JP2006090842A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor in which airtightness is ensured by reducing the gap between an inner peripheral surface of the insertion hole of a holder and a plate surface of a sensor element. <P>SOLUTION: In the gas sensor 1, the sizes of the gaps formed between the inner peripheral surfaces of the insertion holes 22 and 31, which are respectively provided to the holder 21 and a sleeve 30, and the plate surface of the sensor element 10 are together restricted to 0.7 mm or below. By restricting these gaps together, penetration of an exhaust gas into the gaps is suppressed and penetration of the exhaust gas into the gas sensor 1 from the gaps is further suppressed. Accordingly, the airtightness in the gas sensor 1 is ensured. Further, even if vibration is applied to the gas sensor 1, leakage of talc powder 23 charged in the space between the holder 21 and the sleeve 30 to the outside from the gaps is suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas sensor incorporating a sensor element for detecting a specific gas component in exhaust gas discharged from an internal combustion engine.

  Conventionally, a gas sensor including a sensor element that detects a specific gas component in exhaust gas generated from an automobile or the like is known. Such a gas sensor has a sensor element in which a detection unit for detecting a specific gas in the exhaust gas is formed at one end in the longitudinal direction of the plate body, and a form in which the detection unit of the sensor element is exposed. A substantially cylindrical metal shell surrounding the periphery in the radial direction is provided. This sensor element is configured as a long plate-like element having at least one layer made of a solid electrolyte sandwiched between a pair of electrodes, and further includes a plate that heats and activates the sensor element. In general, a stack of heaters in a shape is known. In order to hold the plate-shaped sensor element in the substantially cylindrical metal shell, the holder, the filling powder, and the sleeve held inside the metal shell are from the detection side (hereinafter referred to as the front end side) of the sensor element. In order.

  Among these, the holder and the sleeve are made of ceramic and have an approximately cylindrical appearance. Further, the holder and the sleeve are each provided with a substantially rectangular insertion hole along the central axis along a cross-sectional shape orthogonal to the longitudinal direction of the sensor element. Therefore, the sensor element is inserted and held in each insertion hole. Since the sensor element may be slightly warped in the longitudinal direction in manufacturing, when the sensor element is disposed in the insertion hole of the holder and the sleeve, the inner peripheral surface of each insertion hole of the holder and the sleeve A slight gap is provided between the sensor element and the surface of the sensor element, and the warp of the sensor element is absorbed by the gap. Then, the rear end side of the metal shell is crimped to the sleeve side, and the filling powder is pressurized from the sleeve side toward the holder side, whereby the inside of the metal shell is sealed and the airtightness in the gas sensor is maintained. .

However, since the gas sensor as described above is actually fixed to the exhaust pipe of an automobile, the metal shell expands by receiving heat transferred from the exhaust pipe, and a gap is formed between the metal shell and the holder. was there. When vibration is applied to the gas sensor in which the gap is generated, the filled powder that has been pressure-filled may gradually leak to the front end side of the metal shell through the gap. Therefore, for example, when the talc powder is pressurized by projecting the portion near the sensor element on the end surface facing the talc powder (filled powder) of the holder toward the sleeve side from the portion near the metal shell, A gas sensor that can harden talc powder in the vicinity of the boundary between the holder and the metal shell by receiving stress from the protruding portion has been proposed (see, for example, Patent Document 1).
JP 2002-71626 A

  However, in the gas sensor described in Patent Document 1, even if the gap between the metal shell and the holder is sealed, the gap between the inner peripheral surface of the insertion hole of the holder and the plate surface of the sensor element is as described above. In addition, a gap for absorbing the warp of the sensor element is provided, and if the area when the gap is cut perpendicular to the axial direction is relatively large, the exhaust gas easily enters the gap. However, there is a problem that the exhaust gas easily enters the gas sensor from the gap of the insertion hole of the holder, and the airtightness in the gas sensor is lowered.

  The present invention has been made in order to solve the above-described problems, and by reducing the gap formed between the inner peripheral surface of the insertion hole of the holder and the plate surface of the sensor element, the airtightness in the sensor is improved. It aims at providing the gas sensor which can be ensured.

  In order to achieve the above object, according to the gas sensor of the first aspect of the present invention, a sensor element in which a detection part for detecting gas is formed at one end in the longitudinal direction of the plate member, and a detection part of the sensor element are provided. In an exposed form, a substantially cylindrical metal shell that surrounds the periphery of the sensor element in the radial direction, and a holder that is held inside the metal shell and has a first shaft hole through which the sensor element is inserted. Gas sensor, wherein the sensor element between the plate surface of the sensor element and the inner peripheral surface of the first shaft hole when cut in the longitudinal direction of the sensor element so as to be orthogonal to the plate surface of the sensor element A gas sensor characterized in that the sum of the distances in the short direction perpendicular to the longitudinal direction is 0.7 mm or less.

  Further, according to the gas sensor of the invention of claim 2, in addition to the configuration of the invention of claim 1, the gas sensor is disposed on the opposite side of the detection unit with respect to the holder and on the inner side of the metal shell. And a plate surface of the sensor element when the sensor element is cut in the longitudinal direction of the sensor element so as to be orthogonal to the plate surface of the sensor element. And the inner peripheral surface of the second shaft hole is 0.7 mm or less in total in the short direction perpendicular to the longitudinal direction of the sensor element.

  Further, according to the gas sensor of the invention of claim 3, in addition to the configuration of the invention of claim 2, in the inside of the metal shell, a filling powder is disposed in a gap sandwiched between the holder and the sleeve. It is characterized by being.

  According to the gas sensor of the first aspect of the invention, when the sensor element is cut in the longitudinal direction of the sensor element so as to be orthogonal to the plate surface of the sensor element, the sensor between the plate surface of the sensor element and the inner peripheral surface of the first shaft hole. The sum of the distances in the short direction perpendicular to the longitudinal direction of the element is adjusted to 0.7 mm or less. Thereby, the area when cut perpendicularly to the axial direction of the gap formed between the inner peripheral surface of the first shaft hole and the plate surface of the sensor element becomes relatively small. Therefore, the exhaust gas can be prevented from entering the gap, and the exhaust gas can be prevented from entering the sensor through the gap, so that a gas sensor that ensures airtightness in the sensor can be obtained.

  By the way, as shown above, the gap for absorbing the warp of the sensor element is not only provided between the inner peripheral surface of the insertion hole of the holder and the outer peripheral surface of the sensor element, but also inside the sleeve. It is also provided between the peripheral surface and the outer peripheral surface of the sensor element. At this time, if the area when cut perpendicular to the axial direction of the gap formed between the inner peripheral surface of the insertion hole of the sleeve and the outer peripheral surface of the sensor element becomes relatively large, the exhaust gas flowing into the metal shell The gas can easily enter the gap, and further, the gas can easily enter the sensor through the gap, so that the airtightness of the sensor may be lowered.

  Therefore, according to the gas sensor of the invention of claim 2, in addition to the effect of the invention of claim 1, when the sensor element plate is cut in the longitudinal direction of the sensor element so as to be orthogonal to the plate surface of the sensor element, The sum of the distances in the short direction perpendicular to the longitudinal direction of the sensor element between the surface and the inner peripheral surface of the second shaft hole is adjusted to 0.7 mm or less. As a result, the area of the gap formed between the inner peripheral surface of the second shaft hole and the plate surface of the sensor element when cut perpendicular to the axial direction is also relatively small. Therefore, even if the exhaust gas flows into the metal shell, the exhaust gas can be prevented from entering the gap, so that the airtightness in the sensor is further secured and a more reliable gas sensor can be provided. .

  By the way, as described above, the filling powder is disposed between the holder and the sleeve, and the back end side of the metal shell is crimped to the sleeve side, so that the filling powder is pressurized from the sleeve side toward the holder side. As a result, airtightness in the gas sensor may be secured. However, when such a gas sensor is put into use, vibration may be given to the gas sensor. Thereby, the filling powder arranged inside the gas sensor may leak to the outside through a gap formed between the inner peripheral surface of each insertion hole of the holder or the sleeve and the plate surface of the gas sensor element, and the gas sensor's airtightness is lowered. There is. Therefore, as in the present invention, by setting the total distance of the gaps formed between the holder or sleeve and the gas sensor element to be 0.7 mm or less, even if vibration is given to the gas sensor, the filled powder can be removed from the gaps. Leakage to the outside can be suppressed, and airtightness of the gas sensor can be ensured. In addition, talc is mentioned as a filling powder.

  In addition, it is preferable that the axis | shaft of a sensor element and a holder or a sleeve is substantially the same. By reducing the total distance of the gaps formed between the holder or sleeve and the gas sensor element to 0.7 mm or less, it is possible to suppress the filling powder from leaking outside through the gap, but the shaft of the sensor element and the holder or sleeve Are substantially the same, the gap between one plate surface of the sensor element and the inner peripheral surface of the holder or sleeve, the other plate surface of the sensor element (the side opposite to the one plate surface), and the inside of the holder or sleeve. The distance from the gap to the circumferential surface is substantially the same, and furthermore, the filling powder can be prevented from leaking from the gap.

  Hereinafter, a gas sensor 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cutaway sectional view of a main part of the gas sensor 1, FIG. 2 is an exploded perspective view of the sensor element 10, and FIG. 3 shows a state in which the sensor element 10 is inserted into the insertion hole 22 of the holder 21. 4 is a cross-sectional view taken along line GG shown in FIG. 3, FIG. 5 is a cross-sectional view taken along line HH shown in FIG. 3, and FIG. 7 is a perspective view of the sleeve 30, FIG. 7 is a perspective view showing a state in which the sensor element 10 is inserted into the insertion hole 31 of the sleeve 30, and FIG. 8 is a cross-sectional view taken along line I-I in FIG. FIG. 9 is a cross-sectional view in the direction of arrows JJ shown in FIG. Further, in the following description, when each member is incorporated in the gas sensor 1, the direction toward the detection unit 11 side of the sensor element 10 in the axial direction of the gas sensor 1 (the vertical direction in the drawing of FIG. 1) is the tip side. The opposite direction is the rear end side.

  The gas sensor 1 of the present embodiment is an oxygen sensor that is mounted on an exhaust pipe of an automobile and is used for use, and detects the oxygen concentration in the exhaust gas flowing through the exhaust pipe. As shown in FIG. 1, the gas sensor 1 includes a substantially cylindrical metal shell 2 having a screw portion 24 for fixing to an exhaust pipe (not shown), and is inserted inside the metal shell 2 to exhaust gas. A sensor element 10 that detects the concentration of a specific gas (for example, oxygen) in the gas, and a holder that is stacked in order from the lower side in the cylinder of the metal shell 2 in order to hold the sensor element 10 inside the metal shell 2 21, a talc powder 23 and a sleeve 30, and a connection terminal provided on the rear end side of the sleeve 30 and extending from four lead wires 68 for electrically connecting the sensor element 10 and an external circuit. 69 is inserted, and the rear end side of the sensor element 10 is inserted into itself, whereby an alumina separator 50 that is electrically connected to the connection terminal 69 and a substantially cylindrical shape that surrounds and protects the separator 50. stainless And Ranaru protective cover 70 is fitted into the rear end of the protective cover 70 is configured by mainly a fluorine rubber stopper member 71 fixed by caulking the rear end of the protective cover 70.

  And the detection part 11 of the sensor element 10 is exposed from the front-end | tip part of the metal shell 2 in the front end side (lower side in the figure) of the gas sensor 1. Furthermore, a bottomed cylindrical inner protector 3 that covers and protects the detector 11 and an outer protector 4 that covers the inner protector 3 are fixed to the front end of the metal shell 2 by laser welding. Yes. A plurality of communication holes 5 and 6 are opened in the inner protector 3 and the outer protector 4 so that the detection unit 11 of the sensor element 10 is exposed to the atmosphere around the gas sensor 1.

  Next, the sensor element 10 will be described. As shown in FIG. 2, the plate-like sensor element 10 is held inside the metal shell 2 in a state where its tip end (detection unit 11) protrudes from the tip of the metal shell 2 and is exposed.

As shown in FIG. 1, the sensor element 10 of the present embodiment includes an oxygen concentration cell element 12 and a base 14 laminated on the oxygen concentration cell element 12. The oxygen concentration cell element 12 includes a partially stabilized zirconia detection layer 111 formed by adding yttria (Y ₂ O ₃ ) or calcia (CaO) as a stabilizer to zirconia (ZrO ₂ ). Further, the reference electrode 132 is disposed so as to be in direct contact with the surface of the detection layer 111 facing the base 14, and the detection electrode 131 is in direct contact with the surface of the detection layer 111 opposite to the base 14. Be placed. The detection electrode 131 has a conductor lead portion 133 extending along the longitudinal direction of the detection layer 111, and the reference electrode 132 has a conductor lead portion 134 extending along the longitudinal direction of the detection layer 111. Yes.

  The terminal of the conductor lead part 133 is connected to a connection terminal 69 (see FIG. 1) for connecting an external circuit. Further, the end of the conductor lead part 134 is connected to a signal extraction terminal 114 for connection to the connection terminal 69 through a through hole 115 penetrating the detection layer 111. Examples of the detection electrode 131, the reference electrode 132, the conductor lead portion 133, the conductor lead portion 134, and the signal extraction terminal 114 include Pt, Rh, and Pd.

  On the surface of the detection layer 111, a porous electrode protection layer 155 is formed to protect the detection electrode 131 itself from poisoning so as to sandwich the detection electrode 131. Further, the insulating layer 52 for protecting the detection layer 111 is formed so as to sandwich the conductor lead portion 133 except for the portion connected to the connection terminal 69.

  On the other hand, the base 14 includes a heating resistor 121 formed of Pt, Rh, Pd, or the like. The heat generating resistor 121 is sandwiched between a first base layer 122 and a second base layer 123 formed mainly of alumina having good insulation properties. The heat generating resistor 121 increases the heat generation area as much as possible, and can intensively heat a portion (so-called detection portion) in which the detection electrode 131 and the reference electrode 132 are arranged to face each other with the detection layer 111 interposed therebetween. In addition, the heat generating part 212 is formed in, for example, a meandering shape or a zigzag shape, and the base 14 is further extended from the end of the heat generating part 212 along the longitudinal direction. An end portion 211 is provided on the opposite side of the pair of lead portions 213 from the heat generating portion 212. The end portion 211 is electrically connected to a pair of heater energization terminals 232 connected to the connection terminal 69 for connecting an external circuit via two through holes 231 penetrating the second base layer 123.

  Further, as shown in FIG. 1, an electrode protective layer 19 made of a porous ceramic for preventing poisoning is formed on at least the surface of the electrode (detection electrode) exposed to the exhaust gas in the front end side of the sensor element 10. Is formed.

  Next, the holder 21 will be described. As shown in FIGS. 1 and 3, the holder 21 is formed in a substantially cylindrical shape, and an insertion hole 22 for inserting the sensor element 10 is provided inside thereof. As shown in FIG. 3, the cross section in the direction orthogonal to the central axis of the insertion hole 22 is formed in a substantially rectangular shape along the cross sectional shape of the sensor element 10. Further, a gap A is formed between the inner peripheral surface of the insertion hole 22 and the plate surface of the sensor element 10. The gap A is for absorbing a slight warp that occurs in manufacturing in the longitudinal direction of the sensor element 10 when the sensor element 10 is held by the holder 21 and the sleeve 30. The size of the gap A is limited under the following conditions.

  As shown in FIG. 4, when the holder 21 into which the sensor element 10 is inserted is cut in the longitudinal direction of the sensor element 10 so as to be orthogonal to the plate surface of the sensor element 10, the thickness direction of the sensor element 10 (FIG. 4), the distance of the sum of the gaps A in the left-right direction (4) is a distance B. This distance B is the distance between one plate surface 14a in the thickness direction of the sensor element 10 and the inner peripheral surface 22a of the insertion hole 22 is B1, and is the one plate surface 14a in the thickness direction of the sensor element 10 When the distance between the opposite plate surface 12a and the inner peripheral surface 22b of the insertion hole 22 is B2, the distance is defined as B = B1 + B2. On the other hand, as shown in FIG. 5, the distance C is the total distance of the gaps A in the width direction of the sensor element 10 (left-right direction in FIG. 5). The distance C is defined as a distance between one plate surface 10a in the width direction of the sensor element 10 and the inner peripheral surface 22c of the insertion hole 22 and is opposite to the one plate surface 10a in the width direction of the sensor element 10. When the distance between the plate surface 10b and the inner peripheral surface 22d of the insertion hole 22 is C2, the distance is defined as C = C1 + C2. In the present embodiment, the distance B and the distance C are each limited to 0.7 mm or less. The reason why the distance B and the distance C are limited and the effect will be described later.

  Note that B1 and B2 shown in FIG. 4 or C1 and C2 shown in FIG. 5 indicate that “when the sensor element is cut in the longitudinal direction so as to be orthogonal to the sensor element plate surface, 4 corresponds to “the distance in the short direction perpendicular to the longitudinal direction of the sensor element with respect to the inner peripheral surface of the shaft hole”, and the distance C shown in FIG. 4 and the distance C shown in FIG. 5 correspond to “sum”. Further, the insertion hole 22 shown in FIG. 3 corresponds to a “first shaft hole”.

  As shown in FIG. 1, such a holder 21 is inserted inside a substantially cylindrical metal holder 20 with the sensor element 10 inserted in the insertion hole 22. Further, a metal holder 20 that holds the sensor element 10 and the holder 21 is inserted from the rear end side of the metal shell 2. Further, a stepped portion 9 whose inner diameter becomes narrower toward the tip is formed inside the tip of the metal shell 2. The holder 21 for inserting the sensor element 10 is positioned and fixed inside the metal shell 2 by engaging one end of the metal holder 20 in the axial direction with the stepped portion 9. Furthermore, talc powder 23 is compressed and filled in the metal shell 2 to which the holder 21 is fixed. Thereby, the metal holder 20 and the holder 21 are fixed inside the metal shell 2, and the sensor element 10 is positioned and fixed with respect to the metal shell 2. The talc powder 23 is compressed by being pressed by the sleeve 30 when a sleeve 30 described later is incorporated into the metal shell 2.

Next, the talc powder 23 will be described. The talc powder 23 shown in FIG. 1 is compressed and filled in a gap between the holder 21 and the sleeve 30 inside the metal shell 2. The talc powder 23 used in the present embodiment is mainly composed of talc (hydrous magnesium silicate: 3MgO.4SiO ₂ .H ₂ O) from Haicheng District, China, and sodium silicate (commonly called water glass) is used as the talc. _{: Na 2 O · nSiO 2 ·} xH 2 O, n, x is a mixture of a factor).

  Next, the sleeve 30 will be described. As shown in FIGS. 1 and 6, the alumina sleeve 30 is formed in a multi-stage cylindrical shape. The sleeve 30 is provided with an insertion hole 31 along the axial direction thereof, and the sensor element 10 is inserted into the insertion hole 31. As shown in FIG. 6, like the insertion hole 22 of the holder 21, the cross section in the direction orthogonal to the central axis of the insertion hole 31 is formed in a substantially rectangular shape along the cross-sectional shape of the sensor element 10.

  Further, as shown in FIG. 6, a pair of element guides 33 projecting in the rear end direction (upward in the drawing) along the axial direction of the sleeve 30 protrudes from the rear end surface (upper surface in the drawing) of the sleeve 30. It is installed. Each element guide 33 is provided with a groove 35 continuous from the inner periphery of the insertion hole 31 in order to guide both ends (both edges on the long side) of the sensor element 10 in the short direction. The length of the groove 35 is such a length that the sensor element 10 does not protrude when the sleeve 30 is assembled. The depth of the groove 35 is such that at least a part of the terminal of the conductor lead 133, the signal extraction terminal 114, and the pair of heater energization terminals 232 (see FIG. 2) of the sensor element 10 guided by the groove 35 is exposed. The depth is to be. Further, the width of the groove 35 is formed slightly wider than the thickness of the sensor element 10.

  As shown in FIG. 7, the sensor element 10 is inserted into the insertion hole 31 of the sleeve 30, and both ends of the sensor element 10 in the short direction are guided by a pair of element guides 33. Furthermore, a predetermined gap D is formed between the inner peripheral surface of the insertion hole 31 and the plate surface of the sensor element 10. The gap D is for absorbing a slight warp produced in the longitudinal direction of the sensor element 10 together with the gap A of the holder 21 when the sensor element 10 is held by the holder 21 and the sleeve 30. . And the gap D is limited under the following conditions.

  As shown in FIG. 8, when the sleeve 30 for inserting the sensor element 10 is cut in the longitudinal direction of the sensor element 10 so as to be orthogonal to the plate surface of the sensor element 10, the thickness direction of the sensor element 10 (FIG. The total distance of the gaps D in the horizontal direction of 8) is defined as a distance E. The distance E is a distance between one plate surface 14 a in the thickness direction of the sensor element 10 and the inner peripheral surface 31 a of the insertion hole 31, and is one plate surface 14 a in the thickness direction of the sensor element 10. When the distance between the opposite plate surface 14b and the inner peripheral surface 31b of the insertion hole 31 is E2, the distance is defined as E = E1 + E2. On the other hand, as shown in FIG. 9, the distance F is the total distance of the gaps D in the width direction of the sensor element 10 (left and right direction in FIG. 9). The distance F is the distance between one plate surface 10a in the width direction of the sensor element 10 and the inner peripheral surface 31c of the insertion hole 31 and is opposite to the one plate surface 10a in the width direction of the sensor element 10. When the distance between the plate surface 10b and the inner peripheral surface 31d of the insertion hole 31 is F2, the distance is defined as F = F1 + F2. In the present embodiment, the distance E and the distance F are also limited to 0.7 mm or less, respectively. The reason why the distance E and the distance F are limited and the effect will be described later.

  E1 and E2 shown in FIG. 8 or F1 and F2 shown in FIG. 9 indicate that “when the sensor element is cut in the longitudinal direction so as to be orthogonal to the sensor element plate surface, 8 corresponds to the distance in the short direction perpendicular to the longitudinal direction of the sensor element with respect to the inner peripheral surface of the shaft hole, and the distance F shown in FIG. 8 and the distance F shown in FIG. 9 correspond to “sum”. Further, the insertion hole 31 shown in FIG. 6 corresponds to a “second shaft hole”.

  As shown in FIG. 1, in the state where the sensor element 10 held by the holder 21 and the sleeve 30 is accommodated inside the metal shell 2, the terminal of the conductor lead portion 133 of the sensor element 10 and the signal extraction terminal 114 and the pair of heater energization terminals 232 (see FIG. 2) are exposed from the caulking portion 7 side (the rear end side of the gas sensor 1) of the metal shell 2. Further, when the caulking portion 7 of the metal shell 2 is bent and caulked inward, the sleeve 30 is pressed toward the distal end side of the metal shell 2 via the stainless steel ring member 8 interposed inside. Then, the talc powder 23 is pressurized and the space between the holder 21 and the sleeve 30 is filled without a gap, so that the sensor element 10 held by the holder 21 and the sleeve 30 is airtightly held and fixed in the metal shell 2. Is done.

  Next, the reason why the gap A in the insertion hole 22 of the holder 21 and the gap D in the insertion hole 31 of the sleeve 30 which are the main parts of the present invention are limited will be described. As described above, the gap A and the gap D shown in FIG. 1 absorb a slight warp produced in the longitudinal direction of the sensor element 10 when the sensor element 10 is held by the holder 21 and the sleeve 30. Is. However, if the gap A and the gap D are large, there arises a problem that the talc powder 23 leaks from the gap A and the gap D to the outside. For example, when the gas sensor 1 is fixed in the exhaust pipe with its front end facing below the horizontal plane, the talc powder 23 leaks to the outside from the gap A due to its gravity. On the other hand, when the gas sensor 1 is fixed in the exhaust pipe with its tip end upward from the horizontal plane, the talc powder 23 leaks to the outside through the gap D due to its gravity. Further, when the gap A and the gap D are large, the exhaust gas passing through the exhaust pipe enters from the gap A of the insertion hole 22 of the holder 21 and enters the gap D of the insertion hole 31 of the sleeve 30 via the talc powder 23. Since the gas enters the exhaust gas, the gas sensor 1 is deteriorated in airtightness and the oxygen concentration in the exhaust gas cannot be accurately detected.

  Therefore, in order to prevent these problems, in the gas sensor 1 of the present embodiment, the distance B and the distance C in the gap A shown in FIGS. 4 and 5 and the distance E and the distance F in the gap D shown in FIGS. Are limited to 0.7 mm or less. In the following description, for the sake of convenience, both the distance B and the distance C are referred to as “the distance of the gap A”, and both the distance E and the distance F are referred to as “the distance of the gap D”.

  In order to confirm the effect of the distance A and the distance D (0.7 mm or less) limited by the present invention described above, the performance test of the gas sensor 1 was performed as follows. Hereinafter, a description will be given based on the test results shown in FIG. FIG. 10 is a graph showing the test results. This test was performed by preparing a plurality of gas sensors in which the distances of the gap A and the gap D were both changed, and attaching these gas sensors to the chamber of a differential pressure type leak tester. The leak amount of the atmosphere per minute flowing into the sensor from the gap A and the gap D of the gas sensor 1 at a pressure of 0.6 MPa was measured as a leak amount (ml / min). Furthermore, the reference value of the leak amount was set to 0.15 ml / min as a numerical value at which the talc powder 23 does not leak from the gap A and the gap D. Then, the range of the distance (mm) between the gap A and the gap D of the gas sensor 1 in which the amount of gas leakage is equal to or less than the reference value (0.15 ml / min) was obtained.

  Next, test results will be described. Considering based on the results shown in FIG. 10, when the distance (mm) between the gap A and the gap D exceeds about 0.7 mm, a gas sensor with a leakage amount exceeding 0.15 ml / min was found. And in the gas sensor in which the distance between the gap A and the gap D is longer than 0.7 mm, the gas leak amount tended to increase rapidly. Therefore, in the present invention, the gas sensor 1 that can ensure airtightness in the sensor and prevent external leakage of the talc powder 23 by setting the distance (mm) between the gap A and the gap D to 0.7 mm or less, respectively. Could be provided.

  As described above, in the gas sensor 1 of the present embodiment, the insertion hole 22 and the insertion hole 31 provided in the holder 21 and the sleeve 30 can be used as the inner peripheral surface of each insertion hole and the plate surface of the sensor element 10. The size of the gap A and the gap D is limited. Then, by limiting both the gap A and the gap D to 0.7 mm or less, it is possible to prevent the exhaust gas from entering the metal shell 2 from the gap A. Furthermore, it is possible to prevent the exhaust gas that has entered the metal shell 2 from further penetrating into the talc powder 23 and passing through the gap D, thereby reducing the gas tightness inside the gas sensor 1. Further, the talc powder 23 filled between the holder 21 and the sleeve 30 can be prevented from leaking outside through the gap A and the gap D. Therefore, it is possible to provide a highly reliable gas sensor by preventing external leakage of the talc powder 23 filled in the sensor while ensuring airtightness in the sensor.

  Needless to say, the present invention can be modified in various ways. For example, in the present embodiment, the distances of both the gap A and the gap D between the plate hole of the sensor element 10 in the two insertion holes of the insertion hole 22 of the holder 21 and the insertion hole 31 of the sleeve 30 are 0.7 mm. Although it is below, the clearance gap of at least one of the clearance gap A and the clearance gap D should just be 0.7 mm or less.

Applicable oxygen sensor using the sensor element formed in a plate shape, the wideband air-fuel ratio sensor, various gas sensors, such as NO _X sensor.

2 is a cutaway sectional view of a main part of the gas sensor 1. FIG. 1 is an exploded perspective view of a sensor element 10. FIG. 3 is a perspective view showing a state where the sensor element 10 is inserted into the insertion hole 22 of the holder 21. FIG. It is a GG arrow direction sectional view taken on the line shown in FIG. It is a HH arrow direction sectional view shown in FIG. 3 is a perspective view of a sleeve 30. FIG. 4 is a perspective view showing a state where the sensor element 10 is inserted into the insertion hole 31 of the sleeve 30. FIG. FIG. 8 is a cross-sectional view taken along the line I-I in FIG. 7. FIG. 8 is a cross-sectional view in the direction of arrows JJ shown in FIG. 7. It is a graph shown about a test result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Main metal fitting 10 Sensor element 11 Detection part 21 Holder 22 Insertion hole 23 Talcite powder 30 Sleeve 31 Insertion hole

Claims (3)

A sensor element in which a detection part for detecting gas is formed at one end in the longitudinal direction of the plate body, and a substantially cylindrical metal shell surrounding the sensor element in the radial direction in a form in which the detection part of the sensor element is exposed And a holder having a first shaft hole that is held inside the metal shell and through which the sensor element is inserted,
When cut in the longitudinal direction of the sensor element so as to be orthogonal to the plate surface of the sensor element, the plate surface of the sensor element and the inner peripheral surface of the first shaft hole are perpendicular to the longitudinal direction of the sensor element. A gas sensor characterized in that a sum of distances in a short direction is 0.7 mm or less. The sleeve is disposed on the opposite side to the detection unit with respect to the holder, and is held inside the metal shell, and includes a sleeve having a second shaft hole through which the sensor element is inserted,
When cut in the longitudinal direction of the sensor element so as to be orthogonal to the plate surface of the sensor element, the plate surface of the sensor element and the inner peripheral surface of the second shaft hole are perpendicular to the longitudinal direction of the sensor element. 2. The gas sensor according to claim 1, wherein the sum of the distances in the short direction is 0.7 mm or less. The gas sensor according to claim 2, wherein a filling powder is disposed in a gap between the holder and the sleeve inside the metal shell.

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