JP2001305098A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor of structure hardly causing the breaking of a heater in a reference gas chamber. SOLUTION: A heater holder 2 comprises a cylindrical heater holding part 21 for holding the heater 29; a cylindrical inner electrode connecting part 23 constituted to be conductive to an inner electrode; and a lead part 24 connected to the inner electrode connecting part 23. The heater holding part 21 holds the heater 29 so as to be movable in the heater holding part 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor provided in an exhaust system of a vehicle internal combustion engine and used for controlling combustion between internal combustion engines.

[0002]

2. Description of the Related Art There is known a gas sensor having a sensor element comprising a cup-shaped solid electrolyte body having a bottomed cylindrical shape and having a reference gas chamber provided therein, and having a heater inserted and disposed in a reference gas chamber and held and fixed by a heater holder. ing. FIG.
As shown in FIG. 15, the heater holder 9 includes a cylindrical heater holding portion 91 for holding the heater 291, a cylindrical inner electrode connecting portion 93 configured to conduct with the inner electrode of the sensor element, and the inner electrode connecting portion. The heater holding portion 91 and the inner electrode connecting portion 93 are connected by a narrow neck portion 92.

[0003]

The heater holding section 91
The holding and fixing of the heater 291 in the
Of the heater 291 is brought into contact with the outer side surface 290 of the heater 291. For this reason, the heater 29 is rigidly held and fixed to the heater holding portion 91 with little freedom in the radial direction.

Incidentally, the heater 291 is connected to the heater holding section 9.
1, the heater 291 and the heater holding portion 91
The heater 291 may be held and fixed in a state in which the heater 291 is not coaxial and is inclined with respect to the heater holding unit 91. When the heater holder 9 is inserted into the reference gas chamber in such a state, the inner surface of the reference gas chamber may interfere with the heater 291 and the heater 291 may be broken. Usually, since the heater is made of a ceramic material, its strength is not so strong and brittle.

In the heater holder 9 according to the prior art shown in FIGS. 14 and 15, the neck portion 92 connecting the heater holding portion 91 and the inner electrode connecting portion 93 is converted into an angle, as shown in FIG. And less than β degrees, α is 6
0 and β are set to 120. This allows the neck portion 92 to have flexibility, so that the heater 291 held by the neck portion 92 together with the heater holding portion 91 can move in the reference gas chamber.

According to this configuration, even if the heater 291 is inclined and held by the heater holding portion 91, the neck 92
Of the heater 291 absorbs the inclination of the heater 291,
Can be inserted into the reference gas chamber without causing breakage. However, if the neck portion 92 is made thinner in this way, the strength of the neck portion 92 is reduced, and the buckling of the neck portion 92 may occur.

The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a gas sensor having a structure in which a heater is hardly broken in a reference gas chamber.

[0008]

According to a first aspect of the present invention, a reference gas chamber is provided inside a cylinder having a bottom, and an inner electrode is provided on an inner surface facing the reference gas chamber, and an inner electrode is provided on an outer surface in contact with the gas to be measured. A gas sensor comprising a cup-shaped solid electrolyte body provided with an outer electrode and having a sensor element in which a heater held and fixed by a heater holder is inserted and disposed in the reference gas chamber, wherein the heater holder is a cylindrical heater holding the heater. A holding portion, a cylindrical inner electrode connection portion configured to conduct with the inner electrode, and a lead portion connected to the inner electrode connection portion, wherein the heater holding portion includes the heater inside the heater holding portion. The gas sensor holds the gas sensor so that it can move.

Most notably, in the present invention, the heater holding portion holds the heater so that the heater can move within the heater holding portion.

Next, the operation of the present invention will be described. According to the present invention, since the heater can move within the heater holding portion, the heater can move within the heater holding portion even if the heater is held at an angle with respect to the heater holding portion. It can be inserted and arranged in the reference gas chamber without causing it. That is, when the heater hits the inner surface of the reference gas chamber or the like, the heater moves moderately in the heater holding portion and breakage can be avoided.

In addition, if an impact is applied to the gas sensor in a state after assembly, if the heater is completely fixed at the portion (m) in FIG. 2, if the impact from the sensor element is transmitted to the heater, Since this heater is fixed at both the position (m) and the position (n), the heater is (m)
Will break at the position. Since the heater according to the present invention can move in the holding portion, that is, at the position (m), even if an impact from the sensor element is transmitted to the heater, the impact is mitigated by moving the heater, thereby preventing the heater from breaking.

As described above, according to the present invention, it is possible to provide a gas sensor having a structure in which the heater is hardly broken in the reference gas chamber.

[0013] Next, as in the second aspect of the present invention, the heater holding portion is configured to be smaller in diameter from one end to the other end, and holds the heater at the end having the smallest diameter. (See FIG. 1).
reference). As a result, the heater is held by the narrow end, and the other portion of the heater holding portion hardly comes into contact with the heater. Therefore, the contact area between the heater and the heater holding portion becomes very small, and the heater can be held without being restrained.

Next, as in the third aspect of the present invention, the heater holding portion has a first projecting portion provided on an inner side surface facing the heater, and the first projecting portion holds the heater. Preferably, it is configured. Thus, the heater holding portion can be configured to be in contact with the heater only at the first projecting portion, and the other portion of the heater holding portion not to be in contact with the heater. Therefore, the contact area between the heater and the heater holding portion becomes very small, and the heater can be held without being restrained.

The first protruding portion is formed by appropriately changing the diameter of the heater holding portion and, for example, as shown in FIG. The portion having the smallest diameter can be used as the first protrusion. Further, the inner side surface of the heater holding portion may be partially protruded, and this may be used as a first protruding portion (see FIG. 10).

Next, it is preferable that the heater holding portion has a cut portion provided in parallel with the gas sensor axial direction. As a result, the rigidity of the heater holding portion is reduced, and the degree of freedom of the heater can be increased. As an example, as shown in FIG. 11 to be described later, a state in which cut portions are provided from the distal end portion and the proximal end portion of the heater holding portion, respectively, can be mentioned. Alternatively, only one notch can be provided from the distal end or from the proximal end. Further, a plurality of cut portions can be provided in the circumferential direction.

According to a fifth aspect of the present invention, a reference gas chamber having a bottomed cylindrical shape is provided inside, and an inner electrode is provided on an inner surface facing the reference gas chamber, and an outer electrode is provided on an outer surface in contact with the gas to be measured. A sensor element comprising a cup-shaped solid electrolyte body provided with an outer electrode, wherein the reference gas chamber has a sensor element in which a heater held and fixed by a heater holder is inserted and arranged, wherein the heater holder holds the heater. A cylindrical heater holding portion, a cylindrical inner electrode connecting portion configured to be electrically connected to the inner electrode, and a lead portion connected to the inner electrode connecting portion. Characterized in that the gas sensor is inserted and arranged so as to be able to move in the gas sensor.

In the present invention, even if the heater is temporarily fixed rigidly to the heater holding portion of the heater holder, the heater holder itself can move in the reference gas chamber. The breakage of the heater can be avoided by moving while the heater is being operated. That is, when the heater hits the inner side surface or the like in the reference gas chamber, the heater holder moves appropriately with the heater, and breakage can be avoided. Further, when an impact is applied to the gas sensor after the assembly, the heater moves together with the heater holder, and it is possible to prevent the heater from hitting the side surface of the reference gas chamber and being broken.

As described above, according to the present invention, it is possible to provide a gas sensor having a structure in which the heater is hardly broken in the reference gas chamber.

Next, a second protruding portion is provided on the outer side surface of the inner connecting portion facing the inner side surface of the reference gas chamber. It is preferable to be configured to contact the side surface of the gas chamber.

As a result, the contact area of the heater holder with the reference gas chamber is reduced, so that the heater holder is not restricted by the reference gas chamber, and a certain degree of freedom can be obtained. The diameter of the portion where the second projecting portion is provided needs to be larger than the diameter of the heater holding portion (FIG. 12, FIG.
See FIG. 13).

The second protruding portion is provided, for example, in FIG.
As shown in (1), it can be constituted by a large-diameter portion formed annularly on the outer surface. Further, as shown in FIG. 13 described later, for example, it can be constituted by a plurality of protrusions formed on the outer surface. It is necessary to provide two projections at least at the same projection level and the same projection height in the axial direction. As a result, a stable placement of the heater holder in the reference gas chamber can be realized.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 A gas sensor according to an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. The gas sensor 1 of the present embodiment is shown in FIGS.
As shown in FIG. 2, a reference gas chamber 41 having a bottomed cylindrical shape is provided inside.
And a cup-shaped solid electrolyte body 40 having an inner electrode on the inner surface facing the reference gas chamber 41 and an outer electrode on the outer surface in contact with the gas to be measured. Heater 2 held and fixed by
9 has the sensor element 4 inserted and arranged.

As shown in FIG. 1, the heater holder 2 is configured so as to be electrically connected to a cylindrical heater holding portion 21 for holding a heater 29 having a rectangular cross section (see FIG. 4A) and a substantially circular cross section. And a lead portion 24 connected to the inner electrode connecting portion 23 (not shown, but having a substantially circular cross section). The heater holding section 21 holds the heater 29 so that the heater 29 can move in the heater holding section 21.

This example will be described in detail. The gas sensor 1 of this embodiment is an oxygen sensor which is attached to an automobile engine exhaust system and is used for engine combustion control. As shown in FIG. 2, the gas sensor 1 of the present embodiment includes a housing 10, a sensor element 4 inserted and arranged inside the housing 10, and a measured gas side cover 11 provided to cover the tip side of the sensor element 4. And an atmosphere-side cover 12 provided to cover the base end side of the sensor element 4. An insulator 13 is provided inside the atmosphere side cover 12.

As shown in FIGS. 5 and 6, the sensor element 4 is a cup-shaped solid electrolyte body 40 having a reference gas chamber 41 provided therein, and an outer surface 405 of the solid electrolyte body 40 in contact with the gas to be measured. An outer electrode 401 is provided at a position, and an inner electrode 402 is provided on an inner surface facing the reference gas chamber 41. As shown in FIG.
02 is also configured such that a sensor output can be led out of the sensor element 4 by a lead electrode 403 provided on the outer surface 405 and the inner surface of the solid electrolyte body 40 (lead electrodes for the inner electrode are not shown). I have. Reference numeral 400 in FIG. 5 denotes a protective layer for the outer electrode 401.

As shown in FIG. 6, the outer lead electrode 403 electrically connected to the outer electrode 401 is formed in a cylindrical shape, and the outer electrode connecting portion 43 fitted to the outer surface 405 of the solid electrolyte member 40 and the outer electrode connecting portion 43 are connected to the outer electrode connecting portion 43. The outside lead portion 44 connected to the portion 43 further leads out of the sensor element 3. As shown in FIG. 2, the outer lead portion 44 is connected to a lead wire 192 led out of the gas sensor 1 inside the insulator 13 by a connection fitting 194.

Further, as shown in FIG.
The inner lead electrode (not shown) electrically connected to the inner electrode 02 is also provided with an inner electrode connecting portion 23 provided integrally with the heater holder 2, a lead portion 24 connected thereto, and a lead connected to the lead portion 24 by a connection fitting 193. It is led out of the gas sensor 1 by a line 191. The inner electrode connecting portion 23 is cylindrical and has a diameter substantially equal to the inner diameter near the base end side of the reference gas chamber 41. By inserting the heater holder 2 into the reference gas chamber 41, the inside of the reference gas chamber is naturally formed. It is configured to be in contact with the inner lead electrode formed on the side surface.

Next, the heater holder 2 will be described. As shown in FIG. 1, the heater holder 2 includes a heater holding portion 21, an inner electrode connecting portion 23, a lead portion 24, and a neck portion 22.
And The heater holding portion 21 is annular and has a gap portion 210 provided in the axial direction, and has a C-shaped cross section as shown in FIG. Heater holder 2
1 and the inner electrode connecting portion 23 are connected by a narrow neck portion 22.

The heater holding section 21 is configured so as to become thinner toward the tip, and the tip 211 is the thinnest. The four corners of the heater 29 having a rectangular cross section abut at the front end 211 of the heater holding part 21, and are held and fixed to the heater holding part 21 at the four corners. In portions other than the tip portion 211, the heater 29 is not in contact with the heater holding portion 21, and the four corners are separated as shown in FIG.

In the figure, reference numeral 212 denotes a base end of the heater holding section 21. Reference numeral 230 denotes a flange portion protruding outward in the radial direction. When the heater holder 2 is inserted into the reference gas chamber 41, as shown in FIG. 2, the flange portion 230 comes into contact with the base end surface 49 of the solid electrolyte member 40 and is held and fixed there.

The operation and effect of this embodiment will be described. In the gas sensor 1 of the present embodiment, the heater 29 is
The heater 29 is held only by this contact, and the heater 29 is held. Therefore, the heater holding unit 21
The heater 29 is not rigidly fixed inside the
9 can move easily. Even when the heater 29 is held inclined with respect to the heater holding portion 21, the heater 2
Can move in the heater holding portion 21, so that the heater 29 can be easily inserted and arranged together with the heater holder 2 into the reference gas chamber 41 without causing breakage of the heater 29.

Further, even if an impact is applied to the gas sensor 1 in a state after assembly, the heater 29 remains in the heater holding section 21.
Inside, that is, at the position (m), even if an impact from the sensor element 4 is transmitted to the heater 29,
The movement of the shock absorber 9 alleviates the impact and prevents the heater 29 from breaking.

As described above, according to the present embodiment, it is possible to provide a gas sensor having a structure in which the heater is hardly broken in the reference gas chamber.

In this embodiment, the case where the heater 29 having a rectangular cross section is used has been described. However, as shown in FIG. 3, the same effect as that of the present invention can be obtained by using the heater 291 having a round bar shape. FIG. 4B illustrates a cross-sectional state when the round bar-shaped heater 291 is provided in the heater holding unit 21. This figure is a sectional view taken along the line BB in FIG.

In this embodiment, the case where the integral heater holder 2 is used has been described. However, as shown in FIGS. 7 and 8, the same effect as in this embodiment can be obtained when the heater holder 300 composed of two members is used. Can be obtained. As shown in FIG. 7, the first member 301 includes a heater holding portion 31, a neck portion 32, a tubular portion 33, and a flange portion 330 formed radially outside the tubular portion 33.
Inner electrode connecting portion 340, flange portion 341 formed radially outside of inner electrode connecting portion 340, lead portion 34
And a second member 302 consisting of

The holding of the heater 291 by the heater holder 300 and the insertion into the sensor element 4 are performed as follows. First, the second member 302 is inserted into the sensor element 4. The flange portion 341 contacts the end face 49 of the sensor element 4 and is held here. Further, by the insertion, the inner electrode connection portion 340 comes into contact with the inner lead electrode (not shown) provided on the inner side surface of the reference gas chamber 41.

Next, the heater 29 is attached to the first member 301.
Insert 1. The heater holding portion 31 has the same shape as the above-described heater holding portion 21, and the heater 291 abuts on the heater holding portion 31 at the distal end portion 311 and is held and fixed here. Then, the first member 3 with the heater 291 attached thereto
01 is inserted into the inside electrode connection portion 340 of the second member 302. The flange 330 contacts the proximal end 342 of the inner electrode connection 340 and is held there. Other details are the same as those of the gas sensor according to FIGS.

Embodiment 2 In this embodiment, as shown in FIGS. 9 and 10, a first protrusion is provided on the inner side surface facing the heater, and the first protrusion holds the heater. The holding unit will be described.

The heater holder 21 shown in FIG. 9 has a shape in which two truncated cones are vertically arranged, and the center of the heater holder 21 in the axial direction is the thinnest. This portion becomes the first protrusion 215. Heater 291
Abut on the first protrusion 215 and are held and fixed there. Further, it is preferable that the first protrusion 215 is provided at the center in the axial direction. Other details are the same as in the first embodiment.

The heater holder 2 shown in FIG.
Reference numeral 1 denotes a cylindrical shape having a uniform diameter throughout the axial direction.
A protrusion is provided on the inner side surface, and this is the first protrusion 216.
Becomes As shown in FIG. 10B, the heater 291 abuts on the first protrusion 216 and is held and fixed here. Other details are the same as in the first embodiment.
The position of the protruding portion is preferably at the center in the axial direction. Further, the same effect as that of the first embodiment can be obtained for the gas sensor having the heater holding portion 21 having the above two configurations. Similar effects can be obtained for a heater having a rectangular cross section.

Embodiment 3 In this embodiment, as shown in FIG. 11, a heater holder having a cut portion provided in parallel with the axial direction will be described. FIG.
As shown in FIG. 1, the notch 217 is provided in the heater holder 21.
Is provided at a position facing the gap 210 in the radial direction. The heater 291 comes into contact with the inner side surface of the heater holding portion 21 and is held and fixed thereby. Other details are the same as in the first embodiment.

The heater holder 21 having the shape according to the present embodiment is
A portion having a small width in the axial direction is formed by the provision of the cut portion 217. Reference numeral 218 in FIG. For this reason, the rigidity of the entire heater holding unit 21 decreases. Therefore, the heater 291 can be easily moved together with the heater holding portion 21 to some extent, because it is easy to twist in the direction indicated by the arrow shown in FIG. Therefore, the same operation and effect as those of the first embodiment can be obtained. For the same reason, the same operation and effect can be obtained for a heater having a rectangular cross section.

Embodiment 4 In this embodiment, as shown in FIGS. 12 and 13, a second projecting portion is provided on the outer surface of the inner connecting portion 23 facing the inner surface of the reference gas chamber. The heater holder configured to abut on the side surface of the reference gas chamber in the section will be described.

As shown in FIG. 12, the heater holder 2 of this embodiment has a cylindrical heater holder 21 for holding the heater 291.
And a cylindrical inner electrode connecting portion 23 configured to conduct with the inner electrode, and a lead portion 24 connected to the inner electrode connecting portion 23. The inner electrode connecting portion 23 and the heater holding portion 21 are connected by a neck 22. The heater holding portion 21 rigidly holds the heater 291, and the heater 291 can hardly move inside the heater holding portion 21.

An annular second projecting portion 235 projecting in the radial direction is provided on the outer surface of the inner electrode connecting portion 23. In addition, as shown in FIG. 13, a second protrusion 236 including two protrusions provided in the circumferential direction can be formed. Other details are the same as in the first embodiment.

In this embodiment, the heater 291 is rigidly fixed to the heater holder 21 and cannot move inside the holder 21. However, the second protrusions 235, 2 provided on the inner electrode connection portion 23 of the heater holder 2
Due to 36, a large clearance is formed between the heater holding portion 21 and the inner surface of the reference gas chamber. This is because the outermost protruding ends of the second protrusions 235 and 236 abut against the inner surface of the reference gas chamber, and the second protrusions 235 and 236
This is because the heater holding portion 21 is much thinner than the portion provided with 6 (as is clear from FIGS. 12 and 13).

Therefore, since the heater 291 can move together with the heater holding portion in the reference gas chamber, when the inclined heater hits the inner surface of the reference gas chamber, the heater 291 moves along with the heater 291 to break the heater 291. Can be avoided. As described above, according to the present embodiment, it is possible to provide a gas sensor having a structure in which the heater is hardly broken in the reference gas chamber.

The above embodiments have been described with reference to the oxygen sensor. In addition, the HC sensor, the CO sensor, and the NO sensor may be used.
The same effect can be obtained by applying the present invention to various gas sensors composed of a cup-type solid electrolyte body such as an x sensor and having a structure in which a heater is inserted and arranged in a reference gas chamber. Further, as the oxygen sensor, each of the electromotive force type and the limit current type can be applied.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a heater holder and a heater held therein according to a first embodiment.

FIG. 2 is an explanatory longitudinal sectional view of a gas sensor according to the first embodiment.

FIG. 3 is an explanatory longitudinal sectional view of a gas sensor provided with a heater having a circular section in Embodiment 1;

4A is a diagram showing an embodiment of the present invention, FIG.
FIG. 4 is a sectional view taken along arrow A, and FIG.

FIG. 5 is an explanatory longitudinal sectional view of a main part of a sensor element according to the first embodiment.

FIG. 6 is an explanatory perspective view of a sensor element according to the first embodiment.

FIG. 7 is a perspective developed view of a heater holder composed of two members, a heater, and a sensor element in the first embodiment.

FIG. 8 is an explanatory longitudinal sectional view of a gas sensor including a heater holder composed of two members according to the first embodiment.

FIG. 9 is an explanatory diagram of a heater holder including a heater holding portion having a first protrusion according to a second embodiment.

FIG. 10 is an explanatory diagram of a heater holder including a heater holding portion having a first protrusion according to a second embodiment.

FIG. 11 is an explanatory diagram of a heater holder including a heater holding portion provided with a cut portion according to a third embodiment.

FIG. 12 is a diagram illustrating a heater holder including a heater holding portion having a second protrusion according to a fourth embodiment.

FIG. 13 is an explanatory diagram of a heater holder including a heater holding portion having a second protrusion according to a fourth embodiment.

FIG. 14 is an explanatory view showing a conventional heater holder and a heater held therein.

FIG. 15 is a side view of a conventional heater holding unit.

FIG. 16 is a plan view of a heater holding unit according to the related art.

[Explanation of symbols]

 1. . . Gas sensor, 2. . . Heater holder, 21. . . Heater holding portion, 23. . . Inner electrode connection, 29, 291. . . Heater, 4. . . Sensor element, 40. . . Solid electrolyte body, 41. . . Reference gas chamber,

Claims (6)

[Claims] 1. A reference gas chamber is provided in a cylindrical shape having a bottom,
The reference gas chamber comprises a cup-shaped solid electrolyte body provided with an inner electrode on the inner side facing the reference gas chamber and an outer electrode on the outer side in contact with the gas to be measured, and a heater held and fixed by a heater holder in the reference gas chamber. In a gas sensor having a sensor element inserted and arranged, the heater holder includes a cylindrical heater holding portion for holding a heater, a cylindrical inner electrode connecting portion configured to be electrically connected to the inner electrode, and the inner electrode connecting portion. And a lead portion connected to the heater, wherein the heater holding portion holds the heater so as to move in the heater holding portion. 2. The heater according to claim 1, wherein the heater holding portion is configured to have a smaller diameter from one end to the other end.
A gas sensor characterized in that it is configured to hold the heater at the end having the smallest diameter. 3. The heater according to claim 1, wherein the heater holding portion is provided with a first protrusion on an inner surface facing the heater, and the first protrusion holds the heater. Characteristic gas sensor. 4. The gas sensor according to claim 1, wherein the heater holding portion has a cut portion provided in parallel with the gas sensor axial direction. 5. A reference gas chamber having a cylindrical shape with a bottom and an inside thereof,
The reference gas chamber comprises a cup-shaped solid electrolyte body provided with an inner electrode on the inner side facing the reference gas chamber and an outer electrode on the outer side in contact with the gas to be measured, and a heater held and fixed by a heater holder in the reference gas chamber. In a gas sensor having a sensor element inserted and arranged, the heater holder includes a cylindrical heater holding portion for holding a heater, a cylindrical inner electrode connecting portion configured to be electrically connected to the inner electrode, and the inner electrode connecting portion. Wherein the heater holder is inserted and arranged to be movable in the reference gas chamber. 6. The reference gas chamber according to claim 5, wherein a second protrusion is provided on an outer surface of the inner connection portion facing the inner surface of the reference gas chamber, and the second protrusion contacts the side surface of the reference gas chamber. A gas sensor characterized by being configured as described above.