JP2002202279A - Manufacturing method for gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a gas sensor capable of reducing a manufacturing cost by simplifying a working process and a working installation therefor. SOLUTION: In manufacturing an oxygen sensor 1, a rear end part of a principal fitting 7 is caulked by a two-spindle type press P with a filler member 5 pressurized. This eliminates the problem of buckling the once compressed filler member 5. As a result, heat caulking so far performed for buckling correction is not required and the omission of the heat caulking dispenses with a power supply, a cooling device, or the like, needed therefor. Resultantly, the whole of a manufacturing device can be simply constructed and the manufacturing cost for the oxygen sensor 1 can be reduced as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a gas sensor which is attached to a pipe forming a flow path through which a gas to be measured such as exhaust gas flows and detects a component of the gas to be measured.

[0002]

2. Description of the Related Art Conventionally, as a gas sensor for detecting the concentration of a specific gas component from a mixed gas, an HC sensor or N
Various types such as an Ox sensor are known. As shown in, for example, JP-A-10-054821 and JP-A-10-01082, a gas sensor of this type includes an axial detection element in a cylindrical metal shell (housing) fixed to an exhaust pipe. Is inserted and held, and one end thereof is exposed to the gas to be measured. Then, in order to stably hold the detection element by the metal shell and to prevent the exhaust gas from leaking into the gas sensor, the detection elements are sequentially arranged from below in a manner surrounding the detection element in a cylinder of the metal shell. Are laminated, a talc powder, a pressing member for applying a pressing force to the talc powder, and the like. The detection element is firmly fixed in the metal shell by pressing the talc powder between the metal shell and the detection element by pressing the pressing member.

[0003] In the production of such a gas sensor, in order to fill the talc powder under pressure, a supporting device, a detection element, a talc powder, and a pressing member are inserted into a cylinder of a metal shell by a pressing device. A caulking step of caulking by pressing the end of the metal shell from the outside in the axial direction is performed. This caulking step is performed in stages, and first, a temporary caulking in which the end of the metal shell is pressed down while being drawn down while being cold.
And, only the temporary caulking cannot prevent the subsequent buckling of the talc powder (the once compressed one tries to return to its original state due to its elasticity), so that it is further provided near the end of the metal shell. Heat crimping is performed in which the end portion is pressed in the axial direction while the thin portion is electrically heated.
As a result, the thin portion buckles, and the talc powder is held in a compressed state.

[0004]

However, when such a manufacturing method is employed, it is necessary to use a large-scale apparatus having a power supply for cooling and a cooling device as a device for the caulking process. In addition, since it is necessary to use an expensive crimping die or the like having excellent heat resistance and conductivity, there is a problem that the manufacturing cost is increased.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a gas sensor capable of reducing manufacturing costs by simplifying processing steps and processing equipment.

[0006]

Means for Solving the Problems and Effects of the Invention In view of the above problems, in the method of manufacturing a gas sensor according to the first aspect, in the first step, an axial detection element is provided inside a cylindrical metal shell. Insert coaxially from the tip side. An inwardly protruding step is provided around the inner periphery on the distal end side of the metal shell,
On the other hand, since a support is formed on the outer periphery of the detection element, the support engages with the step at this time,
The detection element is supported by the metal shell.

In the subsequent second step, a filling member is disposed between the inner peripheral surface of the metal shell and the outer peripheral surface of the detection element at a position behind the support portion, and a cylindrical member is provided at a position behind the filling member. The pressing member is coaxially inserted. Up to this point, it is the same as the prior art, but in the subsequent third step, the inner side of the rear end of the pressing member is pressed to the front side in the axial direction to compress the filling member in the axial direction. While the compressed state of the filling member in the three steps is maintained, the peripheral edge of the rear end of the metal shell is pressed from the outside. At this time, the rear end peripheral portion of the metal shell is bent toward the rear end outer side of the pressing member to lock the rear end side of the pressing member.

That is, in the present manufacturing method, the fourth state is maintained while the pressurized state of the filling member in the third step is maintained.
Since the so-called crimping process is performed in the process,
No buckling of the compressed member once compressed occurs between the step and the fourth step. For this reason, there is no need to perform the conventional heat caulking for correcting the buckling, and the manufacturing process is simplified. In addition, since the heat crimping step can be omitted as described above, a power supply, a cooling device, and the like required for this step are not required, and the entire manufacturing facility can be simply configured. As a result, manufacturing costs can be reduced.

Since the purpose of the third step and the fourth step are different, it is not necessary to carry out the steps at the same time. After the completion of the third step, the process proceeds to the fourth step while maintaining its compressed state. Is also good. However, from the viewpoint of manufacturing efficiency, it is preferable to perform the third step and the fourth step simultaneously in parallel, as the manufacturing time can be reduced.

As a device for executing the third step and the fourth step, for example, a press device for controlling the operation of two coaxially mounted cylindrical pressing portions is used. Then, it is conceivable that the third step is executed by controlling those arranged inside, and the fourth step is executed by controlling those arranged outside. This is because the third step and the fourth step can be efficiently performed by using such a press device.

In this case, it is necessary to perform the crimping step by compressing the pressing member while pressing the pressing member inside, and further applying a pressing force from the outside. For this reason, it is necessary to increase the area of the pressing portion on the rear end side of the pressing member to some extent.
On the other hand, since the pressing member is inserted into the metal shell from the distal end side, the cross-sectional size of the insertion portion needs to be formed to some extent small.

Therefore, as described in claim 4, it is preferable that the pressing member is formed by providing an outwardly projecting flange around the outer periphery of the rear end of the cylindrical main body. With this configuration, the pressing area can be sufficiently increased while the main body of the pressing member is held at a size suitable for insertion into the metal shell. In this case, if a high load is applied only to the flange portion, the flange portion may be broken. Therefore, in the third step, the pressing member is pressed at a position at least partially including the main body, and In the four steps, the rear peripheral edge of the metal shell is pressed toward the flange of the pressing member.

However, in this case, when the rear end peripheral portion of the metal shell is bent in the fourth step, the peripheral end of the rear end peripheral portion is disposed inside the two cylindrical pressing portions. If it comes into contact with the outer peripheral surface, not only a sufficient pressing force cannot be applied in this step, but also it becomes difficult to later pull out the inner cylindrical pressing portion.

Therefore, to avoid such a situation,
As described in claim 5, it is preferable that the flange portion is formed in a predetermined size. In addition, when these shapes are different, for example, when the pressing member has a cylindrical shape and the cross-sectional shape of the detecting element is a square shape, a large clearance is generated between the pressing member and the detecting element, There is a concern that the forming material of the filling member flows into the clearance in the three steps. In such a case, a sufficient pressing force is not applied to the filling member, and it is difficult to stably fix the detection element to the metal shell. Also, in this case, if the flow of the filling member is uneven, a force in an eccentric direction is applied to the detection element itself, and in some cases, the detection element may be broken.

Therefore, as described in claim 6, a packing having a hole having a shape substantially equal to the cross-sectional shape of the detection element and covering almost the entire rear end face of the filling member is formed in advance, and this is formed in the second step. Before the third step, it may be inserted into the rear side of the filling member. According to this configuration, even if the shapes of the pressing member and the detecting element are different, the pressing force from the pressing member in the third step is sufficiently applied to the filling member via the packing, so that the above-described problem occurs. Does not occur.

The above-mentioned filling member may be supplied after, for example, talc powder or the like is solidified in a ring shape or may be supplied as it is.

[0017]

Preferred embodiments of the present invention will be described below with reference to the drawings. In this embodiment, the gas sensor is configured as an oxygen sensor, and FIG. 1 is a cross-sectional view illustrating the overall configuration of the oxygen sensor.

As shown in FIG. 1, the oxygen sensor 1 comprises a shaft-shaped detecting element 2 having a rectangular cross section, a casing 3 for accommodating the detecting element 2, and the like. The detection element 2 is formed by laminating a plurality of oxygen concentration cell elements formed in a long plate shape and a plurality of heaters for activating the oxygen concentration cell elements (not shown). A cylindrical support member 4 made of ceramic for locking and fixing itself in the casing 3 is inserted and adhered to the outer periphery near the center in the axial direction to constitute a support portion. A detection unit 2a that is exposed to the gas to be measured and detects a gas component to be measured is provided at the tip side (lower side in the figure) of the detection element 2.
A plurality of (four in the present embodiment) L-shaped metal terminals 11 are provided on the rear end side of the holding member in order to take out the electromotive force of the oxygen concentration cell generated by the detection unit 2a from the outside. 1
Attached via 2.

The casing 3 fixes the oxygen sensor 1 to a mounting portion such as an exhaust pipe, and has a detection element 2 on which the support member 4 is mounted, a filling member 5 made of talc powder, and a metal made of pressing the filling member 5. Is housed inside. The casing 3 is provided with a metal shell 7 for projecting the detection portion 2a of the detection element 2 into an exhaust pipe or the like, and extends above the metal shell 7 to form a predetermined internal space with the detection element 2. And an outer cylinder 8.

The metal shell 7 has an inwardly projecting step 7a on the inner periphery on the distal end side of the cylindrical main body, and by locking the support member 4 to the step 7a, the detecting element 2 can be moved from below. I support it. Further, a filling member 5 is disposed between the inner peripheral surface of the metal shell 7 and the outer peripheral surface of the detection element 2 on the rear side (upper side in the figure) of the support member 4. A cylindrical pressing member 6 is coaxially inserted through a ring-shaped metal packing 15.

A circular upper opening is formed at the upper end (rear end) of the metal shell 7 by the leading edge of a flange portion 7b extending inward. Are locked from above. Then, the lower end opening end of the outer cylinder 8 is covered with the metallic shell 7 so as to cover the upper opening.
The outer cylinder 8 is attached to the metal shell 7 by externally crimping the lower end opening end from outside.

A cylindrical sealing member 13 made of rubber is provided at an upper opening of the outer cylinder 8, and an insulating separator 14 formed in a cylindrical shape of ceramic is mounted at a lower end thereof. I have. The central position of the seal member 13 in the axial direction is caulked in the radial direction via the outer cylinder 8, so that the sealing property between the outer cylinder 8 and the seal member 13 is maintained.

The seal member 13 and the separator 14 have lead wires 20 connected to the electrodes of the detection element 2 respectively.
A through hole for inserting a pair of lead wires (not shown) connected to the heater 21 and the heater is formed, and each of the lead wires is connected and fixed to each of the metal terminals 11 in the separator 14. I have.

On the outer periphery of the distal end side (lower side in the figure) of the metal shell 7, metal double protectors 31, 32 having a plurality of holes and covering a plurality of holes are formed by welding or the like. Installed. Next, a method for manufacturing the oxygen sensor 1 configured as described above will be described with reference to FIGS. Note that this manufacturing method is the same as the conventional method except for the step of fixing and holding the detection element 2 in the metal shell 7, so that only the relevant step will be described and other steps will be omitted.

In this step, first, as shown in FIG. 2A, the detection element 2 on which the support member 4 is mounted is coaxially inserted into the inside of the metal shell 7 from the front end thereof (first step). ). At this time, since the support member 4 is locked to the step 7a, the detection element 2 is eventually supported by the metal shell 7.

Then, from this state, the filling member 5 is disposed between the inner peripheral surface of the metal shell 7 and the outer peripheral surface of the detection element 2 behind the support member 4 (second step). The filling member 5 is formed by compressing talc powder in advance to form a cylindrical solid having a predetermined density, and as shown in FIG. The portion 5 a is formed in a rectangular shape substantially equal to the cross-sectional shape of the detection element 2, and has an outer diameter substantially equal to the inner diameter of the metal shell 7.

Then, after the packing 15 is inserted into the rear side of the filling member 5, the pressing member 6 is inserted (second step). The packing 15 is formed in a ring shape having a predetermined thickness, and as shown in a BB section of FIG.
5a, the outer diameter of which is substantially equal to the inner diameter of the metal shell 7, and is disposed so as to cover substantially the entire rear end face of the filling member 5 from behind.

On the other hand, in this embodiment, the pressing member 6 is formed in a cylindrical shape from the viewpoint of cost. This is because when manufacturing the pressing member 6 by molding a metal material, it is necessary to form an axial hole in the center of a columnar member having a certain height, and to secure the accuracy of the hole to some extent. This is because machining of the hole into a square shape requires advanced technology and increases the cost.

Therefore, as shown in FIG. 5 along the line CC in FIG. 2A, the pressing cross section is smaller than the cross section of the packing 15, and the inner peripheral surface of the pressing member 6 and the outer peripheral surface of the detecting element 2 are formed. A large clearance CL is formed between the surface and the surface. Therefore, in this case, in the pressing step described later, the pressing member 6
Of the filling member 5 when a pressing force is applied to the filling member 5 from
Although there is a concern about the problem of leakage (material flow) to the pressing member 6 side, between the filling member 5 and the pressing member 6 as described above, almost the entire rear end face of the filling member 5 is covered. Since the packing 15 is interposed, there is almost no worry. That is, although the shape of the pressing member 6 and the shape of the detection element 2 do not match, the pressing force from the pressing member 6 is sufficiently applied to the filling member 5 via the packing 15.

Then, the process shifts from this state to a step of pressing the pressing member 6 and the metal shell 7 by the pressing device P. This press device P has two cylindrical pressing portions P installed coaxially.
1 and P2, which can be independently controlled in operation. 2 (a) and 2 (b).
As shown in the figure, in the pressing step, the inner cylindrical pressing portion P
By controlling the operation of the pressing member 6 downward in the axial direction, the pressing member 6 is controlled.
The inner portion of the rear end is pressed forward in the axial direction to compress the filling member 5 in the axial direction (third step), and the outer cylindrical pressing portion P
By controlling the movement of the metal member 2 in the axial direction, the rear end peripheral portion of the metal shell 7 is pressed from the outside and bent toward the rear end outer side of the pressing member 6 (fourth step). The flange 7b described above is formed by the peripheral edge of the metal shell 7 thus bent, and the rear end of the pressing member 6 is locked by the flange 7b.

In this case, the rear end peripheral portion of the metal shell 7 is swaged by the pressing by the cylindrical pressing portion P2, and as a result, the rear end peripheral portion extends inward to form the flange portion 7b. That is, since the outer diameter D1 of the flange portion 6b of the pressing member 6 is sufficiently larger than the outer diameter D2 of the main body portion 6a, the edge of the flange portion 7b has a cylindrical pressing portion P.
2 does not contact the outer peripheral surface.

The filling member 5 subjected to the compressive force in this manner
The material flows into and fills a space surrounded by the detection element 2, the metal shell 7, the support member 4, and the packing 15.
Then, the detecting element 2 and the metal shell 7 are firmly fixed by the elastic force of the filling member 5.

As described above, in the manufacture of the oxygen sensor 1 according to the present embodiment, the rear end of the metal shell 7 is caulked while the pressurized state of the filling member 5 is maintained. The problem of buckling of the filled filling member 5 does not occur. For this reason, there is no need to perform the conventional heat caulking for correcting the buckling, and the manufacturing process is simplified. Further, since the heat crimping step can be omitted, a power supply, a cooling device, and the like required for this step are not required, and the entire manufacturing apparatus can be simply configured. As a result,
As a whole, the manufacturing cost of the oxygen sensor 1 can be reduced.

The embodiments of the present invention have been described above. However, the embodiments of the present invention are not limited to the above-described embodiments, and may take various forms within the technical scope of the present invention. Needless to say. For example, in the above embodiment, in the pressing step, the inner cylindrical pressing portion P
1, the compression of the filling member 5 by the outer cylindrical pressing portion P2 and the caulking of the peripheral edge of the rear end of the metal shell 7 by the outer cylindrical pressing portion P2. Alternatively, the pressing device P may be controlled so that the rear peripheral edge of the metal shell 7 is caulked by the cylindrical pressing portion P2.

In the above embodiment, the pressing member 6 has a cylindrical shape. However, when there is no problem in processing cost, the cross-sectional shape of the hole is substantially equal to the cross-sectional shape of the detecting element 2. A square shape may be used.
Then, the packing 15 is not required, and the number of parts can be reduced. In addition, the step of inserting the packing 15 is not required, and the manufacturing cost can be further reduced.

Further, in the above embodiment, the method for manufacturing a gas sensor according to the present invention is described by using the detection element 2 having a square cross section.
Although an example in which the present invention is applied to the oxygen sensor 1 is shown, it is also possible to apply the present invention to an oxygen sensor 201 in which a hollow shaft-shaped detection element 202 having a circular cross section is used as shown in FIG. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of an oxygen sensor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a main part of a manufacturing process of the oxygen sensor according to the embodiment.

FIG. 3 is an explanatory diagram showing an AA cross section in FIG.

FIG. 4 is an explanatory diagram showing a BB cross section of FIG.

FIG. 5 is an explanatory diagram showing a CC section of FIG. 2A.

FIG. 6 is a cross-sectional view illustrating an overall configuration of an oxygen sensor according to a modification.

[Explanation of symbols]

1 ... oxygen sensor, 2 ... detection element, 3 ...
Casing, 4 ... support member, 5 ... filling member,
6 pressing member, 7 metal shell, 8 outer cylinder, 15 packing, P press machine, P
1 ... cylindrical pressing part, P2 ... cylindrical pressing part

Claims (6)

[Claims] 1. A shaft-like detection element having a support portion formed on the outer periphery inside a cylindrical metal shell having a stepped portion protruding inwardly on the inner periphery on the distal end side, coaxially from the distal end side. A first step of interpolating in a shape and holding the supporting portion by engaging with the step portion; and, after the first step, detecting the inner peripheral surface of the metal shell at the rear side of the supporting portion and the detection. A second step of disposing a filling member between the outer peripheral surface of the element and inserting a cylindrical pressing member coaxially behind the filling member; and after the second step, the pressing member A third step of compressing the filling member in the axial direction by pressing the rear end inner portion toward the front side in the axial direction, and a rear end peripheral portion of the metallic shell while maintaining the compressed state in the third step. A fourth step of pressing the pressing member from the outside and bending the pressing member toward the outside of the rear end thereof to lock the rear end of the pressing member. Method for producing a gas sensor, characterized in that the. 2. The method according to claim 1, wherein the third step and the fourth step are performed simultaneously in parallel. 3. The third step is performed by using a press device that controls the operation of two cylindrical pressing portions installed coaxially, and controlling one of the cylindrical pressing portions that is arranged inside. 3. The method according to claim 1, wherein the fourth step is performed by executing and controlling an element arranged outside. 4. 4. The pressing member is formed by providing an outwardly protruding flange on the outer periphery of a rear end portion of a cylindrical main body, and in the third step, the pressing member is provided at least by the main body. Pressing at a partly included position, In the fourth step, a rear end peripheral portion of the metal shell,
The method for manufacturing a gas sensor according to claim 3, wherein pressing is performed toward a flange portion of the pressing member. 5. The method according to claim 5, wherein when the rear peripheral edge of the metal shell is bent in the fourth step, the peripheral edge of the rear peripheral edge is an inner side of the two cylindrical pressing portions. 5. The method for manufacturing a gas sensor according to claim 4, wherein the gas sensor is formed to have a predetermined size so as not to contact an outer peripheral surface of the gas sensor. 6. Between the second step and the third step,
On the rear side of the filling member, a hole having a shape substantially equal to the cross-sectional shape of the detection element, and a step of inserting a packing that covers substantially the entire rear end surface of the filling member, The compressive force from the pressing member,
The method for manufacturing a gas sensor according to any one of claims 1 to 5, wherein the gas is applied to the filling member via the packing.