JPH0345337B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an oxygen concentration battery-type oxygen sensor used in a combustion device with high-temperature exhaust gas such as an automobile exhaust gas purification device, and in particular to an oxygen sensor having a flange-like portion on the outer periphery. A solid electrolyte tube having a tube shape with one end closed and layered electrodes coated on the inner and outer circumferential surfaces is inserted into a mounting bracket having a tube shape and a step formed on the inner circumference as described above. Below the collar of the solid electrolyte tube (closed end side)
The solid electrolyte tube is inserted so that the surface facing the solid electrolyte tube is in contact with the stepped portion, and an annular stopper is placed in an annular space surrounded by the mounting bracket and the solid electrolyte tube above the collar-shaped portion of the solid electrolyte tube. By crimping the upper edge of the mounting bracket inward and deforming a part of the mounting bracket in the axial direction under heating at a temperature higher than the maximum temperature during use of the oxygen sensor, , relates to an oxygen sensor in which the above-mentioned mounting bracket and the above-mentioned solid electrolyte tube are assembled.

[Prior Art] When used to detect, for example, residual oxygen in the exhaust gas of an internal combustion engine, an oxygen sensor is generally attached to a device in a high temperature state, such as an exhaust pipe, and is heated to a temperature of several hundred degrees Celsius.
Because the ceramic solid electrolyte tube is used at high temperatures, the attachment between the ceramic solid electrolyte tube and the solid electrolyte tube tends to loosen due to the difference in thermal expansion between the ceramic solid electrolyte tube and the attachment fitting that sandwiches the flange-like portion of the tube.

In order to prevent this loosening, a method has been proposed in which a metal ring for compensating for the difference in thermal expansion is made of a material having a larger coefficient of thermal expansion than the above-mentioned mounting bracket (Japanese Patent Publication No. 1983-6235).

[Problems to be Solved by the Invention] However, in the conventional technology, when a mounting bracket is heat-swaged, if a pad inserted to support the heat-swaged portion is used as a compensation ring, the pad also becomes extremely hot. Because it expands more greatly, within the operating temperature of the oxygen sensor, which is lower than the temperature during heat staking, the pad will be in a contracted state compared to when it is heat swaged.
The axial pressing force applied during hot caulking actually becomes smaller during use, which has the disadvantage of causing poor assembly.

SUMMARY OF THE INVENTION An object of the present invention is to provide an oxygen sensor that maintains a state in which sufficient pressure is applied during manufacturing and during use, and that can effectively prevent assembly failures.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configuration.

A solid electrolyte tube having a tube shape with a collar-shaped portion on the outer periphery and a closed end at one end and having layered electrodes adhered to the inner and outer circumferential surfaces of the solid electrolyte tube, which has a tube shape and a stepped portion on the inner periphery. The mounting bracket is inserted into the mounting bracket so that the surface facing downward (closed end side) of the collar-shaped portion of the solid electrolyte tube is in contact with the stepped portion, and the mounting bracket is placed above the collar-shaped portion of the solid electrolyte tube. An annular pad is arranged in the annular space surrounded by the solid electrolyte tube and the upper edge of the mounting bracket is crimped inward, and a part of the mounting bracket is axially moved when the oxygen sensor is used. In an oxygen sensor in which the mounting fitting and the solid electrolyte tube are assembled by pressurizing and deforming them under heating at a temperature higher than the maximum temperature, the thermal expansion coefficient of the material of the fitting is determined by the coefficient of thermal expansion of the material of the fitting. The coefficient of thermal expansion was selected to be smaller than that of the material.

[Operation and Effects of the Invention] (Regarding Claim 1) By making the coefficient of thermal expansion of the material of the pad smaller than the coefficient of thermal expansion of the material of the mounting fitting, the shrinkage due to temperature drop immediately after heat caulking is reduced. The solid electrolyte tube is not weakened by shrinkage of the pad, and the mounting bracket step and the solid electrolyte tube are effectively prevented from coming loose, airtightness is reliably maintained, and performance is stable even during long-term use. Note that airtightness may be maintained between the downward facing surface of the collar-shaped portion of the solid electrolyte tube and the upper surface of the stepped portion of the mounting bracket.

(Regarding Claim 2) The coefficient of thermal expansion of the material of the pad is made smaller than the coefficient of thermal expansion of the material of the mounting fitting, and between the pad and the collar in the annular space, By filling powder as a sealing material, the compressive force applied to the powder sealing material increases and is maintained immediately after heat caulking, making it more effective for loosening the mounting bracket step and solid electrolyte tube. The airtightness is more reliably maintained and the performance is more stable even during long-term use.

(Regarding Claim 3) Since the material of the mounting bracket is austenitic stainless steel and the material of the pad is ferrite or martensitic stainless steel, it is difficult to assemble the step part of the mounting bracket and the solid electrolyte tube. Loosening of the fitting is more effectively prevented, airtightness is more reliably maintained, and performance is more stable even during long-term use.

[Example] Next, the present invention will be explained with reference to the drawings.

1 is a solid electrolyte tube made of an oxygen ion conductive solid electrolyte sintered body such as stabilized zirconia, with one end 2
A porous electrode is formed by depositing platinum in a porous thin film on the inner and outer surfaces of a tubular body 2 which is closed and has a flange-like portion 22 on its outer periphery by a method such as electroplating or chemical plating. 3 and 4 are formed, and a porous ceramic protective layer 5 is formed on the outer surface on the side of the closed end 21 from the brim portion 22, and 6 has a stepped portion 7 formed on the inner periphery. The material of the tube-shaped mounting bracket is austenitic stainless steel here, and reference numeral 8 indicates a ventilation hole 8 fitted into one end of the fitting.
1, which has a skirt portion 82 on the opening side that engages with the stepped portion 7 of the mounting bracket; 9 is an upper case fitted to the other end of the mounting bracket 6; A connecting pipe 11 that is fitted onto the outer covering of the output wire 10 is fitted onto the end portion.
12 has one end fitted into the open end 23 of the solid electrolyte tube 1 and connected to the inner porous electrode 3;
The other end is an insulator tube 13 fitted inside the upper case 9.
A spring-shaped terminal 15 is supported by the skirt part 82 of the protective cap 8 and a collar-shaped part of the solid electrolyte tube 1. A tapered ring 16 is inserted between the collar 2 and electrically connects the stepped portion 7 of the mounting bracket 6 and the outer porous electrode 4 of the collar 22 of the solid electrolyte tube 1;
2 connects the solid electrolyte tube 1 and mounting bracket 6 on the opening side.
A powder sealing material is filled in the annular space A between the two and carbon powder is used here. However, other ceramic sealing powders such as talc may also be used. Reference numeral 17 is a Valka gasket inserted as a presser and in contact with the carbon powder; 18 is a nickel ring inserted into the lower end of the annular space A, which forms a seal for the carbon powder 16;
Reference numeral 9 is formed to have a small outer diameter so that the portion corresponding to the deformed portion 61 of the mounting bracket 6 due to heat caulking can expand during the heat caulking, and its axial dimension (height) is determined from the upper end of the attachment bracket 6. The metal fitting is at least corresponding to the dimension of the mounting bracket 6 side up to the deformed part 61 due to the deformation part 61, and reaches a high temperature by receiving heat from the high temperature deformation part 61 during heat caulking, and the material is the same as that of the mounting bracket 6.
Martensitic stainless steel, which has a smaller coefficient of thermal expansion, was selected. One end is the upper case 9
The other end is engaged with the inner edge 62 of the mounting bracket 6, which is formed by drawing the mounting bracket 6 side in the same process as hot caulking. It is fitted between the mounting bracket 6 and the upper case 9.

Thermal caulking of the mounting bracket 6 is performed by heating the deformed portion 61 due to heat caulking to about 800°C by applying electricity, etc., and then pressing from the direction of arrow K to tighten the inner edge 62.
At the same time as forming, applying pressure to deform the deformable part 61 by caulking, pressing the collar-shaped part 22 of the solid electrolyte tube 1 via the pad 19, the flange 91 of the upper case 9, the packing 17, and the carbon powder, The flange-shaped portion 22 is pressed into contact with the stepped portion 7 of the mounting bracket 6 via the tapered ring 15. During this heat caulking, the pad 19, which is placed close to the deformed portion 61 due to the caulking of the mounting bracket 6, also becomes heated to a high temperature (approximately 600 to 700 degrees Celsius) higher than the temperature in practical use. In the present invention, the coefficient of thermal expansion of the pad 19 is made smaller than that of the mounting bracket 6, so that after heat caulking, the shrinkage due to temperature drop is not reduced by the shrinkage of the pad 19. A large compressive force can be applied even afterwards. The maximum temperature of the mounting bracket 6 and pad 19 when using the oxygen sensor is 500℃.
A compressive force greater than the compressive force immediately after heat caulking applied to the solid electrolyte tube 1 is maintained, and the collar-shaped portion 2 of the solid electrolyte tube 1 is
2 continues to be strongly pressed against the stepped portion 7 of the mounting bracket 6, so that the assembled state is reliably maintained.

In the above embodiment, the collar portion 2 of the solid electrolyte tube 1
2, the annular space surrounded by the mounting bracket 6 and the solid electrolyte tube 1 is filled with a powder sealant 16 (carbon powder) together with an annular pad. When maintaining airtightness between the downward facing surface of the shaped portion 22 and the upper surface of the stepped portion of the mounting bracket 6, the powder sealing material 16 may be omitted and only the pad 19 may be placed in the annular space. .

[Brief explanation of drawings]

FIG. 1 is a sectional view of the oxygen sensor of the present invention. In the figure 1...Solid electrolyte tube, 3, 4...Porous electrode (layered electrode), 6...Mounting bracket, 7...Step part,
16... Powdered sealing material (sealing material), 19... Button, 21... One end, 22... Flange-shaped portion, A... Annular space.

Claims (1)

[Scope of Claims] 1. A solid electrolyte tube having a tube shape with a flange on the outer periphery and a closed end at one end, and having layered electrodes coated on the inner and outer circumferential surfaces. The solid electrolyte tube is inserted into a mounting bracket having a step formed thereon so that the surface facing downward (closed end side) of the brim of the solid electrolyte tube is in contact with the step; An annular stopper is arranged in the annular space surrounded by the above-mentioned fitting and the solid electrolyte tube above the section, and the upper end edge of the above-mentioned fitting is crimped inwardly, and a part of the above-mentioned fitting is axially moved. , an oxygen sensor in which the mounting bracket and the solid electrolyte tube are assembled by pressurizing and deforming them under heating at a temperature higher than the maximum temperature during use of the oxygen sensor; An oxygen sensor characterized in that an expansion coefficient is selected to be smaller than a thermal expansion coefficient of a material of the mounting fitting. 2. The oxygen sensor according to claim 1, wherein powder is filled as a sealing material between the pad and the collar in the annular space. 3. The oxygen sensor according to claim 1 or 2, wherein the mounting fitting is made of austenitic stainless steel, and the pad is made of ferrite or martensitic stainless steel.