JP4398086B2 - Gas sensor and protective cap - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas sensor for detecting a detected gas concentration in a gas to be measured such as exhaust gas discharged from an internal combustion engine or the like , and a protective cap attached to the gas sensor .
[0002]
Conventionally, as a gas sensor for measuring a detected gas concentration in a gas to be measured, for example, an oxygen sensor having a cylindrical element described in JP-A-9-184822 and JP-A-11-295263 is known. Yes. And when conveying these oxygen sensors, what was described in German utility model gazette No. 29803046 is known as an oxygen sensor provided with a protective cap for transportation.
[0003]
[Problems to be solved by the invention]
In the above conventional gas sensor, the element 4 for detecting the detection gas is inserted and accommodated in the metal shell 3, and the protector 2 is provided at the axial end of the gas sensor so as to protect the element 4 so as to cover the element 4. It was. Further, when the gas sensor is transported, a protective cap 1 made of resin is further provided around the protector 2 to protect the element 4 so that the element 4 is not splashed with water or touched by outside air during transport. It was like that. In such a protective cap 1, an annular projection 101 is provided on the inner surface of the protective cap 1 so as to avoid contact of outside air with the element 4 as much as possible, and a detection gas is provided in contact with the element 4 when the gas sensor is used. Through the vent hole 201, the surrounding air is hermetically sealed so as not to contact the element 4.
However, the gas sensor is coated with an anti-seizure agent 303 (Never sheath: manufactured by BOSTIC ) so that the male screw part does not seize on the exhaust pipe when it is attached to the exhaust pipe. 1, even if the solvent contained in the anti-seizure agent 303 evaporates and fills in the protective cap 1, the protective cap 1 does not replace the outside air, so the solvent vapor adversely affects the device characteristics. There was a problem of giving.
Further, since the protective cap 1 needs to be hermetically sealed with the protector 2, various inner diameters of the protrusions need to be prepared according to the size of the protector 2, and it is necessary to use the protective cap 1 properly according to the type of sensor. There was.
[0004]
The present invention has been made in order to solve the above-described problems. The purpose of the present invention is to prevent the solvent evaporating from the anti-seizing agent 303 from being contained in the protective cap 1 by the protective cap 1 attached to the gas sensor when the gas sensor is transported. Therefore, it is to prevent the element characteristics of the gas sensor from being deteriorated.
[0005]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the inventor protrudes from the cylindrical portion inner surface 161 of the protective cap 1 to elastically contact the protector side surface 202 and support the protective cap 1 against the protector 2. In addition, the gap between the cylindrical portion 106 of the protective cap 1 mounted around the protector 2 and the protector 2 is not blocked in the axial direction, and the vapor from the anti-seizing agent 303 is further exhausted to the protective cap 1. The exhaust hole 103 is formed. By doing so, it was possible to prevent the solvent vapor evaporated from the anti-seizure agent 303 from entering the protective cap 1 and consequently adversely affecting the device characteristics.
The protective cap 1 of the present invention is designed to replace the gas in the vicinity of the element with the outside air, so that it is somewhat affected by the outside air, but the protective cap 1 is cylindrical so as to cover the protector 2. Since the portion 106 is formed, direct exposure to water or the like can be prevented to some extent.
[0006]
The support portion 102 may be a plate shape provided radially from the inner surface 161 of the cylindrical portion to the side surface 202 of the protector in the radial direction toward the center of the sensor axis. Since the space between the protective cap 1 and the protector 2 is greatly opened by making the plate like this, ventilation can be further improved. Further, when the protective cap 1 is formed of a soft resin, the plate-like support portion 102 protruding from the inner surface 161 of the cylindrical portion can be easily deformed as shown in FIG. 3 even in the case of the gas sensor of the protector 2 having a large diameter. Therefore, the protective cap 1 having the same shape can be used. Of course, the material of the protective cap is not limited to resin, and may be paper. Furthermore, it is preferable to use an elastic resin such as rubber because it is easy to attach the protective cap to the gas sensor, and it is difficult to come off even in an unexpected accident.
[0007]
If the exhaust hole 103 provided in the protective cap 1 is provided in the front end surface of the protective cap 1, it is possible to prevent water splashing with respect to the gas sensor provided with the vent hole 201 on the protector side surface 202. On the other hand, when the vent hole 201 is provided on the front end surface of the protector 2, the exhaust hole 103 may be provided in the side peripheral portion of the cylindrical portion 106 of the protective cap 1, but when the vent hole 201 is small, the protective cap 1 You may make it provide the exhaust hole 103 in a front end surface. If the air vent 201 is provided in the vicinity of the anti-seizure agent 303, it may seem that the ventilation performance is good, but the air in the vicinity of the element may not be replaced. In this case, the protective cap 1 is located near the air vent 201 of the protector 2. It is preferable to provide an exhaust hole 103 so that air near the element can be easily replaced. If the vent hole 201 of the protector 2 and the exhaust hole 103 of the protective cap 1 are arranged so that there is no element 4 on a path that passes through both holes linearly, it is highly desirable against water splashing.
DETAILED DESCRIPTION OF THE INVENTION
[0008]
Next, an embodiment of the present invention will be described with an example.
FIG. 2 shows a tip portion in a state where the protective cap 1 is attached to a gas sensor for measuring the oxygen concentration in the gas to be measured. The metal shell is formed with a hexagonal portion 301 having a hexagonal opposite side of 22 mm and a thickness of 5 mm at the center in the axial direction, and an M18 male threaded portion 302 at the tip side. A cup-shaped protector 2 whose tip side is closed is joined to the tip side of the male screw portion 302 so as to cover the element 4 by spot welding. A vent hole 201 for allowing the detection gas to flow through the element 4 is formed on the tip side of the protector side surface 202. An anti-seizure agent 303 such as Never Seeds (manufactured by BOSTIC) is applied to the surface of the male screw portion 302. Further, a metal packing 5 is fitted to the base end portion of the male screw portion 302 for sealing so that the exhaust gas does not leak when the gas sensor is attached to the exhaust pipe.
[0009]
Around the protector 2, a protective cap 1 made of polyethylene having a cylindrical portion 106 for protecting the element 4 from water splashing is mounted. In the protective cap 1, a flange portion 105 is formed on the proximal end side of the cylindrical portion 106 so as to project in a hook shape. By forming the collar portion, an operation for attaching or removing the protective cap 1 to or from the gas sensor is facilitated. A skirt portion 104 is further formed from the flange portion 105 toward the base end side, and the base end side end portion 107 of the skirt portion 104 is designed to have a size that fits into the concave portion 501 of the metal packing 5. In the skirt portion 104, the anti-seizure agent 303 of the male screw portion 302 adheres to clothes or a person's hand during transportation of the gas sensor to contaminate them, or the anti-seize agent 303 is removed, and the gas sensor is seized on the exhaust pipe. To prevent that. Further, since the skirt portion 104 is fitted into the recess 501 of the metal packing 5, the skirt portion 104 is not easily displaced even when a force is applied to the skirt portion 104 in the lateral direction, and the anti-seizure agent 303 is applied to the inner surface of the skirt portion 104. Can be prevented.
[0010]
An exhaust hole 103 is formed at the tip of the protective cap 1 so that the vapor of the solvent of the anti-seizure agent 303 is not trapped. If the size of the exhaust hole 103 is too large, water is splashed on the element 4, which is a problem. If it is too small, the vapor of the solvent does not ventilate. In this embodiment, a hole having a diameter of 6 mm is formed. Further, it is desirable that the inner surface 108 of the front end of the protective cap 1 in which the exhaust hole 103 is formed is spaced to some extent from the front end surface of the protector 2. If the interval is too small, the ventilation property to the exhaust hole 103 is deteriorated and the waterproof property to the element 4 is also deteriorated. However, if the interval is too large, it becomes difficult to handle the gas sensor during transportation or the like, and the protective cap 1 is easily detached. In this embodiment, the interval is set to 5 mm.
[0011]
From the cylindrical part inner surface 161 of the protective cap 1, a support part 102 for fitting the protective cap 1 to the gas sensor is formed so as to protrude in a plate shape. The support portion 102 has a function of supporting the protective cap 1 with respect to the protector 2 by the plate side surface 121 elastically contacting the protector side surface 202. Since the support part 102 has the plate surface 122 formed in parallel to the axis of the gas sensor, the air permeability of the gap between the protector 2 and the tubular part 106 can be largely ensured. Therefore, good ventilation from the burn-in preventing agent 303 to the exhaust hole 103 is possible, and the influence of the solvent on the element 4 can be reduced. Three support portions 102 are arranged at equal angular intervals (120 degrees) in the circumferential direction. Although the number of support portions 102 may be two, it is desirable to have three or more support portions 102 because the protective cap 1 is stably supported by the protector 2. However, too much is not preferable because it is difficult to fit when the protective cap 1 is attached. If the plate thickness of the support portion 102 is too thick, it is not preferable because the protective cap 1 is difficult to fit. In the present embodiment, the plate thickness of the support portion 102 is set to 0.5 mm. Since the support portion 102 is easily deformed at this thickness, even when the gas sensor of the protector 2 having a large outer diameter is mounted, the protective cap 1 can be mounted without difficulty by bending as shown in FIG.
[0012]
In addition to the shape of the support portion 102, a plate surface can be provided perpendicular to the axis of the gas sensor as shown in FIG. Alternatively, as shown in FIG. 5, both side surfaces of the plate may be joined to the cylindrical portion 106 so that the plate surface elastically contacts and supports the protector 2.
[0013]
Further, the position of the exhaust hole 103 can be provided not only on the front end surface of the protective cap 1 but also on the side peripheral portion of the cylindrical portion 106 of the protective cap 1 as shown in FIG. In particular, as shown in FIG. 6, when the vent hole 203 is opened in the tip surface of the protector 2, it is possible to prevent the element from being splashed by providing it on the side peripheral portion of the cylindrical portion 106 of the protective cap 1. preferable. In this case, when the vent hole 201 is also opened in the protector side surface 202, the exhaust hole 103 provided in the side peripheral portion of the cylindrical portion 106 of the protective cap 1 passes through both holes linearly. If it is arranged so that the element 4 is not visible on the path, it is highly desirable against water splashing.
[Brief description of the drawings]
FIG. 1 shows a conventional gas sensor with a protective cap attached. FIG. 2 shows a gas sensor with a protective cap according to the present invention (only the tip).
3 is a cross-sectional view of the tip when a protective cap is attached to a gas sensor of a large diameter protector. FIG. 4 is a modified example of the protective cap according to the present invention. FIG. 5 is a modified example of the protective cap according to the present invention. ] Modification of protective cap according to the present invention [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, ... Protective cap 2, ... Protector 3, ... Metal fitting 4, ... Element 5, ... Metal packing 102 ... Support part 103 ... Exhaust hole 104 ... Skirt part 105 ... Saddle part ... Cylindrical part

Claims (6)

An element ( 4 ) for measuring the concentration of the detected gas in the gas to be measured;
Have a protector (2) which is provided so as to cover the axial tip of the element (4), a gas sensor is mounted in an exhaust pipe,
A protective cap ( 1 ) attached to the gas sensor, the protective cap ( 1 ) being detachable from the gas sensor ,
Cylindrical portion surrounding the side surface (202) of the protector (2) and (106),
Wherein without blocking the space in the axial direction between the side surface (202) of the inner surface (161) and the protector (2) of projecting the cylindrical portion from the inner surface (161) (106) of the tubular portion (106) A support ( 102 ) reaching the side ( 202 ) of the protector ( 2 ) ;
An exhaust hole ( 103 ) that circulates inside and outside the protective cap ( 1 ) ,
The gas sensor to which the protective cap (1) is attached is attached to the exhaust pipe with the protective cap (1) removed . The gas sensor of claim 1, wherein the support unit (102) is characterized in that it is a plate shape. The gas sensor of claim 2, wherein the plate surface of the support portion (102) (122) is parallel to the axial direction. Said plate side surface of the support portion (102) (121), a gas sensor according to claim 2, characterized in that in contact with the side surface (202) of the protector (2). The gas sensor according to claim 1, wherein the exhaust hole ( 103 ) is provided at a tip of the protective cap ( 1 ) . A gas sensor having an element (4) for measuring the detected gas concentration in the gas to be measured and a protector (2) provided so as to cover the tip of the element 4 in the axial direction, and attached to the exhaust pipe A protective cap (1) to be mounted,
The protective cap (1) is detachable from the gas sensor,
A cylindrical portion (106) surrounding the side surface (202) of the protector (2);
Projecting from the inner surface (161) of the cylindrical portion (106), the space between the inner surface (161) of the cylindrical portion (106) and the side surface (202) of the protector (2) is not blocked in the axial direction. A support (102) reaching the side (202) of the protector (2);
An exhaust hole (103) that circulates inside and outside the protective cap (1);
Further, the protective cap (1) attached to the gas sensor is removed from the gas sensor when the gas sensor is attached to the exhaust pipe.
Protective cap characterized by that.

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