JP6272171B2 - heater - Google Patents

Description

  The present invention relates to a heater including a ceramic body and a heating resistor provided therein.

  As a heater used for a gas range, an in-vehicle heating device, an oil fan heater, a glow plug of an automobile engine, or the like, for example, a ceramic heater disclosed in Patent Document 1 can be cited.

  The ceramic heater disclosed in Patent Document 1 includes a ceramic base, a heating resistor embedded in the ceramic base, and an electrode portion connected to the heating resistor and drawn to the surface of the ceramic structure.

Japanese Patent Laid-Open No. 10-284219

  In order to burn gaseous fuel using the ceramic heater disclosed in Patent Document 1, it is necessary to first ignite the gaseous fuel. The ignition of the gaseous fuel can be performed by supplying gaseous fuel and oxygen near the surface of the heated ceramic heater. At this time, when the ratio of oxygen is smaller than that of the gaseous fuel, oxygen cannot be sufficiently supplied to the surface of the ceramic heater, and it may take a long time to ignite the gaseous fuel.

  The present invention has been made in view of such a problem, and an object thereof is to provide a heater capable of quickly igniting gaseous fuel.

  A heater according to one aspect of the present invention includes a ceramic body and a heating resistor provided inside the ceramic body, and graphite particles are dispersed and fixed on the surface of the ceramic body. It is characterized by.

  According to the heater based on one aspect of the present invention, the graphite particles are dispersed and fixed on the surface of the ceramic body. Thus, oxygen can be adsorbed on the graphite particles by dispersing and fixing the graphite particles. As a result, the oxygen adsorbed by the graphite particles can be effectively supplied near the surface of the ceramic body at the time of ignition, so that the gaseous fuel can be easily ignited.

It is a top view which shows the heater of the example of embodiment of this invention. It is sectional drawing which cut the heater shown in FIG. 1 in the surface through which a heating resistor passes.

  Hereinafter, a heater according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1 or FIG. 2, the heater 10 according to the embodiment of the present invention includes a ceramic body 1 having a layer structure therein, a heating resistor 2 provided between the layers of the ceramic body 1, and a heating resistor. And an electrode 3 connected to the body 2. The heater 10 can be used, for example, for a glow plug or a gas range of an automobile engine.

  The ceramic body 1 is an insulating member in which a heating resistor 2 is embedded. The ceramic body 1 is formed by laminating a plurality of ceramic layers. By providing the heating resistor 2 inside the ceramic body 1, the environmental resistance of the heating resistor 2 can be improved. The ceramic body 1 is, for example, a rod-shaped or plate-shaped member.

  The ceramic body 1 is made of an electrically insulating ceramic such as insulating ceramic, nitride ceramic, or carbide ceramic. Specifically, the ceramic body 1 is made of alumina ceramic, silicon nitride ceramic, aluminum nitride ceramic, silicon carbide ceramic, or the like.

The ceramic body 1 made of silicon nitride ceramic can be obtained by the following method. Specifically, for example, 5 to 15% by mass of a rare earth element oxide such as Y ₂ O ₃ , Yb ₂ O ₃ or Er ₂ O ₃ as a sintering aid with respect to silicon nitride as a main component; the amount of SiO ₂ contained in the _Al 2 _{O 3} and sintering of 5-5% by weight amount such that 1.5 to 5 wt% is mixed SiO ₂ that has been adjusted. And the ceramic body 1 which consists of silicon nitride ceramics can be obtained by baking at the temperature of 1650-1780 degreeC after shape | molding in a predetermined shape. For the firing, for example, hot press firing can be used.

  When the shape of the ceramic body 1 is a rod shape, more specifically, when the shape is a quadrangular prism shape, the length of the ceramic body 1 is set to 20 to 100 mm, for example. Moreover, the thickness of the ceramic body 1 can be set to 1 to 6 mm and the width to 2 to 40 mm.

  The heating resistor 2 is a member that generates heat when a voltage is applied thereto. The heating resistor 2 is provided between the layers of the ceramic body 1. When a voltage is applied to the heating resistor 2, a current flows and the heating resistor 2 generates heat. The heat generated by this heat generation is transmitted through the inside of the ceramic body 1, and the surface of the ceramic body 1 becomes high temperature. The heater 10 functions when heat is transferred from the surface of the ceramic body 1 to the object to be heated. Examples of the object to be heated that can transfer heat from the surface of the ceramic body 1 include natural gas.

  Both ends of the heating resistor 2 are drawn out to the side surface on one end side of the ceramic body 1. In FIG. 2, the heating resistor 2 does not appear to be drawn out to the side surface of the ceramic body 1, but is actually drawn in a direction perpendicular to the paper surface. The heating resistor 2 has a cross-sectional shape, for example, a folded shape. Specifically, the heating resistor 2 has two parallel linear portions and a connecting portion that has an outer periphery and an inner periphery that are substantially semicircular or substantially semi-elliptical and that folds and connects the two linear portions. Yes. The heating resistor 2 is folded near the other end of the ceramic body 1. The total length of the heating resistor 2 is set to 10 to 50 mm, for example.

  The heating resistor 2 is designed to generate a large amount of heat on the other end side of the ceramic body 1. Specifically, the heating resistor 2 is formed so that the thickness is thinner on the other end side of the ceramic body 1 than on the one end side, thereby increasing the resistance per unit length on the other end side.

The heating resistor 2 contains, for example, a carbide such as tungsten (W), molybdenum (Mo), or titanium (Ti), nitride, silicide, or the like as a main component. When the ceramic body 1 is made of silicon nitride ceramic, it is preferable that the main component of the heating resistor 2 is made of tungsten carbide. Thereby, the thermal expansion coefficient of the ceramic body 1 and the thermal expansion coefficient of the heating resistor 2 can be brought close to each other.

  The electrode 3 is a member for electrically connecting the external power source and the heating resistor 2 together with the lead 4. The electrode 3 is provided on each of the one end side of the ceramic body 1 where the heating resistor 2 is drawn, and each electrode 3 is electrically connected to the end of the heating resistor 2. The electrode 3 is made of, for example, an alloy in which nickel is mixed with iron. The electrode 3 is provided on the ceramic body 1 by brazing. A lead 4 is attached to the electrode 3. The lead 4 is a rod-shaped member made of, for example, nickel or copper. The lead 4 is joined to the electrode 3 by welding.

  In the heater 10 of the present embodiment, the graphite particles 5 are dispersed and fixed on the surface of the ceramic body 1. The graphite particle 5 is a spherical lump and has a size of, for example, about 1 to 100 μm, preferably about 15 to 25 μm. Further, when the surface of the heater 10 is viewed, the graphite particles 5 are dispersed at a ratio of one graphite particle 5 to 10 to 100 particles of the ceramic material constituting the ceramic body 1. ing.

  The heater 10 of the present embodiment can adsorb oxygen to the graphite particles 5 because the graphite particles 5 are dispersed and fixed on the surface of the ceramic body 1. As a result, the oxygen adsorbed by the graphite particles 5 can be efficiently supplied in the vicinity of the surface of the ceramic body 1 at the time of ignition, so that the gaseous fuel can be easily ignited.

This is considered to be due to the following reasons. Specifically, graphite having sp ² hybrid orbitals forms (—C—O—C—) bonds between surface dangling bonds and surrounding oxygen atoms in order to stabilize the surface. . At this time, the graphite particles 5 take in oxygen. Furthermore, since heat energy of about 500 ° C. or higher is required to break the above bond and release oxygen from the graphite particles 5, oxygen atoms can be stably held in a room temperature environment. Can do. On the other hand, when the heating resistor 2 is heated to ignite the gaseous fuel, the retained oxygen atoms can be easily taken out by applying thermal energy of 500 ° C. or higher. For these reasons, by providing the graphite particles 5 on the surface of the ceramic body 1, oxygen can be adsorbed and oxygen can be taken out during ignition. As a result, the gaseous fuel can be easily ignited.

  Further, when the surface temperature of the heater 10 is normal temperature, the graphite particles 5 have a property of easily taking in oxygen and forming dangling bonds again if there is oxygen in the surroundings. Therefore, even if the heater 10 is repeatedly used, the above effect can be obtained.

  Further, the graphite particles 5 are fixed more on the other end side than the one end side on which the electrode 3 is provided in the ceramic body 1. By reducing the number of graphite particles 5 on one end side, the possibility of short-circuiting between the two electrodes 3 via the graphite particles 5 can be reduced. Further, by increasing the number of graphite particles 5 on the other end side, it is possible to facilitate ignition at a location away from the electrode 3. Therefore, the durability of the electrode 3 can be improved.

In the case where the two electrodes 3 are provided on the same surface of the ceramic body 1 as in the heater shown in FIG. 1, the region between the two electrodes 3 on the surface of the ceramic body 1 is It is preferable that the graphite particles 5 are not present. Thereby, the possibility that the two electrodes 3 are short-circuited via the graphite particles 5 can be reduced. As a method for preventing the presence of the graphite particles 5 in the region between the two electrodes 3 in the ceramic body 1, for example, after the graphite particles 5 are provided on the surface of the ceramic body 1, What is necessary is just to perform the process of sandblasting etc. with respect to the area | region between, and to remove the graphite particle 5. FIG.

  The graphite particles 5 can be fixed to the ceramic body 1 by the following method. First, a sheet is prepared in which graphite particles having an average particle diameter of 20 μm are adhered on paper. Moreover, the laminated body of the green sheet used as the ceramic body 1 after baking is prepared. And the sheet | seat to which the graphite particle 5 adheres is contact | adhered to the part which wants to adhere the graphite particle 5 among the surfaces of a laminated body, and a sheet | seat is stuck to a laminated body. In this state, firing is performed by hot pressing. At this time, by setting the particle size of the graphite particles 5 to be larger than the particle size of the ceramic particles of the ceramic body 1 before firing, the graphite particles 5 can be attached to the ceramic body 1 as the ceramic body 1 is sintered. It can be fixed to the surface.

  This is due to the following reason. Specifically, when the graphite particles 5 are inserted into the gaps between the particles on the surface of the ceramic body 1 before firing and firing is performed in this state, the graphite particles 5 are sandwiched between the ceramic bodies 1 and fired. Conclude. Then, due to the difference in thermal expansion coefficient between the graphite particles 5 and the ceramic body 1, a force that holds the graphite particles 5 is generated in the ceramic body 1. Therefore, it is possible to prevent the graphite 5 from being easily detached from the ceramic body 1. In this way, the graphite particles 5 can be fixed to the surface of the ceramic body 1.

  Further, by dispersing the graphite particles 5, unlike the case where the graphite particles 5 are provided on the entire surface of the ceramic body 1, it is possible to suppress current from flowing on the surface of the ceramic body 1. Specifically, when gaseous fuel is ignited and burned, plasma is formed in the flame. At this time, if the graphite particles 5 are provided on the entire surface of the ceramic body 1, Plasma spreads on the surface of the heater through the particles 5. If this state continues for a long time, the surface of the ceramic body 1 may be etched by plasma, and the surface of the ceramic body 1 may be uneven. If irregularities are formed on the surface of the ceramic body 1, there is a high possibility that microcracks will occur starting from the irregularities, and the long-term reliability of the heater 10 may be reduced. On the contrary, by disperse | distributing and providing the graphite particle 5, since it can suppress that a plasma spreads on the surface of the ceramic body 1, the long-term reliability of the heater 10 can be improved.

  Moreover, it is preferable that the graphite particle 5 has a crack. Thereby, since the surface area of the graphite particle 5 can be increased, more oxygen can be easily taken up. As a method for forming cracks in the graphite particles 5, for example, cracks may be generated by applying physical force to the graphite particles 5 in advance before firing by hot pressing.

1: Ceramic body 2: Heating resistor 3: Electrode 4: Lead 5: Graphite particle 10: Heater

Claims (2)

  A heater comprising a ceramic body and a heating resistor provided inside the ceramic body, wherein graphite particles are dispersed and fixed on the surface of the ceramic body.   The ceramic body is rod-shaped, and has an electrode connected to the heating resistor on one end side of the ceramic body, and more graphite particles are fixed on the other end side than the one end side of the ceramic body. The heater according to claim 1, wherein:

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