JP2004093303A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor, in which the reduction in the state of adhesion of an element-side insulator to a housing at high temperatures is slight, and gases to be measured hardly enter the atmospheric environment through between the element-side insulator the housing. <P>SOLUTION: The gas sensor 1 comprises both the element-side insulator 2 which pass through the housing 10 and a sensor element 29 passing through the element-side insulator 2. The element-side insulator 2 comprises a tapered surface. The housing 10 comprises a receiving surface for supporting a tapered surface; a conical spring 21 arranged at the face of the element-side insulator 2 on the side of a base end; and a press member 22 for pressing the coned disc spring 21 against the tip side of the gas sensor 1. The pressing member 22 comprises both a pressing plate 221 for pressing the coned disc spring 21 and a leg part 222, extended from the pressing plate 221 along a side surface 109 of the housing 10 on the side of the base end and fixed to the side surface 109 of the housing 10 on the side of the base end. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
【Technical field】
The present invention relates to a gas sensor used for controlling combustion of an automobile engine.
[0002]
[Prior art]
In order to control the air-fuel ratio of an automobile engine, a gas sensor is sometimes installed in an exhaust pipe or the like that constitutes an exhaust system of the automobile engine.
As shown in FIG. 6, the gas sensor 9 includes a cylindrical housing 90, a cylindrical element-side insulator 91 inserted through the housing 90, a sensor element 29 inserted through the element-side insulator 91, It consists of an air-side insulator 92 arranged on the base end surface 913 of the side insulator 91. Also, the measured gas side cover 101 is provided on the distal end side of the housing 90, and the atmosphere side cover 93 is provided on the proximal end side.
[0003]
The outer surface of the element-side insulator 91 has a tapered surface 911 facing the distal end, and the inner surface of the housing 90 has a receiving surface 901 facing the proximal end supporting the tapered surface 911. The receiving surface 901 and the tapered surface 911 are in contact with each other via a metal packing 912.
[0004]
The atmosphere-side insulator 92 has a diameter that is switched near the base end and has a mounting surface 921 on which the disc spring 922 is mounted facing the base end.
The atmosphere-side cover 93 has a pressing surface 931 that switches the size of the diameter at a position facing the mounting surface 921 and presses the disc spring 922 toward the distal end.
The disc spring 922 located between the pressing surface 931 and the mounting surface 921 is compressed in the gas sensor axial direction by receiving a pressing force toward the distal end when the atmosphere side cover 93 is attached to the housing 90.
[0005]
The compressed elasticity of the disc spring 922 presses the element-side insulator 91 toward the distal end via the atmosphere-side insulator 92, thereby bringing the tapered surface 911 into close contact with the metal packing 912 and the receiving surface 901.
As described above, the element-side insulator 91 has the vicinity of the symbol C where the pressing surface 931, the disc spring 922, and the mounting surface 921 are located, and the vicinity of the symbol B where the tapered surface 911, the metal packing 912, and the receiving surface 901 are located. Between the fixed.
[0006]
[Problem to be solved]
Incidentally, the thermal expansion of metal is large, and the thermal expansion of ceramic is small. Particularly at high temperatures, the difference in thermal expansion between the two becomes large. In the gas sensor 9 having the configuration shown in FIG. 6, the element-side insulator 91 is fixed between the portion B and the portion C, and a metal and a ceramic are mixed between the portions.
[0007]
Therefore, when the temperature becomes high, the expansion of the ceramic insulators 91 and 92 cannot follow the expansion of the metal housing 90 and the atmosphere side cover 93 and the like.
For this reason, a gap is generated between the disc spring mounting surface 921 and the pressing surface 831, and the pressing force by the disc spring 922 decreases.
In the gas sensor 9, the inside of the atmosphere side cover 93 is the atmosphere, and the inside of the measured gas side cover 101 is the atmosphere of the measured gas.
Therefore, a decrease in the pressing force by the disc spring 92 reduces the adhesion between the tapered surface 911, the receiving surface 101, and the metal packing 912, and causes the gas to be measured to enter the atmosphere of the atmosphere-side cover.
[0008]
In order to separate the two atmospheres so that the gas to be measured does not mix with the air atmosphere, airtight fixing between the housing 90 and the element-side insulator 91 and between the element-side insulator 91 and the sensor element 29 are required. There is a need to do.
When the gas to be measured enters the atmosphere, the state of the atmosphere serving as the reference gas in the sensor element 29 becomes unstable, and the detection accuracy of the sensor element 29 may be reduced.
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and when the temperature rises, the state of close contact between the element-side insulator and the housing is slightly reduced. Therefore, it is intended to provide a gas sensor in which the gas to be measured hardly enters the atmosphere.
[0010]
[Means for solving the problem]
A first invention is a gas sensor comprising a cylindrical housing, a cylindrical element-side insulator inserted into the housing, and a sensor element inserted into the element-side insulator.
The element-side insulator has a large-diameter portion having a large outer diameter and a small-diameter portion having a smaller outer diameter than the large-diameter portion, and has a tapered surface facing the gas sensor tip side between the large-diameter portion and the small-diameter portion. Have
The housing has a large-diameter portion having a large internal diameter and a small-diameter portion having a smaller internal diameter than the large-diameter portion. Between the large-diameter portion and the small-diameter portion, facing the gas sensor base end, the tapered surface is formed. Has a receiving surface to support,
A disc spring having elasticity in the gas sensor axial direction and disposed on a base end surface of the element-side insulator, and a pressing member for pressing the disc spring toward the gas sensor tip;
The press member is a press plate that contacts and presses the disc spring, and extends from the press plate along the base side surface of the housing and is fixed to the base side surface of the housing. A gas sensor comprising a leg portion (claim 1).
[0011]
A second invention is a gas sensor comprising a cylindrical housing, a cylindrical element-side insulator inserted into the housing, and a sensor element inserted into the element-side insulator.
The element-side insulator has a large-diameter portion having a large outer diameter and a small-diameter portion having a smaller outer diameter than the large-diameter portion, and has a tapered surface facing the gas sensor tip side between the large-diameter portion and the small-diameter portion. Have
The housing has a large inner diameter portion having a larger inner diameter and a small diameter inner diameter portion having an inner diameter smaller than the large inner diameter portion. Has a receiving surface that supports the surface,
A disc spring having elasticity in the axial direction of the gas sensor and disposed on a base end face of the insulator on the element side; a disc spring extending from the disc spring along a base side face of the housing; The gas sensor according to claim 5, further comprising an integral pressing member including a leg fixed to the base side surface (claim 5).
[0012]
In the gas sensor according to the first and second aspects of the invention, the disc spring and the disc spring portion have elasticity in the gas sensor axial direction, and are deformed by being pressed in this direction. The element-side insulator is pressed against the receiving surface provided on the housing by the restoring force from this deformation. This pressing force is a force for fixing the element-side insulator in close contact with the housing.
[0013]
With the configuration according to the first and second aspects of the present invention, the absolute amount of dimensional change due to the difference in thermal expansion can be made smaller than that of the conventional gas sensor of FIG.
In the gas sensor 9 having the conventional configuration shown in FIG. 6, the element-side insulator 91 is fixed between the portion B and the portion C, and a metal and a ceramic are mixed therebetween.
[0014]
Therefore, when the temperature becomes high, the expansion of the ceramic insulators 91 and 92 cannot follow the expansion of the metal housing 90 and the atmosphere side cover 93 and the like.
For this reason, a gap is generated between the disc spring mounting surface 921 and the pressing surface 831, and the pressing force by the disc spring 922 decreases.
[0015]
In the gas sensor according to the first and second inventions, the element-side insulator is mounted on the housing by using a disc spring and a pressing member (first invention) or an integrated pressing member having a disc spring portion (second invention). , And the element-side insulator is fixed at a shorter distance than before. This is clear when FIG. 1 and FIG. 6 described later are compared.
[0016]
Therefore, even when the housing or the element-side insulator expands in the same manner as before when the temperature rises, the absolute amount of the accumulated dimensional change becomes smaller than before.
For this reason, when the temperature becomes high, the generation of a gap between the disc spring or the disc spring portion and the base end face of the element-side insulator is reduced, and the element-side insulator by the disc spring or the disc spring portion is attached to the housing. It is possible to reduce the decrease in the pressing force that pushes toward.
[0017]
In the first and second inventions, the eccentricity of the force is small and the tapered surface is not fixed indirectly via the air-side insulator as in the prior art, but by fixing the element-side insulator directly to the housing. The force can be transmitted to the receiving surface from the surface.
[0018]
As described above, according to the first and second aspects of the invention, when the temperature of the element-side insulator becomes low, the state of close contact of the element-side insulator with the housing is small, and the gas to be measured passes between the element-side insulator and the housing. A gas sensor that does not easily enter the atmosphere.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Examples of the gas sensor according to the first and second aspects of the present invention include an oxygen sensor for measuring the oxygen concentration in the gas to be measured and a NOx sensor for measuring the NOx concentration. There is also a composite sensor that measures a plurality of types of gas concentrations with one sensor.
[0020]
In the first invention, the fixing between the leg portion of the pressing member and the side surface on the base end side of the housing can be welding fixing.
Thereby, the pressing force of the disc spring can be maintained.
[0021]
Further, in the first invention, the fixing between the leg portion of the pressing member and the side surface on the base end side of the housing can be caulked.
Thereby, the pressing force of the disc spring can be maintained.
[0022]
Further, in the first invention, it is preferable that the pressing member is formed of a radially inwardly swaging portion integrally provided at a base end portion of the housing (claim 4).
Thereby, the pressing force of the disc spring can be maintained.
[0023]
Further, in the second invention, the leg portion of the integral holding member has a projecting portion projecting radially inward, and the base end side surface of the housing is recessed radially inward and corresponds to the projecting portion. With a recess
It is preferable that the leg is fixed to the side surface on the base end side by fitting the projecting portion and the concave portion.
Thereby, the pressing force of the disc spring can be maintained.
[0024]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Example 1)
As shown in FIGS. 1 and 2, this embodiment includes a cylindrical housing 10, a cylindrical element-side insulator 2 inserted through the housing 10, and a sensor element 29 inserted through the element-side insulator 2. Gas sensor 1.
[0025]
As shown in FIG. 2, the element-side insulator 2 has a large-diameter portion 207 having a large outer diameter and a small-diameter portion 209 having a smaller outer diameter than the large-diameter portion 207. And a tapered surface 208 facing the gas sensor tip side.
The housing 10 has a large-diameter portion 103 having a large inner diameter and a small-diameter portion 101 having a smaller inner diameter than the large-diameter portion 103. The housing 10 faces the gas sensor base end between the large-diameter portion 103 and the small-diameter portion 101. And a receiving surface 102 that supports the tapered surface 208.
[0026]
Further, the gas sensor has elasticity in the axial direction and includes a disc spring 21 disposed on the base end surface 205 of the element-side insulator 2 and a pressing member 22 for pressing the disc spring 21 toward the gas sensor tip. .
The pressing member 22 is a pressing plate 221 that contacts and presses the disc spring 21, and extends from the pressing plate 221 along the base side surface 109 of the housing 10, and is connected to the base end of the housing 10. It comprises a leg 222 fixed to the side surface 109.
As shown in FIGS. 1 and 2, the pressing member 22 of this embodiment has a cap-shaped shape that covers the element-side insulator 2 on which the disc spring 21 is disposed.
[0027]
The details are described below.
The gas sensor 1 according to the present embodiment is a composite sensor that is installed in an exhaust pipe of an automobile engine and measures an oxygen concentration and a NOx concentration in exhaust gas and an air-fuel ratio of an engine combustion chamber.
The sensor element 29 incorporated in the gas sensor 1 is a laminated plate-like element in which a solid electrolyte plate and an insulating plate are appropriately laminated, and a monitor cell for measuring and monitoring the oxygen concentration in a gas chamber to be measured provided inside the element. An oxygen pump cell that adjusts the oxygen concentration in the gas chamber to be measured, a sensor cell that measures the NOx concentration in the gas chamber to be measured, and a heater that generates heat when energized are integrally provided.
The voltage application to the heater, the voltage application to each cell, and the output output are performed at terminals provided on the outer surface of the sensor element (not shown).
[0028]
As shown in FIGS. 1 and 2, the gas sensor 1 of the present embodiment includes a cylindrical housing 10 made of a heat-resistant metal, a gas-side cover 100 having a double structure attached to the distal end of the housing 10, And an atmosphere-side cover 13 attached to the camera.
The atmosphere-side cover 13 includes a first cover 131 that is caulked and fixed to the housing 10, and an outer cover 132 that is caulked and fixed to the base end side of the first cover 131 via a water-repellent filter 133.
[0029]
Further, the cylindrical element-side insulator 2 is inserted into the housing 10, and a portion between the large-diameter portion 207 and the small-diameter portion 209 of the element-side insulator 2 forms a tapered surface 208. The space between the large-diameter portion 103 and the small-diameter portion 101 of the housing 10 serves as a receiving surface 102. By inserting the element-side insulator 2 into the housing 10, the tapered surface 208 comes into contact with the receiving surface 102 via the metal packing 28. That is, the receiving surface 102 supports the element-side insulator 2 from the tip side of the gas sensor.
[0030]
The disc spring 21 is placed on the base end surface 205 of the element-side insulator 2, and the pressing member 22 is covered from above the disc spring 21. The pressing member 22 includes a pressing plate 221 for pressing and contracting the disc spring 21 and a leg 222 extending from the pressing plate 221 along the proximal side surface 109 of the housing 10. The element-side insulator 2 is fixed from above in the drawing by welding and fixing the entire circumference with the leg 222.
[0031]
Here, as shown in FIG. 2, the pressing member 22 is a cap type in which the tip side of the gas sensor is open, and the pressing plate 221 has a hole 223 through which the sensor element 29 passes in the center. Similarly, the disc spring 21 also has a hole 213 at the center for passing the sensor element 29, and in a free state before being pressed, has a disk shape in which the radial outside is further raised.
[0032]
The air-side insulator 3 is provided above the element-side insulator 2 and inside the air-side cover 13. A terminal spring (not shown) that conducts with the terminals of the sensor element 29 is disposed inside the air-side insulator 3. The terminal spring is electrically connected to the lead wire 40 through the connection member 409.
[0033]
An elastic insulating member 4 is provided on the base end side of the first cover 131 constituting the atmosphere side cover 13. The elastic insulating member 4 has a lead wire insertion hole (not shown), and the lead wire insertion hole is a through hole penetrating from the base end side to the distal end side of the elastic insulating member 4. The lead wire 40 is drawn into the gas sensor 1 from the outside through the lead wire insertion hole.
[0034]
The operation and effect of this example will be described.
In the gas sensor 1 of the present embodiment, the disc spring 21 has elasticity in the gas sensor axial direction, and is deformed when pressed in this direction. The element side insulator 2 is pressed toward the receiving surface 102 provided on the housing 10 by the restoring force from this deformation. This pressing force is a force for tightly fixing the element-side insulator 2 to the housing 10 via the metal packing 28.
[0035]
With the configuration according to the present example, the absolute amount of the dimensional change due to the difference in thermal expansion can be reduced as compared with the gas sensor 9 of FIG.
In the gas sensor 9 having the conventional configuration shown in FIG. 6, the element-side insulator 91 is fixed between the portion B and the portion C, and a metal and a ceramic are mixed therebetween. Therefore, when the temperature becomes high, the expansion of the ceramic insulators 91 and 92 cannot follow the expansion of the metal housing 90 and the atmosphere side cover 93 and the like. For this reason, a gap is generated between the disc spring mounting surface 921 and the pressing surface 831, and the pressing force by the disc spring 922 decreases.
[0036]
In this embodiment, the absolute amount of the dimensional change due to the difference in thermal expansion can be made smaller than that of the conventional gas sensor of FIG.
Because, conventionally, the element-side insulator is fixed between the portions B and C as shown in FIG. 6, but in this example, the element-side insulator is fixed between the portions B and A as shown in FIG. Fixed distance is shorter. Therefore, the absolute amount of cumulative dimensional change is also small.
Therefore, when the temperature rises, the generation of a gap between the disc spring 21 and the base end surface 205 of the element-side insulator 2 is reduced, and the reduction of the pressing force by the disc spring 21 can be reduced. Therefore, according to this example, the fixed state of the element-side insulator 2 is stabilized.
[0037]
Further, since the element-side insulator 2 is directly fixed to the housing 10 using the disc spring 21 and the holding member 22 instead of the conventional indirect fixing via the atmosphere-side insulator, the eccentricity of the force is reduced. The force can be reliably transmitted from the small tapered surface 208 to the receiving surface 102 via the metal packing 28. Also from this point, the fixed state of the element-side insulator 2 is stabilized.
[0038]
Therefore, according to the present embodiment, when the temperature becomes high, the state of close contact between the element-side insulator 2 and the metal packing 28 with respect to the housing 10 is slightly reduced. It is possible to provide a gas sensor in which the gas to be measured hardly enters the atmosphere.
[0039]
Also, in FIGS. 1 and 2, the leg 222 of the holding member 22 and the base side surface 109 of the housing 10 are fixed by full circumference welding. However, as shown in FIG. It is also possible to abut on the base side surface 109 and caulk from the outside in the radial direction to fix them therebetween.
Also in this case, the same operation and effect as those of the configurations of FIGS. 1 and 2 can be obtained.
[0040]
(Example 2)
As shown in FIGS. 4 (a) and 4 (b), the pressing member of the present embodiment includes a wrapping portion 20 integrally formed on the base end side of the housing 10.
In this example, the housing 10 has a base end side surface 109 extended, and the extended portion serves as a wrapping portion 20 functioning as a holding member.
[0041]
That is, as shown in FIG. 4B, the extended portion is bent toward the disc spring 21 as shown by the arrow.
As a result, the foremost portion of the extended base end side surface 109 becomes the pressing plate 221 for pressing the disc spring 21, and the portion other than the foremost end of the base end side surface 109 becomes the leg portion 224. The leg 224 is integrated with the base side surface 109 of the housing 10. Other configurations of the gas sensor are the same as those of the first embodiment.
[0042]
The configuration according to the present example does not require a pressing member, which is a separate member, and eliminates the need for processing such as welding and swaging, and can reduce processing costs.
Otherwise, the same operation and effect as in the first embodiment can be obtained.
[0043]
(Example 3)
In this embodiment, an integrated holding member 25 in which the disc spring and the holding member shown in the first embodiment are integrated will be described.
As shown in FIG. 5 (a), the integrated holding member 25 according to the present example has elasticity in the gas sensor axial direction, The leg portion 252 extends from the spring portion 251 along the base side surface of the housing and is fixed to the base side surface of the housing.
[0044]
The disc spring 251 has a hole 254 in the center, through which the sensor element is inserted. This hole has a shape combining a circle and a cross.
Further, as shown in FIG. 5B, a cut is provided in the leg portion 252, and the cut is set inward in the radial direction. This cut forms a projection 253 that projects radially inward of the leg 252.
[0045]
Although illustration is omitted, by providing in advance a recess that can be fitted to the protruding portion 253 on the housing and the base end side surface of the gas sensor, when the integrated holding member 25 is covered with the element-side insulator, The protruding portion 253 and the concave portion are fitted to each other, so that more secure fixing can be realized.
After the protrusion 253 and the recess are fitted, the fixing can be further ensured by welding or caulking.
Other configurations of the gas sensor are the same as those of the first embodiment.
[0046]
The configuration according to the present example does not require a pressing member, which is a separate member, and eliminates the need for processing such as welding and swaging, thereby reducing processing costs.
Otherwise, the same operation and effect as in the first embodiment can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory cross-sectional view along the axial direction of a gas sensor according to a first embodiment in which a pressing member and a housing are fixed by welding.
FIG. 2 is a development explanatory view of a main part of the gas sensor according to FIG. 1 in the first embodiment.
FIG. 3 is an explanatory view of a main part of the gas sensor in Embodiment 1 in which the holding member and the housing are fixed by caulking.
FIG. 4 is an explanatory view of a main part of a gas sensor according to a second embodiment, the gas sensor including a holding member formed of a wrapping portion integrally formed with a housing.
5A and 5B are a plan view and a cross-sectional view of an integrated holding member according to a third embodiment.
FIG. 6 is a cross-sectional explanatory view along the axial direction of a conventional gas sensor.
[Explanation of symbols]
1. . . Gas sensor,
10. . . housing,
109. . . Proximal side,
101. . . Small bore,
102. . . Receiving surface,
103. . . Large bore,
2. . . Element side insulator,
20. . . Wrapping part,
205. . . Proximal end face,
207. . . Large diameter portion 208. . . Tapered surface,
209. . . Small diameter section 21. . . Disc spring,
22. . . Holding member,
221. . . Holding plate,
222. . . leg,
25. . . Integrated holding member,
251. . . Disc spring,
252. . . leg,
29. . . Sensor element,

Claims (6)

A gas sensor comprising a cylindrical housing, a cylindrical element-side insulator inserted into the housing, and a sensor element inserted into the element-side insulator,
The element-side insulator has a large-diameter portion having a large outer diameter and a small-diameter portion having a smaller outer diameter than the large-diameter portion, and a tapered surface facing the tip of the gas sensor is provided between the large-diameter portion and the small-diameter portion. Have
The housing has a large-diameter portion having a large internal diameter and a small-diameter portion having a smaller internal diameter than the large-diameter portion. Has a receiving surface to support,
A disc spring having elasticity in the gas sensor axial direction and disposed on a base end face of the insulator on the element side, and a pressing member for pressing the disc spring toward the gas sensor tip side;
The press member is a press plate that contacts and presses the disc spring, and extends from the press plate along the base side surface of the housing and is fixed to the base side surface of the housing. A gas sensor comprising a leg. 2. The gas sensor according to claim 1, wherein the fixing between the leg portion of the pressing member and the base end side surface of the housing is welding fixing. 3. The gas sensor according to claim 1, wherein the fixing between the leg portion of the pressing member and a side surface of the housing on the proximal end side is caulking fixing. 2. The gas sensor according to claim 1, wherein the pressing member comprises a radially inward swaging portion integrally provided at a base end of the housing. A gas sensor comprising a cylindrical housing, a cylindrical element-side insulator inserted into the housing, and a sensor element inserted into the element-side insulator,
The element-side insulator has a large-diameter portion having a large outer diameter and a small-diameter portion having a smaller outer diameter than the large-diameter portion, and a tapered surface facing the tip of the gas sensor is provided between the large-diameter portion and the small-diameter portion. Have
The housing has a large inner diameter portion having a larger inner diameter and a small diameter inner diameter portion having an inner diameter smaller than the large inner diameter portion. Has a receiving surface that supports the surface,
A disc spring having elasticity in the axial direction of the gas sensor and disposed on a base end face of the insulator on the element side; a disc spring extending from the disc spring along a base side face of the housing; A gas sensor comprising an integral holding member comprising a leg fixed to a base side surface. 6. The integrated holding member according to claim 5, wherein the leg portion of the integral holding member has a projecting portion projecting radially inward, and the base end side surface of the housing is recessed radially inward and has a recess corresponding to the projecting portion. Have
A gas sensor, wherein the leg is fixed to the side surface on the base end side by fitting the projection and the recess.

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