JP3529538B2 - Sensor and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a sensor in which a detection element provided on a ceramic substrate is fixed inside a hollow ceramic holder.

[0002]

2. Description of the Related Art Conventionally, for example, as an oxygen sensor,
A method of forming a detection element on a ceramic substrate using the ceramics substrate technology, fixing the detection element to a ceramic member to relieve the stress due to the difference in thermal expansion, and then storing the ceramic member in a metal housing. Is known (Japanese Patent Laid-Open No. 3-246458).

Further, as a method of fixing the ceramics substrate to the metal housing, an oxygen sensor for exhaust gas, which is particularly required to have heat resistance and airtightness (for example, Japanese Patent Laid-Open No. 6-58242).
In the air-fuel ratio sensor described in JP-A-2-148849), there is known a method in which retention by a filling layer and glass seal (sealing) by heat-resistant glass are combined in order to reduce the difference in thermal expansion (Japanese Patent Laid-Open No. 3-12848). No. 257357).

[0004]

However, according to the conventional method, when the materials of the ceramic member and the ceramic substrate forming the detection element are different from each other, or when thermal shock resistance, vibration resistance and shock resistance are required, the following method is used. Problem arises. That is, due to the difference in the coefficient of thermal expansion, thermal stress may be generated in the detection element during cooling / heating cycles, or
Under a use condition in which a load is frequently applied due to impact, the fixation of the detection element by the filling layer is loosened, the adhesion is gradually weakened, and the detection element vibrates. As a result, defects such as cracks or electric wire breakage are likely to occur.

An object of the present invention is that the filling layer filling the space between the ceramic holder and the detecting element provided on the ceramic substrate is sufficient for repeated stress applied by thermal stress or vibration / shock during the thermal cycle. It is intended to provide a sensor having durability and capable of maintaining the holding force of a detection element for a long period of time.

[0006]

According to a first aspect of the present invention, there is provided a detection element having a detection portion provided at one end of a ceramic substrate inside a hollow ceramic holder, and an electrode extending from the other end of the detection element. A sensor including a wire, a glass layer that seals between at least a part of the electrode wire and the other end of the detection element and the holder, and a filling layer that fills between the holder and the detection element. In, the filling layer is made of a mixture of glass and ceramics, and
It is characterized in that the glass content rate of the one end side filling layer disposed on one end side of the detection element is made smaller than the glass content rate of the other end side filling layer of the detection element.

Here, the filling layer may be formed of two layers, one filling layer on one side of the detecting portion of the detection element and the other filling layer on the other side of the extraction side of the electrode wire, and an intermediate layer between them. It may be formed from three layers or more. Further, a gradient may be provided in the glass concentration so that the glass content rate gradually decreases toward the one end side of the detection element. Note that the glass may be so-called crystallized glass that crystallizes at the time of glass sealing, or may be other amorphous glass.

A second aspect of the present invention is characterized in that the glass content rate of the one end side filling layer filled in the detecting portion side of the detecting element is 30% by weight or more and less than 70% by weight. This is because when the glass content is less than 30% by weight, the fixing strength of the filling layer is weak, the sensor warps during the heat cycle, or the filling layer is loosened due to vibration or shock and the detection element is damaged, or the electrode wire is loaded. This is because the wire is easily broken and easily broken. On the other hand, if the amount is less than 70% by weight, the holding force of the filling layer is too strong and cracks are likely to occur in the filling layer or the detection element as in the case of using 100% sealing glass. It depends on the reason.

According to the third aspect of the invention, the material of the ceramic forming the filling layer is talc as a main component. This is for the purpose of realizing the holding of the filling layer having both sufficient heat resistance and flexibility, and magnesia or the like can also be applied. Further, the thermal expansion coefficient of the filling layer is usually alumina, zirconia or a soft mineral such as talc, magnesia or a mixture thereof with the main object of approaching the thermal expansion of a holder and a detection element formed of a mixture thereof. A material to which alumina, zirconia, or a mixture thereof is added is also suitably used.

According to a fourth aspect of the present invention, the detection element is a detection element with a heater adhered to a heater element having a heating pattern formed on a ceramic substrate.

A method for manufacturing a sensor according to claim 5 is
Inside the hollow ceramic holder, a detection element provided with a detection portion at one end of a ceramic substrate is coaxially loosely fitted,
At least three layers or more were sequentially filled in the gap between the detection element and the holder with a mixed powder of glass and ceramics having a low glass content, a mixed powder of glass and ceramics having a high glass content, and a glass powder. later,
It is characterized in that the one end side filling layer, the other end side filling layer and the glass layer are simultaneously formed by performing a temperature treatment at a temperature equal to or higher than the glass softening point of the glass powder.

[0012]

In the structure of the first aspect, the filling layer is made of a mixture of glass and ceramics, and the holding force of the detection element by the holder can be set appropriately by selecting an appropriate mixing ratio. Therefore, it is possible to effectively prevent a crack from occurring in the glass layer or the detection element due to the warp of the detection element due to thermal stress or the deflection of the detection element due to vibration or impact. On the other hand, when the detection element is fixed to the holder with the glass layer, the adhesion force due to the glass layer is too strong and the glass layer is fragile, so the detection element warps due to thermal stress and the detection element shakes due to vibration or shock. Therefore, cracks are likely to occur in the glass layer or the detection element.

Further, the glass content rate of the one end side filling layer disposed on one end side of the detection element is made smaller than the glass content rate of the electrode wire extraction side of the detection element, that is, the other end side filling layer. Therefore, the coercive force of the filling layer can be set to be weaker toward the one end side of the detection element. Therefore, it is possible to obtain the effect that the characteristic vibration generated in the detection element is attenuated and the durability against vibration and impact is improved.

According to the structure of claim 2, the detection element can be favorably held, and the stress relaxation by the filling material can be exhibited more preferably. According to the third aspect of the present invention, by using talc which is a very soft mineral having excellent heat resistance and Mohs hardness of 1 as the filler, a better cushioning effect against thermal shock, vibration and shock can be obtained.

According to the structure of claim 4, by energizing the heater, the temperature of the sensor can be quickly raised to the activation temperature. With the configuration of claim 5, the sensor according to any one of claims 1 to 4 can be easily manufactured.

[0016]

Embodiments of the present invention will be described with reference to FIGS. In this embodiment, the sensor 100 has a plate-like detection element 2 for detecting a gas component or its concentration.
Is bonded to a heater element 3 having the same shape as that of the detection element 2 to form a detection element 20 with a heater, which is fixed in a cylindrical heat-resistant ceramic holder 4. As shown in FIG. 3, this sensor 100 is assembled as an oxygen sensor plug for detecting the oxygen concentration in the exhaust gas of an internal combustion engine.

The detecting element 2 is, for example, zirconia (ZrO).
2) An oxygen concentration reference electrode and an oxygen concentration detection electrode are attached to one end of the strip-shaped ceramic substrate 21 made of platinum by thick film printing, and it is used that a current flows through zirconia between the electrodes due to the concentration of oxygen. Have a configuration. Similarly, a lead pattern is printed on the ceramic substrate 21, a platinum electrode wire 22 is connected to the lead pattern, and a metal terminal 23 is spot-welded to the electrode wire 22.

In the heater element 3, a heater heating pattern and a lead pattern connected to the heater heating pattern and lead patterns connected to the heater heating pattern are formed by printing a platinum paste on a ceramic substrate 31 made of alumina, for example, and another ceramic substrate is laminated thereon. , Fire together. A platinum electrode wire 32 is connected to this lead pattern, and a metal terminal 33 is spot-welded to the electrode wire 32.

The detection element 2 and the heater element 3 are laminated and adhered to each other to form a square prism-shaped detection element 20 with a heater.
A cylindrical ceramic ceramic porcelain tube 24 having a square shaft hole is fitted on one end side of the detection element 20 with a heater, and the fitting surface is bonded with a heat-resistant adhesive. ing.

The holder 4 has a cylindrical shape with an outer periphery having a large-diameter flange portion 42 provided at one end side portion 41, an inner periphery having an inner peripheral edge 43 formed at one end, and a tapered portion 44 provided at the other end. ing. The detection element 20 with a heater is inserted into the holder 4 from one end side, and the ceramic porcelain tube 24 is attached to the inner peripheral edge 4
3 and are coaxially arranged.

In the gap 40 between the heater-equipped detection element 20 and the holder 4, between the outer circumference and the inner circumference of the holder 4, from one end side, the holder 4 and the heater-equipped detection element are made of a mixture of glass and ceramics. 20, the one end side filling layer 45 and the other end side filling layer 46 following the one end side filling layer 45, at least a part of the electrode wire 32, the other end portion of the detection element 20 with a heater, and the holder 4. A glass layer 47 is provided to seal the gap between them.

The glass used for the one end side filling layer 45, the other end side filling layer 46 and the glass layer 47 is preferably borosilicate glass, zinc borate glass, aluminosilicate glass, zinc borosilicate glass, and the like. Talc is suitable as the ceramic main material used for the filling layers 45 and 46. The glass content rate of the one end side filling layer 45 is set lower than that of the other end side filling layer 46, and the glass content rate is preferably 30% by weight or more and less than 70% by weight.

Detection element 20 with heater for holder 4
Is fixed as follows. The detection element 20 with a heater is inserted into the holder 4 which is held vertically, and the ceramic porcelain tube 24 is engaged with the inner peripheral edge 43 and held coaxially.
Next, the gap 40 is filled with a filling layer material in which glass powder and ceramics powder are mixed in a predetermined ratio, and subsequently, a sealing layer material in which glass powder and ceramics powder is mixed in a predetermined ratio. This in a heating furnace at 800 ℃, 1
The glass is sealed by heating for a time to melt or soften the glass.

Table 1 shows a cooling / heating cycle (heating up to 700 ° C. for 100 seconds → 120) using as parameters the glass used for the one end side filling layer 45, the other end side filling layer 46 and the glass layer 47 and the content% by weight thereof. Endurance test by 100 cycles of cooling down to 200 ° C for 200 seconds, and acceleration of 500
The results of the impact test of 0 G impact at 400 times / minute × 30 minutes are shown, and Table 2 shows the properties of the glasses A, B, and C (shown in Table 2) used in this oxygen sensor. This data is obtained by disassembling the endurance test product after the test and evaluating the vibration resistance and impact resistance from the occurrence of cracks in the detection element, the heater element and the sealing glass.

[Table 1]

[Table 2]

As can be seen from this data, when the detecting element is directly fixed to the ceramic holder with 100% glass, the detecting element or the heater element is cracked only by glass sealing. Further, when the entire periphery of the detection element was filled with only talc, there were some cases in which the electrode wire was broken or the heater element was damaged in the vicinity of the porcelain tube by conducting an impact test.

It is presumed that, when the sensor was disassembled and examined after the impact test, all of the filling layer was lost, and the detection element vibrated in the void, so that damage was caused in the vicinity of the porcelain tube which is the fixing point. . In particular, the sensor in which the filling layer on the other end side of the upper portion had a glass content of 30% by weight or more and less than 70% by weight showed no damage to the detection element even in the impact test, and showed good durability.

This oxygen sensor is mounted on a sensor plug having a structure shown in FIG. 3 for mounting on an internal combustion engine. The metal shell 1 has a small-diameter cylindrical portion 11 to which a protector 15 described later is fitted at one end, a screw portion 12 and a hexagonal portion 13 for screwing into a screw hole provided in an exhaust passage in the middle, and heat staking at the rear end. Thus, the holder 4 is held in the metal shell 1 and the connecting tube portion 6 for coaxially connecting the sleeve tube 5 to the metal shell 1 is provided. The connecting tubular portion 6 is composed of a base tubular portion 61 connected to the hexagonal portion 13, a thin shrinking tubular portion 62, an intermediate tubular portion 63, and a thin caulking portion 64.

A small diameter is formed between the threaded portion 12 and the hexagonal portion 13 of the metal shell, a seal ring 14 is externally fitted, and the small-diameter tubular portion 11 is a cylinder having a double-structured ventilation hole. The cap-shaped protector 15 is fitted. Metal shell 1
The inner circumference of the holder is located on the inner circumference of the screw portion 12, and the holder 4
Of the small diameter portion 16 in which the tip end portion of the connecting portion 6 is loosely fitted, the middle diameter portion 17 in which the collar portion 42 is fitted, and the large diameter portion 18 which forms the inner circumference of the connecting tubular portion 6. Medium diameter part 1
An engaging step 10 that engages with one end surface of the collar portion 42 of the holder is provided between the engaging step 10 and the No. 7.

The sleeve tube 5 has a flange portion 52 formed by expanding the end portion of a thin metal pipe at one end portion 51 and the other end portion 5
A plurality of rectangular recesses 54 are provided in the circumference of 3. The connector 7 is fitted to the other end portion 53 of the sleeve tube 5. The connector 7 includes an outer cylinder 73 having one end 72 around which an inner bulging portion 71 engages with the plurality of rectangular recesses 54, and a rubber member fitted inside the other end of the outer cylinder 73. And a connector body 74.

The outer periphery of the middle portion of the holder 4 and the metal shell 1
Stainless steel (SUS403) between the connecting cylinder part 6
A support tube 8 made of metal is fitted therein. The support cylinder 8 has, on one end side, an interposed cylinder portion 81 that is interposed between the holder 4 and the base cylinder portion 61 and that matches the axis of the holder 4 with the axis of the metal shell 1. On the other end side of the support cylinder 8, the holder 4
The large diameter portion 82 is provided between the intermediate cylindrical portion 63 and the intermediate cylindrical portion 63. An outer peripheral side portion of the large diameter portion 82 is an annular contact surface 83.

The oxygen sensor is assembled as follows. The holder 4 incorporating the detection element 20 with a heater is inserted into the metal shell 1 in which the protector 15 is fitted and welded, and one end surface of the collar portion 42 is engaged with the engagement step 10. Next, a talc 25 is filled in a gap between the inner circumference of the metal shell 1 and the outer circumference of the holder 4, and then the support cylinder 8 is fitted therein. Next, one end of the sleeve tube 5 is abutted against the other end of the support cylinder 8 on the flange 52, and the connecting cylinder 6 is heat caulked inward.

[Brief description of drawings]

FIG. 1 is a perspective view of a sensor of the present invention.

FIG. 2 is an assembly diagram of the sensor of the present invention.

FIG. 3 is a cross-sectional view of a sensor plug incorporating the sensor of the present invention.

[Explanation of symbols]

1 metal shell 2 detection element 3 heater elements 4 Ceramic holder 20 Detection element with heater 21 Ceramics substrate 22 electrode wire 25 talc 32 electrode wires 40 gap 45 Packing layer on one end side 46 Packing layer on the other end side 47 glass layer

Front page continuation (72) Inventor Tsuzuki Orthodox 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Japan Special Ceramics Co., Ltd. (72) Inventor Satoshi Teramoto 14-18 Takatsuji-cho, Mizuho-ku, Nagoya Japan Special Ceramics Industry Within the corporation (56) References JP-A-6-27080 (JP, A) JP-A-3-257357 (JP, A) JP-A-3-167461 (JP, A) Actual Kaihei 3-60059 (JP, U) Actual Kaihei 3-60058 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 27/409 G01N 27/41 G01N 27/419

Claims (5)

(57) [Claims] 1. A detection element having a detection part provided at one end of a ceramic substrate inside a hollow ceramic holder, an electrode wire extending from the other end of the detection element, and at least a part of the electrode wire and the detection element. In a sensor comprising a glass layer sealing between the other end of the holder and the holder, and a filling layer filling between the holder and the detection element, the filling layer is a mixture of glass and ceramics. And a glass content rate of the one end side filling layer disposed on one end side of the detection element is smaller than a glass content rate of the other end side filling layer of the detection element. 2. The sensor according to claim 1, wherein a glass content rate of the one end side filling layer is 30% by weight or more and less than 70% by weight. 3. The sensor according to claim 1, wherein the ceramic material forming the filling layer contains talc as a main component. 4. The sensor according to claim 1, wherein the detection element is a detection element with a heater, which is bonded to a heater element having a heating pattern formed on a ceramic substrate. 5. The method for manufacturing a sensor according to claim 1, wherein a detection element having a detection portion provided at one end of a ceramic substrate is coaxially loosely fitted inside a hollow ceramic holder. In the gap between the detection element and the holder, at least three layers of a mixed powder of glass and ceramics having a low glass content, a mixed powder of glass and ceramics having a high glass content, and a glass powder are provided. As described above, the method for manufacturing a sensor, which comprises sequentially filling and then heat-treating at a temperature equal to or higher than the glass softening point of the glass powder to simultaneously form the one end side filling layer, the other end side filling layer and the glass layer.