JP2005227227A - Sensor for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor for internal combustion engines, capable of suppressing thermal degradation of an elastic seal member and preventing the inside of the sensor from being immersed in water through a rear-end opening part of a casing member, over a long period. <P>SOLUTION: The sensor 100 for internal combustion engines is provided with a detection element 120, having a tip side to be exposed to gases to be measured; a tubular casing member 160 made of metal for surrounding the gas detecting element 120; and a grommet 185 for blocking the rear-end opening part 163b, with a lead wire 170 electrically connected to the detecting element 120 inserted in itself. A lateral mica heat insulating member 111 is arranged in between a tip-side part 185h located on the tip side of the grommet 185, in a direction along at least an axis C and a rear-side surrounding member 163 (the casing member 160). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to various sensors for an internal combustion engine used in a high-temperature environment, such as gas sensors such as oxygen sensors, full-range air-fuel ratio sensors, NOx sensors, and temperature sensors.

Conventionally, various sensors for various internal combustion engines used in a high temperature environment such as an oxygen sensor, a gas sensor such as a full-range air-fuel ratio sensor, a NOx sensor, and a temperature sensor have been proposed. Among such sensors for internal combustion engines, for example, an oxygen sensor that is attached to an exhaust pipe and detects the oxygen concentration in the exhaust gas can be cited (see, for example, Patent Document 1 and Patent Document 2).
JP 2001-147213 A JP-A-9-178694

  The oxygen sensor of Patent Document 1 has a lead wire for connecting a detection element and an external device, and this lead wire is a rear end opening located at the rear end of the casing member from the inside of the casing member. And led out of the casing member. Further, a rubber seal member (elastic insulating member) that closes the rear end opening while inserting a lead wire into the sensor so that water or the like does not enter the sensor through the rear end opening of the casing member. Is provided. However, since this oxygen sensor is exposed to an exhaust gas having an extremely high temperature (900 ° C. or higher), the exhaust heat is transmitted to the seal member (elastic insulating member) through the metal casing member, and the seal member ( Even if the elastic insulating member is formed of fluorine rubber or the like having high heat resistance, the sealing member (elastic insulating member) may be thermally deteriorated. As a result, there is a possibility that water cannot be prevented from entering the oxygen sensor.

  On the other hand, in the oxygen sensor of Patent Document 2, a PTFE made of PTFE so as to surround the rubber seal member (rubber bush) between the rubber seal member (rubber bush) and the rear end portion of the casing member. A tube is placed. Since this PTFE tube has better heat resistance than fluororubber, there is no risk of early thermal degradation due to exhaust heat transmitted through a metal casing member. Furthermore, since the rubber seal member (rubber bush) comes into contact with the metal casing member via the PTFE tube, thermal deterioration due to exhaust heat is suppressed, and water intrusion into the sensor is prevented over a long period of time. be able to.

Incidentally, in recent years, there is an increasing demand for downsizing (shortening) of sensors used in internal combustion engines due to the mounting space and the like. However, if the sensor is made short, the rubber seal member (elastic seal member) that closes the rear end opening of the casing member approaches the heat source, so that the elastic seal member is further deteriorated by heat. There is a risk of it. Thus, in recent years, sensors for internal combustion engines tend to be used under conditions where the temperature of the elastic seal member becomes even higher.
On the other hand, in the method of providing a PTFE tube as in the oxygen sensor of Patent Document 2, the PTFE tube has a heat-resistant temperature of about 300 ° C., so the PTFE tube is thermally deteriorated. There is a possibility that water intrusion into the sensor cannot be prevented.

  The present invention has been made in view of the current situation, and is for an internal combustion engine that can suppress thermal deterioration of an elastic seal member and prevent water from entering the sensor through the rear end opening of the casing member for a long period of time. An object is to provide a sensor.

  The solution includes: a detection element that extends in the axial direction and whose tip side is exposed to a gas to be measured; a cylindrical casing member that is made of metal and surrounds the gas detection element; and is electrically connected to the detection element An internal combustion engine sensor comprising: an elastic seal member that closes a rear end opening located at a rear end of the casing member in a state in which the lead wire to be inserted is inserted therein; Of these, a sensor for an internal combustion engine in which a heat insulating member is disposed between at least a tip side portion located on the tip side in the axial direction and the casing member.

Conventionally, in an internal combustion engine sensor in which the tip side is exposed to a high temperature gas to be measured (heat source), the heat is transmitted from the tip side to the rear end side, particularly through a metal casing member. For this reason, the elastic seal member tends to be thermally deteriorated in the portion in contact with the casing member, in particular, the tip side portion located on the tip end side in the axial direction that tends to be close to the heat source and tends to be high temperature.
On the other hand, in the internal combustion engine sensor according to the present invention, a heat insulating member is disposed between the metal casing member and the tip side portion located at least on the tip side in the axial direction of the elastic seal member. Yes. Thereby, since it can suppress that the heat of a heat source is transmitted to the front end side part near a heat source among elastic seal members, the thermal deterioration of an elastic seal member can be suppressed as a result. Therefore, it is possible to prevent water from entering the sensor through the rear end opening of the casing member for a long period of time.

Examples of the sensor for an internal combustion engine of the present invention include a gas sensor such as an oxygen sensor, a full-range air-fuel ratio sensor, and a NOx sensor, a temperature sensor, and the like.
The elastic seal member may be any member as long as it has elasticity and can close the rear end opening of the casing member to prevent water from entering the sensor. As such an elastic seal member, for example, fluorine rubber or silicon rubber having relatively high heat resistance can be suitably used.

  Moreover, the heat insulation member should just be a member which can be arrange | positioned between an elastic seal member and a casing member, and can prevent the heat conduction from a casing member to an elastic seal member. As such a heat insulating member, for example, a mica heat insulating member in which mica scales are laminated to form a layered structure, or a fibrous heat insulating member such as asbestos can be suitably used.

  Furthermore, in the sensor for an internal combustion engine, the heat insulating member is a mica heat insulating member in which mica scales are laminated to form a layered structure, and the mica heat insulating member includes the mica heat insulating member of the casing member. For an internal combustion engine in which the casing-side contact surface in contact with the seal-side contact surface in contact with the mica heat insulating member of the elastic seal member and the stacking direction of the mica heat insulating member are aligned. A sensor is recommended.

In the sensor for an internal combustion engine of the present invention, a mica heat insulating member in which mica scales are laminated to form a layered structure is used as the heat insulating member. It arrange | positions so that the direction where a seal side contact surface faces, and the lamination direction of a mica heat insulation member may correspond.
Since the mica heat insulating member has a property of low thermal conductivity in the stacking direction of the mica scales, the heat transfer from the metal casing member to the elastic seal member is suppressed by arranging the mica heat insulating member as described above. And thermal deterioration of the elastic seal member can be suppressed. Further, the mica heat insulating member has a property that the thermal diffusivity in the stacking direction of the mica scale is as small as about 1/10 of the thermal diffusivity in the direction orthogonal to the stacking direction of the mica scale (that is, the crystal parallel direction). Therefore, also from this viewpoint, it is possible to effectively suppress the heat from the casing member to the elastic seal member by arranging the mica heat insulating member as described above.
Examples of mica scales include mica fragments obtained by pulverizing raw material mica (mica) having a layered structure and constituting each layer of the raw material mica.

  Further, in the sensor for an internal combustion engine, the mica heat insulating member may be a sensor for an internal combustion engine including the mica scale made of soft mica as a main component.

  As described above, the mica heat insulating member is excellent in heat insulating properties, but in order to exhibit this excellent heat insulating property, it must also have heat resistance that can withstand use in a high temperature environment. For this reason, the sensor for internal combustion engines of the present invention uses a mica heat insulating member mainly composed of mica scales made of soft mica. This soft mica (phlogopite) has a high heat resistant temperature among mica, and its thermal decomposition temperature is about 900 to 1000 ° C. Such a mica heat insulating member containing soft mica as a main component is excellent in heat resistance as well as heat insulating properties, and therefore can be suitably used for various internal combustion engine sensors used in a high temperature environment.

  Furthermore, in any one of the above-mentioned sensors for an internal combustion engine, the mica heat insulating member includes at least a side mica heat insulating member disposed on a side of the tip side portion of the elastic seal member, and the side mica The heat insulating member may be a sensor for an internal combustion engine that is arranged by expanding the diameter of the elastic seal member after being disposed between the elastic seal member and the casing member.

In the conventional internal combustion engine sensor, the elastic seal member is fixed by crimping the rear end portion of the casing member radially inward. However, in such a fixing method, when the mica heat insulating member is disposed on the side of the elastic seal member, the mica heat insulating member may be damaged when the casing member is caulked.
On the other hand, in the internal combustion engine sensor of the present invention, after the side mica heat insulating member disposed on the side of the elastic seal member is disposed between the elastic seal member and the casing member, the casing member is not crimped, The elastic seal member is fixed by expanding the diameter. According to such a fixing method, since the entire side surface of the side mica heat insulating member can be elastically pressed and fixed, there is no possibility that the side mica heat insulating member is damaged.

  As a fixing method of the present invention, for example, a cylindrical elastic seal member having a shaft hole is used. First, the side mica heat insulating member is disposed between the elastic seal member and the casing member, and then the elastic seal member. A method of expanding the diameter of the elastic seal member by press-fitting a columnar member into the shaft hole and pressing the side mica heat insulating member against the inner peripheral surface of the casing member is included.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a sensor 100 for an internal combustion engine according to the first embodiment. The internal combustion engine sensor 100 is an oxygen sensor that is attached to an exhaust pipe (not shown) and detects the oxygen concentration in the exhaust gas. The internal combustion engine sensor 100 includes a gas detection element 120, a holding member 130, a casing member 160, a separator 190, a lead wire 170, and a grommet 185. In this embodiment, among the directions along the axis C of the internal combustion engine sensor 100 (the vertical direction in the figure), the tip 120b side (the bottom in the figure) of the gas detection element 120 is the tip in the axial direction, and vice versa. The side (upper side in the figure) is the rear end side in the axial direction, and the same applies to other examples.

The casing member 160 includes a metal shell 161, a protector 162, and a rear end side surrounding member 163.
The metal shell 161 is made of SUS430 and is formed in a substantially cylindrical shape. An inner peripheral stepped portion 161d is provided on the front end side of the inner periphery of the metal shell 161 so as to have a taper with a diameter increasing toward the rear end. Further, a caulking portion 161 b is formed at the rear end portion of the metal shell 161. Further, on the outer periphery of the metal shell 161, there are formed a screw portion 161f for attaching the internal combustion engine sensor 100 to an exhaust pipe (not shown) and an attachment tool engaging portion 161g for engaging an attachment tool such as a torque wrench. Yes.

The protector 162 is made of SUS310S, has a substantially cylindrical shape, and has a plurality of ventilation holes 162b for introducing exhaust gas in an exhaust pipe (not shown) into the internal combustion engine sensor 100. The protector 162 is fixed to the distal end portion of the metal shell 161.
The rear end side surrounding member 163 is made of SUS310S, is a substantially cylindrical tube body, and is coupled to the rear end side of the metal shell 161 by laser welding all around and surrounds the holding member 130, the separator 190, and the like. A rear end portion 163c that is bent radially inward is formed on the rear end side of the rear end side surrounding member 163, and the inner surface of the rear end portion 163c is in close contact with the rear end surface of the grommet 185. ing.

  The gas detection element 120 is a laminated gas detection element, and although not shown, a gas sensitive body made of a metal oxide sensitive body such as titania and an insulating sheet mainly composed of alumina surrounding the gas sensitive body. , A pair of detection electrodes in contact with one surface of the gas-sensitive body, a first substrate mainly composed of alumina, a heating resistor mainly composed of Pt, and a second substrate mainly composed of alumina, Are sequentially stacked. Furthermore, as shown in FIG. 1, terminals 121 to 124 made of Pt are provided on the rear end side of the gas detection element 120. Among these, the terminals 122 and 123 are extended from the pair of detection electrodes, and the terminals 121 and 124 are extended from the heating resistor. Metal lead frames 171 to 174 are connected to the terminals 121 to 124, respectively.

  The holding member 130 is made of an insulating ceramic whose main component is alumina, has a cylindrical shape, and has a flange portion 130 c that protrudes radially outward at a substantially central portion in the axial direction. The holding member 130 holds the gas detection element 120 in a state of being inserted through the inside thereof. Specifically, the gas detection element 120 inserted through the inside of the holding member 130 is fixed to the holding member 130 by a talc filling layer 133 and a glass sealing material 135 obtained by melting and solidifying crystallized glass powder. In the holding member 130, the end portion 130b is supported by the inner peripheral step portion 161d of the metal shell 161 via the metal packing 184, and the collar portion 130c is made of metal by the crimping portion 161b of the metal shell 161. It is pressed toward the tip side through the annular packings 181 and 182 and the talc filling layer 183. Thereby, the holding member 130 holding the gas detection element 120 is fixed inside the casing member 160.

  The lead wire 170 has one end connected to the crimping terminal 170b and the other end connected to an external device (for example, ECU) (not shown). In the internal combustion engine sensor 100 of the present embodiment, four lead wires 170 are provided and are electrically connected to the lead frames 171 to 174 through the crimping terminals 170b, respectively. Thereby, the terminals 121-124 of the gas detection element 120 and an external device (for example, ECU) are electrically connected.

  The separator 190 is made of an insulating ceramic whose main component is alumina, and has a substantially cylindrical shape. Inside the separator 190, four insertion holes 191 for inserting the lead wires 170, the crimping terminals 170b, and the lead frames 171 to 174 are formed so as to penetrate in the axial direction. For this reason, each lead wire 170, the crimping terminal 170b, and the lead frames 171 to 174 are inserted by inserting the lead wires 170, the crimping terminals 170b, and the lead frames 171 to 174 into the insertion holes 191 of the separator 190. Can prevent mutual electrical continuity and electrical continuity with other members.

  The grommet 185 is made of fluorine rubber, has a substantially cylindrical shape, and has four through holes 185b through which the lead wires 170 are inserted, and a shaft hole 185f into which the columnar member 187 is press-fitted. The grommet 185 is in close contact with the rear end portion 163c of the rear end side surrounding member 163 while the lead wires 170 are inserted into the respective through holes 185b, and the rear end opening portion 163b of the rear end side surrounding member 163. Is blocked. In this way, the lead wires 170 are led out to the outside, and the water intrusion into the rear end side surrounding member 163 is prevented.

  By the way, in the internal combustion engine sensor 100 according to the first embodiment, the front end side of the gas detection element 120 is used in such a manner that it is exposed to high-temperature exhaust gas (heat source) circulating in the exhaust pipe. For this reason, the exhaust heat passes through the exhaust pipe, the threaded portion 161f of the metal shell 161, the rear end side surrounding member 163, or through the protector 162, the main metal fitting 161, and the rear end side surrounding member 163. It is transmitted from the side toward the rear end.

  On the other hand, in the internal combustion engine sensor 100 according to the first embodiment, at least to the side of the front end side portion 185 h of the grommet 185, specifically, the outer peripheral surface 185 e of the grommet 185 and the rear end side of the rear end surrounding member 163. A cylindrical side mica heat insulating member 111 is disposed between the inner peripheral surface 163e and the inner peripheral surface 163e. The side mica heat insulating member 111 is obtained by impregnating a laminated mica made of soft mica (phlogopite) scales obtained by pulverizing raw material mica and laminating soft mica scales into a lamellar structure. I am doing. The side mica heat insulating member 111 is formed so that the stacking direction of the soft mica scale pieces matches the radial direction of the side mica heat insulating member 111 (that is, matches the radial direction of the grommet 185), as will be described later. The crystal vertical direction of the soft mica scale is substantially coincident with the radial direction of the grommet 185.

  Since the mica member has a property of low thermal conductivity in the stacking direction of the mica scale, the cylindrical side mica heat insulating member 111 has a lower thermal conductivity in the radial direction than in the axial direction. . In the internal combustion engine sensor 100 according to the first embodiment, the outer peripheral surface 185e of the grommet 185 (the surface of the grommet 185 that contacts the side mica heat insulating member 111) and the rear end side inner peripheral surface of the rear end surrounding member 163. 163e (a surface that contacts the side mica heat insulating member 111 of the rear end side surrounding member 163) (in the first embodiment, matches the radial direction of the grommet 185) and the side mica heat insulating member 111 It arrange | positions so that the lamination direction of a soft mica scale piece may correspond. Thereby, it can suppress effectively that exhaust heat is transmitted to the grommet 185 from the metal casing member 160 (rear end side surrounding member 163). Therefore, since thermal degradation of the grommet 185 made of fluorine rubber can be suppressed, it is possible to prevent water from entering the sensor through the rear end opening 163b of the rear end side surrounding member 163 for a long period of time.

  In particular, the internal combustion engine sensor 100 according to the first embodiment uses the side mica heat insulating member 111 mainly composed of soft mica scales made of soft mica. Soft mica has a high heat-resistant temperature among mica, and its thermal decomposition temperature is about 900 to 1000 ° C. Since the side mica heat insulating member 111 mainly composed of soft mica scales made of such soft mica is excellent in heat resistance as well as heat insulation, there is no possibility of deterioration due to exhaust heat, and appropriately to the grommet 185. Heat conduction can be suppressed.

  By the way, in the conventional sensor for internal combustion engines, the elastic seal member (grommet) is fixed by crimping the rear end portion of the casing member (rear end side surrounding member) inward in the radial direction. However, in such a fixing method, when the mica heat insulating member is disposed on the side of the grommet as in the first embodiment, since the mica has low mechanical strength, the rear end side surrounding member is crimped. Sometimes the mica heat insulating member may be damaged.

  On the other hand, in the internal combustion engine sensor 100 of the first embodiment, the side mica heat insulating member 111 is disposed between the outer peripheral surface 185e of the grommet 185 and the rear end side inner peripheral surface 163e of the rear end side surrounding member 163. After that, the diameter of the grommet 185 is increased by press-fitting a columnar member 187 made of a heat-resistant resin (for example, PEEK) into a shaft hole 185f provided at a substantially central portion of the grommet 185, and the rear end side enclosing member 163 is expanded. The rear end side inner peripheral surface 163e is pressed and fixed. According to such a fixing method, since the entire side surface of the side mica heat insulating member 111 can be elastically pressed and fixed, there is no possibility that the side mica heat insulating member 111 is damaged.

Such an internal combustion engine sensor 100 is manufactured as follows.
First, the metal shell 161 and the protector 162 are integrated by welding. On the other hand, lead frames 171 to 174 are connected to terminals 121 to 124 of the gas detection element 120 by resistance welding. Next, with the gas detection element 120 connected to the lead frames 171 to 174 inserted into the cylinder of the holding member 130 and disposed at a predetermined position, the cylinder of the holding member 130 is pressed and filled with talc powder. The gas detection element 120 is fixed in the holding member 130 by forming the talc filling layer 133 and further solidifying the melted crystallized glass powder to form the glass sealing material 135.

  Next, with the metal packing 184 placed on the inner peripheral step portion 161d of the metal shell 161, the holding member 130 holding the gas detection element 120 is inserted into the metal shell 161 from the front end side in the axial direction. The tip 130b of the holding member 130 is brought into contact with the inner peripheral step 161d of the metal shell 161 through the metal packing 184. Next, the metal packing 181, the talc ring forming the talc filling layer 183, and the metal packing 182 are inserted into the metal shell 161 in this order and placed on the flange 130 c of the holding member 130, and then the metal shell 161 is swaged The holding member 130 holding the gas detection element 120 is fixed by caulking the part 161b.

  Next, the lead frames 171 to 174 are connected to the crimp terminals 170 b connected to the lead wires 170. Next, the separator 190 is disposed on the holding member 130 from the rear end side while each lead wire 170 is inserted into each insertion hole 191. Further, the grommet 185 is disposed on the separator 190 from the rear end side while inserting each lead wire 170 into each through hole 185b. Further, the side mica heat insulating member 111 is disposed so as to surround the side periphery of the grommet 185 while inserting each lead wire 170 into the cylinder.

  Next, the rear end side surrounding member 163 is moved to the front end side in the axial direction until the front end portion 163d abuts on the rear end surface of the tool engaging portion 161g of the metal shell 161 while inserting each lead wire 170 into the cylinder. Then, after the rear end side surrounding member 163 is fitted to the metal shell 161, the front end portion 163d of the rear end side surrounding member 163 is laser welded to the metal shell 161 all around. At this time, the rear end portion 163c of the rear end side surrounding member 163 comes into close contact with the rear end surface of the grommet 185. Thereafter, the columnar member 187 is press-fitted into the shaft hole 185f of the grommet 185, thereby expanding the diameter of the grommet 185 and pressing the side mica heat insulating member 111 against the rear end side inner peripheral surface 163e of the rear end side surrounding member 163. The lead wire 170 is brought into close contact with the through hole 185b of the grommet 185. In this way, the internal combustion engine sensor 100 shown in FIG. 1 is completed.

  Next, an internal combustion engine sensor 200 according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 2 is an enlarged cross-sectional view of the rear end side of the internal combustion engine sensor 200 according to the second embodiment. The internal combustion engine sensor 200 according to the second embodiment is different from the internal combustion engine sensor 100 according to the first embodiment in that a mica heat insulating member 212 is added, and the others are the same.

  As shown in the sectional view of FIG. 2, the mica heat insulating member 212 has a substantially disk shape, and four through holes 212 b through which the lead wires 170 are inserted are formed at equal intervals in the circumferential direction. Similar to the side mica heat insulating member 111, the mica heat insulating member 212 is formed by laminating soft mica scale pieces to form a layered structure, and is formed into the above shape. In the mica heat insulating member 212, the stacking direction of the soft mica scales coincides with the thickness direction (vertical direction in the figure) of the mica heat insulating member 212.

  Such a mica heat insulating member 212 is disposed between the ceramic separator 190 and the grommet 185. Specifically, the direction in which the rear end side surface 190b of the separator 190 (the surface of the separator 190 that contacts the mica heat insulating member 212) and the front end side surface 185c of the grommet 185 (the surface of the grommet 185 that contacts the mica heat insulating member 212) face each other. (In Example 2, it is arranged so that it coincides with the direction of the axis C) and the lamination direction of the soft mica scales of the mica heat insulating member 212.

  In the internal combustion engine sensor 200 according to the second embodiment, the side mica heat insulating member 111 can suppress the exhaust heat from being transmitted to the grommet 185 through the casing member 160 (rear end side surrounding member 163). In addition, the mica heat insulating member 212 can suppress the exhaust heat from being transmitted to the grommet 185 through the separator 190. For this reason, the internal combustion engine sensor 200 according to the second embodiment can further suppress the thermal degradation of the grommet 185 as compared with the internal combustion engine sensor 100 according to the first embodiment. It is possible to prevent water from entering the sensor through the rear end opening 163b of the member 163 over a long period of time.

  Next, an internal combustion engine sensor 300 according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 3 is a cross-sectional view of the internal combustion engine sensor 300 according to the third embodiment. The internal combustion engine sensor 300 according to the third embodiment is different from the internal combustion engine sensor 100 according to the first embodiment in that the rear end side surrounding member, the grommet, and the mica heat insulating member are changed. is there. For this reason, it demonstrates centering on a different point from the sensor 100 for internal combustion engines of Example 1, and description is abbreviate | omitted or simplified about others.

  The internal combustion engine sensor 300 according to the third embodiment includes a first rear end side surrounding member 363 and a second rear end side surrounding member 364 as rear end side surrounding members. The first rear end side surrounding member 363 is made of SUS310S, and is a substantially cylindrical tubular body. The first rear end side surrounding member 363 presses the separator 190 disposed on the holding member 130 toward the front end side in the axial direction. Are coupled by laser welding all around, and surround the holding member 130, the separator 190, and the like. The second rear end side surrounding member 364 is made of SUS304L, and is a substantially cylindrical cylindrical body that surrounds the rear end side of the first rear end side surrounding member 363 while pressing the grommet 385 toward the front end side in the axial direction. The distal end portion 364f is crimped radially inward together with the first rear end side surrounding member 363 and fixed to the first rear end side surrounding member 363. The second rear end surrounding member 364 is formed with a rear end opening 364b through which the lead wire 170 is inserted.

  As shown in the enlarged sectional view of FIG. 4, the grommet 385 has step portions 385 c and 385 d formed at the corners on the front end side and the rear end side as compared with the grommet 185 of the first embodiment. Only the difference. The step portions 385c and 385d are provided to position the mica heat insulating members 311 and 312 as will be described later. The grommet 385 closes the rear end opening 364b of the second rear end side surrounding member 364 while closely contacting the rear end portion 364c of the second rear end side surrounding member 364 via the mica heat insulating member 312. Yes. A lead wire 170 is inserted into the through hole 385b formed in the grommet 385.

  Both the mica heat insulating members 311 and 312 have a layered structure formed by laminating soft mica scales, similarly to the side mica heat insulating member 111 of the first embodiment, and are formed in an annular plate shape.

  Among these, the mica heat insulating member 311 is disposed between the first rear end side surrounding member 363 and the grommet 385. Specifically, it is disposed on the rear end portion 363 c of the first rear end side surrounding member 363 in a form that fits into the stepped portion 385 c of the grommet 385. The mica heat insulating member 311 has a rear end surface 363d of the first rear end side surrounding member 363 (a surface contacting the mica heat insulating member 311 in the rear end portion 363c of the first rear end side surrounding member 363) and a step surface of the grommet 385. 385f (the surface of the stepped portion 385c of the grommet 385 that is in contact with the mica heat insulating member 311) facing (in the third embodiment, coincides with the direction of the axis C) and the lamination of the soft mica scale pieces of the mica heat insulating member 311 It is arranged so that the direction matches. For this reason, it is possible to suppress the exhaust heat from being transmitted to the grommet 385 through the first rear end side surrounding member 363.

  Further, the mica heat insulating member 312 is disposed between the second rear end side surrounding member 364 and the grommet 385. Specifically, it is placed on the grommet 385 so as to be fitted to the stepped portion 385d of the grommet 385, and is in close contact with the inner rear end portion 364d of the second rear end side surrounding member 364. This mica heat insulating member 312 has a step between the inner rear end surface 364d of the second rear end side surrounding member 364 (the surface of the rear end portion 364c of the second rear end side surrounding member 364 that contacts the mica heat insulating member 312) and the grommet 385. The direction of the surface 385g (the surface of the stepped portion 385d of the grommet 385 that contacts the mica heat insulating member 312) facing (in the third embodiment, the direction of the axis C) and the soft mica scale of the mica heat insulating member 312 They are arranged so that the stacking direction matches. For this reason, it is possible to suppress the exhaust heat from being transmitted to the grommet 385 through the second rear end side surrounding member 364.

  In the internal combustion engine sensor 100 according to the first embodiment, the side mica heat insulating member 111 is disposed between the outer peripheral surface 185e of the grommet 185 and the rear end side inner peripheral surface 363e of the rear end side surrounding member 363. I was trying to insulate. On the other hand, in the internal combustion engine sensor 300 of the third embodiment, a mica heat insulating member is not provided between the outer peripheral surface 385e of the grommet 385 and the rear end inner peripheral surface 364e of the second rear end side surrounding member 364. In addition, a gap is provided. Thus, by providing the gap, it is possible to suppress the exhaust heat from being transmitted to the grommet 385 through the second rear end side surrounding member 364.

  As described above, also in the internal combustion engine sensor 300 of the third embodiment, the exhaust heat is prevented from being transmitted to the grommet 385 through the casing member 360 (the first and second rear end side surrounding members 363 and 364). Therefore, thermal degradation of the grommet 385 can be suppressed. Furthermore, since the mica heat insulating members 311 and 312 are mainly composed of soft mica scales made of soft mica having excellent heat resistance, there is no possibility of thermal deterioration due to exhaust heat. For this reason, the mica heat insulating members 311 and 312 and the grommet 385 can prevent water from entering the sensor through the rear end opening 364b of the second rear end side surrounding member 364 for a long period of time.

In the above, the present invention has been described with reference to Examples 1, 2, and 3. Needless to say.
For example, in Examples 1, 2, and 3, the side mica heat insulating members 111, 212, 311 and 312 mainly composed of soft mica scales made of soft mica (phlogopite) were used as the heat insulating members. However, the material of the heat insulating member is not limited to soft mica, and hinders heat conduction from the casing member (rear end side surrounding member) such as hard mica (muscovite) to the grommet (elastic seal member). Any member can be used as long as it can be used. However, soft mica (phlogopite) can be suitably used because it must have heat resistance that can withstand the heat from the heat source and is excellent in heat resistance.

  Further, in the first embodiment, the shape of the side mica heat insulating member 111 disposed on the side of the grommet 185 (between the outer peripheral surface 185e of the grommet 185 and the rear inner peripheral surface 163e of the rear end side surrounding member 163) is set. A cylindrical shape was used. However, the shape of the side mica heat insulating member is not limited to the cylindrical shape, and may be any shape as long as it is a shape along the outer peripheral surface of the grommet and the rear end side inner peripheral surface of the rear end side surrounding member (casing member). For example, it is good also as a cross-sectional arc shape which divided | segmented the cylinder around the axis line.

In the third embodiment, a gap is provided between the outer peripheral surface 135e of the grommet 385 and the rear inner peripheral surface 364e of the second rear end side surrounding member 364 (see FIG. 4). Similarly, a mica heat insulating member may be arranged. Further, in the third embodiment, the mica heat insulating member 312 is disposed between the rear end portion 364c of the second rear end side surrounding member 364 and the grommet 385. However, similarly to the first embodiment, the mica heat insulating member 312 is disposed. Instead, the grommet 385 may be directly brought into close contact with the rear end portion 364c of the second rear end side surrounding member 364. Since the rear end portion 364c of the second rear end side surrounding member 364 is the lowest temperature among the second rear end side surrounding members 364, the mica heat insulating member 312 is not disposed between the second rear end side surrounding member 364 and the grommet 385. This is because the possibility that the grommet 385 is thermally deteriorated is small.

1 is a cross-sectional view of an internal combustion engine sensor 100 according to Embodiment 1. FIG. FIG. 6 is an enlarged cross-sectional view of a rear end side of an internal combustion engine sensor 200 according to a second embodiment. FIG. 6 is a cross-sectional view of an internal combustion engine sensor 300 according to a third embodiment. FIG. 6 is an enlarged cross-sectional view of the rear end side of the internal combustion engine sensor 300 according to the third embodiment.

Explanation of symbols

100, 200, 300 Internal combustion engine sensor 111 Lateral mica heat insulating member (heat insulating member)
212,311,312 Mica heat insulation member (heat insulation member)
120 Gas detection element (detection element)
160, 360 Casing member 170 Lead wire 163 Rear end side surrounding member (casing member)
363 1st rear end side surrounding member (casing member)
364 Second rear end side surrounding member (casing member)
185,385 Grommet (elastic seal member)
163e Rear end side inner peripheral surface (casing side contact surface) of the rear end side surrounding member 163
185e Grommet 185 outer peripheral surface (seal side contact surface)
363d Rear end surface (casing side contact surface) of first rear end side surrounding member 363
364d Inner rear end surface (casing side contact surface) of second rear end side surrounding member 364
385f, 385g Step surface of grommet 385 (sealing side contact surface)

Claims (4)

A detection element that extends in the axial direction and whose tip side is exposed to the gas to be measured;
A cylindrical casing member made of metal and surrounding the gas detection element;
An elastic seal member that closes the rear end opening located at the rear end of the casing member, with a lead wire electrically connected to the detection element inserted through the lead wire;
An internal combustion engine sensor comprising:
A sensor for an internal combustion engine in which a heat insulating member is disposed between at least a tip side portion located on the tip side in the axial direction of the elastic seal member and the casing member. The internal combustion engine sensor according to claim 1,
The heat insulating member is a mica heat insulating member in which mica scales are laminated to form a layered structure,
The mica heat insulating member has a direction in which a casing side contact surface that contacts the mica heat insulating member of the casing member faces a seal side contact surface that contacts the mica heat insulating member of the elastic seal member, and the mica heat insulating member. A sensor for an internal combustion engine, which is arranged so that the stacking direction of the two coincides. The internal combustion engine sensor according to claim 2,
The mica heat insulating member is a sensor for an internal combustion engine comprising the mica scale made of soft mica as a main component. A sensor for an internal combustion engine according to claim 2 or claim 3,
The mica heat insulating member includes at least a side mica heat insulating member disposed on a side of the tip side portion of the elastic seal member,
The sensor for an internal combustion engine, wherein the side mica heat insulating member is disposed by expanding the diameter of the elastic seal member after being disposed between the elastic seal member and the casing member.

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