JPH08160002A - Oxygen sensor structure - Google Patents

Abstract

PURPOSE: To provide an oxygen sensor structure in which the deformation or damage of a metal cylinder due to flying stone can be suppressed to the minimum. CONSTITUTION: The oxygen sensor 1 is so mounted at its outer cylinder 39 at a main body fitting 29 as to cover an inner cylinder 33, a ceramic separator 35, and the outside of a waterproof sealing member 37. The cylinder 39 is formed out of a first cylindrical part 39H1 of the end side having a thickness of 1mm or less, a first stepped part 39D1 bent at about 45 deg. to the part 39H1, a second cylindrical part 39H2 of the center side, a second stepped part 39D2 bent substantially perpendicularly to the part 39H2, and a third cylindrical part 39H3 of the rear end side. The cylinder 39 is welded over the entire outer periphery to the fitting 29 on the lower end side of the part 39H1 having the largest diameter. It is radially clamped by the part 39H3 having the smallest diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor structure applied to, for example, an oxygen sensor for detecting the oxygen concentration in exhaust gas from an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as an oxygen sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine of an automobile or the like, an electromotive force type sensor made of an oxygen ion conductive solid electrolyte (for example, zirconia) and a metal oxide are used. There is a resistance change type such as an object (titania), which is used for the purpose of controlling the air-fuel ratio of the internal combustion engine.

In this type of oxygen sensor, a detection element made of a solid electrolyte or a metal oxide is housed in a container (sensor case) made of a metal shell (for mounting the sensor on an exhaust pipe) and a metal cylinder. The lead wire connected to the detection element extends from the rear end side of the oxygen sensor to the outside of the sensor case.

Further, in recent years, as one method of strengthening the exhaust gas regulation, an oxygen sensor is also attached to the rear of the catalyst so that when one sensor controls the air-fuel ratio, the other sensor discharges the catalyst. It has begun to detect the deterioration of the catalyst from the result of monitoring the state of exhaust gas generated.

[0005]

However, since the oxygen sensor arranged behind the catalyst is usually attached to the lower part of the vehicle body, that is, it is arranged in the immediate vicinity of the road surface, There were various interferences from the road surface.

For example, the oxygen sensor may be completely buried in water accumulated on the road. When the oxygen sensor is submerged in water, water easily enters the inside of the sensor. As a countermeasure, for example, there is a method of sealing a lead wire extending from the detection element to the outside of the sensor case with rubber or the like on the rear end side of the sensor. .

Further, while the vehicle is traveling on an unpaved road, for example, flying stones from the front tires may hit the sensor case, causing deformation or damage to the metal cylinder or the like. When such a deformation occurs, the sealing performance may not be sufficient, and particularly when the above-mentioned submersion occurs when the sealing performance deteriorates, water easily enters the inside of the sensor. Sufficient measures against deformation and damage of the are desired.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an oxygen sensor structure capable of minimizing the deformation or damage of a metal cylinder due to flying stones or the like. .

[0009]

In order to achieve the above-mentioned object, the invention of claim 1 has a metallic shell for mounting an oxygen sensor itself, the tip side of which is directed to a measuring object, at a mounting portion, and a metallic shell on the rear end side. In the oxygen sensor structure provided with the attached metal protective outer cylinder, the metal protective outer cylinder includes three or more types of tubular portions having different arrangement positions in the axial direction, and the distal end side tubular portion has a tubular portion. Two parts are welded all around the metal shell, a waterproof seal member is arranged inside the tubular portion on the rear end side of the tubular portion on the center side, and the adjacent tubular portions are connected to each other. The gist is an oxygen sensor structure including the above-described stress absorbing portion.

According to a second aspect of the present invention, the three or more types of tubular portions have different diameters, the tubular portion on the front end side is the tubular portion having the largest diameter, and the tubular portion on the rear end side is the most tubular portion. The oxygen sensor structure according to claim 1, wherein the oxygen sensor structure is a tubular portion having a small diameter.

The invention of claim 3 is characterized in that the stress absorbing portion is any one of a step, a concave portion and a convex portion formed in an annular shape in the circumferential direction of the metal protective outer cylinder. The gist is the oxygen sensor structure described in 1 or 2.

According to a fourth aspect of the present invention, there is provided an oxygen comprising a metallic shell for mounting an oxygen sensor itself, the tip side of which is directed to an object to be measured, at a mounting portion, and a metal protective outer cylinder mounted at a rear end side of the metallic shell. In the sensor structure, the metal protective outer cylinder is welded to the metal shell at the front end side, and a waterproof seal member is arranged inside the rear end side. An oxygen sensor structure is characterized in that it has a bellows-shaped stress absorbing portion formed in a ring shape.

A fifth aspect of the present invention provides the oxygen sensor structure according to any one of the first to fourth aspects, characterized in that the thickness of the metal protective outer cylinder is in the range of 0.3 to 1 mm. To do. Here, as the detection element, for example, a detection element using a solid electrolyte (eg, zirconia or yttria) whose electromotive force changes depending on the oxygen concentration, or a detection using a metal oxide (eg, titania) whose resistance value changes The element can be adopted.

The waterproof seal member (grommet) preferably has heat resistance, and for example, silicone rubber or fluororubber can be adopted. Either the inner diameter or the outer diameter can be adopted as the diameter of the tubular body. When the metal protective outer cylinder is made of, for example, SUS304 stainless steel, its thickness is preferably about 0.5 mm.

When the ratio of the diameters of the adjacent cylindrical portions of the metal protective outer cylinder is in the range of (small diameter / large diameter) = 0.65 to 0.90, and / or the step difference is 1.0 to. In the case of the range of 3.0 mm, the metal protective outer cylinder is appropriately bent at the step to serve as a cushion, and it is possible to prevent an adverse effect on the seal portion, which is more preferable.

[0016]

According to the invention of claim 1, among the three or more types of tubular portions of the metal protective outer cylinder, the tubular portion on the front end side is welded all around to the metal shell and the tubular portion on the rear end side. A waterproof seal member is disposed inside the, and a stress absorbing portion is provided between the adjacent tubular portions.

Therefore, even if an external force is applied to the metal protective outer cylinder in the lateral direction due to, for example, flying stones, the influence of the external force is relieved by bending at each stress absorbing portion, so that the metal protective outer cylinder is deformed or damaged. Etc. can be minimized. For example, as shown in FIG. 1, even when a stepping stone hits the A part (cylindrical part) of the metal protective outer cylinder and the A part is inclined,
Since the inclination of the A portion is absorbed by the B portion (step),
It is possible to minimize the degree of deformation due to stepping stones and to secure the waterproofness of the seal portion in the A portion, for example. Further, even when flying stones hit the C portion (cylindrical portion) and the C portion inclines, the B portion and the D portion (steps) serve as cushions, and similarly, the degree of deformation is minimized. It is possible to secure the waterproofness in the sealed portion of the portion, and also to mitigate the effect on the welded portion, for example, to maintain the high waterproofness.

According to the second aspect of the present invention, the diameters of the three or more types of tubular portions are different, the tubular portion on the front end side is the tubular portion having the maximum diameter, and the tubular portion on the rear end side is the minimum diameter. Since it is a tubular portion, the diameter of the metal protective outer cylinder becomes smaller toward the rear end side. That is, since the cylindrical portion on the fixed side has the maximum diameter and becomes thinner as it extends, the sensor is stably fixed.

In the invention of claim 3, as the stress absorbing portion,
Any of a step, a concave portion, or a convex portion formed in an annular shape in the circumferential direction of the metal protective outer cylinder can be adopted. Claim 4
In the invention, the metal protective outer cylinder is welded all around to the metal shell at the front end side, and the waterproof sealing member is arranged inside the rear end side. Further, the metal protective outer cylinder is annular in the circumferential direction. It has a formed bellows-shaped stress absorbing portion.

Therefore, similarly to the first aspect of the invention, even when an external force is applied laterally to the metal protective outer cylinder by, for example, stepping stones or the like, it is bent by the bellows-shaped stress absorbing portion and the influence of the external force is exerted. Since it is relieved, it is possible to minimize the deformation and damage of the metal protective outer cylinder.

In the invention of claim 5, since the thickness of the metal protective outer cylinder is in the range of 0.3 to 1 mm, for example, when stepping stones or the like hit the metal protective outer cylinder, the metal is formed at the step or the like. It is possible to prevent the adverse effect on the seal portion by minimizing the degree of deformation by the protective outer cylinder bending appropriately and acting as a cushion.

[0022]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above. In each figure, the upper and lower parts respectively indicate the rear end side and the front end side of the sensor. (Example 1) As shown in FIG. 2, the oxygen sensor 1 of this example
Uses an electromotive force detection type detection element 3 made of an oxygen ion conductive solid electrolyte such as zirconia as an element for detecting oxygen concentration.

The detection element 3 is a cylindrical body having one end (front end side) closed and the other end (rear end side) opened, and a flange 3a outside the center thereof. The inner surface electrode 5 made of, for example, platinum is provided on the side and the outer surface side.
And outer surface electrodes 7 are respectively formed. Further, a terminal fitting 9 (only one of which is shown in the figure) is connected to the electrodes 5 and 7, and lead wires 13 and 14 for extracting a signal to the outside are connected to the terminal fitting 9.

A rod-shaped heater 17 is inserted in the long concave internal space of the detecting element 3 in order to heat the detecting element 3, and a terminal fitting 10 (which is connected to an electrode (not shown) of the heater 17 is connected. Lead wires 15 and 16 are also connected to (only one side is shown in the drawing).

The detecting element 3 is fixed in a metal shell 29 made of heat-resistant metal through a cylindrical holding member 21 made of ceramics, talc powder 25, a cylindrical pushing member 27 made of ceramics and the like. That is, the detection element 3 is fixed with its axial center aligned so that it extends through the metal shell 29 and extends vertically.

Below the metal shell 29, the detection element 3
A protective cap 31 (having an opening 31a) that covers the periphery of the tip side of the is attached. Further, on the upper portion (rear end side) of the metal shell 29, an inner cylinder 33 made of a heat-resistant metal made of, for example, stainless steel is attached by caulking or the like so as to cover the periphery of the detection element 3 and the heater 17. .

Further, the lead wire 13 is provided on the upper part of the inner cylinder 33.
To 16 through which a substantially cylindrical ceramic separator 35 penetrates
And a waterproof seal member 37, which is a heat-resistant grommet rubber (also through which the lead wires 13 to 16 penetrate), is arranged above the ceramic separator 35. There is a step 35a on the outer circumference of the ceramic separator 35, and the upper end (bent inward) 33a of the inner cylinder 33 is locked at the step 35a.

Particularly, in this embodiment, an outer cylinder 39 is attached to the upper portion of the metal shell 29 so as to cover the inner cylinder 33, the ceramic separator 35 and the prevention seal member 37. This outer cylinder 39 has a thickness of 1 mm or less (for example, 0.6 m
m), and from the bottom of the figure, the first with an outer diameter of 19 mm on the tip side
Cylindrical portion 39H1 and first tubular portion 39H1 and first step with a height of 25 mm in the axial direction and a radial step width of 1.5 mm (from the upper end 29a1 of the collar portion 29a of the metallic shell 29) bent at approximately 45 ° Portion 39D1, second cylindrical portion 39H having an outer diameter of 16 mm on the central side
2, axial height 45 mm (also from the upper end 29a1 of the collar portion 29a) bent almost at right angles to the second tubular portion 39H2.
It comprises a second step portion 39D2 having a radial step width of 1.5 mm and a third tubular portion 39H3 having an outer diameter of 12 mm on the rear end side.

The outer cylinder 39 is the first with the largest diameter.
At the lower end side of the tubular portion 39H1, the upper portion 29 of the metallic shell 29 is
It is externally fitted to b and is welded all around by, for example, laser welding for waterproofing. Further, the third cylindrical portion 39H3 having the smallest diameter is crimped in the radial direction, for example, hexagonal crimping, octagonal crimping, round crimping, etc., to press and fix the waterproof seal member 37.

As described above, in this embodiment, the thickness of the outer cylinder 39 is 1 mm or less, the step portions 39D1 and 39D2 are provided at two positions, and the outer diameters of the cylindrical portions 39H1 to H3 are different. Since it is configured, even if an external force is applied to the outer cylinder 39 in the lateral direction by flying stones or the like, the stepped portions 39D1 and 39D2 are bent, so that the influence of the external force can be mitigated. That is, this sensor structure allows the outer cylinder 39
It is possible to minimize the deformation of the above and reduce the distortion or the like of the waterproof seal portion, so that it is possible to secure sufficient waterproofness. As a result, even in a harsh environment such as a bad road, there is a remarkable effect that the oxygen concentration can be satisfactorily detected during the entire usage period of the sensor.

Further, when the oxygen sensor 1 is mounted on the downstream side of the catalyst of the vehicle, when it is submerged in water, the outer cylinder 39 itself tends to deform due to thermal stress, but even in that case, the step portions 39D1 and 39D2 are also formed. As a buffer for stress,
There is an advantage that the deformation can be suppressed and high waterproofness can be secured also in that respect. (Embodiment 2) Next, Embodiment 2 will be described, but the description of the same parts as those in Embodiment 1 will be simplified or omitted.

As shown in FIG. 3, the oxygen sensor 5 of the present embodiment.
1 uses a detection element 53 of a type that detects a change in resistance, which includes a sensing substance made of a metal oxide such as titania, as an element that detects oxygen concentration.
The detection element 53 is a rod-shaped body in which a metal oxide 53b such as titania is arranged on the tip side of a substrate 53a such as alumina, and an electrode (not shown) is connected to the metal oxide 53b. Terminal fittings 55 (only one is shown in the figure) are connected to these electrodes, and lead wires 56 and 57 for taking out signals to the outside are connected to the terminal fittings 55. Further, a heater (not shown) is formed on the substrate 53a to heat the metal oxide 53b, and a lead wire 58, 59 is connected.

The detection element 53 and the terminal fittings 55, 60
Is partially fixed by being sealed with glass 63 in a cylindrical holding member 61 made of ceramics having a flange portion 61a, and the holding member 61 is made of a heat resistant metal through a talc 65. It is fixed in the metallic shell 67. That is, the detection element 53, while being held by the holding member 61, is fixed so that its axial center is aligned so as to penetrate the metal shell 67 and extend vertically.

A ceramic separator 54, through which the lead wires 56 to 59 penetrate, and a waterproof sealing member 71, which is a heat-resistant grommet rubber, are arranged above the detecting element 53. A protective cap 69 is attached to the lower portion of the metallic shell 67 to cover the periphery of the front end side of the detection element 53 (having an opening 69a).

Particularly in this embodiment, an outer cylinder 73 is attached to the upper part of the metal shell 67 so as to cover the outer sides of the holding member 61 and the waterproof seal member 71. This outer cylinder 73 is
The thickness is 1 mm or less (for example, 0.5 mm), and the first tubular portion 73H1 and the first tubular portion 73H1 having an outer diameter of 20 mm on the leading end side are bent at approximately 45 ° from the lower side of the figure (mainly Metal fittings 67
Axial height 15mm (from the upper end 67a1 of the collar 67a)
First radial step portion 73D1 having a radial step width of 1.5 mm, second tubular portion 73H2 having a central outer diameter of 17 mm, and second tubular portion 73H2
Is bent almost at a right angle (also the upper end 67 of the collar portion 67a).
Axial height 40 mm, radial step width 2.0 mm (from a1)
The second step portion 73D2 and the rear end side third cylindrical portion 73H3 having an outer diameter of 13 mm.

The outer cylinder 73 is the first with the largest diameter.
At the lower end side of the tubular portion 73H1, it is fitted onto the step 67b above the metallic shell 67 and welded all around for waterproofing. Further, the third tubular portion 73H3 having the smallest diameter is crimped in the radial direction, for example, hexagonal crimping, octagonal crimping, round crimping, etc., and the waterproof seal member 71 is pressed and fixed.

As described above, in this embodiment, the thickness of the outer cylinder 73 is 1 mm or less, the step portions 73D1 and 73D2 are provided at two places, and the outer diameters of the cylindrical portions 73H1 to H3 are different. Since it is configured, as in the first embodiment, even when an external force is applied to the outer cylinder 73 in the lateral direction due to flying stones or the like, the stepped portions 73D1 and 73D2 are bent to minimize the deformation of the outer cylinder 73. It is possible to suppress the distortion and the like to the waterproof seal portion and secure sufficient waterproofness. As a result, the oxygen concentration can be satisfactorily detected over the entire usage period of the sensor.

Particularly in this embodiment, since the internal space is large, there is an advantage that the adaptability to a larger external force is high. Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it is needless to say that the present invention can be implemented in various modes without departing from the scope of the present invention.

For example, as shown in FIG. 4 (a), the outer cylinder 82 is formed up to the upper part of the waterproof seal member 81, and as shown in FIG. 4 (b), the tubular portion 83 on the tip side. And the tubular portion 84 on the rear end side have the same diameter, as shown in FIG. 4C, the tubular portion 8 on the rear end side on which the waterproof seal member 86 is arranged.
7 is provided with a small-diameter tubular portion 89 at a position closer to the tip end side, one using many stepped portions 90 as shown in FIG. 4 (d), and one shown in FIGS. 4 (e) to 4 (g). Similarly, the stress absorbing portions 91, 92, 93 having concave or convex shapes instead of the steps can be applied.

Further, as shown in FIG. 4 (h), the tubular portion 95
A bellows-shaped stress absorbing portion 96 may be provided in the. That is, in the case of a structure in which the inside is a space, as in the above-described embodiment, most of the heat received at the tip is from the outer cylinder, so by increasing the heat transfer path like a bellows, The heat received by the grommet rubber is reduced, resulting in a shorter overall length.

Further, for example, the angle of the stepped portion in the first and second embodiments is, for example, 3 in a taper shape with respect to the tubular portion.
The angle may be in the range of 0 to 90 °, more preferably 45 ° or more. Further, the side surface of the tubular portion may be parallel to the axial direction, but may be slightly inclined in a taper shape.

Further, for example, when the oxygen sensor described above is arranged, for example, on the downstream side of a catalyst for purifying exhaust gas of a vehicle, the sealing performance is not impaired even if the metal cylinder is deformed by flying stones or the like, and its function is maintained. It is preferable because it can be exerted, but it is not limited to that position. For example, even if it is arranged under the floor of the vehicle, such as upstream of the catalyst, it can sufficiently exhibit its function.

[0043]

As described in detail above, according to the invention of claim 1, of the three or more types of tubular portions of the metal protective outer tube, the tubular portion on the tip side is welded all around to the metal shell. At the same time, a waterproof seal member is arranged inside the tubular portion on the rear end side, and a stress absorbing portion is provided between adjacent tubular portions.

Therefore, even if an external force is applied laterally to the metal protective outer cylinder due to, for example, flying stones, the influence of the external force is mitigated by bending at each stress absorbing portion, so that the deformation of the metal protective outer cylinder is minimized. It can be kept to the limit and sufficient waterproofness can be secured. As a result, there is a remarkable effect that good waterproof performance is exhibited throughout the entire period of use of the sensor, and the measurement accuracy can be maintained and improved.

Further, when the sensor is submerged in water, the metal protective outer cylinder tends to be deformed by thermal expansion due to temperature change. However, since the stress absorbing section can absorb the thermal expansion, the entire deformation of the sensor. Is suppressed, thus
There is an advantage that it is possible to prevent the sealing property of the waterproof sealing portion from being impaired.

According to the second aspect of the present invention, the diameters of the three or more tubular portions are different, the tubular portion on the front end side is the tubular portion with the maximum diameter, and the tubular portion on the rear end side is the minimum diameter. Since it is the tubular portion, the diameter of the metal protective outer cylinder becomes smaller toward the rear end side, and there is an effect that the sensor is stably fixed.

In the invention of claim 3, as the stress absorbing portion,
Any of a step, a concave portion, or a convex portion formed in an annular shape in the circumferential direction of the metal protective outer cylinder can be adopted. Claim 4
In the invention, the metal protective outer cylinder is welded all around to the metal shell at the front end side, and the waterproof sealing member is arranged inside the rear end side. Further, the metal protective outer cylinder is annular in the circumferential direction. It has a formed bellows-shaped stress absorbing portion.

Therefore, as in the first aspect of the present invention, even when an external force is applied to the metal protective outer cylinder in the lateral direction by, for example, flying stones, the metal protective outer cylinder is bent by bending at the bellows-shaped stress absorbing portion. It is possible to minimize deformation and damage of the. In the invention of claim 5, since the thickness of the metal protective outer cylinder is within the predetermined range, the tubular portion is not deformed so much even when an external force in the lateral direction is received, and the metal protective outer cylinder is not deformed at a step or the like. It is possible to prevent the adverse effect on the seal portion by bending the cylinder appropriately and acting as a cushion.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the operation of the oxygen sensor structure of the present invention.

FIG. 2 is an explanatory diagram showing a partial judgment of the oxygen sensor of the first embodiment.

FIG. 3 is an explanatory view showing a partial judgment of an oxygen sensor according to a second embodiment.

FIG. 4 is an explanatory diagram showing another embodiment.

[Explanation of symbols]

1, 51 ... Oxygen sensor 3, 53 ... Detection element 13, 14, 15, 16, 56, 57, 58, 59 ... Lead wire 29, 67 ... Metal shell 33 ... Inner cylinder 37, 71, 81, 86 ... Waterproof seal Member 39, 73, 82 ... Outer cylinder 39H1, 39H2, 39H3, 73H1, 73H2, 73
H3, 83, 84, 87, 39D1, 39D2, 73D1,
73D2, 90 ... Step portion 89, 95 ... Cylindrical portion 91, 92, 93, 96 ... Stress absorbing portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Kojima 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Nihon Special Ceramics Co., Ltd.

Claims (5)

[Claims] 1. An oxygen sensor structure comprising: a metal shell for mounting an oxygen sensor itself, the front end of which is directed toward an object to be measured, at a mounting portion; and a metal protective outer cylinder mounted on a rear end side of the metal shell, The metal protective outer cylinder is provided with three or more kinds of tubular parts having different axial arrangement positions, and is welded all around to the metal shell at the distal end tubular part, and is located behind the central tubular part. A waterproof seal member is arranged inside the end-side tubular portion,
Further, the oxygen sensor structure is characterized in that it is provided with two or more stress absorbing parts as a structure for connecting the adjacent cylindrical parts. 2. The three or more types of tubular portions have different diameters, the tip-side tubular portion is the tubular portion having the largest diameter, and the tubular portion on the rear end side is the tubular portion having the minimum diameter. The oxygen sensor structure according to claim 1, wherein: 3. The step according to claim 1 or 2, wherein the stress absorbing portion is any one of a step, a concave portion and a convex portion formed in an annular shape in the circumferential direction of the metal protective outer cylinder. Oxygen sensor structure. 4. An oxygen sensor structure comprising: a metal shell for mounting an oxygen sensor itself, the tip side of which is directed to an object to be measured, at a mounting site; and a metal protective outer cylinder mounted on a rear end side of the metal shell, The metal protective outer cylinder is welded to the metal shell all around the front end side, and a waterproof seal member is arranged inside the rear end side. Further, the metal protective outer cylinder is formed annularly in the circumferential direction. An oxygen sensor structure having a bellows-shaped stress absorbing portion. 5. The thickness of the metal protective outer cylinder is 0.3 to 1 mm.
The oxygen sensor structure according to any one of claims 1 to 4, wherein the oxygen sensor structure is in a range of.