JP4859123B2 - Gas sensor and gas sensor manufacturing method - Google Patents

Description

The present invention relates to a gas sensor for detecting the concentration of a specific gas component in a gas to be measured such as exhaust gas and a method for manufacturing the gas sensor .

  2. Description of the Related Art Conventionally, an oxygen sensor is known as a gas sensor that is installed in an exhaust system of an internal combustion engine and detects oxygen concentration in exhaust gas and is used for combustion control of the internal combustion engine. This oxygen sensor extends in the axial direction, and has a detection element whose tip is exposed to the gas to be measured, and a cylindrical metal shell that protrudes from the tip of the detection element and that surrounds the detection element. And a cylindrical protector that is attached to the distal end portion of the metal shell and covers the distal end portion of the detection element.

  By the way, the metal parts constituting the metal shell and the protector of the gas sensor are machined from a metal material by a plurality of processes. When machining this metal material a plurality of times, the metal material uses, for example, a lubricant, a lubricant such as a cutting fluid or a grinding fluid for lubrication or cooling during plastic working, cutting or grinding, The oil agent is adhered to a metal material.

The oil agent adhering to the metal material remains in the metal material as it is for lubrication and cooling in the next gas sensor assembly process (for example, the caulking process of the metal shell and the mounting process of the protector and the metal shell). I am letting. However, if the amount of residual oil is too much or too little for the subsequent process, wash away a part of the residual oil or add the same oil to the residual oil and adjust the amount of oil to be suitable for the subsequent process. It is known to increase or decrease. Also, if the type of residual oil in the processed product is not suitable for the post-process and other types of oil are required in the post-process, the processed product will wash out all of the residual oil and use a different type of oil from the residual oil. It is known that a new appropriate amount of the material adheres (see Patent Document 1).
JP 2005-193183 A

  By the way, after the gas sensor assembly process, when the gas sensor is attached to the exhaust pipe with the oil remaining on the protector or the metal shell and used for use, the remaining oil on the protector inner peripheral surface or the metal shell inner peripheral surface is gasified. When the gas leaks into the protector, it mixes with the gas to be measured in the protector, and the gas detection accuracy may be lowered. Therefore, in Patent Document 1, by heating the metal shell and the protector before using the gas sensor, the oil agent adhering to the inner peripheral surface of the metal shell and the inner peripheral surface of the protector is gasified and removed, and the gas sensor is used. Sometimes it has been shown to suppress degradation of gas detection accuracy. However, in recent years, with the tightening of exhaust gas regulations, there has been a demand for higher accuracy in gas detection, and a gas sensor that can sufficiently meet the requirements can be obtained by simply performing heat treatment before using the gas sensor. It's hard to say. In particular, in recent gas sensors, the protector is being downsized. Even if a small amount of oil remains on the inner peripheral surface of the protector or the inner peripheral surface of the metal shell, and the amount of gas that leaks into the protector is small, The detection accuracy tends to decrease.

The present invention has been made in view of such conventional problems, and provides a gas sensor and a gas sensor manufacturing method that suppresses a decrease in gas detection accuracy due to the effect of an oil agent adhering to an inner peripheral surface of a protector or an inner peripheral surface of a metal shell. It is to provide.

Therefore, the gas sensor of the present invention includes a detection element that extends in the axial direction and whose tip is exposed to the gas to be measured, and a cylinder that supports the detection element so that the tip of the detection element protrudes beyond its own tip. In a gas sensor comprising: a metal shell, and a cylindrical protector that is attached to the tip of the metal shell and covers the tip of the detection element;
An oil agent is attached to a part of the inner peripheral surface of the metal shell that is exposed to the gas to be measured and a part of the inner peripheral surface that is exposed to the gas to be measured of the protector. The adhesion amount of the oil agent is less than 0.7 mg.

In this way, by limiting the amount of the oil agent adhering to a part of the inner peripheral surface of the front end side of the metal shell and a part of the inner peripheral surface exposed to the measured gas of the protector to less than 0.7 mg, During use, the amount of oil that remains on the inner peripheral surface of the protector and the inner peripheral surface on the tip side of the metal shell gasifies and oozes into the protector can be kept within a range that does not affect the gas detection accuracy. It can suppress that detection accuracy falls. Incidentally, the adhesion amount of oil adhering to the part of the portion of the distal side inner circumferential face of the metal shell and exposed inner peripheral surface to be measured gas protector is at least 0.7 mg, to obtain the above effect difficult.

And in this invention, it is set as a part of front end side internal peripheral surface exposed to to- be-measured gas, and a part of inner peripheral surface exposed to the to- be-measured gas of a protector as a site | part to which the oil agent adheres. The inner peripheral surface of the metal shell on the tip side and the inner peripheral surface exposed to the measurement gas of the protector (hereinafter also referred to as both inner peripheral surfaces) are in contact with the space inside the protector, and the oil applied to both inner peripheral surfaces When gasified during use of the sensor, it leaks into the protector and mixes with the gas to be measured in the protector. Therefore, by limiting the amount of adhesion of both inner peripheral surfaces to less than 0.7 mg, it is possible to effectively suppress a decrease in gas detection accuracy during use of the gas sensor.

  Furthermore, in the gas sensor of the present invention, it is preferable that the amount of oil to be adhered is less on the inner peripheral surface of the protector than on the inner peripheral surface on the tip side of the metal shell. An oil for lubrication is required when assembling the metal shell and the protector. However, the oil necessary for lubrication only needs to adhere to either the metal shell or the protector. Therefore, the amount of oil applied to the inner peripheral surface of the protector with a larger surface area is less than the amount of oil applied to the inner peripheral surface of the front end of the metal shell with a smaller surface area, so that both the protector and the metal shell can be assembled. It is possible to effectively reduce the adhesion amount of the oil agent on both inner peripheral surfaces without affecting.

  In particular, there is a gas sensor in which the protector is spot-welded or laser-welded to the tip of the metal shell in order to improve the effect of preventing the protector from falling off. In a gas sensor in which the protector is welded to the tip of the metal shell, an oil agent is attached to or remains on the metal shell and the protector before welding for lubrication and cooling. Therefore, if the oil agent is adhered and left as it is, the oil agent applied to the inner peripheral surface of the metal shell at the front end and the inner peripheral surface of the protector oozes out into the protector when it is gasified during use of the sensor. Mix with measurement gas. On the other hand, in the present invention, since the amount of adhesion of both inner peripheral surfaces is limited to less than 0.7 mg, even if the protector is a gas sensor welded to the metal shell, the gas detection accuracy during use is lowered. Can be effectively suppressed.

  Furthermore, in order to improve the detection accuracy of the gas sensor, a powdery seal member is disposed between the inner peripheral surface of the metal shell and the outer peripheral surface of the detection element. There is a gas sensor having a caulking portion that is caulked so as to be airtight. In the gas sensor in which the rear end portion of the metal shell is crimped and the crimped portion is formed, an oil agent is attached to or remains on the metal shell before the crimping for lubrication and cooling. Therefore, if the oil agent is adhered and left as it is, the oil agent applied to the inner peripheral surface on the front end side of the metal shell leaks into the protector when it is gasified during use of the sensor, and mixes with the gas to be measured in the protector. On the other hand, according to the present invention, the amount of adhesion of the inner peripheral surface of the front end side of the metal shell is limited to less than 0.7 mg, so that the rear end portion of the metal shell is crimped to form a crimped portion. Even if it is a gas sensor, the fall of the gas detection precision in use can be suppressed effectively.

  “Sealing the seal member” means that when the temperature of the metal shell is heated to 550 ° C. and the atmosphere is pressurized at 0.4 MPa from the front end side of the metal shell, the space between the detection element and the metal shell is This means that the amount of air that leaks to the rear end side of the metal shell is 10 cc / min or less. In this gas sensor with airtightness, the oil applied to the inner peripheral surface on the front end side of the metal shell leaks into the protector when it is gasified during use of the sensor, and easily mixes with the gas to be measured in the protector. It is effective to use the invention.

  Furthermore, it is preferable that the amount of oil to be attached is less on the inner peripheral surface of the front end side of the metal shell than on the outer peripheral surface of the crimped portion of the metal shell. In other words, the amount of oil applied to the rear end of the inner peripheral surface at the front end side of the metal shell is reduced while the oil is applied to the outer peripheral surface of the caulking portion required for caulking the metal shell. Two effects of improving the gas detection system can be obtained simultaneously.

Further, a detection element that extends in the axial direction and whose tip is exposed to the gas to be measured, and a cylindrical metal shell that supports the detection element so that the tip of the detection element protrudes from its tip, In the gas sensor provided with a cylindrical protector that is attached to the tip of the metal shell and covers the tip of the detection element,
Of the inner peripheral surface of the metal shell, an oil agent is attached to at least a part of the inner peripheral surface of the tip exposed to the gas to be measured and the inner peripheral surface of the protector, and the inner peripheral surface of the front end of the metal shell Alternatively, when the inner peripheral surface of the protector is measured by micro-infrared spectroscopy, a peak is generated in the infrared absorption spectrum obtained by the micro-infrared spectroscopy, and the peak changes in CH. It is preferable not to belong to angular vibration .

  Thus, although the peak is generated in the infrared absorption spectrum of the tip side inner peripheral surface or the protector inner peripheral surface, the angle of change of CH indicating that a large amount of oil is attached to both inner peripheral surfaces. Since vibration does not belong, the amount of oil applied to both inner peripheral surfaces is determined by the amount of oil remaining on the inner peripheral surface of the protector and the inner peripheral surface of the metal shell during use of the gas sensor. The amount that oozes out can be suppressed within a small amount range that does not affect the gas detection accuracy, and a decrease in gas detection accuracy can be suppressed. It should be noted that it is difficult to obtain this effect when the CH bending vibration belongs. The phrase “CH bending vibrations do not belong to the peak” means that there is no CH bending vibration when the functional group is specified for the peak appearing in the infrared absorption spectrum. That is, it means that the peak of the CH bending vibration does not appear.

Furthermore, in another embodiment of the present invention, a detection element that extends in the axial direction and whose tip is exposed to the gas to be measured, and supports the detection element so that the tip of the detection element protrudes from the tip of the detection element. In a method for manufacturing a gas sensor, comprising: a cylindrical metal shell; and a cylindrical protector that is attached to the tip of the metal shell and covers the tip of the detection element;
A preparation step for preparing the metal shell and the protector to which an oil agent is attached, a mounting step for mounting the protector on the metal shell, and an assembly step for supporting the detection element on the metal shell to which the protector is mounted. When deposition amount of the oil agent gas to be measured of the inner circumferential surface is adhered to the inner peripheral surface of the tip side inner circumferential surface and the protector is exposed to the metal shell have a a removal step to be less than 0.7mg The removing step includes a heat treatment step of performing a heat treatment on the metal shell and the protector .

  As described above, the amount of the oil agent attached to at least a part of the inner peripheral surface of the front end side to which the gas to be measured is exposed and the inner peripheral surface of the protector among the inner peripheral surface of the metal shell is less than 0.7 mg. And removing the oil agent from the metal shell or / and the protector, so that the remaining oil agent on the inner peripheral surface of the protector and the inner peripheral surface of the metal shell is gasified during use of the gas sensor. Thus, the gas sensor that can suppress the gas detection accuracy from being lowered within the range that does not affect the gas detection accuracy and can suppress the gas detection accuracy from being lowered can be manufactured efficiently.

  And in this invention, it is made into at least one part of the front end side internal peripheral surface to which a to-be-measured gas is exposed, and the internal peripheral surface of a protector as a site | part which performs a removal process. The inner peripheral surface of the front end and the inner peripheral surface of the protector (hereinafter also referred to as both inner peripheral surfaces) from the support part to the front end of the metal shell are in contact with the space in the protector, and the oil applied to both inner peripheral surfaces is When gasified during use of the sensor, it leaks into the protector and mixes with the gas to be measured in the protector. Therefore, by having a removal step of removing the oil agent from the metal shell or / and the protector so that the adhesion amount of both inner peripheral surfaces is less than 0.7 mg, the gas detection accuracy during use of the gas sensor is reduced. A gas sensor that can be suppressed can be produced effectively and efficiently.

  Furthermore, the present invention includes a heat treatment step in which the removing step heat-treats the metal shell and the protector. By performing the heat treatment step in this manner, the oil agent can be more efficiently removed from the metal shell and / or the protector even after the assembly step.

  Furthermore, in order to improve the detection accuracy of the gas sensor, a filling step of filling a powdery seal member between the inner peripheral surface of the metal shell and the outer peripheral surface of the detection element, and the rear end side of the metal shell are crimped There may be a caulking process. In a gas sensor in which a caulking portion is formed at the rear end portion of the metal shell, it is preferable that an oil agent is applied to the caulking portion in advance during the caulking process. On the other hand, if the oil agent is left attached and left as it is, the oil agent applied to the inner peripheral surface of the front end of the metal shell leaks into the protector when it is gasified during use of the sensor, and mixes with the gas to be measured in the protector. . On the other hand, according to the present invention, the amount of adhesion of the inner peripheral surface of the front end side of the metal shell is limited to less than 0.7 mg, so that the rear end portion of the metal shell is crimped to form a crimped portion. Even if it is a gas sensor, the fall of the gas detection precision in use can be suppressed effectively.

  Further, the present invention provides a cleaning step of cleaning the protector and the metal shell after the preparation step, and a metal shell so that the amount of oil applied to the inner peripheral surface of the front end of the metal shell after cleaning is 0.7 mg to 2 mg. It is preferable to include an attaching step of attaching the oil agent again to the surface. In the mounting process, an oil agent is required on the mounting surface of either the protector or the metal shell, but the inner peripheral surface of the protector has a larger area than the inner peripheral surface on the tip side of the metal shell, and the oil agent gives gas detection accuracy. A large impact. Therefore, the protector is washed after the preparation process, while an appropriate amount of oil is applied again to the metal shell. Thereby, the gas sensor which can acquire two effects of the mounting | wearing property in a mounting | wearing process and a gas detection precision improvement simultaneously can be obtained.

  In addition, if it is less than 0.7 mg, the effect of improving the wearability is poor. On the other hand, if it exceeds 2 mg, it is difficult to remove by heat treatment later. And since an oil agent is removed in a removal process from the metal shell to which the above-mentioned amount of the oil agent is adhered, a gas sensor capable of suppressing a decrease in gas detection accuracy during use of the gas sensor can be efficiently produced.

Furthermore, a detection element that extends in the axial direction and whose tip is exposed to the gas to be measured, and a cylindrical metal shell that supports the detection element so that the tip of the detection element protrudes from its own tip, A cylindrical protector that is attached to the tip of the metal shell and covers the tip of the detection element, and is disposed between an inner peripheral surface of the metal shell and an outer peripheral surface of the detection element, and the metal shell And a powdery seal member that is hermetically sealed by a caulking portion provided at a rear end portion thereof, and an oil agent on at least one of the inner peripheral surface of the metal shell and the inner peripheral surface of the protector A preparation step of preparing the metal shell and the protector to which the metal shell is attached; a cleaning step of cleaning the protector and the metal shell; a mounting step of welding the protector to the metal shell; A filling step in which the detection element is inserted into a metal shell to which a protector is attached and the seal member is filled between an inner peripheral surface of the metal shell and an outer peripheral surface of the detection element; A caulking step for caulking the end portion, and having a second adhering step for adhering the oil agent to the outer peripheral surface of the rear end portion of the metal shell after the cleaning step and before the caulking step . It may be.

  In order to improve the detection accuracy of the gas sensor, a filling process for filling a powdery seal member between the inner peripheral surface of the metallic shell and the outer circumferential surface of the detecting element, and caulking for crimping the rear end side of the metallic shell It may have a process. In a gas sensor in which a caulking portion is formed at a rear end portion of a metal shell manufactured by this manufacturing method, an oil agent is attached to or remains on the metal shell before caulking for lubrication and cooling. Therefore, a sufficient caulking step can be performed by including the second attachment step in which the oil agent is attached to the outer peripheral surface of the rear end portion of the metal shell cleaned in the cleaning step.

  Of the inner peripheral surface of the metal shell, the oil agent is removed from the tip side inner peripheral surface to which the gas to be measured is exposed and the protector inner peripheral surface in the cleaning process. In the oil agent removal by the washing process, since the amount of the remaining oil agent is smaller than the oil agent removal by the heat treatment, the remaining amount of the oil agent can be easily and reliably reduced. On the other hand, in the caulking step, an oil agent is necessary for improving the caulking accuracy. By having the second attachment step of attaching the oil agent to the outer peripheral surface of the rear end portion of the metal shell cleaned in the cleaning step, a sufficient caulking step can be performed without impairing the gas detection accuracy.

  Hereinafter, a gas sensor as an embodiment to which the present invention is applied will be described with reference to the drawings. In the present embodiment (first embodiment), a gas sensor (oxygen sensor) that is attached to an exhaust pipe of an automobile and detects the concentration of oxygen in the exhaust gas will be described. FIG. 1 is a cross-sectional view showing the overall configuration of the gas sensor 1 of the present embodiment.

  As shown in FIG. 1, the gas sensor 1 includes a sensor element 2 having a bottomed cylindrical shape with a closed end, a ceramic heater 3 inserted into the sensor element 2, and a metal shell 4 that holds the sensor element 2 on the inside. Is provided. In the direction along the axis of the sensor element 2 shown in FIG. 1, the side (closed side, lower side in the figure) facing the tip part exposed to the measurement target gas (exhaust gas) is referred to as “tip side”. The side toward the opposite direction (upper side in the figure) will be described as the “rear end side”.

  This sensor element 2 includes a solid electrolyte body 21 having oxygen ion conductivity mainly composed of partially stabilized zirconia in which yttria is dissolved as a stabilizer, and Pt or a Pt alloy on the inner surface of the solid electrolyte body 21. And the external electrode 23 formed on the outer surface of the solid electrolyte body 21. Further, a flange portion 24 that protrudes outward in the radial direction is provided at a substantially intermediate position in the axial direction of the sensor element 2. The sensor element 2 of the present embodiment corresponds to the detection element in the claims. The ceramic heater 3 is formed in a rod shape and includes a heat generating portion 31 having a heat generating resistor therein. When the ceramic heater 3 is energized through heater lead wires 190 and 200, which will be described later, the heat generating portion 31 generates heat, and has a function of heating the sensor element 2 to activate the sensor element 2. Fulfill.

Next, the metal shell 4 and the protector 120, which are the main parts of the present invention, will be described in detail.
The metal shell 4 is made of SUS430, and has a screw portion 41 for attaching the gas sensor 1 to the exhaust pipe, and a hexagonal portion 42 to which an attachment tool is applied when the gas sensor 1 is attached to the exhaust pipe. Further, the gasket 5 is disposed on the tip side of the hexagonal portion 42. Further, the metal shell 4 is provided with a metal-side stepped portion 43 that protrudes radially inward on the inner periphery of the front end side. The support 45 of the metal-side stepped portion 43 is made of alumina via a packing 6. The support member 7 is supported. The flange portion 24 of the sensor element 2 is supported on the support member 7 via the packing 8. A filling member 9 is disposed between the inner surface of the metal shell 4 on the rear end side of the support member 7 and the outer surface of the sensor element 2, and a sleeve 100 and an annular ring are disposed on the rear end side of the filling member 9. 110 are sequentially inserted.

Further, a protector 120 made of SUS310 inserted into the distal end portion 46 of the metal shell 4 is spot welded so as to cover the distal end side of the sensor element 2. The protector 120 has a double structure of an outer protector 122 and an inner protector 123, and has a plurality of gas intake holes 121 in the respective circumferential directions.

  As will be described later, the metal shell and the protector are made from a metal material through a plurality of machining processes, and an oil agent (first oil agent) 250 for lubrication and cooling is applied during the machining process. The oil agent (second oil agent) 251 used in the subsequent caulking process of the metal shell 4 is applied. On the other hand, as shown in FIG. 2, the tip side inner peripheral surface 48 exposed to the gas to be measured from the support portion 45 of the metal shell 4 of the gas sensor 1 to the tip 47 of the metal shell 4, and the inner peripheral surface of the protector 120. 124 (the inner peripheral surface of the outer protector 122 and the inner peripheral surface of the inner protector 123) are attached with the oil agents 250 and 251 and the amount of the oil agents 250 and 251 is limited to less than 0.7 mg. Has been.

  As described above, by limiting the amount of the oil agents 250 and 251 attached to at least a part of the inner peripheral surface 48 of the front end side of the metal shell 4 and the inner peripheral surface 124 of the protector 120 to less than 0.7 mg, A range in which the amount of oil 250 and 251 remaining on the inner peripheral surface 124 of the protector 120 and the distal end side inner peripheral surface 48 of the metal shell 4 is gasified and oozes into the protector 120 during use does not affect the gas detection accuracy. The gas detection accuracy can be suppressed from decreasing.

  This oil agent 250 can be used as lubrication or cooling in a plurality of mechanical processes when the metal shell 4 and the protector 120 are manufactured, and specifically, mineral oil. On the other hand, the oil agent 251 is used when caulking the metal shell 4, and is an oil agent that is liable to affect the deterioration of the gas detection accuracy similarly to 250. However, the oil agent 250 applied to the front end side inner peripheral surface 48 of the metal shell 4 and the inner peripheral surface 124 of the protector 120 is removed by washing, and further, the oil agent 251 applied to the metal shell 4 is attached by heat treatment. It has been removed until less than 0.7 mg.

  In particular, in the gas sensor 1 of this embodiment, in which the protector 120 is spot-welded to the metal shell 4 in order to improve the effect of preventing the protector 120 from falling off, the oil agent 251 is applied to the metal shell 4 before welding in order to improve the wearability. However, the oil agent 250 of the protector 120 is removed by washing. Since the oil agent 250 of the protector 120 having a relatively large surface area is removed in advance by washing, the amount of the oil agent to be removed in the subsequent heat treatment step can be reduced. Further, since the oil 251 is applied to the metal shell 4, the protector 120 can be easily attached to the metal shell 4.

Further, when the inner peripheral surface 124 of the protector 120 and the inner peripheral surface 48 on the front end side of the metal shell 4 are analyzed using micro-infrared spectroscopy, an infrared absorption spectrum as shown in FIG. 3 can be obtained. In this microinfrared spectroscopy, analysis was performed based on the following measurement conditions using a microinfrared spectrometer (IR μs (manufactured by SPECTRA-TECH)).
Light source: Glover, detector: Narrow.MCT (HgCdTe), purge: nitrogen gas, resolution: 8 cm ⁻¹ , integration number: 2048 times or less, measurement mode: transmission method, measurement wave number range: 4000 to 650 cm ⁻¹

  According to FIG. 3, peaks are generated in the infrared absorption spectrum, and peaks of OH stretching vibration, CH stretching vibration, carboxylate, and the like appear. However, no CH bending vibration appears at the peak. As described above, the infrared absorption spectrum of the inner peripheral surface 48 of the distal end side or the inner peripheral surface 124 of the protector 120 has a peak, but a variable vibration of CH indicating that a large amount of oil is attached. Therefore, the amount of oil attached to the inner peripheral surface 48 of the front end side and the inner peripheral surface 124 of the protector 120 is determined so that the inner peripheral surface 124 of the protector 120 and the inner end surface of the metal shell 4 The amount of oil 250, 251 that remains on the peripheral surface 48 is gasified and oozes into the protector 120 can be suppressed within a small amount range that does not affect the gas detection accuracy, and the deterioration of the gas detection accuracy is suppressed. it can.

  Returning to FIG. 1, the front end side of the inner cylinder member 130 is inserted inside the rear end side of the metal shell 4. The inner cylinder member 130 crimps the rear end portion 44 of the metal shell 4 in the inner front end direction in a state in which the opening end portion (front end opening end portion 132) whose diameter is increased on the front end side is in contact with the annular ring 110. Thus, the metal shell 4 is fixed. In addition, by crimping the rear end portion 44 of the metal shell 4, the filling member 9 is compressed and filled via the sleeve 100, whereby the sensor element 2 is placed inside the cylindrical metal shell 4. It is kept airtight.

  As in the present embodiment, a powder filling member 9 is disposed between the inner peripheral surface 48 of the metal shell 4 and the outer peripheral surface of the sensor element 2, and at the rear end side 44 of the metal shell 4. In the gas sensor 1 crimped so that the filling member 9 becomes airtight, the gasified oil agents 250 and 251 are not easily discharged to the rear end side. Therefore, the gasified oils 250 and 251 ooze out into the tip side, that is, in the protector 120 and mix with the gas to be measured in the protector 120. On the other hand, in this embodiment, the amount of adhesion of the front end side inner peripheral surface 48 of the metal shell 4 is limited to less than 0.7 mg, so that the gas sensor 1 formed by crimping the rear end portion 44 of the metal shell 4 is used. Even so, it is possible to effectively suppress a decrease in the accuracy of gas detection during use.

  The inner cylinder member 130 has a stepped portion 133 formed at a substantially intermediate position in the axial direction, and a front end portion 134 disposed on the front end side of the stepped portion 133 and a rear end portion 135 disposed on the rear end side. And divided. The rear end portion 135 is formed such that both the inner diameter and the outer diameter are smaller than those of the front end portion 134, and the inner diameter is slightly larger than the outer diameter of the separator 160 described later. The rear end portion 135 is formed with a plurality of air introduction holes 131 at predetermined intervals along the circumferential direction.

  The outer cylindrical member 150 is formed in a cylindrical shape, is disposed on the front end side with respect to the stepped portion 152 and is disposed on the rear end side with respect to the inner cylindrical member 130, and is disposed on the rear end side with respect to the stepped portion 152, which will be described later. And a rear end portion 153 for fixing the seal member 240 in an airtight manner. In addition, a plurality of air introduction holes 151 are formed in the distal end portion 154 at predetermined intervals along the circumferential direction.

  A cylindrical filter 140 is disposed between the air introduction hole 131 of the inner cylinder member 130 and the air introduction hole 151 of the outer cylinder member 150 to prevent water from entering from the outside. The filter 140 is, for example, a porous fiber structure of polytetrafluoroethylene (trade name: Gore-Tex (Japan Coretex Co., Ltd.), while preventing permeation of liquid mainly composed of water, etc. This is configured as a water repellent filter that allows permeation of gas.

  The filter 140 is fixed by caulking the front end side and the rear end side of the air introduction hole 151 in the front end portion 154 of the outer cylinder member 150. Further, the outer cylinder member 150 and the inner cylinder member 130 are directly crimped on the front end side of the filter 140, whereby the outer cylinder member 150 and the inner cylinder member 130 are fixed.

  Thereby, the atmosphere as the reference gas is introduced into the atmosphere introduction hole 151, the filter 140 and the atmosphere introduction hole 131, and the inner cylinder member 130, and is introduced into the sensor element 2. On the other hand, since water droplets cannot pass through the filter 140, entry into the inner cylinder member 130 is prevented.

  A separator 160 is disposed inside the inner cylinder member 14. The separator 160 is formed such that a separator lead wire insertion hole 161 for inserting the element lead wires 170 and 180 and the heater lead wires 190 and 200 penetrates from the front end side to the rear end side. Further, the separator 160 is formed with a bottomed holding hole 162 opened in the front end surface in the axial direction. The rear end portion of the ceramic heater 3 is inserted into the holding hole 162, and the rear end surface of the ceramic heater 3 abuts against the bottom surface of the holding hole 162, thereby positioning the ceramic heater 3 in the axial direction with respect to the separator 160. .

  Although not shown in detail, each lead wire 170, 180, 190, 200 has a structure in which a conductive wire is covered with an insulating film made of resin, and the rear end side of the conductive wire is a connector terminal provided in the connector. Connected. The leading end side of the conducting wire of the element lead wire 170 is crimped with the rear end portion of the terminal fitting 210 that is externally fitted to the outer surface of the sensor element 2, and the leading end side of the conducting wire of the element lead wire 180 is The rear end portion of the terminal fitting 220 press-fitted into the inner surface of the sensor element 2 is crimped. Thereby, the element lead wire 170 is electrically connected to the external electrode 23 of the sensor element 2, and the element lead wire 180 is electrically connected to the internal electrode 22. On the other hand, the leading ends of the lead wires 190 and 200 for the heater are connected to a pair of heater terminal fittings 230 joined to the heating resistor of the ceramic heater 3, respectively.

  A sealing material 240 made of fluorine rubber or the like having excellent heat resistance is fixed to the rear end side of the separator 160 by caulking the outer cylinder member 150. The seal member 240 is formed with four lead wire insertion holes 241 so as to penetrate in the axial direction.

Next, the manufacturing method of the gas sensor 1 of this embodiment is demonstrated in detail.
First, a steel material of SUS430 is subjected to a plurality of machining operations (plastic processing and cutting) using an oil agent 250 for lubrication and cooling, and a hexagonal portion 42, a screw portion 41, a metal side step portion 43, A cylindrical metal shell 4 having a tip portion 46 and the like is produced. The process of obtaining the metal shell 4 described above corresponds to the preparation process of the claims. The oil agent 250 remains on the surface of the metal shell 4 after molding. Therefore, first, the metal shell 4 to which the oil agent 250 adheres is immersed in a degreasing liquid, and is removed from the degreasing liquid and washed with water, and the oil agent 250 adhering to the metal shell 4 is removed. The above-described process of cleaning the metal shell 4 corresponds to the cleaning process of the claims.

  Next, the metal shell 4 washed with water is immersed in an oil solution to obtain the metal shell 4 to which a new oil agent 251 is newly attached. The oil agent 251 is dissolved by mixing an aqueous oil agent and an activator in warm water. The aqueous solution oil is one in which alkylamine oxide or the like is contained in an aqueous solution having an oil content of about 30%, and the mixing ratio is 50 to 60 ml / l. Moreover, an activator is a nonionic surfactant and the mixing rate is 13-20 ml / l. As a temperature range of warm water, it is 50-60 degreeC. In addition, the process of attaching the oil agent 251 to the metal shell described above corresponds to the attaching process.

  Similarly, the steel material of SUS310 is subjected to a plurality of machining operations (plastic processing and punching processing) to produce an inner protector 123 and an outer protector 122 in which a plurality of gas intake holes 121 are formed. Note that the oil agent 250 for lubrication and cooling is also used during the above-described plurality of machining operations (plastic processing and cutting), and the oil agent 250 is also applied to the surfaces of the outer protector 122 and the inner protector 123 after molding. It remains. And the inner side protector 123 is inserted in the inside of the outer side protector 122, each other is spot-welded and fixed, and the protector 120 is obtained. In addition, the process of obtaining the above protector 120 corresponds to the preparation process of a claim. The oil agent 250 remains on the surface of the protector 120 after molding. Therefore, first, the protector 120 to which the oil agent 250 is adhered is immersed in a degreasing liquid, and the oil agent 250 adhering to the protector 120 is removed by taking out the degreasing liquid and washing it with water. The amount of oil after removal is preferably 0.2 mmg or less. In addition, the process of cleaning the above protector 120 corresponds to the cleaning process of the claims.

  At this time, an oil agent having a coating amount of 0.7 mg to 2 mg is applied to the inner peripheral surface of the metal shell 4 (the portion where the distal end inner peripheral surface 48 is planned) and the inner peripheral surface 124 of the protector 120. ing. Thus, the protector 120 and the metal shell 4 can be efficiently produced from the metal material through a plurality of machining processes by applying the oil agent 250 of 0.7 mg to 2 mg in the application process.

  Next, the protector 120 and the metal shell 4 are fixed by inserting the rear end side of the protector 120 on the outer periphery of the front end portion 46 of the metal shell 4 to provide an overlap portion and spot welding the overlap portion. This process corresponds to the mounting process in the claims.

  Thus, the protector 120 has a cleaning process for cleaning after the preparation process, and is then welded to the metal shell 4 in the mounting process. When the protector 120 is manufactured by machining from a metal material in the preparation process, an oil agent 250 for lubrication and cooling is necessary. However, in the subsequent welding process, the oil agent 251 attached to the metal shell 4 is used for lubrication. Therefore, the oil agent 250 of the protector 120 is not necessary. Therefore, the oil agent 251 of the protector 120 that is necessary for the preparation process is washed in the washing step, so that the oil agent 250 of the protector 120 can be almost removed. Thereby, the gas sensor 1 which can suppress that the gas detection accuracy in use of the gas sensor 1 falls can be produced efficiently.

  On the other hand, after adding 5 mol% of yttria to zirconia and granulating, it is formed into a bottomed cylindrical shape with a closed tip as shown in FIG. 1 and fired at a temperature of 1400 to 1600 ° C. in an electric furnace. A solid electrolyte body 21 was obtained. Next, an external electrode 23 made of platinum is provided on the outer peripheral surface of the solid electrolyte body 21 by vapor deposition, chemical plating, or the like. On the other hand, the internal electrode 22 was similarly provided on the inner side surface of the solid electrolyte body 21 using vapor deposition, chemical plating, or the like, and the sensor element 2 was obtained.

  Then, the packing 6, the support member 7, the packing 8, the sensor element 2, the filling member 9, the sleeve 100, and the annular ring 110 are sequentially inserted into the metal shell 4 to which the protector 120 is fixed. The packing 6 is supported by the metal-side step portion 43 of the metal shell 4, and a support portion 45 is formed on the metal shell 4. Then, with the front end opening end portion 132 of the inner cylinder member 130 in contact with the annular ring 110, the rear end portion 44 of the metal shell 4 is crimped in the inner front end direction, and the lower assembly is manufactured. The process of assembling the sensor element 2 to the metal shell 4 corresponds to the assembling process of the claims, and the process of inserting the filling member 9 corresponds to the filling process of the claims. The process of caulking the portion 44 corresponds to the caulking process in the scope of the claims.

  Next, the lower assembly is placed in a heat treatment furnace to perform heat treatment, and the oil agent 251 is removed. This process corresponds to the removing process in the claims. Specifically, the temperature is raised by heating, and when it reaches 430 ° C., it is held for 60 minutes, and then naturally cooled. It should be noted that the oil agent 250 adhering to the protector 120 and the metal shell 4 that could not be removed in the cleaning process can also be removed during this heat treatment. Then, the adhesion amount of the oil agents 250 and 251 adhering to the inner peripheral surface 48 of the front end side of the metal shell 4 and the inner peripheral surface 124 of the protector 120 can be limited to less than 0.7 mg. As described above, the oil agent 250 is removed from the metal shell 4 and the protector so that the amount of the oil agents 250 and 251 adhering to the inner circumferential surface 48 of the metal shell 4 and the inner circumferential surface 124 of the protector 120 is less than 0.7 mg. And the removal step of removing from the gas sensor 1 during use of the gas sensor 1, the remaining oil agents 250 and 251 on the inner peripheral surface 124 of the protector 120 and the distal end inner peripheral surface 48 of the metal shell 4 are gasified to protect the protector 120. The amount that oozes out can be suppressed within a range that does not affect the gas detection accuracy, and the gas sensor 1 that can suppress a decrease in gas detection accuracy can be efficiently manufactured.

  On the other hand, the element lead wires 170 and 180 are joined to the terminal fittings 210 and 220, respectively, and the heater lead wires 190 and 200 are joined to the heater terminal fitting 230 of the ceramic heater 3. Then, the lead wires 170, 180, 200, and 210 are inserted into the separator lead wire insertion holes 161 of the separator 160 with the ceramic heater 3 positioned inside the terminal fitting 220. Next, the lead wires 170, 180, 190, and 200 are inserted into the lead wire insertion holes 241 of the seal member 240 and moved until the front end surface of the seal member 240 contacts the rear end surface of the separator 160. In this way, the upper assembly is produced.

  Then, the separator 160 of the upper assembly is positioned in the inner rear end portion 135 of the inner cylinder member 130 of the lower assembly. Thereby, the terminal fitting 220 is inserted into the sensor element 2 together with the ceramic heater 3, and is electrically connected to the inner electrode 22. Further, the terminal fitting 210 is fitted on the outer surface of the sensor element 2 and is electrically connected to the outer electrode 23.

  And the filter 140 is arrange | positioned in the outer periphery of the air | atmosphere introduction hole 131 of the inner cylinder member 130, and the sealing member 240 of the sealing member 240 is put in the state which passed each lead wire 170, 180, 190, 200 to own inner side after that. It is moved from the rear end side and moved until it overlaps the outside of the front end portion 134 of the inner cylinder member 130. Next, the outer cylinder member 150 and the grommet 240 are respectively crimped to complete the gas sensor 1.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the embodiment, and various design changes can be made within a range in which the object of the present invention can be achieved.

  For example, as another embodiment of the present invention, there is one in which the adhesion amount of the oil agent is relatively increased to 0.7 mg to 2 mg, while the airtightness between the metal shell and the detection element is relatively lowered. . As a method for reducing the airtightness, a method of reducing the axial length (thickness) of the filling member 9 or adjusting the particle size of the ceramic powder used for the filling member 9 can be mentioned. Thus, when the airtightness between the metal shell and the detection element is relatively low, that is, the temperature of the metal shell is heated to 550 ° C., and the atmosphere is 0.4 MPa from the front end side of the metal shell. When the amount of air leaking to the rear end side of the metal shell through the detection element and the metal shell when pressurized is 10 cc / min to 50 cc / min, the adhesion amount of the oil is 0.7 mg to 2 mg. Even so, most of the gasified oil agent easily passes between the metal shell and the detection element and is discharged to the rear end side, so that adverse effects on detection accuracy are suppressed.

Further, a reference embodiment of the present invention will be described with reference to FIG. Note that the manufacturing method of the reference embodiment is only partially different from the manufacturing method of the first embodiment. Therefore, it demonstrates centering on the difference part, and the other part is simplified or abbreviate | omitted.

In the reference form, after molding, the metallic shell 4 and the protector 120 to which the oil agent 250 is adhered are immersed in a degreasing liquid, and are removed from the degreasing liquid and washed with water to remove the oil agent 250. The amount of oil after removal is preferably 0.2 mg or less.

Next, in the first embodiment, the protector 120 is mounted after separately applying the oil 251 to the metal shell 4, but in the reference embodiment, the protector 120 is mounted without applying the oil 251 to the metal shell 4. That is, the protector 120 and the metal shell 4 are fixed by inserting the rear end side of the protector 120 on the outer periphery of the front end portion 46 of the metal shell 4 to provide an overlap portion and spot welding the overlap portion.

  Next, an oil agent liquid is applied to the rear end portion 44 of the metal shell 4 to newly attach a new oil agent 251. The oil agent 251 is dissolved by mixing an aqueous oil agent and an activator in warm water. The aqueous solution oil is one in which alkylamine oxide or the like is contained in an aqueous solution having an oil content of about 30%, and the mixing ratio is 50 to 60 ml / l. Moreover, an activator is a nonionic surfactant and the mixing rate is 13-20 ml / l. As a temperature range of warm water, it is 50-60 degreeC.

  In order to increase the accuracy in the caulking process, the oil agent 251 is attached to the metal shell before caulking. On the other hand, the oil agent can be removed more easily and more efficiently than the heat treatment by removing the oil agent from the front end side inner peripheral surface 48 of the metal shell 4 and the inner peripheral surface 124 of the protector 120 in the cleaning process.

  Then, the packing 6, the support member 7, the packing 8, the sensor element 2, the filling member 9, the sleeve 100, and the annular ring 110 are sequentially inserted into the metal shell 4 to which the protector 120 is fixed. The packing 6 is supported by the metal-side step portion 43 of the metal shell 4, and a support portion 45 is formed on the metal shell 4. Then, with the front end opening end portion 132 of the inner cylinder member 130 in contact with the annular ring 110, the rear end portion 44 of the metal shell 4 is crimped in the inner front end direction, and the lower assembly is manufactured.

In the reference form, the oil agent 250 used at the time of molding the metal shell 4 and the protector 120 is removed by washing before the assembly process. Further, since the oil agent 251 is applied only to the caulking portion, it does not adversely affect the detection accuracy of the gas sensor, and therefore it is not necessary to remove it by heat treatment or the like.
However, if it is necessary to further remove the oil agent 250 remaining after the cleaning step, it is not hindered to perform a separate heat treatment. Even in such a case, since the amount of the oil agent is greatly reduced in the cleaning process, the burden of removing the oil agent in the heat treatment can be significantly reduced.

In the above embodiment, the sensor element 2 is supported on the metal-side step part 43 of the metal shell 4 via the packing 6, the support member 7, and the packing 8. The sensor element 2 may be directly supported. In this case, a portion where the sensor element 2 contacts the stepped portion 43 is the support portion 45.
Moreover, in the said embodiment, although the double protector of the outer side protector 122 and the inner side protector 123 was used as the protector 120, the single protector 120 limited to this may be sufficient.
Moreover, in the said embodiment, although the bottomed cylindrical sensor element 2 was used, not only this but a plate-shaped sensor element may be used.
Furthermore, in the said embodiment, although the oil agent 250 is apply | coated to both the metal shell 4 and the protector 120, not only this but the oil agent may be apply | coated to one of the metal shell 4 or the protector 120. .

It is sectional drawing of the gas sensor 1 of 1st Embodiment and reference form. It is a principal part expanded sectional view of the gas sensor 1 of 1st Embodiment. It is the infrared absorption spectrum which analyzed the metal shell 4 of the gas sensor 1 of 1st Embodiment by micro infrared spectroscopy.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gas sensor 2 ... Sensor element 3 ... Heater 4 ... Main metal fitting 9 ... Filling member 44 .... Rear end part (caulking part) of main metal fitting
48 .. Front end side inner peripheral surface 120 of the metal shell ... Protector 124 ... Protector inner peripheral surface 250 ... First oil agent 251 ... Second oil agent

Claims (8)

A detection element that extends in the axial direction and whose tip is exposed to the gas to be measured;
A cylindrical metal shell that supports the detection element so that the tip of the detection element protrudes from the tip of the detection element;
In the gas sensor provided with a cylindrical protector that is attached to the tip of the metal shell and covers the tip of the detection element,
An oil agent is attached to a part of the inner peripheral surface of the metal shell that is exposed to the gas to be measured and a part of the inner peripheral surface that is exposed to the gas to be measured of the protector. A gas sensor characterized in that the amount of oil attached is less than 0.7 mg. The gas sensor according to claim 1, wherein
The gas sensor is characterized in that the amount of the oil to be adhered is less on the inner peripheral surface of the protector than on the inner peripheral surface on the front end side of the metal shell. The gas sensor according to claim 1 or 2,
The gas sensor according to claim 1, wherein the protector is welded to the tip of the metal shell. The gas sensor according to any one of claims 1 to 3,
Between the inner peripheral surface of the metal shell and the outer peripheral surface of the detection element, a powdery seal member is disposed,
The gas sensor according to claim 1, further comprising: a caulking portion that caulks the seal member so as to be airtight at a rear end portion of the metal shell. The gas sensor according to claim 4 Symbol mounting,
The gas sensor is characterized in that the adhesion amount of the oil agent is less on the inner peripheral surface of the distal end side of the metal shell than on the outer peripheral surface of the crimped portion of the metal shell.
  A detection element that extends in the axial direction and whose tip is exposed to the gas to be measured;
A cylindrical metal shell that supports the detection element so that the tip of the detection element protrudes from the tip of the detection element;
  In a method for manufacturing a gas sensor, comprising: a cylindrical protector that is attached to the distal end portion of the metal shell and covers the distal end portion of the detection element;
  A preparation step of preparing the metal shell and the protector to which an oil agent is attached;
  A mounting step of mounting the protector on the metal shell;
  An assembly step of supporting the detection element on the metal shell to which the protector is attached;
  A removal step in which the amount of the oil attached to the inner peripheral surface of the front end side to which the gas to be measured is exposed and the inner peripheral surface of the protector is less than 0.7 mg, of the inner peripheral surface of the metal shell,
  The method of manufacturing a gas sensor, wherein the removing step includes a heat treatment step of performing a heat treatment on the metal shell and the protector.   In the manufacturing method of the gas sensor according to claim 6,
  A powdery seal member is disposed between the inner peripheral surface of the metal shell and the outer peripheral surface of the detection element, and a caulking portion that makes the seal member airtight at the rear end of the metal shell Is formed,
  The assembly step includes a filling step of filling the seal member between an inner peripheral surface of the metal shell and an outer peripheral surface of the detection element;
  And a caulking step for caulking a rear end portion of the metal shell.   In the manufacturing method of the gas sensor according to claim 7,
  After the preparation step,
  A cleaning step of cleaning the protector and the metal shell;
  An attaching step of attaching the oil agent again to the metal shell so that the amount of the oil agent applied to the inner peripheral surface of the distal end side of the metal shell after cleaning is 0.7 mg to 2 mg;
A method for manufacturing a gas sensor, comprising: