JPH0545234A - Temperature sensor - Google Patents

Abstract

PURPOSE:To construct a temp. sensor excellent in thermal shock property and thermal responsiveness, which is applied to a burning apparatus such as gas table using a gaseous or liquid fuel. CONSTITUTION:A pair of electrodes 5 are furnished on at least one of the surfaces of a metal base 1 through an electric insulative layer or layers 3, and a thermo-sensitive resistor 4 is provided on the surface of the electric insulative layer 3 in such a way as straddling the two electrodes 5. A temp. sensor according to the invention is embodied in such a constitution that an overcoat layer 7 is provided over the surface of this thermo-sensitive resistor 4, that at least one of the electric insulative layers 3 is made of crystallized glass containing MgO type crystal phase, and that the composition is, by wt, 16-50% MgO, 0-50% Bad, 0-20% CaO, 0-40% La2O3, 5-34% B2O3, 7-30% SiO2, 0-5% MO2 (M is at least one of Zr, Ti, Sn, Zn), and 0-5% P2O5. This constitution can yield a temp. sensor excellent in the thermal shock property and thermal resposniveness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor used in a combustion device such as a gas table which uses a gas or liquid fuel.

[0002]

2. Description of the Related Art In recent years, various safety sensors have been mounted in order to ensure the safety of combustion equipment. As an example, an empty cooking prevention sensor used in a gas table will be described with reference to the drawings.

FIG. 3 shows the structure of a conventional sensor for preventing empty cooking. As shown in the figure, a sensing element such as a SiC thermistor or platinum is adhered to the inner bottom surface of the bottomed cylindrical metal member with glass, and the inner bottom surface of the bottomed cylindrical metal member is biased by a coil spring, It is configured to detect the temperature by contacting it with a temperature detection object such as a pan or frying pan.

As shown in the figure, the metal substrate 11 constitutes the bottom surface of the bottomed cylindrical metal member 12, and the alumina substrate 13 has a temperature sensitive resistor 14 made of a SiC thermistor or platinum on one surface thereof for detecting the temperature. Is provided over the pair of electrodes 15, and the other surface of the alumina substrate 13 is adhered to the metal substrate 11 by the glass adhesive layer 16. The entire surface of the temperature sensitive resistor 14 and a part of the pair of electrodes 15 are covered and protected by an overcoat layer 17. The coil spring 18 is located above the supporting metal base 19 and is in contact with the inner bottom surface of the bottomed cylindrical metal member 12, that is, the metal substrate 11, to bring the metal substrate 11 into contact with the temperature detection object.

Next, the operation of the temperature sensor having the above structure will be described. The metal substrate 11 is biased by the coil spring 18 and is in contact with a temperature detecting object such as a pan or a frying pan to constantly detect the temperature, and the water and contents in the pan or the frying pan are evaporated by continuous heating, When the temperature of the pan or frying pan rises abnormally, the temperature is transmitted from the metal substrate 11 to the temperature-sensitive resistor 14, and its resistance value changes, and the change causes the cutoff circuit to operate and fuel such as gas or kerosene. It cuts off the supply of water and prevents empty cooking.

[0006]

However, in such a conventional temperature sensor for preventing empty cooking, when a SiC thermistor is used as the temperature sensitive resistor (sensing element) 14, the resistance value changes linearly with temperature. Does not change to As a result, the circuit for processing the signal becomes complicated. Further, in the case where platinum is used as the sensing element, the resistance value changes linearly with temperature, so that the circuit for processing the signal becomes very simple. However, since the platinum film is formed on the alumina substrate, there is a problem that when the temperature sensing object is strongly brought into contact with the sensing element, the alumina substrate is often broken because the mechanical strength of the alumina substrate itself is weak.

As a remedy for this, as shown in FIG. 1, a pair of electrodes 3 are provided on the inner bottom surface of the bottomed cylindrical metal member 2 with a vitreous electrical insulation layer 7 in between, and the electrodes 3 are straddled between the pair of electrodes 3. Then, the temperature sensitive resistor 8 is provided on the surface of the electric insulating layer 7,
Further, there has been proposed a temperature sensor for preventing empty cooking in which the overcoat layer 4 is provided on the surface of the temperature sensitive resistor 8. This sensor is configured to detect the temperature by urging the inner bottom surface of a bottomed cylindrical metal member by a coil spring 5 and bringing it into contact with the bottom of a temperature detection object such as a pan or frying pan. Since this method is a method in which the vitreous material 7 is directly baked on the metal substrate 1, it is superior in mechanical strength and thermal shock resistance to the method formed on the alumina substrate. However, a drawback of this method is that the oxide removal step is necessary because the metal surface undergoes thermal oxidation when baking glass.
Also, since the metal surface of the temperature sensor that detects the temperature by contacting a temperature-sensing object such as a pan or frying pan is exposed, it will be heated and oxidized if used in a combustor such as a gas table, or spilled from the pan. Is significantly corroded by
There was a problem of lacking reliability as a sensor.

The present invention is intended to solve such problems, and an object of the present invention is to provide a temperature sensor having excellent thermal shock resistance, thermal oxidation resistance, and corrosion resistance.

[0009]

In order to solve this problem, the present invention provides a pair of metal base plates forming the inner bottom surface of a bottomed cylindrical metal base material with one or a plurality of electrically insulating layers interposed therebetween. An electrode, across the pair of electrodes, a temperature-sensitive resistor provided on the surface of the electrical insulating layer, and a configuration including an overcoat layer provided on the surface of the temperature-sensitive resistor, The outer bottom surface of the bottomed cylindrical metal base is brought into contact with the temperature detection object by the urging force of a coil spring provided in contact with the bottom bottom cylindrical metal base to detect the temperature of the temperature detection object. It was done.

Further, at least one of the electric insulating layers is made of Mg.
It is a crystallized glass having an O-based crystal phase, and its composition is wt%, MgO 16 to 50%, BaO 0 to 5
0%, CaO 0-20%, La ₂ O ₃ 0-40%, B
₂ O _{3 5 to} 34%, SiO ₂ 7 to 30%, MO ₂ (M is Z
at least one of r, Ti, Sn, Zn) 0 to 5%,
The temperature sensor is mainly composed of P ₂ O ₅ 0 to 5%.

[0011]

According to this structure, the electrically insulating layer made of crystallized glass provided on the metal substrate, the pair of electrodes provided on the electrically insulating layer, and the temperature sensitive resistor and the overcoat layer extending over the pair of electrodes. By forming a temperature sensor to form a temperature sensor, the mechanical strength is strengthened and the temperature sensor is not destroyed even when a strong impact force is applied. In addition, since a metal thin film resistor such as platinum, ruthenium, or rhodium is used as the temperature sensitive resistor, the relationship between the temperature change and the resistance value change becomes linear and can be controlled by a simple signal processing circuit. ..

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A temperature sensor according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1A shows the configuration of the temperature sensor for preventing empty cooking of this embodiment. As shown in the figure, a sensing element such as a SiC thermistor or platinum is adhered to the inner bottom surface of the bottomed cylindrical metal substrate with glass. The inner bottom surface of this bottomed cylindrical metal substrate is configured to contact the temperature detection object such as a pan or frying pan with the force of a coil spring to detect the temperature.

As shown in the figure, the metal substrate 1 constitutes the bottom surface of the bottomed cylindrical metal substrate 2, and a pair of temperature sensitive resistors 4 made of SiC thermistor or platinum are provided on the upper surface of the electric insulating layer 3. Is provided over the electrode 5 to form a temperature detecting element. The entire surface of the temperature sensitive resistor 4 and a part of the pair of electrodes 5 are covered and protected by an overcoat layer 7. The coil spring 8 is located above the supporting metal base 9 and is in contact with the inner bottom surface of the bottomed cylindrical metal substrate 2, that is, the metal substrate 1, and plays a role of bringing the metal substrate 1 into contact with the temperature sensing object pair. ..

Next, the operation of the above-mentioned empty cooking prevention sensor will be described. The metal substrate 1 is in contact with a temperature detecting object such as a pan or a frying pan by the coil spring 8 to constantly detect the temperature. The water and contents in the pan or the frying pan are evaporated by continuous heating, and the temperature of the pan or the frying pan is increased. When the temperature rises abnormally, the temperature is transmitted from the metal substrate 1 to the temperature sensitive resistor 4, and the resistance value changes. Due to the change in the resistance value, the cutoff circuit operates to cut off the supply of fuel such as gas and kerosene, thereby preventing the air from being cooked. (1) Metal Substrate For the metal substrate 1 used in the present invention, a steel plate for holo, a stainless steel plate, a silicon steel plate, various alloys such as nickel-chromium-iron, nickel-iron, kovar, invar and clad materials are selected. It Processing of these metal base materials into a desired shape, drilling, etc. are carried out by an ordinary machining method, etching processing method, laser processing method or the like.

In order to improve the adhesion of the metal base 1 to the electric insulating layer 3, after degreasing the surface, various platings of nickel, cobalt, etc. are applied, or an oxide coating layer is formed by thermal oxidation treatment. .. (2) Electrical Insulation Layer The electrical insulation layer 3 is required to have high electrical insulation and heat resistance, and is therefore made of alkali-free crystallized glass. Its glass composition, for example, SiO ₂ 7 to 30 wt% B ₂ O ₃ 5~34 wt% MgO 16 to 50 wt% CaO 0 to 20 wt% BaO 0 to 50 wt% ZrO ₂ 0 to 5 wt% P ₂ O ₅ 0-5 wt% La ₂ O ₃ it is 0 to 40% by weight of the composition. The reason why the glassy layer having this composition range is selected is that the electrode 5 and the resistor layer 4 formed on the electrical insulating layer 3 are selected.
This is to withstand the high heat applied during the printing and firing process.

Further, as a method for coating the above-mentioned crystallized glass on a metal substrate, there are a usual spray method, a powder electrostatic coating method, a printing method, an electrophoretic electrodeposition method and the like. Among these, the electrophoretic electrodeposition method is superior in terms of the denseness and the electrical insulation of the coating. However, the printing method is superior in terms of mass productivity and cost.

In the electrophoretic electrodeposition method, glass powder is admixed with alcohol and a small amount of water and ground in a ball mill for about 20 hours and mixed to give an average glass particle size of about 1 to 5 μm. The obtained slurry is put in an electrolytic cell and the liquid is circulated. The metal substrate prepared in (1) is immersed in this slurry, and 100 to 400 V is applied to cause negative polarization to deposit glass particles on the surface of the metal substrate. After being dried, it is baked at 850 to 900 ° C. for 10 minutes to 1 hour to obtain an electric insulating layer.

In the printing method, oil such as terpineol and a slight amount of a thickener are added to glass powder, and the mixture is kneaded with a three-roller to prepare a printing paste, and this paste is printed through a mesh screen or the like. After drying this,
An electrical insulating layer is obtained by firing at 900 ° C. for 10 minutes to 1 hour.

It is necessary that at least the MgO-based crystal phase be deposited in these electrically insulating layers by firing. The reason is as shown in the thermal expansion curve of FIG. 2, even in the above composition, in the case of (a) in the glass state (amorphous state),
It has a yield point at 600 to 700 ° C. However, when this is heat-treated (calcined) to precipitate at least the MgO-based crystal phase, the yield point becomes 900 ° C. or higher as shown in (b), and the heat resistance is improved. Further, since the MgO-based crystal layer has a large linear expansion coefficient, when the crystal is deposited, the linear expansion coefficient of the insulating layer shifts to the high expansion side, and it becomes easy to match the expansion coefficient with the metal material.

In addition to the first layer having a MgO-based crystal phase, the electrically insulating layer has a second layer as an intermediate layer in order to match the expansion coefficient with the electrode layer and the temperature sensitive resistor layer. It is also possible to provide a layer of. (3) Electrode layer, temperature-sensitive resistor layer On the crystallized vitreous electrical insulation layer 3 shown in FIG.
A conductive circuit is formed as shown in FIG. The material of the temperature sensitive resistor 4 is selected from ruthenium, rhodium, platinum and the like.

The pattern forming method may be a plating method, a thermal spraying method, a screen printing method or the like, but a screen printing method in which the crystallized vitreous electric insulating layer 3 and the electrode 5 and the temperature sensitive resistor 4 layer have good adhesion. Is desirable. In this method, the electrode 5 and the temperature sensitive resistor 4 are formed by printing and firing the ink on the electric insulating layer 3 through a mesh screen having a desired pattern shape. The electrode 5 and the temperature sensitive resistor 4 are usually 5
Since it is fired in a firing furnace at 00 to 850 ° C., the electric insulation layer 3 is required to have heat resistance. Further, since the circuit pattern is sometimes required to have a fine pattern, the surface property of the electrical insulating layer is important and affects the printing yield.

Specific examples will be described below. (Example 1) Crystallized glass having a composition shown in (Table 1) to (Table 5) was synthesized. In addition, according to the above manufacturing process, SUS
430 metal substrate (100 mm x 100 mm x 0.5 mm) 1 having a 100 μm thick crystallized vitreous layer electrophoretically deposited on the surface and baked at 880 ° C. for 10 minutes to form an electrically insulating layer 3 Various properties such as surface roughness, waviness and heat resistance were measured. The measurement results are shown in (Table 1) to (Table 5).

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

The surface roughness was measured by a Talysurf surface roughness meter and indicated by the surface center line average roughness Ra, and the waviness was expressed by the difference Rmax between the peak and the valley obtained by the Talysurf surface roughness meter.

Regarding the heat resistance, the sample was put in an electric furnace at 850 ° C. for 10 minutes, taken out of the furnace, and allowed to cool naturally for 30 minutes. A spalling test was repeated, and the state of cracking and peeling of the sample was examined. .. For the detection of cracks, the sample was immersed in red ink, the surface was wiped off, and the presence or absence of the cracks was checked by visual observation. In the table, ∘ indicates that cracking was not observed even after 10 or more cycles, Δ indicates 5 to 9 cycles, and x indicates 4 cycles or less.

The adhesion was evaluated by conducting a bending test of the substrate, and x when the holo layer was peeled off to expose the metal part, Δ when the metal part was partially exposed, and Δ when the metal part was not exposed. ○

Based on the above evaluations, a comprehensive evaluation was performed, and the results are shown by ◯, Δ, and x. Nos. 1 to 8 are obtained by changing SiO ₂ and B ₂ O ₃ while keeping other components constant, N
o 9 to 15 make SiO ₂ / B ₂ O ₃ almost constant,
No. 16 to 19 in which the amount of O was changed was also Ca.
The amount of O changed. No. 20 to 24 are also B
A change in the amount of aO. No25-29 are the same
The amount of La ₂ O ₃ was changed. No30~42 respectively show the effect of _{ZrO 2, TiO 2, SnO 2} , P 2 O 5, ZnO.

As is apparent from the table, if SiO ₂ is increased, the heat resistance is improved, but the surface property and the adhesion are deteriorated. On the contrary, if the amount of B ₂ O ₃ is increased, the surface property and the adhesion are certainly improved, but the heat resistance is decreased. Therefore, in this embodiment, SiO _{2 is} 7 to 30 wt%, B _{2 is}
It is desirable that the amount of O _{3 be 5 to} 34% by weight.

The amount of MgO has a correlation with the crystallinity, and if it is 16% by weight or less, the precipitation of crystals is insufficient and the heat resistance is poor. Also,
If it is 50% by weight or more, crystals are likely to precipitate, it is difficult to crystallize when the glass melts, it is difficult to obtain a homogeneous glass, and the surface roughness becomes large.

When the amount of CaO is 20% by weight or more, the surface property is deteriorated, which is not desirable. BaO content is 50% by weight
If the above amount is added, heat resistance and adhesion are deteriorated, which is not desirable. When the amount of La ₂ O ₃ is 40% by weight or more, heat resistance deteriorates, which is not preferable.

Other components that can be added are ZrO ₂ , Ti
Examples thereof include O ₂ , SnO ₂ , P ₂ O ₅ , and ZnO.
It can be added up to a weight% of less.

Example 2 As shown in FIG. 1 (A), a stainless metal substrate 1 having a thickness of 400 μm and a diameter of 18 mm was degreased, washed with water, pickled, washed with water, nickel-plated and washed with water to perform pretreatment. After that, it was immersed in a slurry composed of No. 7 glass particles (Table 1) having an average particle size of 2.5 μm, and a DC voltage was applied between the counter electrode and the metal substrate 1 (Table 1) glass of No. 7 composition. The particles were electrodeposited on one side of the metal substrate and with a glass coating area of 15 mm in diameter and a thickness of 100 μm as shown in FIG. 1 (B). The un-deposited portion of the metal base material is the exposed metal portion and is the area for welding the cylindrical metal base material 2 and the metal base material 1. Then, it dried and baked and the electric insulation layer 2 was formed.
Further, a conductive circuit of the temperature sensor was formed thereon by a printing method. Next, this substrate was welded to a cylindrical metal base material 2 having a diameter of 18 mm to form a dry cooking prevention sensor. (Embodiment 3) With the same structure as in Embodiment 2, only the method of forming the electric insulating layer 3 was changed to the printing method. The electrically insulating layer 3 was obtained by forming a glass paste having a composition of No. 7 (Table 1) to a thickness of about 100 μm by screen printing, drying and firing. (Comparative Example 1) A conductive circuit similar to that of Example 1 was formed on a circular alumina substrate having a diameter of 15 mm by a printing method, and this temperature sensor was mounted on a circular stainless steel substrate having a thickness of 400 μm and a diameter of 18 mm, and a linear expansion coefficient. Was sealed with glass of 70 × 10 ⁻⁷ / ° C. Next, this substrate was welded to a cylindrical metal base material having a diameter of 18 mm to form an empty cooking prevention sensor. (Comparative Example 2) A SiC thermistor formed by vapor deposition was sealed on a stainless steel substrate having a thickness of 400 µm and a diameter of 18 mm with glass having a coefficient of linear expansion of 70 × 10 ^-7 / ° C. Next,
This substrate was welded to a cylindrical metal base material having a diameter of 18 mm to form an empty cooking prevention sensor.

Thermal shock tests were conducted on the temperature sensors of Examples 2 and 3 and Comparative Examples 1 and 2 described above. As a test method, the sample was held at 500 ° C. for 10 minutes, immersed in water, dried, and the resistance value was measured. This was repeated 100 cycles. The results are shown in (Table 6).

[0038]

[Table 6]

As described above, the glass substrate is made of metal and the alumina substrate is made.
Both Comparative Example 1 and Comparative Example 2 in which
Peeling occurred between the glass layer and the metal substrate with the icicle. this
Is the coefficient of linear expansion of glass (76 × 10^-7) Of the alumina substrate
Coefficient of linear expansion (70 × 10^-7) Is almost equal to
Therefore, a metal having a larger linear expansion coefficient (114 × 1
0 ^-7) And the adhesive glass layer, distortion occurs and
The strain increases as you add the tress several times.
It is considered that the peeling occurred.

On the other hand, the linear expansion coefficient of the crystallized glass of Examples 2 and 3 is 110 × 10 ⁻⁷ , which is almost equal to the linear expansion coefficient of the metal, so that strain is unlikely to occur and, as a result, It is considered that peeling did not occur even after the 100-cycle test.

[0041]

As is apparent from the above description of the embodiments, the temperature sensor of the present invention is particularly excellent in thermal shock resistance, and therefore can be used as an empty cooking prevention sensor such as a gas table. Further, since the temperature sensor of the present invention has the crystallized glass layer directly formed on the metal base material, the temperature sensor has a higher thermal resistance than the sensors of Comparative Examples 1 and 2 in which the adhesive layer is provided on the metal base material. Excellent responsiveness.

[Brief description of drawings]

FIG. 1 (A) is a cross-sectional view of a temperature sensor for preventing empty cooking according to an embodiment of the present invention (B) is a plan view of the temperature sensor.

FIG. 2 is a diagram showing temperature characteristics of linear expansion coefficient of the crystallized glass.

[Fig. 3] Configuration diagram of a conventional temperature sensor for preventing empty cooking

[Explanation of symbols]

 1 Metal Substrate 2 Cylindrical Metal Substrate 3 Electrical Insulation Layer 4 Temperature Sensitive Resistor 5 Electrode 7 Overcoat Layer 8 Coil Spring 9 Supporting Metal Substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Yoshida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A pair of electrodes provided on a metal substrate forming an inner bottom surface of a bottomed cylindrical metal base material with one layer or a plurality of electrically insulating layers interposed between the pair of electrodes and the pair of electrodes. A structure comprising a temperature-sensitive resistor provided on a surface of the electrical insulating layer and an overcoat layer provided on a surface of the temperature-sensitive resistor, which constitutes a bottom surface portion of the bottomed cylindrical metal base material. A temperature sensor for detecting the temperature of a temperature detection object by bringing a metal substrate into contact with a temperature detection object by an urging force of a coil spring provided in contact with the inner bottom surface of the bottomed cylindrical metal base material. 2. At least one of the electrically insulating layers is a crystallized glass having a MgO-based crystal phase, and its composition is in a weight percentage of 16 to 50% MgO and 0 to 50% BaO.
CaO 0-20%, La ₂ O ₃ 0-40%, B ₂ O ₃
5 to 34%, SiO ₂ 7 to 30%, MO ₂ (M is Zr,
At least one of Ti, Sn, and Zn) 0 to 5%, P ₂ O ₅
The temperature sensor according to claim 1, which is mainly composed of 0 to 5%.