JP5102167B2 - Sensor - Google Patents

Description

  The present invention relates to a sensor for introducing outside air into the inside through a ventilation filter.

Conventionally, a long detection element that detects a gas to be measured such as O ₂ gas and N ₂ gas, a metal shell that holds the detection element, and a rear end side of the metal shell, and is inserted from the front opening. There is known a sensor including an outer tube that houses a rear end portion of the detection element.

  Such a sensor includes a lead wire disposed inside the outer cylinder from the outside of the outer cylinder through the rear end opening of the outer cylinder and connected to the detection element, and inside the rear end opening of the outer cylinder. And an elastic member (hereinafter referred to as a grommet) that holds the lead wire in a state of covering the radial periphery of the lead wire.

Among the sensors configured as described above, for example, an oxygen sensor, such as an oxygen sensor, introduces outside air into the sensor, and detects the physical quantity of the measurement object based on the introduced physical quantity of the outside air as a reference. A through hole for introducing outside air into the sensor is provided in the grommet. And the ventilation filter which has air permeability and waterproofness is arrange | positioned so that the rear-end opening part in this through-hole may be covered. This ensures ventilation without passing moisture through the ventilation filter (see, for example, Patent Document 1 and Patent Document 2).
JP 2000-249678 A (FIG. 2) JP 2002-286682 A (FIG. 10)

  However, the ventilation filter described in Patent Document 1 is disposed in a state of being sandwiched between the inner peripheral surface of the through hole provided in the grommet and the cylindrical insertion member inserted into the through hole. The end is disposed inside the sensor. For this reason, the moisture adhering to the ventilation filter may travel along the surface of the ventilation filter, and the moisture may enter the sensor through the gap between the inner peripheral surface of the through hole and the ventilation filter.

  In addition, the ventilation filter described in Patent Document 2 is disposed in a state of covering substantially the entire upper surface of the grommet, and a protective member is provided so as to cover the ventilation filter. The protective member is joined to the outer cylinder, and the end of the ventilation filter is disposed in the gap between the protective member and the grommet. For this reason, the moisture adhering to the ventilation filter is transmitted along the surface of the ventilation filter, and further wraps around the end of the ventilation filter, passes through the gap between the upper surface of the grommet and the ventilation filter, and the rear end opening of the through hole There was a risk that moisture would enter the inside of the sensor.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique for suppressing moisture adhering to the ventilation filter from entering the inside of the sensor through the surface of the ventilation filter.

In order to achieve the above-mentioned object, the invention according to claim 1 holds the detection element so that the tip of the detection element extending in the axial direction is exposed to the gas to be measured, and the rear end in the axial direction of the detection element is open. A cylindrical casing extending in the axial direction and a through-hole penetrating along the axial direction for introducing outside air into the casing are formed, and are arranged to close the rear end opening of the casing. A sensor comprising a first elastic member, a cylindrical holding inner cylinder partially inserted into the through hole of the first elastic member, and a rear end of the holding inner cylinder having air permeability and waterproofness A vent filter that closes the opening, one or a plurality of vent holes penetrating along the axial direction, and an outer cylinder blocking portion that covers the ventilation filter, and is connected to the outer cylinder blocking portion, and is connected to the outer peripheral surface of the holding inner cylinder. An outer cylinder that partially surrounds the outer cylinder Anda holding outer tube having an outer tube blocking portion covers the rear end opening of the holding inner tube, the open area rate of the vent holes, smaller than the rear end opening of the holding inner tube, the ventilation filter is held An annular region along the holding inner cylinder is compressed by the rear end portion of the inner cylinder and the outer cylinder blocking portion of the holding outer cylinder.

  In the sensor configured as described above, a ventilation filter having air permeability and waterproofness closes the rear end opening of the holding inner cylinder. For this reason, outside air can be introduced into the sensor through the ventilation filter without passing moisture through the ventilation filter.

  In the ventilation filter, the annular region along the holding inner cylinder is compressed by the rear end portion of the holding inner cylinder and the outer cylinder blocking portion of the holding outer cylinder. This forms a gap between the ventilation filter and the rear end of the holding inner cylinder in an annular region along the holding inner cylinder, and a gap between the ventilation filter and the holding outer cylinder (outer cylinder blocking portion). It becomes difficult. For this reason, the moisture adhering to the surface of the ventilation filter facing the holding outer cylinder (hereinafter referred to as the surface of the ventilation filter) wraps around the end of the ventilation filter, and the rear surface of the ventilation filter and the holding inner cylinder Reaching the rear end opening of the through hole through the gap with the rear end can be suppressed. That is, it is possible to suppress moisture adhering to the ventilation filter from entering the sensor. There may be one or more vent holes.

  Further, in the sensor according to claim 1, as described in claim 2, the ventilation filter is provided between the rear end portion of the holding inner cylinder and the ventilation filter or between the outer cylinder blocking portion and the ventilation filter. You may make it arrange | position the 2nd elastic member which has waterproofness along the area | region compressed circularly.

  In the sensor configured as described above, the second elastic member disposed between the rear end portion of the holding inner cylinder and the ventilation filter has a gap between the rear end portion of the holding inner cylinder and the ventilation filter, or the ventilation. A gap between the filter and the holding outer cylinder can be filled. For this reason, it can further suppress that the water | moisture content adhering to the ventilation | gas_flowing filter enters into a sensor along the clearance gap between the back surface of an ventilation | gas_flowing filter, and a holding | maintenance inner cylinder.

  Further, in the sensor according to claim 1 or 2, the holding inner cylinder and the holding outer cylinder are held in a state in which the ventilation filter is compressed by the rear end portion of the holding inner cylinder and the outer cylinder blocking portion of the holding outer cylinder. In order to fix, as described in claim 3, the outer cylindrical portion may have a first crimping portion crimped in the circumferential direction toward the holding inner cylinder, 6. The second screw according to claim 5, wherein the first thread is provided on the inner peripheral surface of the outer cylindrical portion of the holding outer cylinder, and the first screw thread is engaged with the outer peripheral surface of the holding inner cylinder. Mountains may be provided.

  Further, in the sensor according to claim 3, as described in claim 4, the outer peripheral surface of the holding inner cylinder may have a second caulking portion that is caulked by the first caulking portion. Good. Thereby, a holding inner cylinder and a holding outer cylinder can be fixed more firmly.

  In the sensor according to any one of claims 1 to 5, as described in claim 6, the inner side of the holding inner cylinder is such that the rear end side of the holding inner cylinder faces the front end side of the holding inner cylinder. You may have the bending part turned up.

  In the sensor configured as described above, the ventilation filter is compressed between the bent portion of the holding inner cylinder and the outer cylinder blocking portion of the holding outer cylinder. And since the bent part is turned back, the surface is formed smoothly, and the member (for example, the above-mentioned ventilation filter or the 2nd elastic member) which contacts the bent part will be damaged by this contact. Can be suppressed.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating the overall configuration of an oxygen sensor 1 according to an embodiment to which the present invention is applied, FIG. 2 is a cross-sectional view illustrating the configuration of a seal unit 10, and FIG. 3 is a plan view of a holding outer cylinder 14.

In the present embodiment, the lower end side of the oxygen sensor 1 in FIG. 1 corresponds to the “sensor front end side” in the present invention, and similarly, the upper end side of the oxygen sensor 1 corresponds to the “sensor rear end side”. .
As shown in FIG. 1, the oxygen sensor 1 includes a detection element 2 formed in a hollow shaft shape whose tip is closed by a solid electrolyte body mainly composed of ZrO ₂ , and a shaft-shaped ceramic disposed in the detection element 2. The heater 3 and the internal structure of the oxygen sensor 1 are accommodated, and the oxygen sensor 1 is composed of a casing 4 and the like that are fixed to an attachment portion such as an exhaust pipe.

  Among these, the casing 4 holds the detection element 2 and extends the detection part 25 into the inside of the exhaust pipe or the like, and extends between the upper part of the metal shell 5 and the reference element 2. It is comprised from the outer cylinder 6 which forms gas space.

  The metal shell 5 has a cylindrical main body and supports the detection element 2 from below, a filling member 52 made of talc powder filled in the upper part of the support member 51, and presses the filling member 52 from above. The sleeve 53 and the like to be stored are accommodated inside.

  An inwardly protruding step portion 54 is provided on the inner periphery on the lower end side of the metal shell 5, and the support member 51 is locked to the step portion 54 via a packing 55, thereby detecting the detection element. 2 is supported from below. Further, a filling member 52 is disposed between the inner peripheral surface of the metal shell 5 on the upper side of the support member 51 and the outer peripheral surface of the detection element 2, and a cylindrical sleeve 53 and a packing 56 are further provided above the filling member 52. Are inserted into the metal shell 5 in a coaxial manner, and the upper end of the metal shell 5 is crimped inward (downward), so that the filling member 52 is pressurized and filled, whereby the detection element 2 is attached to the metal shell 5. It is firmly fixed against it. In addition, on the outer periphery on the lower end side of the metal shell 5, metal double protectors 57 and 58 having a plurality of holes are attached by welding while covering the protruding portion of the detection element 2.

  And after the lower end opening end part of the outer cylinder 6 is extrapolated to the said metal shell 5 so that the upper opening part of the metal shell 5 may be covered, welding is given to this lower end opening end part from the outside, and the outer cylinder 6 Is attached to the metal shell 5.

  Further, in the vicinity of the rear end opening 61 of the outer cylinder 6, an insulating separator 7 made of ceramic and formed in a cylindrical shape is inserted. The separator 7 has a flange portion 71 projecting outward on the outer peripheral surface near the center in the axial direction, and the lower end surface of the flange portion 71 is placed on the upper portion of the outer tube 6 when the outer tube 6 is crimped from the outside. It is held in the outer cylinder 6 in a locked manner.

  Further, lead wires 21 and 22 respectively connected to the electrodes of the detection element 2 and a pair of lead wires (not shown) connected to the ceramic heater 3 are led out to the rear end opening 61 of the outer cylinder 6 respectively. A seal unit 10 is provided for preventing moisture and oil from entering the oxygen sensor 1.

  As shown in FIG. 2, the seal unit 10 includes a cylindrical grommet 11 that closes the rear end opening 61 of the outer cylinder 6, and a holding inner portion that is inserted into a through hole 41 that passes through the center of the grommet 11 in the axial direction. From the cylinder 12, the ventilation filter 13 that closes the rear end opening 36 of the holding inner cylinder 12, the holding outer cylinder 14 that covers the ventilation filter 13, and the O-ring 15 that prevents moisture from entering from the rear end opening 36. It is configured.

  Of these, the grommet 11 is made of fluoro rubber, and has four through holes 42 (only two are shown in FIGS. 1 and 2) for inserting the through hole 41, the lead wires 21 and 22, and the heater lead wire. And are formed. The four insertion holes 42 are disposed so as to surround the through hole 41 disposed at the center.

  The holding inner cylinder 12 is made of stainless steel such as SUS304, and is disposed in the through hole 41 of the grommet 11. Further, a bent portion 81 is formed on the rear end side of the holding inner cylinder 12 so as to be smoothly bent and folded back toward the inner side of the holding inner cylinder 12 so as to face the front end side of the holding inner cylinder 12. Furthermore, a locking portion 82 that is bent toward the outside of the holding inner cylinder 12 is formed on the distal end side of the holding inner cylinder 12 to prevent the grommet 11 from coming off.

  The ventilation filter 13 is a porous fiber structure (for example, trade name: obtained by stretching a non-fired molded body of polytetrafluoroethylene (PTFE) in a uniaxial direction at a heating temperature higher than the melting point of PTFE, for example. By Gore-Tex (Japan Gore-Tex Co., Ltd.), it is configured as a ventilation filter that blocks the permeation of liquid such as water droplets and allows the permeation of gas (air, water vapor, etc.). In the present embodiment, the thickness of the ventilation filter 13 is 0.3 mm.

  The holding outer cylinder 14 is made of stainless steel such as SUS304, and is formed in a bottomed cylinder shape having an outer cylinder closing portion 31 and an outer cylinder cylindrical portion 32. Of these, the outer cylinder blocking portion 31 covers the ventilation filter 13, and is specifically formed in a size that can block the rear end opening 36 of the holding inner cylinder 12. As shown in FIGS. 2 and 3, the outer cylinder closing portion 31 is formed with a plurality of ventilation holes 33 having an opening area sufficiently smaller than the opening area of the rear end opening 36 of the holding inner cylinder 12.

  The outer cylindrical portion 32 is disposed in the through hole 41 of the grommet 11 so as to cover the holding inner cylinder 12. The outer cylindrical portion 32 has a crimping portion 26 that is crimped in the circumferential direction toward the holding inner cylinder 12. Further, the holding inner cylinder 12 has a caulking portion 27 that is caulked by the caulking portion 26.

The O-ring 15 is an annular member made of fluororubber and is disposed between the ventilation filter 13 and the holding inner cylinder 12.
Then, the seal unit 10 is formed by assembling the grommet 11, the holding inner cylinder 12, the ventilation filter 13, the holding outer cylinder 14, and the O-ring 15 as shown below.

First, the ventilation filter 13 is arranged in the bottomed cylindrical holding outer cylinder 14. Further, an O-ring 15 is disposed in the holding outer cylinder 14. Thereafter, the holding inner cylinder 12 is inserted into the holding outer cylinder 14.
As a result, the O-ring 15 and the ventilation filter 13 are sandwiched between the outer cylinder blocking portion 31 of the holding outer cylinder 14 and the holding inner cylinder 12. Further, the O-ring 15 and the ventilation filter 13 are compressed between the outer cylinder blocking portion 31 of the holding outer cylinder 14 and the holding inner cylinder 12, and in this state, the outer cylinder cylindrical portion 32 of the holding outer cylinder 14 is moved. The caulking portion 26 and the caulking portion 27 are formed by caulking in the radial direction. Thus, the state in which the ventilation filter 13 is compressed by the bent portion 81 of the holding inner cylinder 12 and the outer cylinder closing portion 31 of the holding outer cylinder 14 is held, and the holding inner cylinder 12 and the holding outer cylinder 14 are fixed.

  In this way, the outer cylindrical portion 32 of the holding outer cylinder 14 and the ventilation filter 13 are in close contact, the ventilation filter 13 and the O ring 15 are in close contact, and the O ring 15 and the bent portion 81 of the holding inner cylinder 12 are in close contact. To do. The ventilation filter 13 is fixed in a state where the rear end opening 36 is closed. The unit in which the holding inner cylinder 12, the ventilation filter 13, the holding outer cylinder 14, and the O-ring 15 are integrated as described above is hereinafter referred to as a filter unit 19.

Thereafter, the filter unit 19 is inserted into the through hole 41 to create the seal unit 10.
The seal unit 10 thus formed is arranged inside the rear end opening 61 of the outer cylinder 6, and the grommet 11 is caulked in the radial direction via the outer cylinder 6. In this way, the outer cylinder 6 and the grommet 11 are brought into close contact with each other, and the sealing performance is further ensured. Then, air is introduced into the reference gas space from the atmosphere side through the ventilation path formed inside the holding inner cylinder 12 while maintaining the breathability and waterproofness by the ventilation filter 13.

  In the oxygen sensor 1 configured as described above, the ventilation filter 13 having air permeability and waterproofness closes the rear end opening 36 of the holding inner cylinder 12. For this reason, outside air can be introduced into the oxygen sensor 1 through the ventilation filter 13 without passing moisture through the ventilation filter 13.

  The ventilation filter 13 is annularly compressed along the bent portion 81 of the holding inner cylinder 12 by the bent portion 81 of the holding inner cylinder 12 and the outer cylinder closing portion 31 of the holding outer cylinder 14. Thereby, in the area | region which contacts the bending part 81 of the holding | maintenance inner cylinder 12 in the ventilation filter 13, the clearance gap between the ventilation filter 13 and the bending part 81 of the holding | maintenance inner cylinder 12, and the ventilation filter 13 and the holding | maintenance outer cylinder 14 It is difficult to form a gap between them. For this reason, moisture adhering to the surface of the ventilation filter 13 facing the holding outer cylinder 14 (hereinafter referred to as the surface of the ventilation filter 13) goes around the end of the ventilation filter 13 and Reaching the rear end opening of the through hole 41 through the gap between the back surface and the bent portion 81 of the holding inner cylinder 12 can be suppressed. That is, it is possible to suppress moisture adhering to the ventilation filter 13 from entering the oxygen sensor 1.

  Further, an O-ring 15 is disposed between the bent portion 81 of the holding inner cylinder 12 and the ventilation filter 13 along a region where the ventilation filter 13 is annularly compressed. Thereby, the gap between the bent portion 81 of the holding inner cylinder 12 and the ventilation filter 13 or the gap between the ventilation filter 13 and the holding outer cylinder 14 can be filled. For this reason, it is possible to further suppress the moisture adhering to the ventilation filter 13 from entering the oxygen sensor 1 through the gap between the back surface of the ventilation filter 13 and the holding inner cylinder 12.

  Further, since a caulking portion 27 swaged by the caulking portion 26 is formed on the outer peripheral surface of the holding inner cylinder 12, compared with the case where only the caulking portion 26 is formed, the holding inner cylinder 12 The cylinder 12 and the holding outer cylinder 14 can be more firmly fixed.

  Moreover, since the surface of the bending part 81 is smooth, it can suppress that the member (O ring 15 in this embodiment) which is contacting the bending part 81 is damaged by this contact.

  In the embodiment described above, the oxygen sensor 1 is the sensor according to the present invention, the grommet 11 is the first elastic member according to the present invention, the O-ring 15 is the second elastic member according to the present invention, and the crimping portion 26 is the first pressure member according to the present invention. The fastening part and the crimping part 27 are the second crimping part in the present invention.

(Second Embodiment)
A second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, only parts different from the first embodiment will be described.

FIG. 4 is a cross-sectional view showing the configuration of the seal unit 10 according to the second embodiment, and FIG. 5 is a plan view of the holding outer cylinder 114.
The second embodiment is different from the first embodiment in that a filter unit 119 is provided instead of the filter unit 19 as shown in FIG.

  The filter unit 119 protects the holding inner cylinder 112 inserted into the through-hole 41 penetrating the center of the grommet 11 in the axial direction, the ventilation filter 113 closing the rear end opening 121 of the holding inner cylinder 112, and the ventilation filter 113. The holding outer cylinder 114, an O-ring 115 for preventing moisture from entering from the rear end opening 121, and a washer 116 having an outer diameter substantially equal to the outer diameter of the rear end opening 121 of the holding inner cylinder 112. ing.

Among these, the holding inner cylinder 112 has a thread 122 formed on the outer peripheral surface thereof.
The holding outer cylinder 114 is formed in a bottomed cylinder shape having an outer cylinder blocking part 131 and an outer cylinder cylindrical part 132. The outer cylinder closing portion 131 is formed with a size that can close the rear end opening 121 of the holding inner cylinder 112. In addition, as shown in FIGS. 4 and 5, a plurality of vent holes 133 having an opening area that is sufficiently smaller than the opening area of the rear end opening 121 of the holding inner cylinder 112 are formed in the outer cylinder closing portion 131. The outer cylindrical portion 132 is disposed in the through hole 41 of the grommet 11 so as to cover the holding inner cylinder 112, and the outer cylindrical portion 132 is formed on the inner peripheral surface of the holding inner cylinder 112. A screw thread 134 that is screwed onto the screw thread 122 is formed.

The washer 116 is an annular member made of SUS304, and is disposed between the O-ring 115 and the holding inner cylinder 112.
The filter unit 119 is formed by assembling the holding inner cylinder 112, the ventilation filter 113, the holding outer cylinder 114, the O-ring 115, and the washer 116 as shown below.

  First, the ventilation filter 113 is disposed in the bottomed cylindrical holding outer cylinder 114. Further, an O-ring 115 is disposed in the holding outer cylinder 114. Then, the washer 116 is disposed in the holding outer cylinder 114. Thereafter, the holding inner cylinder 112 is inserted from the tip opening 135 of the holding outer cylinder 114 so as to face the tip opening 135 of the holding outer cylinder 114 and the rear end opening 121 of the holding inner cylinder 112. Further, the holding inner cylinder 112 is held by rotating the holding inner cylinder 112 with respect to the holding outer cylinder 114 in a state where the thread 122 of the holding inner cylinder 112 and the screw thread 134 of the holding outer cylinder 114 are screwed together. It enters toward the outer cylinder 114. Finally, the ventilation filter 113 is compressed between the holding outer cylinder 114 and the holding inner cylinder 112 and is fixed in a state of closing the rear end opening 121, whereby the filter unit 119 is completed.

  A washer 116 is disposed between the ventilation filter 113 and the holding inner cylinder 112. Accordingly, the ventilation filter 113 is prevented from being twisted when the holding inner cylinder 112 is inserted into the holding outer cylinder 114 and the holding inner cylinder 112 is rotated with respect to the holding outer cylinder 114.

  In the oxygen sensor 1 configured as described above, the ventilation filter 113 having air permeability and waterproofness closes the rear end opening 121 of the holding inner cylinder 112. For this reason, outside air can be introduced into the oxygen sensor 1 through the ventilation filter 113 without passing moisture through the ventilation filter 113.

  The ventilation filter 113 is compressed by the rear end portion of the holding inner cylinder 112 and the outer cylinder closing portion 131 of the holding outer cylinder 114. This makes it difficult to form a gap between the ventilation filter 113 and the rear end portion of the holding inner cylinder 112 and a gap between the ventilation filter 113 and the holding outer cylinder 114. For this reason, the moisture adhering to the surface of the ventilation filter 113 facing the holding outer cylinder 114 (hereinafter referred to as the surface of the ventilation filter 113) goes around the end of the ventilation filter 113 and Reaching the rear end opening of the through hole 41 through the gap between the back surface and the rear end of the holding inner cylinder 112 can be suppressed. That is, it is possible to suppress the moisture adhering to the ventilation filter 113 from entering the oxygen sensor 1.

  In the embodiment described above, the O-ring 115 is the second elastic member in the present invention, the thread 134 is the first thread in the present invention, and the thread 122 is the second thread in the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.
For example, in the above-described embodiment, the seal unit 10 used for the oxygen sensor is shown. However, the present invention is not limited to the oxygen sensor, and any sensor that introduces outside air into the sensor via a ventilation filter may be used.

Moreover, in the said embodiment, although it was the cylindrical detection element 2, it is not restricted to this, A plate-type detection element may be sufficient.
In the above embodiment, the vent holes 33 and 133 formed by drilling the plate-like outer cylinder blocking portions 31 and 131 are shown as the vent holes of the present invention. Good. For example, a holding outer cylinder may be formed by forming a sheet member (for example, SUS mesh) formed in a mesh shape into a bottomed cylindrical shape. A sheet member formed in a mesh shape (hereinafter referred to as a mesh sheet member) is used as an outer cylinder blocking portion, and a cylindrical metal member separate from the mesh sheet member is used as an end of the mesh sheet member. You may make it comprise a holding | maintenance outer cylinder by connecting in an edge part and making this metal member into an outer cylinder cylindrical part.

In the second embodiment, the washer 116 is disposed. However, a leaf spring may be disposed instead of the washer 116.
In the second embodiment, the thread 122 of the holding inner cylinder 112 and the thread 134 of the holding outer cylinder 114 are directly screwed together. However, a seal is provided between the thread 122 and the thread 134. The waterproof performance may be improved by interposing and screwing.

  In the first embodiment, the outer cylindrical portion 32 of the holding outer cylinder 14 is crimped. However, the outer cylindrical portion 32 of the holding outer cylinder 14 and the holding inner cylinder 12 are welded. Thus, the holding outer cylinder 14 may be fixed to the holding inner cylinder 12.

  In the above embodiment, the O-rings 15 and 115 are disposed between the ventilation filters 13 and 113 and the holding inner cylinders 12 and 112. However, as shown in FIG. You may arrange | position between the cylinders 14. 6 is the same shape as the first embodiment except for the arrangement of the O-ring 215 and the shape of the rear end side of the holding inner cylinder 212.

  In the above embodiment, the ventilation filters 13 and 113 are annularly compressed along the holding inner cylinders 12 and 112 by the holding inner cylinders 12 and 112 and the holding outer cylinders 14 and 114. Are bonded or welded to the holding inner cylinders 12 and 112 or the holding outer cylinders 14 and 114 in advance using an adhesive, and then the ventilation filters 13 and 113 are held by the holding inner cylinders 12 and 112 and the holding outer cylinders 14 and 114. Alternatively, compression may be performed annularly along the holding inner cylinders 12 and 112.

  Further, although the bent portion 81 is provided on the rear end side of the holding inner cylinder 12 of the first embodiment, the present invention is not limited to this, and the rear end side of the holding inner cylinder 112 is in the axial direction as in the second embodiment. The rear end side of the holding inner cylinder 212 may be an arc-shaped convex portion 281 as shown in FIG.

1 is a cross-sectional view illustrating an overall configuration of an oxygen sensor 1. FIG. It is sectional drawing showing the structure of the seal unit 10 of 1st Embodiment. It is a top view of holding outer cylinder 14 of a 1st embodiment. It is sectional drawing showing the structure of the seal unit 10 of 2nd Embodiment. It is a top view of holding | maintenance outer cylinder 114 of 2nd Embodiment. It is sectional drawing showing the structure of the seal unit 10 of another embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Oxygen sensor, 2 ... Detection element, 3 ... Ceramic heater, 4 ... Casing, 5 ... Main metal fitting, 6 ... Outer cylinder, 7 ... Separator, 10 ... Seal unit, 11 ... Grommet, 12, 112, 212 ... In holding | maintenance Tube, 13, 113 ... Ventilation filter, 14, 114 ... Holding outer tube, 15, 115, 215 ... O-ring, 19, 119 ... Filter unit, 26, 27 ... Clamping portion, 31, 131 ... Outer tube closing portion, 32, 132 ... outer cylindrical tube part, 33, 133 ... vent hole, 36, 121 ... rear end opening, 41 ... through hole, 42 ... insertion hole, 61 ... rear end opening, 81 ... bent part, 82 ... locking Part 116, washer 122, 134 thread 281, convex part

Claims (6)

A cylindrical casing that extends in the axial direction and that holds the detection element so that the tip of the detection element extending in the axial direction is exposed to the gas to be measured, and is formed by opening a rear end of the axial direction in the axial direction. ,
A first elastic member formed with a through-hole penetrating along the axial direction for introducing outside air into the casing and disposed so as to close a rear end opening of the casing,
A cylindrical holding inner cylinder partially inserted into the through hole of the first elastic member;
A ventilation filter having breathability and waterproofness, and closing a rear end opening of the holding inner cylinder;
One or a plurality of vent holes penetrating along the axial direction and an outer cylinder blocking portion that covers the ventilation filter, and connected to the outer cylinder blocking portion, and a part of the outer peripheral surface of the holding inner cylinder A holding outer cylinder having an outer cylindrical cylinder part surrounding the circumferential direction,
The outer cylinder blocking portion covers a rear end opening of the holding inner cylinder,
The opening area of the vent hole is smaller than the rear end opening of the holding inner cylinder,
In the ventilation filter, an annular region along the holding inner cylinder is compressed by a rear end portion of the holding inner cylinder and the outer cylinder blocking portion of the holding outer cylinder. Between the rear end portion of the holding inner cylinder and the ventilation filter, or between the outer cylinder blocking portion and the ventilation filter, along the region where the ventilation filter is annularly compressed, waterproof. The sensor according to claim 1, wherein a second elastic member is disposed. The sensor according to claim 1, wherein the outer cylindrical portion includes a first crimping portion that is crimped in a circumferential direction toward the holding inner cylinder. The sensor according to claim 3, wherein a second caulking portion that is caulked by the first caulking portion is provided on an outer peripheral surface of the holding inner cylinder. A first thread is provided on an inner peripheral surface of the outer cylindrical portion of the holding outer cylinder;
The sensor according to claim 1, wherein a second screw thread that is screwed into the first screw thread is provided on an outer peripheral surface of the holding inner cylinder. The rear end side of the holding inner cylinder has a bent portion that is folded back toward the inner side of the holding inner cylinder so as to face the front end side of the holding inner cylinder. A sensor according to any one of the above.

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