JP5097283B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor for detecting a predetermined gas component from a gas to be measured.

  Various gas sensors are attached to an exhaust pipe of an automobile in order to detect a predetermined gas component (for example, NOx) in the exhaust gas. This type of gas sensor is generally configured as shown in FIG.

  That is, the gas sensor includes, for example, a sensor element 1 having a function of detecting NOx, a bolt member 2 sheathed on the sensor element 1, and a protective cover that is fixed to the bolt member 2 and protects the sensor element 1 3 is provided. Further, a boss 5 having a nut portion for attaching the gas sensor is fixed to the exhaust pipe 4.

  The gas sensor is attached to the exhaust pipe 4 by the bolt member 2 being screwed into the nut portion of the boss 5. At this time, a gasket 6 is mounted on the contact surface between the bolt member 2 and the boss 5 as a seal member.

  However, in the gas sensor, since the sensor element 1 and a drive circuit unit (not shown) for driving the sensor element 1 are connected via a connector via a cable, the gas sensor being driven by electromagnetic waves entering from the connector. Was affected by noise. Therefore, in order to prevent the influence of noise, a high-performance integrated gas sensor in which the sensor element 1 and the drive circuit unit are connected by a cable without using a connector has been provided.

  However, when the gas sensor having the integrated structure is to be attached to the exhaust pipe, there is a problem in that the entire gas sensor including the drive circuit unit must be rotated and screwed into a boss fixed to the exhaust pipe. There is a concern that the displacement of the center position between the gas sensor having an integral structure and the boss is likely to occur, and the mounting accuracy is deteriorated.

  Further, in the conventional gas sensor, the sealing performance is remarkably changed due to the accuracy of the surface roughness of the contact surface between the bolt member 2 provided in the gas sensor and the boss 5 fixed to the exhaust pipe 4. Therefore, it is necessary to improve the accuracy of the surface roughness of the contact surface. For this reason, there has been a problem that the manufacturing cost increases.

  Further, in the conventional gas sensor, the pressing stress generated by the screwing of the bolt member 2 works only to press the gasket 6 against the boss 5. Accordingly, if the tightening force by the bolt member 2 is increased, the sealing performance is naturally improved. However, due to restrictions such as the strength of the bolt member 2, the tightening force is limited. Sealability was not completely guaranteed.

  Even if a high-performance gas sensor that prevents the intrusion of noise while driving the sensor by connecting the sensor element and the drive circuit unit to each other by cable connection is attached to the exhaust pipe, It is an object of the present invention to provide a gas sensor that can simplify the work and can improve the sealing performance of a contact portion between a bolt member provided in the gas sensor and a boss fixed to the exhaust pipe.

The gas sensor according to the present invention is a gas sensor for detecting a predetermined gas component from a gas to be measured, and includes a sensor element having a detection function, and an attachment part for attaching the sensor element to the attachment part. mounting portion, the contact with the mounting portion constitutes a seal portion includes a sealing member which have a cylindrical shape, and a bolt member screwed into the attached part, the sealing member, the bolt member The first cylindrical portion that is in contact with the inner peripheral surface of the first cylindrical portion, the second cylindrical portion that is in contact with the inner peripheral surface of the attached portion, and the attached portion that is provided between the first cylindrical portion and the second cylindrical portion. And an annular first protrusion that contacts the tip of the bolt member, an annular first surface that faces the first surface, and an inner peripheral surface of the attached portion that contacts the first protrusion. Two surfaces, and between the first surface and the second surface, And a third surface facing the attachment portions, and wherein the outer diameter of the second cylindrical portion is larger than the outer diameter of the first cylindrical portion.

Thus, in the gas sensor according to the present invention, when the gas sensor is attached to the exhaust pipe of an automobile, the attaching operation can be simplified, and the contact between the attachment portion provided in the gas sensor and the exhaust pipe can be simplified. Ru can be improved portion of the sealing performance.

In the gas sensor having the above-described configuration, the attached portion may have a nut portion that is screwed with the bolt member of the attaching portion and faces the third surface of the annular protrusion in a non-contact manner. Good. The gas sensor can be attached to the exhaust pipe without rotating the entire gas sensor.

Furthermore, it may be integrally connected via a cable without using the driver circuit portion and the connector for driving the sensor element and the sensor element. As a result, the gas component can be detected without being affected by noise.

  As described above, according to the present invention, there is provided a high-performance gas sensor that prevents intrusion of noise during sensor driving by connecting the sensor element and the driving circuit unit to each other to form an integral structure. Even when it is attached to the exhaust pipe, it is possible to simplify the mounting operation, to significantly improve the mounting accuracy, and to shorten the time required for the mounting operation.

  In addition, according to the present invention, compared with the conventional structure in which a gasket is inserted, a high sealing performance can be exhibited regardless of the accuracy of the surface roughness of the contact surface. The effect of suppressing the increase in cost can be obtained.

1 is an overall view of an integrated gas sensor. It is assembly sectional drawing of the gas sensor which concerns on this invention attached to the exhaust pipe. In the gas sensor which concerns on this invention, it is an expansion explanatory view of the contact part of an attaching part and a to-be-attached part. It is a graph explaining the relationship between the tightening torque value of an attachment member, and the amount of gas leakage from the contact part of an attachment member and a boss | hub in an experiment example. It is assembly sectional drawing of the conventional type gas sensor attached to the exhaust pipe.

  Preferred embodiments of the gas sensor according to the present invention will be given and described in detail below with reference to the accompanying drawings.

  As shown in FIG. 1, the gas sensor 10 according to the present embodiment is a gas sensor for detecting a predetermined gas component (for example, NOx or the like), and a drive circuit unit 12 for driving the gas sensor 10; It has a detection unit 14 for detecting gas. The drive circuit unit 12 and the detection unit 14 are integrally connected by a cable 16. Therefore, there is no intrusion of noise during driving of the gas sensor, and a highly accurate detection result can be obtained. The drive circuit unit 12 is connected to an electronic control unit of the automobile by a cable (not shown).

  As shown in FIG. 2, the detection unit 14 includes a sensor element 18 having a gas detection function and a mounting portion 20 that is externally mounted on the sensor element 18, and an end portion of the mounting portion 20 (the driving unit). A protective cover 22 for protecting the sensor element 18 is fixed to the side where the circuit unit 12 is not connected. A boss 42 having a nut portion 40 is fixed to the exhaust pipe 44.

  The mounting portion 20 includes a seal member 24 that contacts the boss 42 and forms a seal portion, and a bolt member 26 that is rotatably attached to the seal member 24. The bolt member 26 is connected to the nut portion. The gas sensor 10 is attached to the exhaust pipe 44 by being screwed to 40.

  The taper angle θ with respect to the horizontal direction of the taper surface 28 formed on the seal member 24 and the taper angle ψ with respect to the horizontal direction of the taper surface 36 formed on the boss 42 are always in contact with the seal member 24 and the boss 42. It is formed at an angle that exhibits a state. In the present embodiment, as shown in FIG. 3, the taper angle θ is formed smaller than the taper angle ψ. On the other hand, the taper angle θ may be formed larger than the taper angle ψ.

  The seal member 24 has an annular placement surface 30, and the bolt member 26 is placed on the placement surface 30. A substantially circular cut portion 32 is formed on the side of the bolt member 26 that is not placed on the placement surface 30. A metal stopper 34 for preventing the bolt member 26 from being detached from the seal member 24 is inserted into the notch 32. A barb 38 is formed at the tip of the stopper 34 so as to spread outward.

  Next, an operation for attaching the gas sensor 10 configured as described above to the exhaust pipe 44 will be described.

  When attaching the gas sensor 10 to the exhaust pipe 44, first, the center position of the bolt member 26 constituting the attachment portion 20 is matched with the center position of the boss 42 fixed to the exhaust pipe 44. The bolt member 26 is screwed into the nut portion 40 provided in the boss 42 while maintaining the state. Here, the bolt member 26 is tightened until the tapered surface 28 formed on the seal member 24 comes into contact with the tapered surface 36 formed on the boss 42.

  At this time, a frictional stress is generated at a contact portion between the seal member 24 and the bolt member 26 by a tightening force for fastening the bolt member 26, that is, a pressing stress. Due to this frictional stress, contact portions of the seal member 24 and the bolt member 26 rub against each other to generate a scraped material. When the scraped material enters the voids of the surface roughness of the contact portions, the adhesion between the contact portions is enhanced. Therefore, the sealing performance between the seal member 24 and the bolt member 26 is improved, and the exhaust gas can be prevented from leaking to the outside as much as possible.

  Here, in the conventional gas sensor, since it is necessary to rotate the entire gas sensor including the drive circuit unit at the time of mounting, it takes time, and the center position of the bolt member which is the mounting unit and the boss fixed to the exhaust pipe There is a concern that misalignment with the center position of the lens is likely to occur and the mounting accuracy is deteriorated.

  On the other hand, in the present embodiment, the bolt member 26 is rotatable with respect to the seal member 24, so that it can be moved independently, and there is no need to rotate the entire gas sensor 10 including the drive circuit unit 12. The screwing operation can be performed only by rotating only the bolt member 26. Thereby, in this Embodiment, compared with the conventional structure, an installation operation is simplified at a stretch, the effect that a time required for an installation operation can be shortened while mounting accuracy improves markedly.

  Here, one experimental example is shown. In this experimental example (see FIG. 4), the relationship between the tightening torque value of the mounting member and the amount of gas leakage from the contact portion between the mounting member and the boss is determined according to the gas sensor of the present embodiment (Example 1: solid line A). 2) and a conventional gas sensor (Comparative Example 1 to Comparative Example 3) in which a gasket 6 is mounted as a seal member.

  Among them, Comparative Example 1 (see the broken line B) has the worst surface roughness accuracy of the contact surface between the bolt member and the boss, and Comparative Example 3 (see the two-dot chain line D) is the bolt member. The surface roughness accuracy of the contact surface between the boss and the boss is the best, and in Comparative Example 2 (see the alternate long and short dash line C), the surface roughness accuracy of the contact surface between the bolt member and the boss is the same as in Comparative Example 1. It has an intermediate roughness with that of Comparative Example 3.

  In the experimental example, for example, when the tightening torque value is 20 Nm, the gas leakage amount of the gas sensor of the comparative example 3 is the smallest and the gas leakage amount of the gas sensor of the comparative example 1 is the largest. However, in the gas sensor of Example 1, the amount of gas leakage is almost zero regardless of the tightening torque value.

  As is apparent from the experimental results, a scraped material is generated by the frictional force generated between the seal member 24 and the boss 42, and the scraped material provides a close contact between the seal member 24 and the bolt member 26. The enhanced gas sensor of the present embodiment (Example 1) is higher than the conventional gas sensor (Comparative Examples 1 to 3) in which the gasket 6 is inserted regardless of the accuracy of the surface roughness of the contact surface. The sealing performance can be exhibited, and the labor for improving the accuracy of the surface roughness can be remarkably saved, and the effect of suppressing the increase in the manufacturing cost can be obtained. In addition, the fact that the sealing performance is not influenced by the tightening torque value is a factor that can reduce the time required for the mounting operation.

  In addition, the gas sensor according to the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Gas sensor 12 ... Drive circuit part 16 ... Cable 18 ... Sensor element 20 ... Mounting part 22 ... Protection cover 24 ... Seal member 26 ... Bolt member 28, 36 ... Tapered surface 34 ... Stopper 38 ... Return 40 ... Nut part 42 ... boss

Claims (3)

In a gas sensor for detecting a predetermined gas component from a gas to be measured,
A sensor element having a detection function;
An attachment portion for attaching the sensor element to the attachment portion;
The mounting portion, the contact with the mounting portion constitutes a seal portion includes a sealing member which have a cylindrical shape, and a bolt member screwed into the attached part,
The sealing member is
A first cylindrical portion that is in contact with an inner peripheral surface of the bolt member;
A second cylindrical portion that is in contact with an inner peripheral surface of the attached portion;
An annular protrusion provided between the first cylindrical portion and the second cylindrical portion and protruding toward the attached portion;
The annular protrusion is
An annular first surface with which the tip of the bolt member contacts;
A second surface facing the first surface and in contact with the inner peripheral surface of the attached portion;
It is located between the first surface and the second surface, and is composed of a third surface facing the attached portion,
The gas sensor, wherein an outer diameter of the second cylindrical portion is larger than an outer diameter of the first cylindrical portion. The gas sensor according to claim 1, wherein
The gas sensor according to claim 1, wherein the attached portion includes a nut portion that is screwed with a bolt member of the attaching portion and faces the third surface of the annular protrusion in a non-contact manner. The gas sensor according to claim 1 or 2,
A gas sensor, wherein the sensor element and a drive circuit unit for driving the sensor element are integrally connected via a cable without a connector.

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