JP5357906B2 - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor which uses heat that a protector receives from exhaust gas and the like for rising temperature of a gas detection element, shortens arrival time at activation temperature of the gas detection element, and improves a light-off property. <P>SOLUTION: A gas sensor 21 comprises: a cylindrical gas detection element 22 whose tip is exposed to gas to be measured and which has an element side reception part 22b protruding outward in a radial direction; a cylindrical main body metal fitting 25 which surrounds the gas detection element and has a main body metal fitting side reception part 25a protruding inward in the radial direction; and a cylindrical protector 40 whose rear end side is housed at the inside of the main body metal fitting and which surrounds the tip of the gas detection element. A projection part 40f having enlarging diameter is formed at the rear end side of the protector. The protector has higher heat conductivity than the gas detection element, and is fixed in a state where the projection part is sandwiched between a surface of the main body metal fitting side reception part, facing the rear end and a surface of the element side reception part, facing the tip. The surface of the element side reception part, facing the tip and the projection part are directly in contact with each other, or another member is interposed therebetween. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a gas sensor unit in which a gas sensor having a gas detection element and a sensor cap attached to the gas sensor and transmitting the output of the gas sensor to the outside are combined.

Conventionally, various gas sensors having gas detection elements have been proposed. Examples of these gas sensors include those having a gas detection element made of a solid electrolyte having oxygen ion conductivity. The gas sensor is attached to an attachment object such as an exhaust pipe or an engine head of an internal combustion engine, and detects the concentration of a specific gas (for example, oxygen) in the exhaust gas with a pair of electrodes disposed on the front end side of the gas detection element. .
In general, in such a gas sensor, the gas detection element is surrounded and held by a metal shell, and a cylindrical protector that protects the detection portion is welded and fixed to the tip of the metal shell (see Patent Document 1). In addition, a metal fitting side latching part that protrudes inward is provided on the front end side of the metal shell, so that welding to the tip of the metal shell of the protector is not required and workability and sensor performance are improved. The technique which provided the protector side latching | locking part which protrudes outside is disclosed (refer patent document 2). In this technique, the protector-side locking portion is held and held between the ceramic holder and the metal shell-side locking portion.
There is also known a gas sensor that is used without being provided with a heater and being heated to an activation temperature only by receiving heat from exhaust gas (see Patent Document 3).

JP-A-6-235714 Japanese Patent Application Laid-Open No. 11-190715 JP 2009-63330 A

However, in the heaterless gas sensor, the temperature is raised to the activation temperature only by receiving heat from the exhaust gas as described above. At this time, the protector exposed to the exhaust gas is also heated, but since the protector is connected to the metal shell, the heat received by the protector escapes to the metal shell and cannot be utilized (the gas sensor is not used in the engine head). Since the metal shell is cooled by drawing heat to the body to be attached, the heat of the protector heated by the exhaust gas escapes to the metal shell). In other words, the gas detection element (detection unit) in the protector is only heated directly by the exhaust gas from the protector hole and cannot use the heat stored in the protector, so it takes time until the gas detection element reaches the activation temperature. The light-off characteristics are poor.
In the case of the technique described in Patent Document 2, since the protector rear end and the gas detection element are in contact with each other through a ceramic holder, it is difficult for the heat of the protector to be transmitted to the gas detection element, and there is room for improving the light-off characteristics. .
Therefore, the present invention uses the heat received by the protector from the gas to be measured such as exhaust gas to raise the temperature of the gas detection element, thereby shortening the arrival time of the gas detection element to the activation temperature and improving the light-off characteristic. An object is to provide a gas sensor that can be improved.

In order to solve the above-described problems, a gas sensor according to the present invention includes a cylindrical gas detection element having an element-side receiving portion that extends in the axial direction and is exposed to a gas to be measured and has a device-side receiving portion that protrudes radially outward. A cylindrical metal shell that surrounds the gas detection element and has a metal shell-side receiving portion that protrudes radially inward, and a rear end side of the metal metal shell that is housed inside the metal shell, A cylindrical protector that protrudes from the front end of the metal shell and surrounds the front end of the gas detection element, and the protector has a higher thermal conductivity than the gas detection element, and is disposed on the rear end side of the protector. The protector is formed in a state in which a projecting portion that expands radially outward is formed and the projecting portion is sandwiched between a rear end facing surface of the metal shell side receiving portion and a front end facing surface of the element side receiving portion. Is fixed, One of at least the element-side receiving portion forward-facing surface and is in direct contact said projection, or the and through the other member which thermal conductivity is made of a metal having high than the gas detection element, and said protector and said metal shell A space is provided in at least a part of the space .
According to such a gas sensor, since the protector that is heated by being exposed to a gas to be measured such as exhaust gas is in contact with the gas detection element directly or through another member, the protector is removed from the gas to be measured. The received heat can also be used to raise the temperature of the gas detection element, improving the light-off characteristics. In particular, when the tip-facing surface of the element side receiving part and the protruding part are in direct contact with each other, the effect of raising the temperature of the gas detection element due to the heat received by the protector is great.
The "cylindrical protector that surrounds the tip of the gas detection element" is sufficient if it surrounds the tip of the gas detection element from the radial direction, and the protector is formed in a cylindrical shape without having a bottom. Also good.
Moreover, according to such a gas sensor, it is possible to prevent the heat received by the protector from being drawn to the metal shell before reaching the gas detection element.

The protector may be exposed to the outside.
An outer electrode exposed to the gas to be measured may be formed on the outer surface of the gas detection element, and the outer electrode may be electrically grounded with respect to the metal shell.
As described above, the present invention can be applied particularly effectively in the case of a gas sensor in which it is a precondition that the outer electrode is electrically grounded with respect to the metal shell.

The protector may include a plurality of protector portions having different diameters in the radial direction, and the protruding portion may be formed on the outermost protector portion among them.
According to such a gas sensor, the heat of the outermost protector that receives the most heat from the gas to be measured such as exhaust gas can be transmitted to the gas detection element.

An attachment portion for attaching the gas sensor to an attachment target body is provided on the outer surface of the metal shell, and at least a part of the space may overlap the attachment portion along the axial direction.
Since the heat of the metal shell is drawn through the attachment portion to the object to be attached and cooled, the attachment portion is most easily cooled. Therefore, by arranging the space so as to overlap the mounting portion, it is possible to more effectively prevent the heat received by the protector from being drawn to the metal shell.

The contact area between the tip-facing surface of the element side receiving portion and the protruding portion, or the contact area between the other member and the protruding portion is the contact between the rear end facing surface of the metal shell-side receiving portion and the protruding portion. It is preferable that it is larger than the area.
According to such a gas sensor, since the area of the protruding portion that contacts the protector is larger in the gas detection element than in the metal shell, the heat received by the protector can be effectively transmitted to the gas detection element. In addition, when the above-mentioned other member is interposed between the tip-facing surface of the element side receiving portion and the protruding portion, the contact area between the other member and the protruding portion is used as a reference.

  When the heater for heating the gas detection element is not provided, the gas detection element can be heated up to the activation temperature only by receiving heat from the exhaust gas. Therefore, the present invention is particularly effective.

  When the metal shell is made of an iron-based member, it is particularly effective to apply the present invention because it is easy to draw heat and the heat is transmitted to the metal shell and the gas detection element is easily cooled.

  When the protector is made of stainless steel, the heat conductivity is poor, so heat is easily trapped in the protector and heat is not easily transferred to the metal shell, so that the heat received by the protector from the gas to be measured is more effectively applied to the gas detection element. It is possible to raise the temperature of the gas detection element.

The length of the attachment portion along the axial direction may be ½ or more of the distance from the tip of the gas detection element to the tip of the contact area between the element side receiving portion and the protrusion.
The longer the length of the attachment part, the more securely the gas sensor can be attached to the object to be attached such as the engine head.However, since heat is transferred from this attachment part to the object to be attached and the gas detection element is easily cooled, It is effective to apply the present invention.

  According to the present invention, the heat of the protector heated by the gas to be measured such as exhaust gas can be used for raising the temperature of the gas detection element, so that the time to reach the activation temperature is shortened and the light-off characteristic is improved. can do.

It is sectional drawing which follows the axial direction of the gas sensor concerning the 1st Embodiment of this invention. It is sectional drawing which follows the axial direction of the gas sensor unit formed by attaching a sensor cap to a gas sensor. It is a figure which shows the heat transfer from a protector to a gas detection element. It is sectional drawing which follows the axial direction of a sensor cap. It is explanatory drawing of a cap terminal, (a) is a front view, (b) is a bottom view. It is sectional drawing which follows the axial direction of the gas sensor concerning the 2nd Embodiment of this invention. It is sectional drawing which follows the axial direction of the gas sensor concerning the 3rd Embodiment of this invention. It is sectional drawing which follows the axial direction of the gas sensor concerning the 4th Embodiment of this invention. It is sectional drawing which follows the axial direction of the gas sensor concerning the 5th Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view taken along the direction of the axis O of the gas sensor 21 according to the first embodiment. The gas sensor 21 is an oxygen sensor that measures the oxygen concentration in the exhaust gas. The gas sensor 21 does not have a heater, is attached to the engine head, and is used after being heated to the activation temperature by receiving heat from the exhaust gas.
The gas sensor 21 includes a gas detection element 22, a ceramic enclosure 23, a terminal member 24, a metal shell 25, and a protector 40. In the following description, in the direction along the axis O, the side to which the sensor cap is attached will be referred to as the rear end side, and the opposite side will be referred to as the front end side.

The gas detection element 22 is made of a solid electrolyte having oxygen ion conductivity, and has a bottomed shape with a closed end 22a and a cylindrical shape extending in the direction of the axis O. In addition, a flange-like protruding portion 22b is formed in the radially outer side in the center of the gas detection element 22 in the axis O direction, and the tip-facing surface of the protruding portion 22b has a taper shape with a diameter decreasing toward the tip. Yes. The protruding portion 22b corresponds to an “element side receiving portion” in the claims.
An outer electrode 28 is formed on the outer peripheral surface of the distal end portion 22 a of the gas detection element 22. The outer electrode 28 is made of porous Pt or Pt alloy. The outer electrode 28 is provided up to the tip side surface of the protruding portion 22b, and is electrically connected to the inner peripheral receiving portion 25a of the metal shell 25 as described later. Therefore, the potential of the outer electrode 28 can be taken out from the metal shell 25. That is, the outer electrode 28 is in a state of being electrically grounded (grounded) with respect to the metal shell. On the other hand, an inner electrode 29 is also formed on the inner peripheral surface of the gas detection element 22. This inner electrode 29 is also made of Pt or a Pt alloy formed porous.
As the solid electrolyte constituting the gas detection element 22, for example, ZrO _{2 in} which Y ₂ O ₃ or CaO is dissolved is representative, but other alkaline earth metal or rare earth metal oxides can be used. A solid solution with ZrO ₂ may be used. Furthermore, HfO ₂ may be contained therein.

The metal shell 25 is made of SUS430 and is formed in a cylindrical shape. The metal shell 25 includes an inner periphery receiving portion 25a for supporting the protruding portion 22b of the gas detection element 22 and has a tapered inner periphery receiving a diameter decreasing toward the tip side (downward in FIG. 1). The portion 25a is circumferentially provided so as to protrude radially inward from the inner peripheral surface. Here, the inner periphery receiving portion 25a corresponds to a “metal fitting side receiving portion” in the claims.
Further, a screw portion 25b for attaching the gas sensor 21 to the exhaust pipe (attachment target body) is formed outside the metal shell 25, and on the rear end side (upward in FIG. 1) of the screw portion 25b. Is provided with a collar portion (hexagonal portion) 25c that engages an attachment tool for screwing the screw portion 25b into the exhaust pipe. The flange portion 25 c protrudes radially outward from the other outer surface of the metal shell 25. An annular gasket 27 for sealing when the gas sensor 21 is attached to the exhaust pipe is fitted to the tip-facing surface of the flange portion 25c. Here, the screw portion 25b corresponds to an “attachment portion” in the claims.

Inside the metal shell 25, a rear end side of a cylindrical protector 40 that covers a front end portion 22 a of a gas detection element 22 described later is accommodated, and the front end side of the protector 40 protrudes from the front end of the metal shell 25. Further, a flange portion 40f ("protruding portion" in the claims) is formed at the rear end edge of the protector 40 so as to taper outward in the radial direction. The protector 40 is a metal bottomed cylindrical body, and has a plurality of vent holes 40a on the tip (bottomed portion) side for introducing exhaust gas in the exhaust pipe into the gas sensor 21. And the front-end | tip part 22a of the gas detection element 22 protruded from the front-end | tip of the metal shell 25 is exposed to exhaust gas (measuring gas) through the vent hole 40a while being surrounded by the protector 40, and is specified in the measuring gas. Detect the gas concentration.
As will be described later, the gas detection element 22 is mainly made of a solid electrolyte (excluding electrodes and the like), and the protector 40 is made of a metal having a higher thermal conductivity than the gas detection element 22.

Here, the outer diameter of the inner peripheral receiving portion 25 a of the metal shell 25 is slightly larger than the outer diameter of the protruding portion 40 f of the protector 40. Further, the diameter of the inner surface 25i of the metal shell 25 on the distal end side from the inner peripheral receiving portion 25a is larger than the outer diameter of the protector 40 on the distal end side from the protruding portion 40f. And while the rear end side of the protector 40 is accommodated inside the metal shell 25, the front end side surface (tip-facing surface) of the protruding portion 22 b of the gas detection element 21 and the surface (rear end) of the inner peripheral receiving portion 25 a of the metal shell 25. The protector 40 is fixed in a state where the projecting portion 40f is sandwiched between it and the facing surface.
In this way, at least the tip-facing surface of the protrusion 22b and the protrusion 40f are in direct contact with each other, and the heat of the protector 40 is transmitted to the gas detection element 22 to raise the temperature of the gas detection element 22 as described in FIG. . It should be noted that the tip-facing surface of the protrusion 22b and the protrusion 40f may be in direct contact with each other, and depending on the configuration of the gas detection element, there are various types of gaps between the inner periphery receiving portion 25a and the protrusion 40f of the metal shell 25. Packing and heat insulating material may be interposed.
Furthermore, in this embodiment, the space G is opened between the inner surface 25i of the metal shell 25 and the outer surface of the protector 40 along the radial direction, and the heat of the protector 40 escapes to the metal shell 25 as described later. Is suppressed.

Next, other components of the gas sensor 21 will be described.
The ceramic enclosure 23 is made of an insulating ceramic (specifically, alumina) and has a cylindrical shape. This ceramic enclosure 23 is a ceramic formed from talc in such a manner that the thickened tip side portion 23a surrounds the portion of the gas detection element 22 on the rear end side of the protruding portion 22b. Along with the powder 30, it is held so as to be interposed between the gas detection element 22 and the metal shell 25.

  The terminal member 24 is made of, for example, Inconel (trade name of Inconel, UK), and has a cylindrical shape, and includes an output side terminal portion 24a, an element side terminal portion 24b, and a terminal connection portion 24c that couples both. Among these, the output-side terminal portion 24a has a cylindrical shape having a substantially C-shaped cross section perpendicular to the axis O. The output side terminal portion 24a is inserted inside itself by relatively moving an insertion portion 751c (see FIG. 4) of a cap terminal 751 described later in a direction along the axis O (vertical direction in FIGS. 1 and 2). When it does, it is comprised so that it may expand elastically. Further, convex portions 241a protruding radially inward are formed at four positions in the circumferential direction on the rear end side (upward in FIG. 1) of the output side terminal portion 24a.

  Further, in the output side terminal portion 24a, a part of the output side terminal portion 24a is punched out and bent radially inward at three positions in the circumferential direction on the tip side (downward in FIG. 1) from the convex portion 241a. An inner bent portion 242a and an outer bent portion 243a bent outward in the radial direction are formed. Among these, as will be described later, the inner bent portion 242a is elastically radially outward when the insertion portion 751c (see FIG. 4) of the cap terminal 751 is inserted and connected to the inner side of the output side terminal portion 24a. It is bent so that when the insertion portion 751c is inserted to a predetermined position, the bending returns and a click feeling is generated. Further, as shown in FIG. 1, the outer bent portion 243 a comes into contact with the tip surface (step surface) of the step portion 23 b of the ceramic enclosure 23 when the terminal member 24 is assembled to the gas sensor 21, and outputs It plays the role of preventing the side terminal portion 24a (terminal member 24) from coming off.

  On the other hand, among the terminal members 24, the element-side terminal portion 24 b also has a cylindrical shape whose cross section perpendicular to the axis O is substantially C-shaped. As shown in FIG. 1, the element-side terminal portion 24 b is inserted into the gas detection element 22 while being elastically reduced in diameter, and is electrically connected to the inner electrode 29. Therefore, in the gas sensor 21 of the present embodiment, the element side terminal portion 24b is electrically connected while pressing the inner electrode 29 from the inner side toward the outer side in the radial direction.

  Such a terminal member 24 is formed by integral molding by pressing using a single metal plate having a predetermined shape. For this reason, it is easy to form and low cost. Further, in the terminal member 24 of the present embodiment, the metal plate is bent, and the output-side terminal portion 24a and the element-side terminal portion 24b located on the tip side in the axis O direction (downward in FIG. 1) are cylindrically formed. Since it is molded, the reference gas (outside air) taken into the sensor cap 700 can be introduced to the inside (inner electrode 29) of the gas detection element 22.

Such a gas sensor 21 is manufactured as follows. First, as shown in FIG. 1, the protector 40 is inserted into the metal shell 25 from the rear end side of the metal shell 25, and the surface of the inner periphery receiving portion 25 a of the metal shell 25 (the rear end facing surface) is placed on the protector 40. The tip-facing surface of the protrusion 40f is locked. Next, when the gas detection element 22 provided with the outer electrode 28 and the inner electrode 29 is inserted into the protector 40, the side surface of the protrusion 22 b of the gas detection element 21 faces the rear end-facing surface of the protrusion 40 f of the protector 40. (Tip facing surface) abuts.
In this state, a predetermined amount of ceramic powder 30 is filled in the gap portion between the metal shell 25 and the gas detection element 22. Next, the ceramic enclosure 23 is inserted so that the distal end portion 23 a is interposed between the gas detection element 22 and the metal shell 25, and is brought into contact with the ceramic powder 30. Next, the ceramic enclosure 23 is pressurized toward the distal end side, and under the pressurized state, a caulking ring 32 is interposed between the caulking portion 25d of the metal shell 25 and the ceramic enclosure 23, and the caulking portion. Clamp 25d. In this manner, the above-described components are integrally fixed in a state where the protruding portion 40 f of the protector 40 is sandwiched between the metal shell 25 and the gas detection element 22.

Finally, the terminal member 24 is inserted inside the ceramic enclosure 23 and the gas detection element 22. Specifically, the element side terminal portion 24 b of the terminal member 24 is inserted into the gas detection element 22 while being elastically reduced in diameter, and is electrically connected to the inner electrode 29. At the same time, the output side terminal portion 24a is pushed to the tip side, and the stopper portion 244a formed in a petal shape perpendicular to the axis O and radially outward from the rear end of the output side terminal portion 24a is surrounded by a ceramic. The body 23 is brought into contact with the rear end surface. In this way, the output side terminal portion 24 a is arranged inside the ceramic enclosure 23.
The output side terminal portion 24a is pushed in until the stop portion 244a contacts the rear end surface of the ceramic enclosure 23, whereby the outer bent portion 243a bent inward in the radial direction is released and returned, and the ceramic enclosure 23 is returned. Since the front end surface (step surface) of the step portion 23b is engaged, the terminal member 24 can be prevented from coming off. In this way, the gas sensor 100 is completed.

  FIG. 2 is an explanatory view showing a gas sensor unit 600 in which the sensor cap 700 is attached to the gas sensor 21, and a state when the gas sensor unit 600 is used, and is a cross-sectional view along the axis O direction. The gas sensor unit 600 includes a sensor cap 700 disposed on the rear end side (upward in FIG. 1) of the gas sensor 21 in the axis O direction. This gas sensor unit 600 is fastened to an exhaust pipe (attachment object) of a vehicle in a form in which a tip portion of the gas sensor 21 protrudes into the exhaust pipe, and measures the oxygen concentration in the exhaust gas.

Next, heat transfer from the protector 40 to the gas detection element 22 will be described with reference to FIG. As described with reference to FIG. 1, the tip-facing surface of the protrusion 22 b of the gas detection element 22 and the protrusion 40 f of the protector 40 are in direct contact with each other. The protector 40 has a higher thermal conductivity than the gas detection element 22. Therefore, at least a part of the heat of the protector 40 is transmitted to the gas detection element 22 side through the contact portion described above, and contributes to raising the temperature of the gas detection element 22.
In this embodiment, since the protrusion 40f is a flange, the surface of the protrusion 40f facing the rear end is larger than the surface of the protrusion 40f by the thickness of the protector 40. Therefore, even if the projections 22b (the front end facing surface) of the gas detection element 22 and the inner periphery receiving portions 25a (the rear end facing surface) of the metal shell 25 are in contact with the entire surface of the projection 40f, respectively. Since the contact area 22L between the protrusion 40f and the protrusion 22b of the gas detection element 22 is larger than the contact area between the protrusion 40f and the inner periphery receiving portion 25a of the metal shell 25, the heat of the protector 40 is increased by gas. It becomes easy to be transmitted to the detection element 22 side.

Furthermore, in this embodiment, since the space G is opened between the inner surface 25i of the metal shell 25 and the outer surface of the protector 40, the contact area between the actual protrusion 40f and the inner periphery receiving portion 25a of the metal shell 25 25L becomes even smaller, and heat transfer from the protector 40 to the metal shell 25 does not occur in the space G. As a result, the amount of heat H ₁ transferred from the protector 40 to the gas detection element 22 is increased, and the amount of heat H ₂ transferred from the protector 40 to the metal shell 25 is decreased, so that the effect of raising the temperature of the gas detection element 22 is increased. . The space G includes all of the screw portions 25b of the metal shell 25 along the axis O direction. The screw portion 25b is attached to an attachment target body such as an engine head, and the protector 40 is cooled by the attachment target body to become a heat escape portion. However, by providing a space G in the screw portion 25b, heat escape is prevented. And the amount of heat H ₂ can be further reduced.
As described above, since at least a part of the heat of the protector 40 is transmitted to the gas detection element 22, it is possible to shorten the time required for the gas detection element 22 to reach the activation temperature and improve the light-off characteristics.

  Next, the sensor cap 700 will be described with reference to the drawings. FIG. 4 is a partially broken cross-sectional view of the sensor cap 700. The sensor cap 700 includes a cap terminal 751, a covering member 752 that covers and holds the cap terminal 751, a lead wire 753, and a filter member 754.

  The cap terminal 751 (see FIGS. 4 and 5) is made of, for example, stainless steel (SUS310S or the like), and is formed by forming a plate material into a double substantially cylindrical shape by drawing or the like. Further, the cap terminal 751 has a concentric annular plate-like annular portion 751a with respect to the axis O, and a grip that protrudes to one side (downward in FIG. 5A) along the axis O, continuing to the outer peripheral edge of the annular portion 751a. Part 751b, and cylindrical insertion part 751c which continues to the inner periphery of annular part 751a and protrudes on the same side as grip part 751b. The annular portion 751a, the grip portion 751b, and the insertion portion 751c are integrally molded with each other.

Among these, as shown in FIG. 5, the gripping portion 751b is connected to the outer peripheral edge of the annular portion 751a and protrudes in a C-shape, and slits SL1, SL2, SL3, SL4 from the base end portion 751ba. , And a divided gripping portion 751bb that is divided into five by SL5 and extends. The slits SL1, SL2, and SL3 have a shape extending in the direction of the axis O.
Each of the above-described divided gripping portions 751bb is formed with a protruding portion 751bc that protrudes inward. Specifically, the five protrusions 751bc are arranged in the circumferential direction at an angle of 72 degrees from each other.
As will be described later, five protrusions 751bc are brought into contact with the outer peripheral surface 23c (see FIG. 1) of the ceramic enclosure 23 of the gas sensor 21, respectively, and the gripping portion 751b of the cap terminal 751 serves as the rear end portion of the ceramic enclosure 23. Fit in this part so that it surrounds. In this case (see FIG. 2), the five divided grip portions 751bb are elastically bent outward in the radial direction due to the presence of the divided slits SL1, SL2, SL3, SL4, and SL5. Then, the cap terminal 751 elastically holds the ceramic enclosure 23 by this reaction force.

  On the other hand, as described above, the insertion portion 751c has a cylindrical shape with the axis O as the center, and has a rigidity that prevents deformation such as a reduced diameter and an increased diameter. Therefore, as will be described later, when the gas sensor 21 is inserted into the output side terminal portion 24a and brought into contact with the output side terminal portion 24a, the output side terminal portion 24a can be expanded without deforming itself. The insertion portion 751c is a cylindrical portion having a relatively large diameter from the annular portion 751a side, and a conductive portion 751ca that is relatively long in the direction of the axis O, a small diameter portion 751cb that is smaller in diameter than the conductive portion 751ca, and a small diameter portion 751cb. The insertion tip portion 751cc having a larger diameter is provided in this order.

When the holding portion 751b of the cap terminal 751 is fitted into the ceramic enclosure 23 of the gas sensor 21 (see FIG. 2), the insertion portion 751c is inside the ceramic enclosure 23 and the output side terminal portion 24a of the terminal member 24. Inserted inside. At this time, the conducting portion 751ca contacts the convex portion 241a of the output side terminal portion 24a and is electrically connected to the output side terminal portion 24a. Further, an inner side bent portion 242a of the output side terminal portion 24a is located on the outer side in the radial direction of the small diameter portion 751cb, and when the cap terminal 751 is detached from the terminal member 24, the inner side bent portion 242a is inserted. The portion 751cc is engaged so that it cannot be easily removed. Further, when the insertion portion 751c of the cap terminal 751 is completely inserted into the output-side terminal portion 24a of the terminal member 24, the inner bent portion 242a is released from the state in contact with the insertion tip portion 751cc, and a click feeling is generated. .
As shown in FIG. 2, the annular portion 751 a is an output side terminal portion located on the rear end surface of the ceramic enclosure 23 in a state where the insertion portion 751 ca is inserted into the output side terminal portion 24 a of the terminal member 24. By abutting against the stopper 244a of 24a, the insertion portion 751c of the cap terminal 751 is further prevented from being inserted into the distal end side.

The covering member 752 is formed into a hollow shape using an insulating fluorine-based rubber, and constitutes a cap terminal accommodating space SPS that accommodates the cap terminal 751. Then, the surface of the covering member 752 is subjected to texturing. The covering member 752 includes a terminal surrounding portion 752a having an insertion hole 752aa surrounding the cap terminal 751 and the rear end side of the ceramic enclosure 23 at the time of the gas sensor unit 600 (see FIG. 2), and from the rear end side of the terminal surrounding portion 752a. A filter surrounding portion 752b that surrounds the periphery of the filter member 754 that is provided so as to protrude radially and closes the communication hole 752ba, and is provided so as to protrude radially from the rear end side of the terminal surrounding portion 752a. A lead wire surrounding portion 752c surrounding the lead wire 753.
The terminal surrounding portion 752a further has a skirt portion 752ap that extends further toward the distal end and has a diameter larger than that of the periphery. The skirt 752ap is separated from the metal shell 25 while completely surrounding the ceramic enclosure 23 at least. In addition, along the axis O direction, the tip 752x of the skirt 752ap is on the tip side of the rear end 25e of the metal shell 25 and extends to the same position as the rear end 25ce of the flange portion 25c.
Further, as shown in FIG. 4, the inner wall 752w of the skirt 752ap has a plurality of shapes while following the contour of the metal shell 25 toward the distal end side so as to be separated from each part of the outer surface of the metal shell 25 at approximately the same distance. The diameter is expanded stepwise. Corresponding to the expansion of the inner wall 752w of the skirt 752ap, the outer diameter of the skirt 752ap is expanded stepwise from the periphery (the rear end side of the terminal surrounding portion 752a) in order to ensure the thickness of the skirt 752ap. It has a diameter.

  On the other hand, the rear end side (upward in the drawing) of the terminal surrounding portion 752a is located around the grip portion 751b of the cap terminal 751, and the grip portion 751b and the terminal surrounding portion 752a are in contact with each other. On the other hand, on the distal end side (downward in the drawing) of the terminal surrounding portion 752a with respect to the gripping portion 751b, there is a rib 752ab dimensioned to be in close contact with the outer peripheral surface 23c (see FIG. 1) of the ceramic surrounding body 23 of the gas sensor 21. . Two ribs 752ab are provided in the direction of the axis O. The rib 752ab has a rear end side (upward in the drawing) engaged with the tip of the grip portion 751b of the cap terminal 751. The rib 752ab supports the cap terminal 751 in the terminal surrounding portion 752a. doing.

  Next, the filter surrounding portion 752b will be described (see FIG. 4). The filter surrounding portion 752b surrounds the periphery of the filter member 754 disposed so as to close the communication hole 752ba. Specifically, the filter member 754 is made of PTFE having a continuous porous structure in which fine pores are continuous, and includes a cylindrical main body 754a and a smoothing processing unit 754b surrounding the main body 754a in an annular shape. This is a filter member 754.

  Further, an annular projecting portion 752bb projecting inward is provided in the communication hole 752ba of the filter surrounding portion 752b, and the projecting portion 752bb is brought into close contact with the outer peripheral surface of the filter member 754 to hold the filter member 754. .

  Next, the lead wire surrounding portion 752c will be described (see FIG. 4). The lead wire surrounding portion 752c surrounds the lead wire 753 and is disposed on the opposite side of the filter surrounding portion 752b with the cap terminal 751 interposed therebetween. The lead wire surrounding portion 752c has a lead wire communication hole 752ca that allows the lead wire 753 to communicate therewith.

  The lead wire 753 has a coating material in addition to the core wire. The leading end side of the lead wire 753 is inserted into the insertion portion 751c of the cap terminal 751, and is crimped by the crimping portion 755a of the lead wire fixing member 755 inside the connection portion 751c.

The lead wire fixing member 755 has a substantially cylindrical shape, and includes a fitting portion 755c that fits into the inner wall of the insertion portion 751c of the cap terminal 751 in addition to the crimping portion 755a. Note that an output signal from the inner electrode 29 of the gas detection element 22 of the gas sensor 21 is transmitted to an external device (for example, an engine control unit (ECU)) through the lead wire 753 by the crimping portion 755a and the fitting portion 755c. It becomes possible. Further, it further includes a substantially C-shaped covering material fixing portion 755b that is positioned between the crimped portion 755a and the fitting portion 755c and fixes the lead wire (covering material). In addition, a joint portion 755d is formed on the rear end side of the fitting portion 755c so as to protrude radially outward and is joined to the annular portion 751a of the cap terminal 751. The joint portion 755d and the annular portion 751a of the cap terminal 751 are joined by welding or the like.
As a result, as shown in FIG. 4, the lead wire 753 is bent along the axial direction of the insertion portion 751c in the insertion hole 752aa of the terminal surrounding portion 752a and fixed to the cap terminal 751.
The gas sensor unit 600 is configured as described above.

  Next, with reference to FIGS. 6-9, the gas sensor concerning the 2nd-5th embodiment of this invention is demonstrated. 6-9 is sectional drawing which follows the axis line O direction of each gas sensor 21B-21E. In addition, since each gas sensor 21B-21E is the same as the gas sensor 21 concerning 1st Embodiment except the shapes of a protector or a metal shell differing, the same code | symbol is attached | subjected about the same part and description is abbreviate | omitted.

In FIG. 6, the gas sensor 21 </ b> B according to the second embodiment has a double protector 43 instead of the protector 40. The double protector 43 includes an inner protector portion 42 having a small diameter and an outer protector portion 41 having a diameter larger than that of the inner protector portion 42. The inner protector portion 42 is accommodated in the outer protector portion 41, while the inner protector 41 is disposed on the bottom surface of the outer protector portion 41. The bottom surface of the protector part 42 is welded concentrically. Further, the length of the inner protector portion 42 in the axis O direction is shorter than the length of the outer protector portion 41 in the axis O direction, and the rear end of the inner protector portion 42 expands into a flange shape so as to contact the inner surface of the outer protector portion 41. ing.
In the double protector 43, a flange-like protrusion 41 f is formed on the rear end side of the outermost protector portion 41. With such a configuration, heat is transferred from the protector 41 that receives the heat of the exhaust gas most at the outermost side in the double protector 43 to the gas detection element 22 through the protrusion 41f. It is possible to improve the light-off characteristic by shortening the arrival time of. The inner protector portion 42 and the outer protector portion 41 have an inner protector vent hole 42a and an outer protector vent hole 41a, respectively.

In FIG. 7, in the gas sensor 21C according to the third embodiment, a region 25e at the rear end of the inner surface of the metal shell 25 on the front end side from the inner peripheral receiving portion 25a protrudes radially inward from the substantially center in the axis O direction. Then, it comes into contact with the outer surface of the protector 40. For this reason, the space G is opened between the inner surface 25i of the metal shell 25 excluding the region 25e and the outer surface of the protector 40 along the radial direction. On the other hand, since the metal shell 25 and the protector 40 are in contact with each other in the region 25e, the rate at which the heat of the protector 40 escapes to the metal shell 25 is larger than that in the first embodiment.
However, in the case of the third embodiment, since the rear end portion of the protector 40 is held by the region 25e of the metal shell 25, it is difficult for the protector 40 to swing in the axis O direction and the radial direction, and the protector 40 is securely fixed. Can do. Also in the case of the third embodiment, at least a part of the protector 40 (portion facing the inner surface 25i) opens the metal shell 25 and the space G along the radial direction, so that the space G cannot be opened. In comparison, it is difficult for the heat of the protector 40 to escape to the metal shell 25. Further, since the space G overlaps at least a part of the screw portion 25b of the metal shell 25 along the axis O direction (specifically, the tip side of the screw portion 25b), the protector 40 is an attachment target body that becomes a heat escape portion. Can be prevented from being cooled.
In the case of the third embodiment, the inner diameter of the inner peripheral receiving portion 25a is almost the same as the outer diameter of the protector 40 except for the protruding portion 40f. However, as already described with reference to FIG. Therefore, the surface of the protruding portion 40f facing the rear end is larger in surface area than the surface facing the front end. Therefore, even if the protrusions 22b (the front end facing surface) of the gas detection element 22 and the inner periphery receiving portions 25a (the rear end facing surface) of the metal shell 25 are in contact with the respective surfaces of the protrusion 40f, the protrusions 22f protrude. Since the contact area 22L between the portion 40f and the protrusion 22b of the gas detection element 22 is larger than the contact area between the protrusion 40f and the inner peripheral receiving portion 25a of the metal shell 25, the heat of the protector 40 is increased. It becomes easy to be transmitted to the 22 side.

In FIG. 8, in the gas sensor 21D according to the fourth embodiment, in the inner surface of the metal shell 25 on the front end side from the inner periphery receiving portion 25a, the tip region 25f protrudes radially inward from the substantially center in the axis O direction. It comes in contact with the outer surface of the protector 40. For this reason, the space G is opened between the inner surface 25i of the metal shell 25 excluding the region 25f and the outer surface of the protector 40 along the radial direction. On the other hand, since the metal shell 25 and the protector 40 are in contact with each other in the region 25f, the rate at which the heat of the protector 40 escapes to the metal shell 25 is larger than that in the first embodiment.
However, in the case of the fourth embodiment, the protector 40 is held by the metal shell 25 at the two preceding and following locations (specifically, the rear end portion of the protector 40 is held by the inner peripheral receiving portion 25a, and the tip portion is the region 25f). Therefore, the protector 40 is less likely to swing in the direction of the axis O and the radial direction, and the protector 40 can be more reliably fixed. Also in the case of the fourth embodiment, at least a part of the protector 40 (the part facing the inner surface 25i) opens the metal shell 25 and the space G along the radial direction. In comparison, it is difficult for the heat of the protector 40 to escape to the metal shell 25. Furthermore, since the space G overlaps at least a part of the threaded portion 25b of the metal shell 25 along the axis O direction (specifically, the portion excluding the tip side of the threaded portion 25b), the object to be attached that becomes a heat escape portion. Thus, the protector 40 can be prevented from being cooled.

In FIG. 9, the gas sensor 21 </ b> E according to the fifth embodiment is provided with a plurality of protrusions 40 p that protrude outward on the outer surface of the protector 40. The protrusion 40p is substantially in point contact or line contact with the inner surface 25i of the metal shell 25, and a space G is opened between the metal shell 25 and the outer surface of the protector 40 at a portion where the protrusion 40p is not in contact.
When the protrusion 40p is provided on the outer surface of the protector 40, the protector 40 is held by the metal shell 25 at at least two locations of the inner periphery receiving portion 25a and the protrusion 40p, so that the protector 40 is difficult to swing in the axis O direction and the radial direction. 40 can be more reliably fixed. Further, by making the protrusion 40p substantially point-contact or line-contact with the metal shell 25, the heat of the protector 40 can be increased compared to the third and fourth embodiments in which the metal shell 25 and the protector 40 are in surface contact in the regions 25e and 25f. It becomes difficult to escape to the metal shell 25.
If the protrusion 40p is hemispherical, it can be brought into substantially point contact with the metal shell 25, and if the protrusion 40p is made into a bowl shape continuous in the circumferential direction, it can be brought into substantially line contact with the metal shell 25. Further, if a plurality of protrusions 40p are formed along the axis O direction, the protector 40 is held by the metal shell 25 at a plurality of locations along the axis O direction, and the protector 40 can be more reliably fixed.

Needless to say, the present invention is not limited to the above embodiments, and various modifications are possible. For example, the tip-facing surface of the element side receiving part of the gas detection element and the protruding part of the protector are not in direct contact with each other, but through both other members (packing or the like) made of metal having higher thermal conductivity than the gas detection element. You may touch. In this case, heat transfer is inferior compared to the case where the gas detection element and the protector are in direct contact with each other. However, when the two are assembled, even if the protector is not easily deformed, it is adapted to the element side receiving portion by other members. As a result, assembly is easy and reliable. However, the thermal conductivity of the other member is made higher than that of the gas detection element so that heat transfer from the protector to the gas detection element is not hindered. When using other members, the outer electrode is grounded through the other members.
Examples of the other member include a packing (gasket) made of copper or a copper alloy.

The gas sensor 21 is not limited to an oxygen sensor or a heaterless type. However, in the heaterless type that does not have a heater for heating the gas detection element, the gas detection element can be raised to the activation temperature only by receiving heat from the exhaust gas. Therefore, the present invention is particularly effective.
Further, the protector is not limited to the bottomed shape, and the flange at the rear end of the protector is not tapered and may extend vertically in the axial direction. Furthermore, the protruding portion of the protector is not limited to the flange, but protrudes from the outer surface of the protector slightly at the front end side of the protector rear end edge (for example, like a single protrusion in FIG. It may be a shape protruding in a shape. Further, the protruding portion of the protector is not limited to the one that terminates at the flange, but extends in a cylindrical shape from the flange portion to the rear end, and the cylindrical portion is in contact with the outer periphery of the element side receiving portion to increase the contact area with the gas detection element. You may comprise as follows. Moreover, the front end of the gas detection element 22 may be disposed on the rear end side of the front end of the metal shell 25 (the front end of the gas detection element 22 may not protrude from the front end of the metal shell 25).

In addition, when the metal shell is made of an iron-based member, it is particularly effective to apply the present invention, because it is easy to draw heat (good heat conductivity), and heat is transmitted to the metal shell and the gas detection element is easily cooled. is there. The “iron-based member” is, for example, low carbon steel.
In addition, if the protector is made of stainless steel, the heat conductivity is inferior, so heat is easily trapped in the protector and it is difficult for heat to be transferred to the metal shell, so the heat received by the protector from the gas to be measured is more effective for the gas detection element. It is possible to raise the temperature of the gas detection element.

The distance the length L ₁ of the mounting portion 25b (see FIG. 1) along the axial direction, from the tip of the gas detection element 22, to the tip of the contact area of the protrusion 40f of the element-side receiving portion 22b and the protector L _When the ratio is 1/2 or more of _2, the present invention is particularly effective.
As the length L ₁ of the mounting portion 25b is long, can be attached firmly to the gas sensor 21 to a mounting object such as an engine head, the mounting portion 25b heat is transmitted to the mounting object member from cold gas detection element This is because it becomes easier.
In the case mounting portion 25b is threaded, the length including the incomplete thread portion and L _1.

21, 21B-21E Gas sensor 22 Gas detection element 22b Eaves part (element side receiving part)
22L Contact area between the tip-facing surface of the element side receiving portion and the protruding portion 25 Metal shell 25a Inner circumference receiving portion (metal shell side receiving portion)
25b Metal fitting attachment part 25L Contact area between the rear end facing surface of the metal fitting side receiving part and the protruding part 40, 43 Protector 40f, 41f Protector protruding part 41, 42 Multiple protector parts G Space between protector and metal fitting O Axis direction L Length of the mounting part along the ₁ axis direction L ₂ Distance from the tip of the gas detection element to the tip of the contact area between the element side receiving part and the protrusion of the protector

Claims (10)

A cylindrical gas detection element having an element side receiving portion that extends in the axial direction and is exposed to a gas to be measured and has a tip portion that protrudes radially outward.
A cylindrical metal shell that surrounds the gas detection element and has a metal shell side receiving portion that protrudes radially inward,
A cylindrical protector surrounding the front end portion of the gas detection element by projecting the front end side of the metal shell while accommodating the rear end side of the metal shell inside the metal shell,
The protector has higher thermal conductivity than the gas detection element,
The rear end side of the protector is formed with a protrusion that expands radially outward,
The protector is fixed in a state where the protrusion is sandwiched between the rear end facing surface of the metal shell side receiving portion and the front end facing surface of the element side receiving portion, and at least the front end of the element side receiving portion The surface and the protrusion are in direct contact with each other, or through another member made of a metal having a higher thermal conductivity than the gas detection element ,
The gas sensor which provided the space in at least one part between the said protector and the said main metal fittings . The gas sensor according to claim 1 , wherein the protector is exposed to the outside . The gas sensor according to claim 1, wherein an outer electrode exposed to the gas to be measured is formed on an outer surface of the gas detection element, and the outer electrode is electrically grounded to the metal shell. The gas sensor according to claim 1 or 2, wherein the protector includes a plurality of protector portions having different diameters in a radial direction, and the protruding portion is formed on an outermost protector portion among them . On the outer surface of the metal shell, an attachment portion for attaching the gas sensor to an attachment object is provided,
The gas sensor according to claim 4, wherein at least a part of the space overlaps with the attachment portion along the axial direction.   The contact area between the tip-facing surface of the element side receiving portion and the protruding portion, or the contact area between the other member and the protruding portion is the contact between the rear end facing surface of the metal shell-side receiving portion and the protruding portion. The gas sensor according to any one of claims 1 to 5, which is larger than an area.   The gas sensor according to claim 1, wherein the gas sensor does not have a heater for heating the gas detection element.   The gas sensor according to claim 1, wherein the metallic shell is made of an iron-based member.   The gas sensor according to claim 1, wherein the protector is made of stainless steel.   The length of the attachment portion along the axial direction is ½ or more of the distance from the tip of the gas detection element to the tip of the contact area between the element side receiving portion and the protrusion. The gas sensor in any one of.

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