JPH0479539B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas detector for detecting gas components or their concentrations.

[Prior Art] Conventionally, oxide semiconductors such as SnO ₂ , ZnO, TiO ₂ , CoO, etc. are used as gas detection elements as gas detectors for detecting the presence or concentration of gases in the atmosphere. Gas is detected using the characteristic that the electrical resistance changes when gas comes into contact with it. In recent years, in order to simplify the structure and improve productivity of this type of gas detector, hybrid technology has been developed, in which the gas detection element and its electrodes are thick-film printed on a substrate made of insulating ceramic material. Things that apply this technology are being developed.

[Problems to be Solved by the Invention] Conventionally, gas detectors have been housed in a housing for gripping the detector so that it can be fixed at the location where the gas is to be detected. The gas detection element as described above has a simple structure, can be manufactured in a small size, and has good productivity, but when the element is configured as a detector,
On the other hand, its small size made it difficult to assemble.

One example of this is the part where a thin electrode wire provided on the gas detection element is connected to an external lead wire for extracting a signal to the outside. The one that uses swaged terminals has the best workability, but it requires a wide space between the electrode wires for work, and it is difficult to secure enough space for gas detectors that have multiple electrode wires, making it difficult to downsize. It becomes impossible. On the other hand,
Welding is less reliable for external lead wires made of stranded wires because it is not possible to weld all the thin wires even if the external lead wires are welded as they are.

Therefore, an object of the present invention is to provide a detector that can be reliably connected even to a detector with a narrow electrode spacing.

[Means for Solving the Problems] That is, the gas component detector of the present invention includes a ceramic carrier that holds a gas detection element whose electrical resistance value changes depending on the gas component, and a ceramic sheet, one end of which is laminated and crimped in advance. Welding the other end of the electrode wire and one end of the electrode terminal at a narrow interval using an electrode wire, an electrode terminal, and a connection terminal to which an external lead wire made of a twisted wire is crimped and fixed in advance, The vicinity of the joint between the ceramic carrier and the electrode wire is covered with a glass seal, and the connecting terminal and the electrode wire are welded together at an interval wider than the welding interval between the other end of the electrode wire and one end of the electrode terminal. An outer cylinder whose one end is sealed with a sealing material is attached to the main metal fitting holding the ceramic carrier, and the electrode wire, the electrode terminal, the connection terminal, and the external lead are welded to the electrode terminal. A portion of the wire is housed therein, and the lead wire is drawn out from the sealing material.

[Function] In the gas component detector of the present invention, first, one end of an electrode wire is laminated and crimped between a ceramic carrier holding a gas detection element whose electrical resistance value changes depending on the gas component and a ceramic sheet. I'll keep it.
The other end of the electrode wire and one end of the electrode terminal are welded at a narrow interval. Welding of the electrode wire and the electrode terminal can be easily performed even in a narrow space, and a complete connection can be achieved.

Next, the vicinity of the joint between the ceramic carrier and the electrode wire is covered with a glass seal. This glass seal prevents leakage of the gas to be detected, and protects weak parts such as the joint between the ceramic carrier and the electrode wire, the electrode wire, and the connection between the electrode wire and the electrode terminal. As a result, durability is improved because external forces (vibrations) such as tension after connecting the lead wires are not applied directly to the electrode wires. In addition, unlike sealing materials made of elastomer materials or pasty silicone rubber, glass seals are less susceptible to thermal history due to repeated heating and have good sealing properties against water, etc. It can successfully protect against harsh conditions such as exposure to cold and water. Furthermore, the glass seal can fix the ceramic carrier, electrode wire, and electrode terminal in advance, making it easier to weld the connection terminal connected to the external lead wire and the electrode terminal in the subsequent process, improving work efficiency. It can be improved significantly and reliably.

Separately, an external lead wire made of twisted wire is crimped and fixed to the connection terminal in advance. Since crimping and fixing can be performed in advance in a wide space, there is no problem in downsizing. Furthermore, it is efficient because the wires can be crimped one by one, and all the thin wires can be connected without causing the twisted wires to come apart. Therefore, the generation of whiskers due to the looseness of thin wires is eliminated, and short circuits with adjacent lead wires and the occurrence of whiskers penetrating the sealing material (rubber, etc.), which impairs the sealing performance, are eliminated. Further, since the external lead wire is processed as a single item without being bonded to the ceramic carrier, there is an advantage that the caulking work can be performed efficiently.

Then, this connection terminal and the other end of the electrode terminal are welded at a wider interval than the interval at which the other end of the electrode and one end of the electrode terminal are welded together. By this welding, the electrode wire and the external lead wire are completely connected via the electrode terminal and the connection terminal. This welding is not a welding between a thin wire and a flat plate, but a welding between two solid bodies having approximately the same capacity as one plate, so it is highly reliable and the occurrence of defects can be extremely reduced. Furthermore, the current during welding can be appropriately set, sputtering, etc. will not occur, and the life of the electrode rod will be extended. In addition, this welding is performed at a wider interval due to the welded distance between the other end of the electrode wire and one end of the electrode terminal, but compared to the caulking method, the jig and tools can be made smaller, so the electrode wire pitch is narrower. The work can be performed easily and reliably, and a plurality of electrode wires can be arranged in a narrow space, so that an extremely small gas component detector can be manufactured.

Further, an outer cylinder whose one end is sealed with a sealant is attached to the metal shell that holds the ceramic carrier. Here, the electrode wire is inserted into the outer cylinder (and sealing material).
The electrode terminal, connection terminal, and part of the external lead wire are housed and protected. Further, the lead wire is drawn out from the sealing material and can be connected to an external electronic circuit, power source, etc.

[Example] Hereinafter, a case where the terminal structure of the present invention is applied to an oxygen sensor will be described as an example.

FIG. 1 is a partially sectional side view of an example oxygen sensor. In the figure, 10 is a ceramic carrier provided with a gas detection element 11 on a ceramic substrate, 12
13 is a metal shell formed in a cylindrical shape for gripping the ceramic carrier 10 and attaching the sensor to an internal combustion engine; 13 is attached to the end 12a of the metal shell 12 on the internal combustion engine side;
14 is an inner cylinder for holding the ceramic carrier 10 together with the metal shell 12. It is held by the inner cylinder 14. Further, a threaded portion 12b for attaching an internal combustion engine is provided on the outer periphery of the metal shell 12, and a gasket 18 is provided at a portion where the internal combustion engine comes into contact with the wall surface to prevent exhaust gas from leaking.

Here, the filling powder 16 is made of talc and glass.
1, for fixing the ceramic carrier 10 in the inner cylinder 14, and a glass seal 1.
Reference numeral 7 is made of low melting point glass, which prevents leakage of the gas to be detected and also serves as an electrode terminal 31 to 33, which will be described later.
The inner cylinder 14 is filled to cover a part of the ceramic carrier 10 and the connecting portion between the electrode wire made of a platinum wire and the electrode terminal, which will be described later.

19 is an outer cylinder attached to the metal shell 12 so as to cover the inner cylinder 14; 20 is a sealing material made of silicone rubber; Electrode terminals 31 to 33 protruding from the seal 17
This is to protect the connection between the

Further, as shown in FIG. 3, the sealing material 20 and the external lead wires 21 to 23 are placed in the outer cylinder 19 in advance, and metal connection terminals 24 to 26 are added to the tips of the external lead wires 21 and 23 in advance. Connections between the external lead wires 21 to 23 and the electrode terminals 31 to 33 are made by tightening and then welding the connection terminals 24 to 26 to the electrode terminals 31 to 33.

Next, the ceramic carrier 10 is prepared, for example, according to the procedure shown in FIGS. 4 to 7. In addition, A shown in FIGS. 4 to 7 shows a front view, and B shows a sectional view taken along the line A-A.

Here, in each of the above figures 4 to 7, 40 and 41 are Al ₂ O ₃ 92 with an average particle size of 1.5 μm.
wt%, _SiO2 4wt%, CaO2 wt% and MgO2
12 parts by weight of butyral resin and 6 parts by weight of dibutyl phthalate (DBP) are added to 100 parts by weight of mixed powder consisting of % by weight, mixed in an organic solvent to form a slurry, and a green sheet is formed using a doctor blade. , that is, a ceramic sheet before firing. The green sheet 41 has a thickness of 1
mm, and the green sheet 41 was prepared in advance to have a thickness of 0.2 mm.

In addition, 42 to 47 are 7% Al ₂ O ₃ with respect to Pt.
42 and 43 are electrode patterns which become electrodes of the gas sensing element 11, and 44 is a pattern printed with a thick film using platinum paste added with
A heating resistor pattern 45 to 47 serves as a heater for heating the heating resistor pattern 44.
This is an electrode pattern for connecting a power source to the gas detection element 11 or extracting a detection signal.

To manufacture the ceramic carrier 10, as shown in FIG. 4, first, each of the patterns 42 to 47 described above is thickly printed with platinum paste on a green sheet 40. Next, as shown in FIG. 5, an electrode pattern 45 is formed.
Electrode wires 48 to 50 made of platinum wires having a diameter of 0.2 mm are arranged on top of electrode wires 48 to 47, respectively.

Next, as is clear from FIG. 6, the electrode pattern 4
A green sheet 4 in which an opening 51 is formed by punching so that the tips of 2 and 43 are exposed.
1 is a green sheet 40 to cover all patterns except the tips of the electrode patterns 42 and 43.
Laminated on top and bonded under heat. Here, the electrode wire 4
One end of 8 to 50 is laminated and crimped, and the other parts are protruded to the outside.

In this way, the laminate shown in FIG. 6 in which a portion of the electrode wires 48 to 50 are protruded from the green sheet 40 and the tips of the electrode patterns 42 and 43 are exposed is created. board
It is fired by leaving it in the atmosphere at 1500°C for 2 hours.

Next, as shown in FIG. 7, the opening 51 of the fired body
The gas detection element 11 will be installed in the
1 mole part of platinum black was added to 100 mole parts of TiO ₂ powder, 3% by weight of ethyl cellulose was added to the total powder, and butyl carbitol (2-
(2-butoxyethoxy)ethanol trade name)
After printing a thick film of TiO ₂ paste mixed in a chamber and adjusting the viscosity to 300 poise so as to fill the opening 51 and adhere to the tips of the electrode patterns 42 and 43, the paste was left in the atmosphere at 1200° C. for 1 hour. It is formed by baking.

Ceramic carrier 10 created in this way
Electrode wires 48 to 50 partially protruding from
The connections between the electrode terminals 31 and 33 are made as shown in FIG. In the figure, A is a front view,
B shows a right side view.

As shown in FIG. 8, the electrode terminals 31 to 33 are integrally formed in advance by etching a 0.3 mm thick nickel plate, and each electrode terminal is arranged on the electrode wires 48 to 50, respectively. The connection is made by spot welding the protruding parts. After that, a part of the ceramic carrier 10, the electrode wire 4
The connecting portions between 8 to 50 and the electrode terminals 31 to 33 and a portion of the electrode terminals 31 to 33 are protected by the glass seal 17 and fixed in the inner cylinder 14, and then cut to a predetermined length. Ru.

By applying the glass seal 17, the ceramic carrier 10, the electrode wires 48 to 50, and the electrode terminals 31 to 33 can be fixed to the inner cylinder 14 in advance, and therefore the connection terminals and electrode terminals connected to the external lead wires in the subsequent process can be fixed in advance. This makes welding work easier and improves work efficiency.

External lead wires 21 to 23 made of stranded wires as core wires
are crimped in advance on the side of the connection terminals 24 to 26 using a normal method. This work is efficient because the wires can be crimped one by one, and the strands do not come apart, and the external lead wires 21 to 23 are processed as single pieces without being joined to the ceramic carrier 10. Therefore, it has the advantage of being able to perform caulking work more efficiently.

Electrode terminals 31 to 33 are spot welded to the other end of the connection terminal to which the external lead wire has been crimped.
Welding requires smaller jigs and tools than caulking, so the work can be done easily even if the electrode wire pitch is narrow.

Next, the sealing material 20 is inserted into the inner cylinder 17 attached to the metal shell 12, and while pressing the outer cylinder 19 from above, the outer cylinder 19 and the metal shell 12 are connected at 52 points.
Weld with.

Although this embodiment has described a flat detector, a cylindrical ceramic carrier with a pellet-shaped gas-sensitive element as disclosed in Utility Model Application No. 59-131054 (Utility Application No. 58-24871) may also be used. It can also be applied to detectors with

[Effects of the Invention] As described above, the gas component detector based on the present invention can be downsized with stable workability, especially in a structure that requires a large number of lead wires, such as a three-terminal type. Moreover, high reliability can be maintained even under severe conditions such as in automobiles where the device is exposed to intense vibration and rapid heating and cooling.

[Brief explanation of drawings]

FIG. 1 is a side view with a main part cut away to explain the overall structure of a gas detector according to an embodiment of the present invention, and FIG.
Figure 3 is a cutaway side view of the main part of an intermediate product to explain the manufacturing process of the gas component detector shown in the figure, and Figure 3 is a main part of the intermediate product to explain the manufacturing process of the gas component detector following Figure 2. A broken side view, FIG. 4 is a drawing for explaining the manufacturing process of the ceramic carrier of the embodiment shown in FIG. 1, and FIG. 5 is a drawing for explaining the manufacturing process of the ceramic carrier following FIG. Figure 6 is a diagram for explaining the manufacturing process of the ceramic carrier following Figure 5, Figure 7 is a diagram for explaining the manufacturing process of the ceramic carrier following Figure 6, and Figure 8 is shown in Figure 1. FIG. 9 is a drawing explaining a method of providing an electrode terminal on the ceramic carrier of the embodiment. FIG. 9 is a drawing explaining a method of providing a connecting terminal in the manufacturing process of the embodiment shown in FIG. 10...Ceramic carrier, 11...Gas detection element, 17...Glass seal, 19...Outer cylinder, 20
... Sealing material, 21-23 ... External lead wire, 2
4-26...connection terminal, 31-33-electrode terminal,
48-50...electrode wire.

Claims (1)

[Scope of Claims] 1. An exterior consisting of an electrode wire whose one end is laminated and crimped in advance with a ceramic carrier and a ceramic sheet that hold a gas detection element whose electrical resistance value changes depending on the gas component, an electrode terminal, and a twisted wire. Welding the other end of the electrode wire and one end of the electrode terminal at a narrow interval using a connecting terminal to which a lead wire is crimped and fixed in advance, and welding the vicinity of the joint between the ceramic carrier and the electrode wire. covered with a glass seal, the connection terminal and the other end of the electrode terminal are welded at a wider interval than the welding interval between the other end of the electrode wire and one end of the electrode terminal, and the ceramic carrier is covered with a glass seal; An outer cylinder sealed at one end with a sealing material is attached to the metal shell holding the metal shell, and the electrode wire, the electrode terminal, the connection terminal, and a part of the external lead wire are housed in the outer cylinder, and the lead wire is A gas component detector, characterized in that it is drawn out from the sealing material.