JP6348405B2 - Gas sensor - Google Patents

Description

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

Conventionally, a gas sensor for detecting the concentration of a specific component (oxygen, NOx, etc.) in exhaust gas of an internal combustion engine has been used. In general, a gas sensor includes a gas sensor element extending in the axial direction, a cylindrical metal shell that fixes the gas sensor element, a metal outer cylinder that is provided in a surrounding manner on the rear end side of the metal metal shell, and a distal end side in the outer cylinder. And a rubber grommet disposed in order.
And the technique of providing the cap-shaped protection member which covers a grommet spaced apart from an outer cylinder, and prevents a stepping stone etc. colliding with an outer cylinder and applying an impact to a grommet and its internal filter part is disclosed. Patent Document 1).
Also, a technique for dissipating heat by attaching a metal heat dissipating member to the outer periphery of the outer cylinder at the tip side of the grommet is disclosed in order to prevent the grommet from being deteriorated by high heat of an exhaust pipe or the like where the gas sensor is installed. (See Patent Document 2). Since this heat radiating member also covers the grommet while being separated from the outer cylinder, it has a function of preventing an impact caused by a flying stone or the like.

Japanese Patent No. 5002032 JP 2012-154774 A

By the way, there are many cases where other members (separator or the like) are also arranged inside the outer cylinder on the tip side of the grommet. However, in the techniques described in Patent Documents 1 and 2, the outer cylinder is exposed without being covered with the heat radiating member at the separator portion on the tip side of the grommet. For this reason, when a stepping stone or the like collides with this part of the outer cylinder, an impact is transmitted to the internal separator, and the separator may be damaged, or the connection terminal attached to the separator may be displaced to break the electrical connection.
Then, an object of this invention is to provide the gas sensor which can prevent that an impact is added to the internal member arrange | positioned inside and in contact with an outer cylinder.

In order to solve the above-described problems, a gas sensor according to the present invention is attached to the metal shell, a gas sensor element extending in the axial direction, a metal shell that surrounds the circumference of the gas sensor element in the radial direction, and holds the gas sensor element. A gas sensor comprising: a metal outer cylinder extending to a rear end from the metal shell; and an internal member disposed inside the outer cylinder while being in contact with the outer cylinder, wherein the gas sensor includes one or more internal members. And further comprising a cylindrical protective member attached to the outer periphery of the outer cylinder, the protective member being closer to the distal end than the distal end of the contact position between the outermost inner member and the outer cylinder in the axial direction. And a connecting portion connected to the outer cylinder, and a main portion that extends from the connecting portion toward the rear end side, covers the contact position, and is separated from the outer periphery of the outer cylinder.
In the gas sensor, since the tip side of the outer cylinder is closer to the ground or the like, a stepping stone or the like is likely to collide. Therefore, by connecting the connecting portion to the outer cylinder at the front end side of the contact position of the innermost member on the front end side in the axial direction among at least one internal member arranged inside the outer cylinder, The main part extending to the rear end side of the connecting part covers this contact position, and protects the contact position where the flying stones and the like are more likely to collide. Thereby, it can prevent that an impact is added to the internal member inside a contact position.

In the gas sensor of the present invention, an opening may be provided in the main part.
According to this gas sensor, it is possible to prevent drainage inside the main part and heat from being accumulated inside the main part.

In the gas sensor of the present invention, the opening is configured as a gap between a plurality of notches that are notched leaving one side extending in the axial direction and pushed inward in the radial direction, and the plurality of notches are arranged along the circumferential direction. The one side may be arranged in the same direction.
According to this gas sensor, when outside air such as traveling wind hits the main part from a certain direction, the outside air is introduced from one side to the inside of the main part using the notch as a guide. For this reason, outside air is introduced as a swirl flow around the axial direction inside the main part, and the gas sensor part (outer cylinder) inside the main part is equally applied as the swirl flow to cool the portion of the gas sensor that is the back of the outside air. Cooling efficiency is improved.

In the gas sensor of the present invention, a straight portion in which at least the rear end side of the main portion extends along the axial direction may be formed.
According to this gas sensor, the diameter of the main part can be made smaller than the case where the entire main part is expanded by a taper or the like, and the outer part can be separated from the outer cylinder, and the gas sensor can be downsized.

  According to the present invention, in the gas sensor, it is possible to prevent an impact from being applied to the internal member that is in contact with the outer cylinder and disposed inside thereof.

It is a whole sectional view in alignment with an axial direction of a gas sensor concerning an embodiment of the present invention. It is a perspective view of a protection member. It is a perspective view which shows the modification of a protection member.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is an overall cross-sectional view along the axis AX direction of a gas sensor 100 according to an embodiment of the present invention, and FIG. 2 is a perspective view of a protective member. The gas sensor 100 is a so-called full-range air-fuel ratio sensor that is mounted on an exhaust pipe of an internal combustion engine or the like and linearly detects the oxygen concentration in the exhaust gas that is the measurement gas from the rich region to the lean region.

In FIG. 1, an axis AX is a virtual central axis of the gas sensor 100, and the gas sensor 100 has a shape that extends along the direction of the axis AX. The gas sensor 100 includes a gas sensor element 120 that outputs a signal corresponding to the oxygen concentration, and a metal shell 110.
The metal shell 110 is a cylindrical metal member having a through-hole 110c along the axis AX direction. The metal shell 110 surrounds the periphery of the gas sensor element 120 in the radial direction and holds the gas sensor element 120. The metal sensor 100 is connected to the exhaust pipe. For fixed mounting. On the outside of the metal shell 110, a screw part 110a that is screwed into a thread groove for mounting the gas sensor 100 provided in the exhaust pipe, or a tool such as a spanner or a wrench is engaged when the gas sensor 100 is mounted. The tool engaging portion 110b is formed.

A double bottomed cylindrical protector 101 is fixed to the front end side of the metal shell 110 by laser welding. In the double protector 101, a plurality of introduction holes 101c are formed in each of the inner and outer wall portions so that the exhaust gas can be introduced into the interior when the gas sensor 100 is attached to the exhaust pipe.
A cylindrical metal outer cylinder 103 is fixed to the rear end side of the metal shell 110 by laser welding. Inside the gas sensor 100, there are two sensor lead wires 193, 194 and 195 for electrically connecting the gas sensor 100 and an external control circuit from the rear end side end portion of the outer cylinder 103. The heater lead wires 196 and 197 are inserted. Note that a fluoro rubber grommet 191 for sealing the inside of the outer cylinder 103 is attached to the rear end side end portion of the outer cylinder 103, and the five types of lead wires 193 to 197 include the grommet 191. It penetrates and is inserted into the outer cylinder 103.
The grommet 191 can be formed from, for example, silicon rubber or fluorine rubber.

The gas sensor element 120 has a laminated structure in which elongated plate members are laminated, and has a quadrangular prism shape in which a cross section perpendicular to the axis AX is a substantially rectangular shape. The gas sensor element 120 is fixedly held in the through hole 110 c of the metal shell 110 and is accommodated along the axis AX direction inside the gas sensor 100. In FIG. 1, the first and second surfaces 120a and 120b facing each other along the stacking direction of the gas sensor elements 120 are directed to the left side and the right side, respectively.
A gas detection unit 121 configured to be able to detect the oxygen concentration in the exhaust gas is provided at the end of the gas sensor element 120 on the front end side (the lower side in the drawing). The gas detection unit 121 is accommodated and arranged inside the protector 101. Accordingly, when the gas sensor 100 is attached to the exhaust pipe, the gas detection unit 121 is exposed to the exhaust gas introduced from the introduction hole 101c.

Here, a separator 181 which is a cylindrical insulating member having a through hole 181c along the axis AX direction is fixedly held in the outer cylinder 103 on the rear end side (the upper side in the drawing) of the metal shell 110. . Specifically, the separator 181 is held in the outer cylinder 103 in a state of being urged toward the grommet 191 by a substantially cylindrical urging metal member 190 disposed on the outer periphery. The end of the gas sensor element 120 on the rear end side is accommodated in the through hole 181c of the separator 181.
The grommet 191 and the urging metal fitting 190 are disposed inside the outer cylinder 103 while being in contact with the outer cylinder 103, and thus correspond to an “inner member” in the claims. Further, the separator 181 is disposed inside the outer cylinder 103 while being separated from the outer cylinder 103 via a biasing metal fitting 190 that is an internal member.

At the rear end portion of the gas sensor element 120, three electrode pads 125, 126, 127 for sensors are arranged in parallel in the depth direction of the paper on the first surface 120a side, and two on the second surface 120b side. The heater electrode pads 128 and 129 are arranged in parallel in the depth direction of the drawing. Further, in the through hole 181c of the separator 181, three sensor connection terminals 182, 183, 184 and two heater connection terminals 185, 186 are provided to the corresponding electrode pads 125 of the gas sensor element 120. 129 so as to be in contact with 129. Each of the connection terminals 182 to 186 is electrically connected to five lead wires 193 to 197 inserted through the gas sensor 100 via the grommet 191.
Each of the connection terminals 182 to 186 provided on the separator 181 has a leaf spring structure that is bent from the front end side to the rear end side of the gas sensor 100, and the corresponding electrode pads 125 to 225 are bent by its elastic force. 129 is pressed.

The gas sensor element 120 is fixedly held on the metal shell 110 with the following configuration in the cylinder of the metal shell 110. On the front end side of the through hole 110c of the metal shell 110, a stepped portion 111 that protrudes radially inward is formed. In the through hole 110 c of the metal shell 110, a metal cup 116 having a through hole 116 c on the bottom surface is disposed with the outer peripheral end of the bottom surface engaged with the stepped portion 111.
A ceramic holder 113 is disposed in the internal space on the bottom side of the metal cup 116. The ceramic holder 113 is made of alumina (Al ₂ O ₃ ), and a rectangular through hole 113c for inserting the gas sensor element 120 is formed in the center.

  Inside the metal cup 116, a first powder filling layer 114 (talc) is formed to hold the gas sensor element 120 inserted through the through hole 116c of the metal cup 116 and the through hole 113c of the ceramic holder 113 in an airtight manner. Has been. The first powder filling layer 114 is formed by filling talc powder on the ceramic holder 113. Thus, the gas sensor element 120 is held in the through-hole 110c of the metal shell 110 in a state where the metal cup 116, the ceramic holder 113, and the first powder filling layer 114 are integrated.

In the through hole 110c of the metal shell 110, the airtightness between the rear end side of the metal shell 110 and the gas detection part 121 of the gas sensor element 120 is further secured on the first powder filling layer 114. The second powder filling layer 115 (talc) is formed by filling talc powder. A ceramic sleeve 170 is disposed on the second powder filling layer 115.
The ceramic sleeve 170 is a cylindrical body having a rectangular shaft hole 170c along the axis AX direction through which the gas sensor element 120 is inserted. The ceramic sleeve 170 can be made of alumina. The ceramic sleeve 170 is fixed to the metal shell 110 while being pressed toward the second powder filling layer 115 by bending and crimping the end portion 110k on the rear end side of the metal shell 110 inward in the radial direction. . A caulking ring 117 is disposed between the end portion 110 k on the rear end side of the metal shell 110 and the ceramic sleeve 170.

Further, a cylindrical metal protection member 150 is fixed to the outer periphery of the outer cylinder 103. The protection member 150 includes a connection portion 150a connected to the outer periphery of the outer cylinder 103 by laser welding or the like, and a main portion 150b extending from the connection portion 150a to the rear end side and spaced from the outer periphery of the outer cylinder 103. The main portion 150b includes a tapered portion 150b1 that extends in a tapered shape from the connecting portion 150a toward the rear end side, and a straight portion 150b2 that extends along the axis AX direction from the tapered portion 150b1 toward the rear end side. The rear end 150e of the straight portion 150b2 is open.
The protection member 150 is made of, for example, SUS.

Here, the grommet 191 and the urging bracket 190 that are internal members are in contact with the outer cylinder 103 at the contact positions 103b and 103a, respectively, but because the tip side of the outer cylinder 103 is closer to the ground or the like, there is a stepping stone or the like. Easy to collide. Therefore, by connecting the connection portion 150a to the outer cylinder 103 at the front end side of the front end F of the contact position 103a of the biasing fitting 190 which is the innermost member on the front end side in the axis AX direction, The main portion 150b extending to the end side covers the contact position 103a, and protects the contact position 103a where a stepping stone or the like is more likely to collide. This prevents an impact from being applied to the urging bracket 190 inside the contact position 103a. As a result, the impact is transmitted to the separator 181 held by the urging bracket 190, so that the connection terminals 182 to 186 attached to the separator 181 It is possible to prevent the electrical connection with each of the electrode pads 125 to 129 from being disconnected.
The main portion 150b may not completely cover the contact position 103a in the direction of the axis AX, and may cover at least a part including the tip of the contact position 103a. Further, since the contact position 103b located on the rear end side of the outer cylinder 103 is less likely to collide with stepping stones or the like than the contact position 103a on the front end side, the contact position 103b may not necessarily be covered with the main portion 150b. However, it is preferable that the main portion 150b covers all contact positions.

Further, the heat of the gas sensor 100 is transmitted from the outer cylinder 103 to the connection portion 150a, but the connection portion 150a is disposed on the distal end side with respect to the contact position 103a of the urging metal 190 which is the innermost member on the distal end side in the axis AX direction. Thus, the distance between the grommet 191 located on the rear end side of the urging bracket 190 and the connecting portion 150a can be increased. For this reason, the rate at which the heat from the outer cylinder 103 is dissipated from the connection portion 150a to the main portion 150b increases, and heat transmitted from the outer cylinder 103 to the grommet 191 can be reduced to prevent thermal degradation of the grommet 191. . Here, the thickness of the protection member 150 is not particularly defined, but is preferably thinner than the outer cylinder 103. This is because if the protective member 150 is thinner than the outer cylinder 103, heat is easily radiated.
In this embodiment, since the rear end side of the main portion 150b forms the straight portion 150b2, the outer diameter of the main portion 150b is reduced while reducing the diameter of the main portion 150b as compared with the case where the entire main portion 150b is expanded by a taper portion or the like. The gas sensor 100 can be separated from the cylinder 103 and the gas sensor 100 can be downsized. In addition, although the straight part 150b2 may be provided stepwise from the connection part 150a without providing the taper part 150b1, it is preferable to provide the tapered part 150b1 from the viewpoint of workability.

Furthermore, as shown in FIG. 2, a plurality of openings 152 are provided in the main portion 150b. The opening 152 has a function of preventing drainage inside the main portion 150b and the accumulation of heat inside the main portion 150b. However, in the present embodiment, the protective member 150 further turns outside air as a swirling flow around the axis AX direction. It has the effect | action introduced into the inside.
In other words, the opening 152 is formed as a gap between the notches 154 that are cut out in a U shape leaving one side 154L extending in the axis AX direction and pushed inward in the radial direction. The notches 154 are arranged along the circumferential direction with one side 154L in the same direction (in the example of FIG. 2, each side 154L faces the right side).
Accordingly, for example, when a traveling wind W that is outside air hits the main portion 150b from the right side of FIG. 2, the traveling wind W is introduced into the main portion 150b from the right side with the notch 154 as a guide on the front side of the main portion 150b. be introduced. Further, on the back side of the main portion 150b, due to the negative pressure along the flow of the traveling wind W introduced on the front side, the traveling wind W is introduced into the main portion 150b from the left side with the notch 154 as a guide. For this reason, traveling air W is introduced as a swirling flow clockwise around the axis AX in the main portion 150b (protective member 150), and comes out from the opening of the rear end 150e of the main portion 150b. In this way, the traveling wind W can evenly strike the gas sensor 100 (outer cylinder 103) inside the main portion 150b as a swirling flow, and the portion of the gas sensor 100 that is the back surface of the traveling wind W can be cooled. Will improve.

It goes without saying that the present invention is not limited to the above-described embodiment, but extends to various modifications and equivalents included in the spirit and scope of the present invention.
For example, in the above embodiment, the opening is provided in the main part of the protection member. However, as illustrated in FIG. 3, the opening may not be provided in the main part 160 b of the protection member 160. Although not shown, the opening may be a through hole, and the shape thereof may be circular or elliptical.
Further, as the gas sensor element, in addition to the above-described oxygen sensor element (entire region air-fuel ratio sensor element), a λ sensor element, a NO _x sensor element, and an ammonia sensor element can be used. It may be a shaped element.

DESCRIPTION OF SYMBOLS 100 Gas sensor 103 Outer cylinder 103a, 103b Contact position 110 Main metal fitting 120 Gas sensor element 150,160 Protection member 150a, 160a Connection part 150b, 160b Main part 150b2 Straight part 152 Opening 154 Notch part 154L One side of the notch part extending in the axial direction 190 Inside Member (energizing bracket)
191 Internal members (grommets)
AX Axis F The tip of the contact point of the tip in the axial direction

Claims (4)

A gas sensor element extending in the axial direction;
A metal shell surrounding the gas sensor element in the radial direction and holding the gas sensor element;
A metal outer cylinder attached to the metal shell and extending to the rear end from the metal shell,
It is an internal member that is disposed inside the outer cylinder while being in contact with the outer cylinder, and has one or more internal members in itself,
A gas sensor comprising:
A cylindrical protective member attached to the outer periphery of the outer cylinder;
The protective member is
A connecting portion connected to the outer cylinder on the distal end side than the distal end of the contact position between the inner member on the most distal end side and the outer cylinder in the axial direction;
A gas sensor having a main portion that extends from the connection portion toward the rear end side and covers the contact position and is spaced from the outer periphery of the outer cylinder.   The gas sensor according to claim 1, wherein an opening is provided in the main part. The opening is configured as a gap between a plurality of notches that are notched leaving one side extending in the axial direction and pushed inward in the radial direction,
The gas sensor according to claim 2, wherein the plurality of notches are arranged in the same direction along the circumferential direction.


  The gas sensor according to any one of claims 1 to 3, wherein at least a rear end side of the main portion forms a straight portion extending along the axial direction.

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