JPH02251015A - Ceramic heater for ignition - Google Patents

Abstract

PURPOSE:To enable lowering the operative surface temperature set for ignition so as to achieve an improvement in the durability by enclosing a heater assembly in a sheath in such a manner as to provide some space therebetween and by forming a plurality of openings in the sheath. CONSTITUTION:With rise of the temperature at the surface of a heater assembly 10, the temperature of a sheath 22 which encloses the heater assembly 10 also rises by its heating. Between the sheath 22 and the heater assembly 10 is provided a space which permits entry of fuel gas mixed with air. The mixture of fuel gas and air which enters this space slows down in the rate of passage and, during the passage, is exposed to heating by the heater assembly 10 and the sheath 22. Therefore, the time for which the fuel gas mixture is heated is lengthened and its temperature rises sufficiently high for the ignition. As a result, the fuel gas can be easily ignited. Thus the lengthening of the time for heating the fuel gas permits the heating to be moderated in temperature and the temperature of a ceramic heater can be set at a lower point.

Description

[Detailed Description of the Invention] [Field of Application] The present invention relates to a ceramic heater in which a heat generating resistor is embedded inside a ceramic, and in particular to improvements in ignitability and durability when used for igniting gaseous fuel. This invention relates to an improved ceramic heater.

BACKGROUND OF THE INVENTION [0002] In gas combustion appliances such as water heaters and space heaters used in general households, discharge ignition type ignition devices that apply a high voltage between electrodes to generate a spark discharge are often used.

In addition, in recent years, control devices using microcomputers have been installed to control the temperature during heating and stabilize the combustion state.

However, the spark ignition type tends to generate noise due to spark discharge, and when used for a long period of time, it becomes even more likely to generate noise, and depending on the aging of the combustion equipment, the generated noise may be harmful to the control device. It is conceivable that there may be cases where this could have an impact.

Therefore, instead of the conventional discharge ignition type ignition device, it is considered to use a ceramic heater, which is not affected by carbon noise, as the ignition bag HH of the combustion equipment for the control device.

For example, as shown in FIG.
is sealed. This involves printing a resistor paste that will become the heating resistor 13 on a ceramic base made by dry pressing silicon nitride powder, which will become the ceramic plate 11, and then overlaying the dry-pressed ceramic base in the same manner as in Section I. These are fired simultaneously to form a C.

Therefore, ceramic heaters are not usually made into complicated shapes, and their surfaces are often plain and flat.

[Problems to be Solved by the Invention] However, when attempting to ignite °C1 gaseous fuel using a ceramic heater whose surface is a pure flat surface, the heating time is approximately 100°C compared to the gaseous fuel. Not given.

Therefore, in order to raise the temperature of the gaseous fuel to the ignition temperature, the surface temperature of the ceramic heater must be raised to a sufficiently high temperature in a short time.

In particular, city gas, which is supplied to general households as a gaseous fuel, is recently being converted to natural gas.As this natural gas has methane as its main component, it has poor ignitability, so it is difficult to ignite it using a ceramic heater. For this purpose, a high surface temperature of about 1100'C is required for the ceramic heater.

When used repeatedly at such high temperatures, even ceramic heaters using silicon nitride, which has excellent heat resistance and durability, tend to deteriorate in durability and have a shortened lifespan.

An object of the present invention is to provide a ceramic heater mainly used for igniting gaseous fuel, which can set a low surface temperature during ignition operation and, as a result, improve durability. .

[Means for Solving the Problems] The ceramic heater for ignition of the present invention has a heating resistor inside the ceramic, and includes a heater heating section that generates heat in response to an electric current applied to the heating resistor, and the heater heating section. and a beater support part that supports the heater heat generating part, and the heater heat generating part is arranged with a space between the heater heat generating part and the cover part, and a beater support part that supports the heater heat generating part. The technical means is that a plurality of openings are formed.

[Function] In the present invention, when the ceramic heater ignites the 'C gas fuel, when the heat generating resistor is energized and generates heat, the temperature of the surface of the heater heat generating portion rises, and
The cover portion covering the heater heat generating portion is heated, and the temperature of the cover portion also rises.

On the other hand, the heater heat generating part is covered by a cover part having an opening, and there is a space between the cover part and the heater heat generating part, and there is a space into which gaseous fuel mixed with air can enter.

Therefore, when the mixture of gaseous fuel and air enters this space, its passage speed becomes slow, and when passing through this space, it receives heat from the heater heat generating part and heat from the cover part. This increases the heating time,
The temperature rises to the ignition temperature in 4 minutes. Therefore, gaseous fuel is easily ignited.

[Effects of the Invention] In the present invention, since the heating time of the gaseous fuel I\ is longer,
There is no need to raise the heating temperature to the required amount 1.

Therefore, the temperature of the ceramic heater can be set low. As a result, the durability of the ceramic heater can be improved, and the life of the ceramic heater can be extended.

[Example] The present invention will be explained based on embodiments shown in the drawings.

FIG. 1 shows a ceramic heater 1 (hereinafter referred to as "heater 11") according to the present invention.

The heater 1 consists of a heater heat generating part 10 and an insulator 20 for insulation, and is provided with lead wires 4.5 for conducting electricity.

The heater heat generating section 10 is, for example, shown in FIG. 2, and as described above, includes two ceramic plates 11 made of silicon nitride.
A heating resistor 13 is sealed and integrated between the ceramic plates 11 and 12, and a metallized surface (not shown) is formed on the surface of the ceramic plate 11.12. The conductor pattern 14.15 provided between the ceramic plates 11, 12 is electrically connected to this metallized surface, and is also electrically connected to the -1 line 4.5 connected to this metallized surface.

1iji 7-20 is a support part for supporting the heater heat generating part 10, and includes a fixing part 21 for fixing the heater heat generating part 10, and a cylindrical part 22 for covering the heater heat generating part 10.
It is integrally formed with.

The cylindrical part 22 has a cylindrical shape, one end of the cylindrical part 22 becomes an open part 23, and the other end becomes the fixed part 2.
It is integrated with 1 and ζ.

As shown in FIGS. 3 and 4, the cylindrical portion 22 is spaced apart from the heater heat generating portion 10 to provide a space into which the gaseous fuel to be ignited can enter.

Here, as shown in FIG. 4, it is desirable that the clearance C [mm 1 between the heater heat generating part 10 and the inside of the cylindrical part 22 is set to be C=0.5 to 2.0. The inner diameter of the cylindrical portion 22 must satisfy this clearance C.

Further, the distance ρ between the position of the opening part S23, which is the tip of the cylindrical portion 22, and the tip 16 of the heater heat generating portion 10 is
For f￥D, 〃=0-2D:;9 is determined.

Further, an opening 2/1.25 is formed in the cylindrical portion 22 at a position that encloses the heater heat generating portion 10.

Here, as shown in FIG. 5, the openings 24 and 25 are circular, and the diameter d is set to be C1 d=D/2 to D with respect to the inner diameter of the cylindrical portion 22.

The heater heat generating part 10 is fitted into a hole 26 formed in the fixing part 21- of the insulator 20 and bonded with a heat-resistant inorganic adhesive.

In the ceramic heater 1 of the present invention having the following configuration 1-, as shown in FIG.
It is easily ignited because it is heated.

As an example based on the above conditions, when the heater heat generating part 10 has a width of -4mm, a thickness of 2IIIT11, and a length L of the exposed part from the fixing part 21 = 33 mm, 99%
Methane, 200 ++n++A
Sample 1 as the second embodiment and Trial 1 as the third embodiment shown in FIG. 6 and FIG. 7, respectively. This is shown in Table 1 together with a comparative example of a heater that is not provided.

Table 1 (Opening diameter d-=3 [mm'J, inner diameter D-=6
[mm1l] As is clear here, the heater 1 provided with the cylindrical portion 22 can ignite the gaseous fuel at a surface temperature T that is 25-40° C. lower than a heater without the cylindrical portion 22. Note that this surface temperature ゛ is the temperature ゛ζ obtained by gradually changing the applied current, and is the so-called surface temperature 1 ゛ in a steady state.

Therefore, compared to the heater 1 without the cylindrical portion 22, the overload can be reduced, so that the durability of the heater 1 can be improved and the service life can be extended.

FIG. 9 shows the relationship between the surface temperature of the heater heating section] 0 and the durability life.

Here, energization and de-energization are performed alternately at 1-minute intervals.
This is considered as one cycle, and the durability life is shown.

The surface temperature 1゛1 here means that the surface temperature 1゛ in steady state is 1゛.
000'C2]090°C1] is expressed including the overshoot at the time of rapid temperature rise, which is an overload when current is applied at a current value of 80°C, and the surface temperature 1゛1 is
1100℃ for each surface temperature of 1゛ during steady state
, 1200'C1] at 300°C.

As a result, in the ceramic heater 1 in which the ceramic plates 11 and 12 are made of silicon nitride, the surface temperature 1 in the steady state is 1065 to 107 as shown in Table 1.
In the heater 1 according to the present invention, which is equipped with the cylindrical portion 20 that can be ignited at 5°C, the surface temperature 1', including overshoot, is approximately 1180'C, so the surface temperature during steady state for ignition is approximately 1180'C. Surface temperature when temperature T is 1100°C and includes overshoot]゛1 is 1200°
Compared to a heater that does not have a cylindrical part, it is about C1.
5 to 2 times longer life can be obtained.

Therefore, compared to a heater without a cylindrical portion, the life of the 'ζ Peter 1 can be significantly extended.

In this embodiment, since the fixing part that supports the heater heat generating part and the cylindrical part that covers the heater heat generating part are integrally formed, the entire ceramic heater assembly can be made smaller and lighter. It also facilitates assembly and installation of the combustion equipment t\.

In this example, a cylindrical shape is used for ease of manufacture and for easy fitting and fixing of the heater heat generating part, but the shape is not limited to the cylindrical shape as long as an appropriate clearance is maintained. .

Further, the number of openings in the cylindrical part is not limited to 1 or 2, but may be 3 or more, and the positions of the openings are not limited to only in the same direction of the cylindrical part, but may be provided surrounding the heater heat generating part. , may be provided on opposite sides, and each opening may have a different size.

Further, although a cylindrical portion having an opening at one end is provided as a cover portion for covering the heater heat generating portion, the end of the cylindrical portion does not necessarily have to be an opening and may be closed.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a first embodiment of the ceramic heater of the present invention, Fig. 2 is a perspective view showing the structure of the heater heat generating part of this embodiment, and Fig. 3 shows the ceramic heater of the first embodiment. A front view, FIG. 4 is a side view showing the ceramic heater of the first embodiment, FIG. 5 is a view seen from direction A in FIG. 3, and FIG. 6 shows the second embodiment of the ceramic heater of the present invention. cross section,
Fig. 7 is a sectional view showing a third embodiment of the ceramic heater of the present invention, Fig. 8 is a front view showing a ceramic heater not according to the invention, and Fig. 9 is the relationship between the surface temperature and the durable life of the ceramic heater. This is a graph showing. In the figure, 1... Ceramic plate, 10... Heater heating part, 11.12... Ceramic plate (ceramic),
DESCRIPTION OF SYMBOLS 13... Heating resistor, 20... Insulator (heater support part), 22... Cylindrical part (cover part), 23... Opening part (opening), 24.25... Opening. Agent Patent Attorney Kenji Ishiguro To OO ω pus-(t)(t)(he)(he)

Claims (1)

[Scope of Claims] 1) A heater heat-generating portion that has a heat-generating resistor inside the ceramic and generates heat in response to a current applied to the heat-generating resistor; and a cover portion for covering the heater heat-generating portion; a heater support part that supports the heater heat generating part, and the heater heat generating part is disposed at a distance from the cover part, and a plurality of openings are formed in the cover part. Features a ceramic heater for ignition.