 of 22 mm and a thickness T7 of 6.7 mm at the center part in the axial direction, and an M18P1.5 male screw part below the hexagonal part. The length L1 of the cylindrical portion from the upper end surface of the hexagonal portion to the upper end surface of the metal shell is 15.8 mm. The lower part of the cylindrical portion is formed with a height L2 of 3 mm perpendicularly to the upper end surface of the hexagonal portion so as to be laser-welded to the outer cylinder 8 and has a height T3 of the heat crimped portion. Is cut to 0.85 mm, and the length L3 is formed over 2.5 mm.
The bent portion is formed by seating the inner wall to a depth L4 of 1.8 mm by the stepped portion 116 to be bent, and the thickness T4 at the foremost portion of the bent portion is 0.7 mm.

An element 2 and a filling member 3,
After inserting 4,6, it is crimped from above by a crimping die at a crimping load of 25 KN for 1 second. At the time of caulking, a current is supplied from the caulking mold P via the contact surface of the bent portion 102, and the current flows through the heat caulking portion 112, so that the heat caulking portion 112 generates heat and is heated. As a result, the heat crimping portion 112 is deformed in a state where it is heated at a high temperature, and contracts by being cooled to bend the bent portion 1.
Pressure is applied to the filling members 3, 4, and 6 via the valve 02.

As a comparative example, a sensor was manufactured using a metal shell of the same dimension as that of the present invention except that the fourth counterbore in the vicinity of the bent portion 101 was not formed, and the airtightness between the element and the metal shell was measured according to the present invention. Compared to gas sensor. FIG. 9 shows the results. As can be seen from this figure, while the airtightness of the comparative example varies, the width of the variation is reduced in the gas sensor of the present invention. When the airtightness after the durability test was compared, the gas sensor of the present invention showed no significant deterioration in the airtightness even after the durability test.

[Brief description of the drawings]

FIG. 1 is a gas sensor for measuring the concentration of oxygen in a gas to be measured according to the present invention.

FIG. 2 is an explanatory view of a conventional gas sensor caulking process (with a heat caulked portion)

FIG. 3 is an explanatory view of a caulking process of a conventional gas sensor.

FIG. 4 is an explanatory view of a caulking process of the gas sensor of the present invention (with a heat caulked portion).

FIG. 5 is an explanatory view of a caulking process of a modified example of the gas sensor of the present invention.

FIG. 6 is an explanatory view of a caulking process of the gas sensor according to the present invention (without a heat caulking portion).

FIG. 7 is a modified example of the gas sensor of the present invention.

FIG. 8 is a cross-sectional view of the metal shell before assembly according to the present invention.

FIG. 9 shows comparison data of hermetic sealing performance between the gas sensor of the present invention and a gas sensor of a comparative example.

FIG. 10 is a conventional gas sensor for measuring the oxygen concentration in a gas to be measured.

[Explanation of symbols]

 1, metal shell 2, element 3, filling member (sleeve) 4, filling member (talc) 5, caulking packing 6, holder 7, lower packing 8, outer cylinder 101, bent portion 102, bending part 104, outer wall 105, inner space 106, inner wall 107, upper end opening 109, 115, soft part 110, lower end opening 111, shoulder surface 112, heat caulking part 113, 114, ... groove 116, 117, ... step

Claims (9)

[Claims] 1. An element 2 and a metal shell 1 that accommodates the element 2 and has an inner space 105 that is opened in the vertical direction. The metal shell 1 has an inner opening 105 at an upper end opening 107 of the inner space 105. A bent portion 102 is provided. Near the bent portion 101 supporting the bent portion 102, a step-shaped step portion 11 is formed on an inner wall 106 of the metal shell 1.
6. A sensor, wherein 6 is formed. 2. The gas sensor according to claim 1, wherein the metal shell has a small thickness at the bent portion side and a large thickness at the opposite side near the bent portion 101. 3. An element 2 and an inner space 105 which accommodates the element 2 and is open in the vertical direction.
The metal shell 1 is provided with a bent portion 102 bent inward at an upper end opening 107 of the inner space 105, and the bending supporting the bent portion 102 is provided. A sensor in which grooves 113 and 114 are formed in the metal shell 1 near the portion 101. 4. The groove 113 is provided on the inner wall 10 of the metal shell 1.
6. The sensor according to claim 3, wherein the sensor is formed in the sensor. 5. The groove 114 is formed on the outer wall 10 of the metal shell 1.
4. The sensor according to claim 3, wherein the sensor is formed on the sensor. 6. An element 2 and a metal shell 1 accommodating the element 2 and having an inner space 105 opened in a vertical direction. The metal shell 1 has an inner opening 105 at an upper end opening 107 of the inner space 105. A bent portion 102 is provided. In the vicinity of the bent portion 101 supporting the bent portion 102, soft portions 109 and 115 having lower hardness than other portions are provided.
Is formed. 7. The soft part 109 is formed on the outer wall 104 of the metal shell.
7. The sensor according to claim 6, wherein is formed by annealing by laser irradiation. 8. The soft part 115 is provided on the inner wall 106 of the metal shell.
7. The sensor according to claim 6, wherein is formed by annealing by laser irradiation. 9. The gas sensor in which the metallic shell 1 is mounted on an exhaust pipe of an internal combustion engine.
The space between the inner wall of the metal shell 1 and the metal shell 1 is filled with a filler 4 for hermetically separating the inside and the outside of the exhaust pipe, and the bent portion 102 is compressed into the filler 4 by being bent. 9. The sensor according to claim 1, wherein the sensor has an operation of maintaining a state in which a stress is applied.