JP6778125B2 - Exhaust gas sensor - Google Patents

Description

The present invention relates to an exhaust gas sensor that detects components in exhaust gas.

Exhaust gas sensors that are attached to the exhaust pipe of an internal combustion engine mounted on a vehicle or the like to detect components of exhaust gas flowing in the exhaust pipe (for example, oxygen, NOx, CO, HC (hydrocarbon), etc.) are known.

For such an exhaust gas sensor, for example, as shown in Patent Document 1 (see FIG. 1 of Patent Document 1), in consideration of the relationship with the main metal fitting, the annular main body portion of the main metal fitting and the main metal fitting It is located on the tip side of the main body and is attached to the exhaust pipe or placed inside the exhaust pipe, and on the rear end side of the main metal fittings and placed outside the exhaust pipe. There is a form consisting of an outer part. In such an exhaust gas sensor, the exhaust gas sensor is fixed to the exhaust pipe by using the main metal fitting, such as screwing and fixing the male screw part of the main metal fitting to the female screw portion provided in the sensor mounting portion of the exhaust pipe. At the same time, the tip side portion is arranged in the exhaust pipe. On the other hand, the outer portion is arranged outside the exhaust pipe, and the connection wiring for connecting to the power supply wiring and the network wiring such as the CAN bus extends.

The outer portion of the exhaust gas sensor has an outer cylinder in a form that surrounds the radial direction orthogonal to the axis of the exhaust gas sensor, and protects each member inside the outer portion. For example, in the exhaust gas sensor shown in Patent Document 1, the outer cylinder has a three-stage cylindrical shape whose diameter becomes smaller toward the rear end side. The vicinity of the opening end on the front end side of the outer cylinder (lower end in FIG. 1 of Patent Document 1) is fixed to the main metal fitting, while the opening end on the rear end side of the outer cylinder (upper end in FIG. The connection wiring (lead wire) extends to the rear end side through the grommet.

Japanese Unexamined Patent Publication No. 2015-132491

However, when the main metal fitting of the exhaust gas sensor of this form is fixed to the exhaust pipe and attached to the exhaust pipe, the outer cylinder is fixed to the main metal fitting near the front end side opening end, while the rear end side opening end. Is in an unfixed cantilevered state. Here, when the internal combustion engine is driven or the vehicle is driven, the vicinity of the rear end side opening end repeatedly vibrates in the direction orthogonal to the axis line due to the vibration of the connection wiring extending from the rear end side opening end. Receive a load. Then, of the outer cylinders, from the stepped first step portion connecting between the first cylinder portion on the base end side and the second cylinder portion in the center, to the rising portion (corner portion) where the second cylinder portion rises. It has become clear that stress is concentrated and defects such as cracks may occur in this part.
This case has been made in view of such a problem, and provides an exhaust gas sensor having a highly reliable outer cylinder.

One aspect for solving the above-mentioned problems is an annular main body of the main metal fitting and a tip that is located on the tip side of the main body of the main metal fitting and is attached to or placed in the exhaust pipe. An exhaust gas sensor having a side portion and an outer portion located on the rear end side of the main metal fitting with respect to the main body portion and arranged outside the exhaust pipe, and holding a gas sensor element inside. The outer portion has a cylindrical shape connecting the front end side opening end and the rear end side opening end, and has an outer cylinder forming an outer shell of the outer portion, and the outer cylinder is from the front end side opening end to the rear end side. A cylindrical first cylinder that extends and is fixed to the main metal fitting at the tip of the first cylinder, and a cylindrical portion that is smaller in diameter than the first cylinder and is located on the rear end side and extends to the rear end side. The second cylinder has a smaller diameter than the second cylinder and is located on the rear end side and extends to the rear end side, and the connection wiring extends to the rear end side to form a rear end side open end. A three-cylinder portion, a stepped first step portion located between the first cylinder portion and the second cylinder portion, and a stepped portion located between the second cylinder portion and the third cylinder portion. The second cylindrical portion has a rising portion rising from the first step portion to the rear end side with a predetermined radius of curvature R and a predetermined gradient θt following the rising portion. The exhaust gas sensor includes a tapered portion formed of a linear tapered portion whose diameter becomes smaller toward the rear end side, and a cylindrical connecting cylindrical portion extending from the tapered portion toward the rear end side and connected to the second stage portion.

Also in the exhaust gas sensor of the present invention, by fixing the main metal fitting to the exhaust pipe, the vicinity of the opening end on the tip side of the outer cylinder (the tip portion of the first cylinder portion) is fixed, and then the opening end on the rear end side of the outer cylinder When a force is applied in the direction orthogonal to the axis line, stress is concentrated on the rising portion (corner portion) of the tapered portion from the first step portion to the second cylinder portion.
However, in this exhaust gas sensor, a linear tapered portion is provided in the second cylinder portion of the outer cylinder having a three-stage cylindrical shape in addition to the rising portion that rises and extends from the first stage portion. Therefore, the degree of stress concentration on the rising portion can be reduced as compared with the case where the linear tapered portion is not provided. It is probable that the concentration of stress on the rising portion (rising portion of the tapered portion) of the second cylinder portion could be alleviated by providing the linear tapered portion between the connecting cylindrical portion and the rising portion of the second cylinder portion. .. Thus, it is possible to obtain a highly durable exhaust gas sensor in which the outer cylinder is suppressed from breaking near the rising portion (the rising portion of the tapered portion) of the second cylinder portion due to the vibration of the connection wiring or the like.

The radius of curvature R of the rising portion provided on the second cylinder portion is preferably half to 1.5 times the thickness of the outer cylinder. If the predetermined gradient θt of the linear taper portion is larger than 0 degrees, the stress relaxation effect is achieved, but if it is at least 2.5 degrees or more, the linear taper portion is not provided (that is, when θt = 0 degrees). The stress generated in the rising portion can be significantly relaxed as compared with the above.

In the exhaust gas sensor described above, the linear tapered portion of the second cylinder portion of the outer cylinder has a gradient θt of 5 degrees or more (θt ≧ 5 deg), and the outer cylinder measured from the first stage portion. It is preferable to use an exhaust gas sensor having a length y in the axial direction of 6.0 mm or more (y ≧ 6.0 mm).

This exhaust gas sensor has a form of a linear taper having a gradient θt ≧ 5 deg and a length y ≧ 6.0 mm on the rear end side of the tapered portion of the second tubular portion of the outer cylinder having a three-stage cylindrical shape. And said. Therefore, by fixing the main metal fitting of the exhaust gas sensor, the tip of the first cylinder of the outer cylinder (near the opening end of the tip of the outer cylinder) is fixed, and then the axis line is attached to the opening end on the rear end side of the outer cylinder. When a force in the direction orthogonal to is applied, the stress generated in the rising portion of the second cylinder portion (rising portion of the tapered portion) is significantly larger than that in the case where the tapered portion is not provided in the second cylinder portion. Can be reduced to. Therefore, it is possible to obtain a highly durable exhaust gas sensor in which the outer cylinder is suppressed from breaking near the rising portion of the second cylinder portion due to the vibration of the cable or the like.

Alternatively, in the exhaust gas sensor, the linear tapered portion of the second cylinder portion of the outer cylinder has a gradient θt of 10 degrees or more (θt ≧ 10 deg), and the outer cylinder measured from the first stage portion. It is preferable to use an exhaust gas sensor having a length y in the axial direction of 3.0 mm or more (y ≧ 3.0 mm).

This exhaust gas sensor has a shape of a linear taper having a gradient θt ≧ 10 deg and a length y ≧ 3.0 mm on the rear end side of the tapered portion of the second tubular portion of the outer cylinder having a three-stage cylindrical shape. And said. Therefore, by fixing the main metal fitting of the exhaust gas sensor, the tip of the first cylinder of the outer cylinder (near the opening end of the tip of the outer cylinder) is fixed, and then the axis line is attached to the opening end on the rear end side of the outer cylinder. When a force in a direction orthogonal to is applied, the stress generated in the rising portion (rising portion of the tapered portion) of the second cylinder portion can be reduced as compared with the case where the tapered portion is not provided.

It is a half sectional view of the gas sensor which concerns on embodiment. It is an enlarged sectional view of the part C in FIG. It is explanatory drawing which shows a mode that the front end side opening end end is fixed, and the force in the direction orthogonal to the axis line is applied to the rear end side opening end of the outer cylinder used for an embodiment and a conventional gas sensor.

(Embodiment)
Hereinafter, embodiments of the present invention will be described.
First, the gas sensor (oxygen sensor) 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. The direction along the axis AX of the gas sensor 1 shown in FIG. 1 (vertical direction in the figure) is defined as the axis direction AH, and among the axis directions AH, the front end side AH1 (lower in the figure) and the rear end side AH2 (FIG. 1). (Middle, upper), and the orthogonal direction BH orthogonal to the axis AX are defined as shown in FIG.

The gas sensor 1 shown in FIG. 1 is a mounting portion EPH of an exhaust pipe EP of an internal combustion engine (not shown) shown by a broken line in FIG. 1 by assembling an annular main metal fitting 2 and a sensor element 10 or the like to the main metal fitting 2. It can be installed. The gas sensor 1 extending in the axial direction AH is located on the main body 2A of the main metal fitting 2 and the tip side of the main body 2A in the axial direction AH, and is mounted on the exhaust pipe EP or arranged in the exhaust pipe EP. The tip side portion 3 and the outer portion 4 located on the rear end side of the main body portion 2A and arranged outside the exhaust pipe EP are provided, and a plate-shaped sensor element 10 extending in the axial direction AH is held inside. doing.

The main metal fitting 2 has a cylindrical shape, a cylindrical main body portion 2A, and a mounting portion 2B having a male screw portion 2BS on the outer surface extending from the main body portion 2A to the tip side AH1 and being fixed to the exhaust pipe. It has a cylindrical rear end side portion 2C extending from the main body portion 2A to the rear end side AH2 and forming a caulking portion 2CC whose rear end portion is crimped inward. The main metal fitting 2 holds the sensor element 10 inward with the front end portion 10S of the sensor element 10 protruding toward the front end side and the rear end portion 10K protruding toward the rear end side from the main metal fitting 2. Specifically, between the inner peripheral surface of the main metal fitting 2 and the outer peripheral surface of the sensor element 10, a ceramic annular holding member 12 and a powder filler (talc powder) 13 surrounding the outer peripheral surface of the sensor element 10 , 14 and the ceramic sleeve 15 are held in the main metal fitting 2 in this order from the tip side. Then, the sensor element 10 is fixed in the main metal fitting 2 by crimping the caulking portion 2CC located at the rear end of the main metal fitting 2 and pressing the sleeve 15 toward the tip side via the packing 16.

The tip side portion 3 of the gas sensor 1 is mounted on the mounting portion EPH of the exhaust pipe EP or is arranged in the exhaust pipe EP. That is, when the male screw portion 2BS formed in the mounting portion 2B of the main metal fitting 2 is screwed into the mounting portion EPH of the exhaust pipe EP, the portion of the AH1 on the tip side of the male screw portion 2BS of the mounting portion 2B is inside the exhaust pipe EP. (See FIG. 1). A metal protector 21 that surrounds the tip portion of the sensor element 10 is mounted on the outer periphery of the AH1 on the tip side of the mounting portion 2B on the tip side of the male screw portion 2BS by laser welding. Of the tip 10S of the sensor element 10, the detection unit 10P that detects gas is covered with a porous protective layer.

On the other hand, the main body portion 2A of the main metal fitting 2 and the outer portion 4 of the rear end side AH2 thereof are arranged outside the exhaust pipe EP. Of the sensor element 10, the rear end portion 10K protruding toward the rear end side AH2 from the rear end side portion 2C of the main metal fitting 2 is surrounded by a cylindrical ceramic separator 31. Electrode pads 10e (two on each surface, for a total of four) are exposed at the rear end portion 10K, and the terminal fittings 32 held by the separator 31 come into contact with the electrode pads 10e, respectively. It is conducting.
A grommet 35, which is a cylindrical and rubber sealing member, is arranged on the rear end side AH2 of the separator 31 so as to be separated from the separator 31, and a lead wire 33 conducting to the terminal fitting 32 is passed through the grommet 35. It extends to the rear end side AH2 (upper in FIG. 1).

Of the outer portion 4 of the gas sensor 1, the separator 31, the grommet 35, and the rear end side portion 2C of the main metal fitting 2 are made of metal and are formed by deep drawing to form an outer shell of these, a three-stage cylindrical outer cylinder 50. It is covered with. The outer cylinder 50 has a three-stage cylindrical shape connecting between the front end side opening end 50S of the front end side AH1 and the rear end side opening end 50K of the rear end side AH2. The outer cylinder 50 has a cylindrical first cylinder portion 52 extending from the front end side opening end 50S to the rear end side AH2, and is located at the rear end side AH2 with a smaller diameter than the first cylinder portion 52 and is located on the rear end side AH2. A cylindrical second cylinder portion 54 that extends and a cylindrical third cylinder that is smaller in diameter than the second cylinder portion 54 and is located at the rear end side AH2 and extends to the rear end side AH2 to form a rear end side opening end 50K. A stepped first step 53 located between the first cylinder 52 and the second cylinder 54, and a step 53 located between the second cylinder 54 and the third cylinder 56. It has a second stage portion 55 of the above. The tip side portion of the outer cylinder 50, that is, the tip portion 52B of the first cylinder portion 52 is welded and fixed to the rear end side portion 2C of the main metal fitting 2 by the welded portion 52L over the entire circumference.

The separator 31 presses the holding metal fitting 34 outerly fitted to the separator 31 to form a caulking portion 52C by crimping so that a part of the first cylinder portion 52 of the outer cylinder 50 is recessed inward. Therefore, it is locked between the holding metal fitting 34 and the first step portion 53 of the outer cylinder 50.

Further, the second cylinder portion 54 of the outer cylinder 50 has a length y (in this embodiment, y = 7 mm) that rises from the first step portion 53 to the rear end side AH2 and extends to the rear end side AH2. Includes a tapered portion 54T and a cylindrical connecting cylindrical portion 54D extending from the tapered portion 54T to the rear end side AH2 and connected to the second step portion 55 (see also FIG. 2).

Of these, the tapered portion 54T is connected to the rising portion 54TU that rises from the first step portion 53 to the rear end side (upper in the figure) and the rear end side AH2 of the rising portion 54TU, and has a gradient θt (θt = in this embodiment). It is composed of a linear taper portion 54TL having a linear taper shape of 95deg).
The rising portion 54TU is also a rising portion 54U of the second cylinder portion 54. The rising portion 54TU is bent by the radius of curvature R and rises from the first step portion 53, and the radius of curvature R is half to 1.5 of the thickness Th of the outer cylinder 50 (thickness Th in the first step portion 53). It is said to be twice as large (R = 0.5Th to 1.5Th). In the gas sensor 1 of the present embodiment, specifically, Th = 0.5 mm and R = 0.5 mm.

In the second cylinder portion 54 of the outer cylinder 50, the tapered portion 54T including the linear tapered portion 54TL is not provided as in the present embodiment, but only the same rising portion as the rising portion 54TU is provided as shown by the broken line in FIG. In the case of a conventional outer cylinder in which most of the second cylinder portion 54 is composed of a cylindrical portion similar to the connecting cylindrical portion 54D, the outer cylinder breaks at the rising portion when the internal combustion engine and the vehicle on which the second cylinder portion 54 is continuously subjected to vibration. There was a case. The lead wire 33 vibrates due to the vibration of the vehicle or the like, and the rear end side opening end 50K of the outer cylinder 50 vibrates in the orthogonal direction BH together with the grommet 35. That is, as shown by the broken line in FIG. 3, the outer cylinder 50 is vibrated to the rear end side opening end 50K of the third cylinder portion 56 in a state where the vicinity of the front end side opening end 50S of the first cylinder portion 52 is fixed. The force F is repeatedly applied in the orthogonal direction BH. Therefore, it is considered that the stress caused by this is concentrated on the rising portion of the second cylinder portion 54, causing the fracture.

On the other hand, in the gas sensor 1 of the present embodiment, the second cylinder portion 54 of the outer cylinder 50 having a three-stage cylindrical shape is provided with a linear tapered portion 54TL in addition to the rising portion 54TU that rises and extends from the first stage portion 53. It is provided. Therefore, the degree of stress concentration on the rising portion 54TU (rising portion 54U) can be reduced as compared with the conventional outer cylinder not provided with the linear tapered portion 54TL. By providing the linear tapered portion 54TL between the connecting cylindrical portion 54D and the rising portion 54TU of the second tubular portion 54, the stress on the rising portion 54U of the second tubular portion 54 (the rising portion 54TU of the tapered portion 54T) is applied. This is probably because the concentration could be eased. Thus, with the highly durable gas sensor 1 that suppresses the outer cylinder 50 from breaking near the rising portion 54U of the second cylinder portion 54 (the rising portion 54TU of the tapered portion 54T) due to the vibration of the lead wire 33 or the like. can do.

As shown in FIG. 3, the outer cylinder 50 is orthogonal to the rear end side opening end 50K of the third cylinder portion 56 in a state where the tip end side opening end 50S of the first cylinder portion 52 is fixed to the fixing plate FI. When stress analysis was performed by the finite element method in which the force F in the direction BH was applied, when the gradient θt of the linear tapered portion 54TL was 95 degrees or more (θt ≧ 95 deg), the length y of the tapered portion 54T was 6.0 mm or more. It was found that by setting (y ≧ 6.0 mm), the stress causing breakage was lower.

Further, when the gradient θt of the linear tapered portion 54TL is 100 degrees or more (θt ≧ 100 deg), the length y of the tapered portion 54T is set to 3.0 mm or more (y ≧ 3.0 mm) to break the fracture. It was found to be less than the stress generated.
When the gradient θt is increased, the effect of stress dispersion in the vicinity of the rising portion 54TU becomes higher, so that it is considered that the same effect can be obtained even if the length y is small.

In the above, the present invention has been described according to the embodiment, but it goes without saying that the present invention is not limited to the above-described embodiment and can be appropriately modified and applied without departing from the gist thereof.

1 Gas sensor (exhaust gas sensor)
AH Axial direction AH1 (Axial direction) Tip side AH2 (Axial direction) Rear end side BH (Orthogonal to the axis) Orthogonal direction 2 Main bracket 2A Main body 2B Mounting part 2C Rear end side part 3 Tip side part 4 Outer part 10 Sensor element 33 Lead wire (connection wiring)
35 Grommet 50 Outer cylinder 50S (Outer cylinder) Tip side opening end 50K (Outer cylinder) Rear end side opening end 52 1st cylinder part 52B (1st cylinder part) Tip part (1st cylinder part tip part)
52L Welded part 52C Caulking part 53 1st step part 54 2nd cylinder part 54U (2nd cylinder part) Rising part 54T Tapered part θt (Tapered part) Gradient y (Tapered part) Length 54TU (Tapered part) Rising part R (Rising part) Curvature Th (Outer cylinder) Thickness 54TL Linear taper part 54D Connecting cylindrical part 55 Second stage part 56 Third cylinder part

Claims (3)

The annular body of the main metal fittings and
The tip side portion of the main metal fitting, which is located on the tip side of the main body portion and is mounted on the exhaust pipe or arranged in the exhaust pipe,
The main metal fitting is provided with an outer portion located on the rear end side of the main body portion and arranged outside the exhaust pipe.
An exhaust gas sensor that holds a gas sensor element inside.
The outer part is
It has a tubular shape that connects the front end side opening end and the rear end side opening end, and has an outer cylinder that forms the outer shell of the outer portion.
The above outer cylinder is
A cylindrical first cylinder portion extending from the tip end side opening end to the rear end side and fixed to the main metal fitting at the tip end portion of the first cylinder portion.
A tubular second cylinder that has a smaller diameter than the first cylinder and is located on the rear end side and extends toward the rear end.
A cylindrical third cylinder portion having a diameter smaller than that of the second cylinder portion, located on the rear end side and extending to the rear end side, and the connection wiring extending to the rear end side to form an open end on the rear end side.
A stepped first step portion located between the first cylinder portion and the second cylinder portion,
It has a stepped second step portion located between the second cylinder portion and the third cylinder portion.
The second cylinder part is
A tapered portion consisting of a rising portion rising from the first step portion on the rear end side with a predetermined radius of curvature R and a linear tapered portion having a predetermined gradient θt following the rising portion and having a smaller diameter toward the rear end side. as well as,
An exhaust gas sensor including a cylindrical connecting cylindrical portion extending from the tapered portion to the rear end side and connected to the second stage portion. The exhaust gas sensor according to claim 1.
The linear tapered portion of the second tubular portion of the outer cylinder is
The gradient θt is 5 degrees or more (θt ≧ 5deg).
An exhaust gas sensor having an axial length y of the outer cylinder measured from the first stage portion of 6.0 mm or more (y ≧ 6.0 mm). The exhaust gas sensor according to claim 1.
The linear tapered portion of the second tubular portion of the outer cylinder is
The gradient θt is 10 degrees or more (θt ≧ 10deg).
An exhaust gas sensor having an axial length y of the outer cylinder measured from the first stage portion of 3.0 mm or more (y ≧ 3.0 mm).

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