JPS6030605Y2 - Ignition heater - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ignition heater suitable for igniting high-calorie gas.

Up until now, heaters for igniting heating equipment using natural gas, city gas, etc. as fuel have been spark ignition type heaters that use piezoelectric ceramics or high-voltage circuits, and metal or ceramic heating elements that are energized to generate red heat. A heating element ignition type is generally used.

Incidentally, in recent years oil atomization gas, a high-calorie gas, has become popular as a heating fuel, but in order to ignite it in the air, a temperature much higher than that required in the past is required. be done.

For example, the ignition temperature of propane is 510°C, the ignition temperature of hydrogen is 530°C, and the ignition temperature of methane is 645°C.
In reality, complete ignition cannot be achieved unless the temperature is several hundred degrees higher than the above-mentioned ignition temperature, and the higher the calorie, the higher the actual ignition temperature must be.

However, the conventional piezoelectric ceramics described above cannot ignite high-calorie gas because of the small amount of discharge, and the ones using high-voltage circuits do not ignite unless the discharge time is considerably long. However, these spark ignition type devices had the disadvantage of causing radio wave interference.

On the other hand, those using metal heating elements such as nichrome wire and iron-chromium wire lack durability because they deteriorate due to oxidation when heated in an atmosphere containing hydrogen gas such as high-calorie gas. SiC.

Products using ceramic heating elements such as LaCrO3 and ZrO2 have high-temperature resistance, but have low mechanical strength, and if they are made with a composition that reinforces this, they have the disadvantage of not being able to withstand rapid heating for ignition. .

In addition, heaters with a structure in which a metal heating element is sealed between two plates made of heat-resistant materials such as alumina ceramics and are isolated from the outside world have been proposed, but such general-purpose ceramics have poor thermal shock resistance. It is not practical as a heater for igniting high-calorie gas because it will break if it is insufficiently heated and repeatedly heated and cooled.

As described above, all of the conventional ignition heaters have some drawbacks when used for igniting heating equipment using high-calorie gas or petroleum atomized gas as fuel, and improvements have been desired for practical purposes.

Therefore, the purpose of this invention is to overcome the drawbacks of conventional ignition heaters, to have excellent durability, high temperature resistance, and mechanical strength, without causing radio interference or deterioration due to oxidation, and to be usable for high-calorie gases. To provide an ignition heater that can quickly ignite even when

As a result of various studies to achieve this objective, the inventors of the present invention discovered that in so-called heating element ignition type ignition heaters, the electric resistor, which traditionally plays the role of the heating element, comes into direct contact with the fuel gas and the atmosphere. However, due to the fact that the heater is heated, and the coefficient of thermal expansion of the ceramics used in ceramic-filled heaters is large, it cannot handle rapid heating and cooling, which can lead to damage due to thermal shock, resulting in deterioration and mechanical damage. Focusing on the cause of the lack of electrical strength, we discovered that the above purpose could be achieved by creating a structure that shields this electrical resistor from the atmosphere using a special ceramic, and based on this knowledge, we We came up with this idea.

That is, according to the present invention, the ignition heater is made of two flat plate-shaped pieces with raised peripheral edges, each made of ceramics or glass ceramics whose main components are β-spodumene, cordierite, aluminum titanate, or zircon. An electrical resistor having terminal portions at both ends is sandwiched between the bodies, and the electrical resistor is supported by inserting both terminal portions into a pair of openings provided at the peripheral edge of the flat plate-like body. , using a high-temperature adhesive of ceramics or glass ceramics having a coefficient of thermal expansion comparable to that of the ceramics or glass ceramics, the peripheral edges of the flat bodies and the contact areas between these and the terminals are melt-sealed. The above object can be achieved by constructing a structure in which the electrical resistor is blocked from the outside world.

The present invention will be described in detail below based on the accompanying drawings.

The drawing is a longitudinal cross-sectional view showing one embodiment of the present invention, in which an electric resistor 1 having terminal portions 3, 3 at both ends is made of two ceramic or glass ceramics with raised peripheral edges. It is sandwiched between the plate-like bodies 2.2 with a space 4 in between, and has a structure isolated from the outside world.

As the material of the electric resistor 1, those commonly used as heating elements of conventional ignition heaters, such as nichrome, iron chromium, tungsten, molybdenum, and molybdenum silicide, can be used.

This electrical resistor 1 can be in the form of a plate-shaped body with a thickness of 0.01 to 0.2 rrvn and a linear body with a diameter of 0.01 to 0.2 TIrIIX.

In addition, the material of the plate-shaped bodies 2, 2 is β-spodumene ceramic (thermal expansion coefficient: 0.5x10-610C).
), aluminum titanate ceramics (thermal expansion coefficient 3.Ox 10-6/℃), zircon ceramics (
Thermal expansion coefficient 3.5X 10-67℃), β-spodumene glass ceramics (thermal expansion coefficient 1.2X 10
-6/°C), cordierite glass ceramics (thermal expansion coefficient 2.3X 10-6/°C), and these are alumina ceramics (thermal expansion coefficient 17.5X 10-6/°C). ) has a significantly lower coefficient of thermal expansion than commonly used heat-resistant materials, so it exhibits excellent thermal shock resistance.

The thickness of this plate-like body is usually about 0.5 to 5 rMt,
The periphery is slightly raised so that when the two sheets are stacked and joined, a void is formed inside.

In order to form an ignition heater with such a structure, a recess into which the terminal portion 3°3 can fit is provided in each of the two plate-like bodies 2, 2 made of ceramic or glass ceramic, as shown in the figure. The electric resistor 1 and its terminal portion are sandwiched, and the two plate-like bodies are brought into close contact with each other at the skin-removed portions of each periphery.

Then, powder of a high-temperature adhesive is applied in the form of a paste over the entire surface of the contact areas between the plate-shaped bodies and the contact areas of each plate-shaped body with each terminal, and heated to a high temperature of 1250°C or higher to melt and bond. let

At this time, it is necessary to use ceramics or glass ceramics having a coefficient of thermal expansion comparable to that of the plate-shaped body 2 as the high-temperature adhesive.

This is because when an ignition heater with such a structure is heated from room temperature to a high temperature capable of igniting, the sealing state of the electrical resistor 1 is damaged mainly due to the gap between the plate-shaped body and the high-temperature adhesive material. However, this cranking can be prevented by making the coefficients of thermal expansion of the plate-shaped body and the high-temperature adhesive substantially the same.

This melt bonding using the high temperature adhesive is preferably carried out in the air or in a non-oxidizing atmosphere.

In this way, a gas-tight bond is formed so that the electrical resistor is completely isolated from the outside world.

The plate-like bodies 2, 2 of the present invention have anodized edges,
Since the two are bonded at that part, a gap is formed inside.

Therefore, even though there is a significant difference in thermal expansion between the plate-shaped body and the electrical resistor, the stress generated between them is alleviated.
Destruction due to thermal shock is suppressed.

As described above, the ignition heater of the present invention has a structure in which the electric resistor is isolated from the outside world, so even when heated to high temperatures, the material does not deteriorate due to oxidation etc. The contacting plates are made of ceramics or glass ceramics whose main composition is β-spodumene, cordierite, aluminum titanate, or zircon, which has low thermal expansion and high mechanical strength, so it can withstand high temperatures. It has the advantage of exhibiting excellent thermal shock resistance and mechanical strength.

It was confirmed that when repeated ignitions were performed under the conditions of use: the temperature required to ignite high-calorie city gas such as 13A, and the presence of high-temperature hydrogen, it could withstand use for several dozen directions.

On the other hand, conventional ignition heaters that use a metal heating element directly exposed to the atmosphere deteriorate after being used several hundred times under the above conditions, so they must be replaced frequently.

In addition, as mentioned above, the ignition heater of the present invention can withstand rapid heating even when made smaller and thinner because the contact part with the outside world is made of a special low-thermal-expansion, high-density material. It is possible to obtain a product with a good rise.

Next, the present invention will be explained in more detail with reference to Examples.

Examples The thickness of various ceramics shown in the following table is 0.5rrI! r
A thickness of 0.2 va is placed between two plate-like bodies with anodized edges of L.
n.

A nichrome foil with a width of 0.5rIrIn is sandwiched, and both plate-like bodies are glued together with terminals made of nichrome rods connected to both ends of the nichrome foil, resulting in a total thickness of 1.5 mm and a width of 4 m.
An ignition heater with a length of 25 mm and a length of 25 mm was manufactured.

For bonding at this time, a high-temperature adhesive having the same composition as the ceramic or glass ceramic forming the plate-like body was used.

When an electric current was passed through the ignition heater thus obtained, the temperature reached 600°C in about 4 seconds, and reached 900°C in seconds for fishing.

A thermal shock resistance test was conducted on this ignition heater by raising the temperature to 6000C or 900C, and then cooling it by dropping cold water at 10C 100 times.The results shown in the table below were obtained. Ta.

For comparison, the same ignition heater was made using alumina ceramics ((coefficient of thermal expansion 7.5 x 10-67°C)) and a similar thermal shock resistance test was conducted.
C. and 900.degree. C., cracks occurred at one time.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view showing one embodiment of the present invention. In the figure, reference numeral 1 is an electric resistor, 2 is a ceramic or glass ceramic plate, 3 is a terminal portion, and 4 is a space formed inside.

Claims (1)

[Scope of utility model registration request] An electrical device with terminals at both ends between two plate-like bodies with raised peripheral edges, made of ceramics or glass ceramics whose main components are β-spodumene, cordierite, aluminum titanate, or zircon, respectively. By sandwiching the resistor and inserting both terminal portions into a pair of openings provided at the periphery of the flat plate-shaped body, the electric resistor is supported and has a thermal expansion comparable to that of the ceramic or glass-ceramic. Using high-temperature adhesives of ceramics or glass-ceramics with modulus,
The ignition heater has a structure in which the peripheral edges of the flat plate-shaped body and the contact portion between these and the terminal portion are melt-sealed, and the electrical resistor is isolated from the outside world.