JP4817419B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor that detects the concentration of a specific gas component in a gas to be measured such as exhaust gas.

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. As this oxygen sensor, a filter having air permeability and water repellency is formed by forming a through hole for introducing outside air serving as a reference gas in the center of a seal member provided at the upper part of the oxygen sensor and closing the through hole. The structure which provided this is known (refer patent document 1). Specifically, this oxygen sensor has a sheet-like water-repellent filter sandwiched between the outer peripheral surface of a cylindrical insertion member that can be inserted into the through-hole and the inner peripheral surface of the through-hole. It is fixed to.
JP 2001-208724 A

  However, the oxygen sensor of Patent Document 1 has a form in which the filter can be visually recognized when the oxygen sensor is viewed in the axial direction from the rear side, and the filter may be directly subjected to external impact or the like, and the filter may be broken. there were. As a result, when the gas sensor flies, water may enter the gas sensor, causing an abnormality in the output of the gas sensor or shorting the terminals.

  The present invention has been made in view of such conventional problems, and in a gas sensor having a configuration in which a filter is arranged on a seal member fixed to a casing, the filter is prevented from being broken, and water enters the inside of the gas sensor. The present invention provides a gas sensor that prevents the above.

Therefore, the gas sensor of the present invention extends in the axial direction, detects a specific gas component in the gas to be measured, and exposes the tip of the detection element to the gas to be measured by projecting from the tip of the gas, A casing that surrounds the periphery of the detection element, a seal member that is fixed behind the detection element and inside the rear end of the casing, and has a through-hole that penetrates in the axial direction, and is fitted into the through-hole. A gas sensor comprising a filter part having air permeability and water repellency,
When the gas sensor is viewed from the rear side in the axial direction, a cover portion that covers the filter portion so that the filter portion cannot be visually recognized, and a communication portion that communicates with the through hole and allows ventilation from the outside into the through hole. A filter covering member that is coupled to the rear side of the seal member, and when the communication portion is viewed in the longitudinal direction of the communication portion from its own opening, the filter portion is not visible. It characterized that you have been placed in the through hole.

  As in the present invention, a filter covering member including a covering portion that covers the filter portion is coupled to the seal member, so that the filter portion cannot be directly visually recognized when the gas sensor is viewed in the axial direction from the rear side. . Therefore, the filter unit is not directly subjected to external impact and the like, and the filter unit is prevented from being broken by the impact and the like, and as a result, water can be prevented from entering the gas sensor.

  In addition, the coating | coated part should just cover this filter part so that a filter part cannot be directly recognized, From the cross-sectional area (cross-sectional area orthogonal to the axis line of a gas sensor) of the rear-end opening of the through-hole by which a filter part is arrange | positioned As long as it has a shape having a large cross-sectional area. Furthermore, it does not have to be the same shape as the through hole (for example, when the through hole is circular, the covering portion is also circular), and may be a polygon such as a triangle or a quadrangle.

  The filter covering member includes a communicating portion that communicates with the through hole. The communicating portion only needs to allow ventilation from the outside into the through hole (or inside the casing), and the outer surface of the filter covering member. The opening formed in the filter covering member may be formed in the circumferential direction of the filter covering member, or may be formed in the rear end facing surface of the filter covering member. Further, it may be formed in a straight line from the opening of the communication part formed on the outer surface of the filter covering member to the through hole, or refracted between the opening of the communication part and the through hole. Also good. In addition, when the communication part is formed in a linear shape, the formation position of the communication part and the arrangement position of the filter part are arranged so that the filter part cannot be visually recognized when viewed in the longitudinal direction of the communication part from the opening of the communication part. It is preferable to set. This is because even if high-pressure water enters the longitudinal direction in the communicating portion from the opening of the communicating portion, it does not directly hit the filter portion, and the filter portion can be reliably prevented from being broken.

  As described above, the communication part is formed in a linear shape, and as a specific configuration in which the filter part is not visible when viewed in the longitudinal direction of the communication part from the opening of the communication part, the communication part is It can be set as the structure extended in the circumferential direction of a filter coating | coated member.

  Furthermore, in the gas sensor of the present invention, it is preferable that the communication portion is a groove cut out from the rear end surface of the filter covering member. By forming the communication portion as a groove in this way, a communication portion capable of allowing ventilation from the outside to the inside of the through hole (or inside the casing) can be easily provided in the filter covering member.

  Further, in the gas sensor according to the present invention, the filter covering member includes a plurality of the communication portions, and one communication portion of the plurality of communication portions is visually recognized from the opening in the longitudinal direction of the communication portion. Sometimes, it is preferable that a plurality of communication portions are arranged so that openings of other communication portions can be visually recognized. As a result, even if high-pressure water, engine oil, gasoline, or the like intrudes in the longitudinal direction from the opening of one communication portion, it does not stay in the through hole of the seal member and passes through the other communication portion to the outside. It becomes easy to come off. Therefore, it can prevent that the air permeability of a filter part falls.

  Furthermore, in the gas sensor of the present invention, it is preferable that the seal member and the filter covering member are integrally formed. Since the seal member and the filter covering member are integrally formed, there is no need to separately use an adhesive or the like, and the seal member and the filter covering member can be easily formed, thereby reducing the cost of the gas sensor. it can.

  By the way, as a filter part, the form which arrange | positions a sheet-like filter in a through-hole by the form clamped between the outer peripheral surface of the cylindrical insertion member which can be inserted in a through-hole, and the inner peripheral surface of a through-hole, A form in which a columnar filter is arranged in a through-hole is known, but the sheet-like filter is prevented from being broken by using the present invention for a filter part in which a more easily torn sheet-like filter is arranged. It is particularly effective.

  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, a gas sensor (oxygen sensor) that is attached to an exhaust pipe of an automobile and detects the concentration of oxygen in 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 a bottomed hole 21 of the sensor element 2, and the sensor element 2 inside thereof. The metal shell 4 is held. In the present embodiment, among the directions along the axis of the sensor element 2 shown in FIG. 1, the side (closed side, lower side in the drawing) toward the tip exposed to the measurement target gas (exhaust gas) is used. In the following description, the “front end side” is referred to as the “rear end side” and the side facing the opposite direction (upper side in the drawing) is referred to.

  The sensor element 2 is made of a solid electrolyte body having oxygen ion conductivity mainly composed of partially stabilized zirconia in which yttria is solid-solved as a stabilizer, and has a detection unit 22 at the tip. An internal electrode layer 24 formed in a porous shape by Pt or a Pt alloy so as to cover almost the entire surface of the bottomed hole 21 in the detection unit 22, and an internal electrode layer 24 on the outer surface of the detection unit 22. The external electrode layer 23 is formed in a porous shape in the same manner as in FIG. Further, an engagement flange portion 25 that protrudes radially outward 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 a “detection element” in the claims. On the other hand, 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 390 and 420, 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.

  The metal shell 4 has a screw part 41 for attaching the gas sensor 1 to the attachment part of the exhaust pipe, and a tool engaging part 42 to which an attachment tool is applied when the gas sensor 1 is attached to the attachment part of the exhaust pipe. The metal shell 4 is provided with a metal-side step 43 that protrudes radially inward on the inner periphery of the front end side, and the support member 5 is locked to the metal-side step 43 through the packing 8. I am letting. The sensor element 2 is supported by the metal shell 4 when the engagement flange portion 25 is supported on the support member 5 via the packing 9. A filling member 6 is disposed between the inner surface of the metal shell 4 on the rear end side of the support member 5 and the outer surface of the sensor element 2, and a sleeve 7 and an annular ring 10 are further provided on the rear end side of the filling member 6. It arrange | positions in the state inserted sequentially coaxially. The sensor element 2 is fixed to the metal shell 5 by caulking the metal-side rear end 44 of the metal shell 4 in the inner tip direction. Note that the gas sensor 1 has a structure in which the filling member 6 is compressed and filled through the sleeve 7 by crimping the metal-side rear end 44 of the metal shell 4, whereby the sensor element 2 has a cylindrical shape. The metallic shell 4 is held in an airtight manner.

  On the other hand, the outer cover 15 is joined to the distal end portion 26 of the metal shell 4. The outer cover 15 has a bottomed cylindrical shape that covers the periphery of the detection portion 22 of the sensor element 2 protruding from the metal shell 4. Further, an inner cover 16 is formed inside the outer cover 15. Similar to the outer cover 15, the inner cover 16 has a bottomed cylindrical shape that covers the detection unit 22 of the sensor element 2. The outer cover 15 and the inner cover 16 are respectively formed with vent holes 151 and 161 for exposing the exhaust gas to the sensor element 2.

  Further, the front end portion of the outer cylinder member 11 is joined to the inner side of the rear end side of the metal shell 4. The outer cylinder member 11 is formed with an outer cylinder stepped portion 111 at a substantially intermediate position in the axial direction. The outer cylinder stepped portion 111 is formed at the tip side of the outer cylinder stepped portion 111 as an outer cylinder tip side body portion 112, and the outer cylinder stepped portion is formed. The rear end side of the portion 111 is formed as the outer cylinder rear end side body portion 113. Among these, in the outer cylinder rear end side body portion 113, a first crimping portion 114 for holding a holding member 17 described later and a second crimping portion for fixing a seal member 13 described later in an airtight manner. 115 is formed. The metal shell 4 and the outer cylinder member 11 of the present embodiment correspond to a “casing” in the claims.

  The separator 12 disposed in the outer cylinder rear end side body portion 113 of the outer cylinder member 11 via the holding member 17 passes through the element lead wires 400 and 410 and the heater lead wires 390 and 420. The separator lead wire insertion hole 121 is formed so as to penetrate from the front end side to the rear end side. Further, the separator 12 is formed with a bottomed holding hole 122 opened in the tip end surface in the axial direction. The rear end portion of the ceramic heater 3 is inserted into the holding hole 122, and the rear end surface of the ceramic heater 3 abuts against the bottom surface of the holding hole 122, whereby the ceramic heater 3 is positioned in the axial direction with respect to the separator 12. . The separator 12 has a separator flange portion 123 extending outward in the circumferential direction.

  The element lead wires 400 and 410 and the heater lead wires 390 and 420 pass through the separator lead wire insertion hole 121 of the separator 12, the seal member 13 described later, and the lead wire insertion hole 131 of the filter covering member 400. 11 is pulled out from the inside to the outside. Note that these four lead wires 390, 400, 410, and 420 are externally connected to a connector (not shown). Then, external signals such as an ECU and the lead wires 390, 400, 410, 420 are input / output via the connector.

  Although not shown in detail, each lead wire 390, 400, 410, 420 has a structure in which the 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 400 is crimped with the rear end portion of the terminal fitting 14 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 410 is It crimps with the rear-end part of the terminal metal fitting 14 press-fit with respect to the inner surface of the sensor element 2. FIG. As a result, the element lead wire 400 is electrically connected to the external electrode layer 23 of the sensor element 2, and the element lead wire 410 is electrically connected to the internal electrode layer 24. On the other hand, the leading ends of the lead wires 390 and 420 for the heater are respectively connected to a pair of heater terminal fittings joined to the heating resistor of the ceramic heater 3.

Next, the seal member 13 and the filter covering member 200 which are the main parts of the present invention will be described in detail.
As shown in FIGS. 1 and 2, the sealing member 13 disposed inside the rear end side of the outer cylinder member 11 includes two element lead wires 400 and 410 electrically connected to the sensor element 2, ceramic, and the like. Four lead wire insertion holes 131 for inserting two heater lead wires 390 and 420 electrically connected to the heater 3 are formed so as to penetrate from the front end side to the rear end side. Furthermore, an air introduction hole 132 is formed in the approximate center of the seal member 13 from the front end side toward the rear end side. The seal member 13 is made of fluorine rubber or the like. Note that the air introduction hole 132 of this embodiment corresponds to a “through hole” in the claims.

  Further, a filter portion 136 is disposed inside the air introduction hole 132. The filter 136 includes a cylindrical metal cup 134 covered with a sheet-like filter 133, and is fixed so that the filter 133 is sandwiched between the air introduction hole 132 and the metal cup 134. The filter 133 is made of a material such as PTFE, for example, and has air permeability and water repellency. Moreover, this metal cup 134 has the cylinder part 135 extended in the axis line O direction, and the protrusion part 137 which protrudes in the radial direction at the front end side of the cylinder part 135 (refer FIG. 5). An air insertion hole 138 is formed on the rear end side of the cylinder portion 135, and the atmosphere can be introduced into the outer cylinder member 11 from the outside through the air insertion hole 138 and the filter 133.

  The filter covering member 200 is coupled to the rear side of the seal member 13. In the present embodiment, the seal member 13 and the filter covering member 200 are integrally formed. In this way, by integrally forming the seal member 13 and the filter covering member 200, it is not necessary to separately bond the seal member 13 and the filter covering member 200 with an adhesive or the like. Also in this filter covering member 200, lead wire insertion holes 131 connected to the four lead wire insertion holes 131 of the seal member 13 are formed so as to penetrate from the front end side to the rear end side. Further, as shown in FIG. 3, a covering portion 201 that covers the filter 133 of the filter portion 136 is formed in the approximate center of the filter covering member 200. The covering portion 201 is formed to have a larger diameter than the outer shape of the opening portion of the air introduction hole 132.

  Thus, by providing the filter covering member 200 with the covering portion 201, the filter portion 136 (filter 133) cannot be visually recognized when the gas sensor 1 is viewed in the axial direction from the rear side. Accordingly, the filter 133 is not directly subjected to external impact or the like, and the filter 133 is prevented from being broken by the impact or the like. As a result, water can be prevented from entering the gas sensor 1.

  Further, as shown in FIGS. 3 and 4, a communication portion 203 is formed so as to communicate with an air introduction hole 132 of the seal member 13 from an opening 202 formed on the outer periphery of the filter covering member 200. The communication portion 203 is a groove that extends in a straight line shape in the circumferential direction and is cut out from the rear end surface of the filter covering member 200. 3 and 4 are views before the seal member 13 and the filter covering member 200 are attached to the gas sensor 1, and FIG. 4 is a side view as viewed from the direction A in FIG.

  Thus, by providing the filter covering member 200 with the communication portion 203 formed in a linear shape in the circumferential direction, when viewed from the opening 202 of the communication portion 203 in the longitudinal direction of the communication portion 203, the filter portion 136 (filter 133) cannot be visually recognized. Therefore, even if high-pressure water enters the longitudinal direction in the communication portion 203 from the opening 202 of the communication portion 203, it does not directly hit the filter 133, and the filter 133 can be reliably prevented from being broken. Furthermore, since the communication part 203 is formed as a groove cut out from the rear end face of the filter covering member 200, the communication part 203 can be easily provided in the filter covering member 200.

  Further, as shown in FIG. 3, four communication portions 203 are provided in the filter covering member 200, and the first communication portion 204 and the third communication portion 206, and the second communication portion 205 and the fourth communication portion 207. Are paired, and when viewed in the longitudinal direction from the opening of the first communication portion 204 (second communication portion 205), the opening of the third communication portion 206 (fourth communication portion 207) is visually recognized. It can be arranged.

  In this way, the filter covering member 200 is provided with a plurality of communication portions 203, and when one communication portion 203 is visually recognized from the opening in the longitudinal direction among the plurality of communication portions 203, the other communication portions are provided. Since the opening 203 is visible, for example, even if high-pressure water, engine oil, gasoline, or the like enters from the opening of the first communication portion 204 in the longitudinal direction in the first communication portion, the air introduction hole of the seal member 13 Without staying in 132, it can easily pass through the third communication portion 206 to the outside, and the air permeability of the filter 133 can be prevented from being lowered.

Next, the manufacturing method of the gas sensor 1 of this embodiment is demonstrated in detail.
First, after adding 5 mol% of yttria to zirconia and granulating, it was formed into a bottomed cylindrical shape with a closed tip, and fired at a temperature of 1400 to 1600 ° C. in an electric furnace to obtain a solid electrolyte body. . Next, an external electrode layer 23 made of platinum is provided on the outer peripheral surface of the solid electrolyte body by vapor deposition, chemical plating, or the like. On the other hand, the internal electrode layer 24 was similarly provided on the inner surface of the solid electrolyte body using vapor deposition, chemical plating, or the like, and the sensor element 2 was obtained.

  Next, the outer cover 15 in which the inner cover 16 is inserted is inserted into the distal end portion 26 of the metal shell 4 and is welded all around by laser welding. Then, packing 8, support member 5, packing 9, sensor element 2, filling member 6, and sleeve 7 are sequentially inserted into the metal shell 4, and the metal-side rear end 44 of the metal shell 4 is swaged to prepare a sensor lower intermediate body. To do.

  On the other hand, the element lead wires 400 and 410 are joined to the terminal fittings 14 and 14, respectively, and the heater lead wires 390 and 420 are joined to the heater terminal fittings of the ceramic heater 3. Then, the lead wires 390, 400, 410, 420 are inserted into the separator lead wire insertion holes 121 of the separator 12 with the ceramic heater 3 positioned inside the terminal fitting 14.

  Next, as shown in FIG. 5, the metal cup 134 formed with the cylindrical portion 135 and the protruding portion 137 is press-fitted into the air introduction hole 132 of the seal member 13 through the sheet-like filter 133 to form the filter portion 136. . Then, the seal member 13 having the filter portion 136 is disposed on the rear end side of the outer cylinder member 11. The seal member 13 and the filter covering member 200 are integrally formed. When the seal member 13 is disposed on the rear end side of the outer cylinder member 11, the filter covering member 200 is disposed on the rear side of the outer cylinder member 11. It becomes a state.

  Next, with the lead wires 390, 400, 410, 420 inserted through the lead wire insertion holes 131 of the seal member 13 and the filter covering member 200, the front end surface of the seal member 131 comes into contact with the rear end surface of the separator 12. As described above, the separator 12 is disposed in the outer cylinder member 11. Then, the holding member 17 is inserted from the tip of the separator 12. In this way, the sensor upper intermediate is produced.

  Then, the outer cylinder member 11 of the sensor upper intermediate body is inserted into the rear end side of the metal shell 4, and the overlapping portion between the outer cylinder member 11 and the metal shell 4 is crimped. Further, the outer cylinder member 11 is caulked so as to hold the holding member 17, and the first caulking portion 114 is formed. Furthermore, the outer cylinder member 11 is crimped so as to hold the elastic seal member 13, thereby forming a second crimped portion 115. The caulking was performed by Happomaru caulking. The overlapping portion is fixed by laser welding to complete the gas sensor 1.

Although the present embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various design changes can be made.
For example, another embodiment is shown in FIG. In this alternative embodiment, the seal member 13 and the filter covering member 200 are integrally formed as in the present embodiment, and are formed separately and joined together. This is different from the shape of the filter covering member 200. In the following description, different parts will be mainly described, and the same parts as the present embodiment will be omitted. FIG. 6 is a partial cross-sectional view of the state in which the seal member 13 and the filter covering member 200 are removed from the gas sensor 1.

  In another embodiment, as shown in FIG. 6, the seal member 13 and the filter covering member 300 are formed separately. Specifically, the filter covering member 300 is disposed on the substantially central rear side of the seal member 13 and coupled together. The filter covering member 300 has a cylindrical shape having a smaller diameter than the seal member 13. A cover portion 301 that covers the filter 133 of the filter portion 136 is formed on the rear end side of the filter cover member 300. In addition, a communication portion 303 is formed so as to communicate with an air introduction hole 132 of the seal member 13 from an opening 302 formed on the outer periphery of the protruding portion 301. The communication portion 303 extends in a linear shape in the circumferential direction. Also in this other embodiment, when the filter covering member 300 includes the covering portion 301, the filter portion 136 (filter 133) cannot be visually recognized when the gas sensor 1 is viewed in the axial direction from the rear side. As a result, the filter 133 is not directly subjected to external impact or the like, and the filter 133 is prevented from being broken by the impact or the like. As a result, the detection accuracy of the gas sensor 1 is prevented from being lowered.

  In this embodiment or another embodiment, the filter unit 136 is configured such that the cylindrical metal cup 134 is covered with the sheet-like filter 133 and the filter 133 is sandwiched between the air introduction hole 132 and the metal cup 134. However, the present invention is not limited to this. For example, a columnar filter inserted into the air introduction hole may be used.

It is sectional drawing of the gas sensor 1 of this embodiment. It is a partial expanded sectional view near seal member 13 and filter covering member 200 arranged in gas sensor 1 of this embodiment. It is the figure which looked at the sealing member 13 and the filter coating | coated member 200 before attaching to the gas sensor 1 of this embodiment from the back side. It is a side view of seal member 13 and filter covering member 200 before attaching to gas sensor 1 of this embodiment. It is explanatory drawing at the time of inserting the filter 133 and the metal cup 134 of this embodiment in the sealing member 13 and the filter coating | coated member 200. FIG. It is a partial cross section side view of the seal member 13 and the filter coating | coated member 300 before attaching to the gas sensor 1 of another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gas sensor 2 ... Sensor element 3 ... Metal shell 11 ... Outer cylinder member 13 ... Seal member 132 ... Air introduction hole 133 ... Filter 134 ... Metal cup 135 ... Tube part 136 ... Filter part 200, 300 ... Filter covering member 201, 301 ... Cover part 202, 302 ... Opening part 203, 303 ... Insertion Part

Claims (6)

A detection element that extends in the axial direction and detects a specific gas component in the gas to be measured;
A casing that surrounds the periphery of the detection element;
A seal member provided with a through-hole that is fixed to the rear side of the casing on the rear side of the detection element and inside the casing, and penetrates in the axial direction;
A filter part having air permeability and water repellency disposed in the through hole;
In a gas sensor comprising:
A filter covering member coupled to the rear side of the seal member, the cover portion covering the filter portion so that the filter portion cannot be visually recognized when the gas sensor is viewed in the axial direction from the rear side; And a filter covering member having a communication portion that allows ventilation from the outside to the inside of the through-hole, and when the communication portion is viewed in the longitudinal direction of the communication portion from its own opening, the filter portion is the gas sensor in which the filter unit so as not to be visually recognized is characterized that you have been placed in the through hole. The gas sensor according to claim 1, wherein
The gas sensor according to claim 1, wherein the communication portion extends in a circumferential direction of the filter covering member. The gas sensor according to claim 2, wherein
The gas sensor according to claim 1, wherein the communication part is a groove cut out from a rear end surface of the filter covering member. The gas sensor according to any one of claims 1 to 3,
The filter covering member is provided with a plurality of the communication portions,
Among the plurality of communication parts, when one communication part is viewed from the opening in the longitudinal direction of the communication part, the plurality of communication parts are arranged so that the opening of the other communication part can be visually recognized. A gas sensor. The gas sensor according to any one of claims 1 to 4,
The gas sensor, wherein the seal member and the filter covering member are integrally formed. The gas sensor according to any one of claims 1 to 5,
A gas sensor, wherein a sheet-like filter is disposed in the filter unit.