JPH02251011A - Ignition device using ceramic heater - Google Patents

Abstract

PURPOSE:To improve the durability of a ceramic heater by closing the rear end of a cylindrical body which has an inlet of gas flow-in formed and is made of a heat resistant material by a ceramic heater which has an electric resistor buried in a ceramic insulation body and at the same time inserting the ceramic heater until its tip end reaches the inlet of gas flow-in. CONSTITUTION:The rear end of a cylindrical body is closed with a ceramic heater 1 which has an electric resistor 33 buried in a ceramic insulation body 32 and at the same time the ceramic heater is inserted so as to make its end reach an inlet 23 for gas flow-in. This ceramic heater 1 is made to generate heat by electrification, and when a fuel gas is sent from the inlet 23 of gas flow-in, ignition occurs near the inlet of gas flow-in. Here, since the gas flow channel of the fuel gas is covered by the cylindrical body 2 made of a heat resistant material, the gas flow channel is not likely to be subject to heat loss due to the coldness of the air blast, etc., and it is heated efficiently by the ceramic heater 1. The gas passing through the gas flow channel is thereby ignited by a low ignition temperature in comparison with the case in which there is no cylindrical body 2 made of a heat resistant material. Further, it is possible to reduce the heat generation temperature of the ceramic heater because the ignition temperature can be lowered and it is possible to attempt to raise the durability of the heater.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ignition device that does not generate noise radio waves in the field of fuel gas, and is particularly suitable for igniting difficult-to-ignite fuel (natural gas). Regarding.

[Prior Art] Discharge ignition devices are known that ignite liquid fuel (vaporized) such as petroleum or gas such as methane gas by spark discharge. However, since noise radio waves are generated during discharge, strict shielding was required to prevent interference with the electronic control circuit of the combustion appliance equipped with this ignition device and nearby electronic circuits.

Therefore, in recent years, ignition devices using ceramic heaters that do not generate noise radio waves have attracted attention.

The ceramic heater used in this ignition device is manufactured by embedding an electric resistor in a ceramic insulator.

[Problem to be solved by the invention] Normally, when igniting city gas, mainly natural gas, the surface temperature of the ceramic heater is set to 11.
00°C or higher (12% overload at 10% overload)
10℃ or higher). Therefore, if heating and cooling are repeated, even a ceramic heater using a silicon nitride-based ceramic substrate has a shortened durability life.

An object of the present invention is to provide an ignition device that can reliably ignite refractory fuel gas even if the ignition temperature is reduced, thereby improving the durability of a ceramic heater.

[Means for Solving the Problem] In order to achieve the above object, the present invention has a cylindrical shape, and
A cylindrical body made of a heat-resistant material is formed with at least one gas inlet on the side surface, and a ceramic heater having an electric resistor embedded in a ceramic insulator is used to close the rear end of the cylindrical body, and the tip of the heater is connected to the gas inlet. The heater is fitted in such a way that it reaches the inlet, the heater is energized to generate heat, and fuel gas is sent in from the gas inlet to ignite it.

[Operation and Effects of the Invention] The ignition device is a ceramic heater in which an electric resistor is embedded in a ceramic insulator in a cylinder made of a heat-resistant material and having a cylindrical shape and at least one gas inlet formed on the side surface. The rear end of the cylindrical body is closed and the heater is fitted so that its tip reaches the gas inlet.

When this ceramic heater is energized to generate heat and fuel gas is fed through the gas inlet, ignition occurs near the gas inflow date. This ignition flame is ejected from the opening at the tip of the heat-resistant cylinder due to the pressure of the fuel gas.

Here, since the gas flow path of the fuel gas is surrounded by a cylindrical body made of a heat-resistant material, it is hardly affected by heat loss due to wind cooling, and can be efficiently heated by the ceramic heater. Therefore, the fuel gas passing through the gas flow path is ignited at a lower ignition temperature than in the case where there is no cylinder made of heat-resistant material.

Furthermore, since the temperature can be reduced, the heat generation temperature of the ceramic heater can be lowered, and the durability of the heater can be improved.

[Example] Next, the present invention will be described based on a first example shown in FIGS. 1 to 4.

Ignition device A using a ceramic heater shown in FIG.
Ceramic heater 1 used for igniting methane gas.
The outer cylinder 2 is fitted into the outer cylinder 2. This ignition device WA is attached near the main burner 100 of a gas cooker (not shown).

In the ceramic heater 1, the rear end (not shown) of the heater body 3 is embedded in an insulator 4 (cylindrical), and the tip 31 protrudes from the tip surface 41 of the insulator 4. Heater body 3
is a ceramic sintered body (flat plate) mainly composed of silicon nitride.
32, a tungsten wire 33 is buried in a substantially W-shape. Both ends of this tungsten wire 33 are energized by lead wires 11 and 12 taken out from the rear end surface 42 of the insulator 4. Note that the dimensions of the tip 31 (protruding portion) of the heater main body 3 are 4 mm in width, 2 mm in thickness, and 33 mm in length.

The outer cylinder 2 is formed of a ceramic sintered body mainly composed of silicon nitride, and the rear end 21 has a slightly larger diameter and is fitted into the tip 43 of the insulator 4. Furthermore, one gas inlet 23 is formed in the side surface 22 . An opening 52 of a gas jet pipe 51 is arranged opposite to this gas inlet 23 . In addition, each dimension (shown in FIG. 3) is as follows.

The tip 24 of the outer tube 2 has a length of 38 mm and an inner diameter i=6 mm. The gas inlet 23 has a diameter, j = 3 mm, and a tip opening 2.
5 to the center of the gas inlet 23 is 1.1 mm. The distance 111 between the tip surface 34 of the heater body 3 and the tip opening 25 is 5 mm.

<About heater surface temperature to ensure ignition> Ignition device WA
As shown in Fig. 2, when 99% methane gas (200 mmAq) 5 was introduced from the gas inlet 23, ignition was ensured by setting the surface temperature of the tip 31 of the heater body 3 to 1060°C or higher. It turns out it's possible.

A comparison product E is obtained by removing the outer cylinder 2 from this ignition device A.
(shown in FIG. 8), and when similarly measured, it was found that the surface temperature needed to be 1100° C. or higher.

<About durability test> The ceramic heater 1 draws a durability life curve as shown in FIG. Here, the horizontal axis is the surface temperature of the tip 31 when the heater main body 3 is energized for 1 minute, and the vertical axis is the life when one cycle consists of energizing for 1 minute and stopping energizing for the next 1 minute. This is the number of cycles up to.

In actual use, since the heater 1 is used in an overload range of about 1-0%, the surface temperatures of the igniter A and the comparative product E during use are considered to be 1160°C and 11210°C, respectively. In other words, from the life curve in Figure 4, ignition device A can be expected to have approximately three times the durability.

FIG. 5 shows an ignition device B which is a second embodiment of the present invention.

In the ignition device B, the length of the tip 24 of the outer cylinder 2 is shortened, and the distance 1fdk between the tip surface 34 and the tip opening 25 is set to Omm. The other method is the same as the ignition device.

In ignition device B, the heater surface temperature that ensures ignition is 1075°C (10% overload temperature 11725°C).

The durability is improved by more than 2 times compared to the comparative crystal.

FIG. 6 shows an ignition device 0 which is a third embodiment of the present invention.

The ignition device C is the same as the ignition device WA except that the diameter of the gas inlet 23 is 6 mm.

In the ignition device C, the igniter surface temperature for reliable ignition is 1070°C (10% overload temperature 1177°C).

FIG. 7 shows an ignition device I) which is a fourth embodiment of the invention.

The ignition device is the same as the ignition device A except that three gas inlets 23 are formed at equal intervals of 3 mm.

The surface temperature of the heater in the ignition system to ensure ignition is 1070°C (10% overload temperature 1177°C).

The durability of the ignition device D (also the ignition device Hc) is approximately twice as high as that of the comparative product (T).

Next, the clearance 9 between the corner 35 of the heater body 3 and the inner wall 26 of the outer cylinder 2, and the distance between the tip opening 25 of the outer cylinder 2 and the tip surface 34 of the heater body 3, shown in FIGS. 9 to 11. Mk,
and the appropriate range of the diameter j of the gas inlet 23.

The appropriate clearance ρ is in the range of 0.5 mm to 2.0 mm. If the groove length is less than 0.5 mm, the passage of methane gas 5 will be inhibited, and if it exceeds 2.0 mm, the heat generation efficiency will deteriorate.

The distance WLk is appropriately within the range of O (mm) to 2 i (mm). When the distal end surface 34 of the heater body 3 protrudes from the distal end opening 25 of the outer cylinder 2, the ejection of the ignition flame 6 (see No. 21N+) ejected from the distal end surface [I25] is inhibited, and the ignition flame 6 also The temperature of the protruding portion of the main body 3 rises excessively. Moreover, if it exceeds 2i (mm), heat loss increases.

The appropriate diameter, j, is in the range of 0.5i (mm) to □i (mm).

If it is less than 0.5 ] (mm), the inflow of methane gas 5 will be poor, and if it exceeds i (mm), the reduction in ignition temperature will be poor.

The present invention includes the following embodiments in addition to the first embodiment.

In the embodiments a and l, the ignition device uses methane gas, but it may also be applied to ignite gaseous fuels such as liquefied petroleum gas, oil scum, coal gas, water gas, and blast furnace gas.

b. The shape of the ceramic insulator may be a square bar shape or a round bar shape.

C. As for the material of the ceramic insulator and the heat-resistant material cylinder, other ceramics such as alumina, Murai 1, and silicon carbide may be used. Further, the cylinder made of heat-resistant material may be made of heat-resistant metal such as stainless steel or nickel alloy.

d. In addition, molybdenum, tantalum, alloys thereof, or conductive ceramics may be used for the electric resistor.

e. Ceramic insulators may be manufactured by laminating Clean Sea 1 to ζ, and electrical resistors may be manufactured by applying conductive paste.

[Brief explanation of drawings]

Fig. 1 is an assembled perspective view of the ignition device according to the first embodiment of the present invention, Fig. 2 is an explanatory diagram explaining the ignition principle of the ignition device, and Fig. 3 is an illustration showing the ignition device. The partial sectional view, FIG. 4, is a graph showing the relationship between the heater surface temperature and the durable life curve of the ceramic heater. FIG. 5 is a partial sectional view showing an ignition device according to a second embodiment of the present invention, FIG. 6 is a partial sectional view showing an ignition device according to a third embodiment of the present invention, and FIG. It is a partial sectional view showing the ignition device of the fourth example. FIG. 8 is a side view of a comparative product. FIG. 9, FIG. 10, and FIG. 11 are explanatory diagrams for explaining appropriate dimensions of each part. In the diagram: 1...Ceramic heater 2...Outer tube (tube made of heat-resistant material) 3...Heater body 4...Insulator (
Insulator) 5...Methane gas (fuel gas) 21...
Rear end 22...Side surface 23...Gas inlet 31.
... Tip 32 ... Ceramic sintered body (ceramic insulator) 33 ... Tungsten wire (electrical resistor) A, B
, C, D...Ignition device

Claims (1)

[Claims] 1) A cylindrical body made of a heat-resistant material, which has a cylindrical shape and has at least one gas inlet on the side surface, and a ceramic heater in which an electric resistor is embedded in a ceramic insulator. An ignition device using a ceramic heater that closes the rear end and is fitted so that the tip of the heater reaches the gas inlet, the heater is energized to generate heat, and fuel gas is fed from the gas inlet to ignite it. .