JP2015141858A - heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a heater.SOLUTION: A heater 10 includes: a rod-like ceramic body 1; a heating resistor 2 embedded in the ceramic body 1; a conductor layer 3 which is provided on a surface of one end of the ceramic body 1 and electrically connected with the heating resistor 2; a ceramic cylinder 4 into which the one end of the ceramic body 1 is inserted; and a sealing material 5 which seals an end part of the ceramic cylinder 4, into which the ceramic body 1 is inserted, with the ceramic body 1, the sealing material 5 made of an insulation material. The structure reduces the possibility that the conductor layer 3 contacts with a combustion gas even if the other end of the ceramic body 1 is disposed in a combustion gas atmosphere.

Description

  The present invention relates to a heater used in an atmosphere in combustion gas.

  Ceramic heaters are known as heaters used for in-vehicle heating devices, petroleum fan heaters, or glow plugs of automobile engines. As a ceramic heater, the ceramic heater of patent document 1 is mentioned, for example.

  The ceramic heater described in Patent Document 1 includes a ceramic structure, a heating resistor embedded on the front end side of the ceramic structure, and an electrode provided on the surface on the rear end side of the ceramic structure. This ceramic heater is used with the tip of a ceramic structure provided in a combustion gas atmosphere. In the ceramic heater, a metal fitting is attached between the front end and the rear end of the ceramic structure, and the rear end is hermetically sealed. Thereby, the possibility that the electrode and the combustion gas react due to the electrode provided at the rear end coming into contact with the combustion gas is reduced.

JP 2005-190948 A

  In the ceramic heater described in Patent Document 1, the electrode of the ceramic heater is exposed inside the metal fitting. When using a ceramic heater, if the ceramic heater is heated to a higher temperature than before, there is a risk that large thermal expansion will occur in the metal fitting, which may prevent the metal fitting from being sealed. there were. As a result, the electrode and the combustion gas react with each other, and there is a possibility that the ceramic heater cannot be operated normally.

  The present invention has been devised in view of the above problems, and an object of the present invention is to provide a heater capable of suppressing the reaction between the electrode and the combustion gas by keeping the electrode sealed. It is in.

  A heater according to one aspect of the present invention includes a rod-shaped ceramic body, a heating resistor embedded in the ceramic body, and provided on the surface of one end of the ceramic body and electrically connected to the heating resistor. A conductive layer, a ceramic cylinder in which the one end of the ceramic body is inserted, and a sealing material made of an insulating material that seals the end of the ceramic cylinder in which the ceramic body is inserted together with the ceramic body; It is provided with.

According to the heater according to one aspect of the present invention, a conductor layer is provided on the surface of one end (rear end) of the ceramic body, and further, among the ceramic cylinder into which one end of the ceramic body is inserted, and the ceramic cylinder And a sealing material made of an insulating material for sealing the end portion into which the ceramic body is inserted together with the ceramic body. Thereby, even if the heater is heated to a temperature higher than that of the conventional case, the ceramic cylinder does not cause a large thermal expansion unlike the metal fitting, so that one end of the ceramic body can be kept airtight. Therefore, the possibility that the conductor layer and the combustion gas react due to the conductor layer touching the combustion gas can be reduced. As a result, the durability of the heater can be improved.

It is sectional drawing which shows the heater of the example of embodiment of this invention. It is sectional drawing which shows the heater of the modification 1 of embodiment of this invention. It is sectional drawing which shows the heater of the modification 2 of embodiment of this invention. It is sectional drawing which shows the heater of the modification 3 of embodiment of this invention.

  Hereinafter, some embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the heater 10 according to the embodiment of the present invention includes a ceramic body 1, a heating resistor 2 embedded in the ceramic body 1, and one end of the ceramic body 1 (hereinafter also referred to as a rear end). The conductor layer 3 provided on the surface of the ceramic body 4, the ceramic cylinder 4 in which one end of the ceramic body 1 is inserted, and a sealing material for sealing the end of the ceramic cylinder 4 where the ceramic body 1 is inserted together with the ceramic body 1 And 5. The heater 10 can be used, for example, for gas heating, gas range ignition, a car engine glow plug, and the like. Specifically, the heater 10 is used with the other end (hereinafter, also referred to as the front end) of the ceramic body 1 disposed in a combustion gas atmosphere.

<Configuration of ceramic body>
The ceramic body 1 is a member in which a heating resistor 2 is embedded. 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 oxide 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 is preferably made of silicon nitride ceramics. This is because silicon nitride ceramics is superior in terms of strength, toughness, insulating properties, and heat resistance. 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 by mixing SiO ₂ amount is adjusted to be 1.5 to 5 wt%, molded into a predetermined shape Then, by firing at a temperature of 1650 to 1780 ° C., the ceramic body 1 made of silicon nitride ceramic can be obtained. For the firing, for example, hot press firing can be used.

In addition, when using silicon nitride ceramics for the ceramic body 1 and further using a compound such as Mo or W for the heating resistor 2 described later, MoSi ₂ or WSi ₂ or the like is further mixed with the ceramic body 1. It is preferable to keep it. By dispersing the metal silicide used for the heating resistor 2 in the ceramic body 1, 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. As a result, the durability of the heater 10 can be improved.

  When the shape of the ceramic body 1 is a plate shape, the length of the ceramic body 1 is set to, for example, 30 to 60 mm, the width is set to 4.7 to 9 mm, and the thickness is set to 1.3 to 6 mm.

<Configuration of heating resistor>
The heating resistor 2 is a member that generates heat when a current flows. The heating resistor 2 is embedded in 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. As a to-be-heated material from which the heat | fever is transmitted from the surface of the ceramic body 1, the light oil etc. which are supplied inside the diesel engine for motor vehicles etc. are mentioned, for example.

  The heating resistor 2 is provided on the tip side of the ceramic body 1. The heating resistor 2 has a longitudinal cross-sectional shape (a cross section parallel to the length direction of the heating resistor 2), for example, a folded shape. Specifically, the heating resistor 2 has a plurality of folded portions near the tip of the ceramic body 1. The total length of the heating resistor 2 is set to 28 to 52 mm, for example. Note that the shape of the cross section of the heating resistor 2 (the plane perpendicular to the length direction of the heating resistor 2) can be set to a circular shape, an elliptical shape, a rectangular shape, or the like.

  The heating resistor 2 has, for example, a carbide, nitride, silicide, or the like such as W, Mo, or Ti 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. Furthermore, tungsten carbide is excellent in heat resistance.

  Further, when the ceramic body 1 is made of silicon nitride ceramic, it is preferable that the heating resistor 2 contains tungsten carbide as a main component and 20% by mass or more of silicon nitride is added. By adding silicon nitride to the heating resistor 2, the thermal expansion coefficient of the heating resistor 2 and the thermal expansion coefficient of the ceramic body 1 can be brought close to each other. Thereby, the thermal stress produced by the thermal expansion difference between the heating resistor 2 and the ceramic body 1 when the heater 10 is heated or lowered can be reduced.

<Configuration of conductor layer>
The heater 10 has two conductor layers 3. The conductor layer 3 is a member for electrically connecting the heating resistor 2 and an external power source (not shown). The conductor layer 3 functions as an electrode portion of the heater 10. The conductor layer 3 is electrically connected to the heating resistor 2. The conductor layer 3 is provided on the surface of one end of the ceramic body 1. The conductor layer 3 is made of a metal material such as Ag or Cu. The conductor layer 3 is formed by, for example, screen printing. The shape of the surface of the conductor layer 3 is, for example, a square shape. The dimensions of the conductor layer 3 can be set, for example, such that the length in the length direction of the ceramic body 1 is 5 mm, the width is 6 mm, and the thickness is 100 μm.

<Configuration of lead terminal>
The lead terminal 6 is a member for transmitting electricity from the external power source to the heating resistor 2. The lead terminal 6 is provided separately on each conductor layer 3. One end of the lead terminal 6 is connected to the conductor layer 3, and the other end is drawn out of the ceramic cylinder 4. The lead terminal 6 drawn out of the ceramic cylinder 4 is connected to an external power source. The lead terminal 6 and the conductor layer 3 are joined by a brazing material. As the brazing material, for example, silver brazing, gold-copper brazing, or silver-copper brazing can be used. The lead terminal 6 is made of Ni, for example. The region other than the portion joined to the electrode or the portion connected to the external power source in the lead terminal 6 is covered with an insulating tube. The tube is made of, for example, a resin material. In particular, it is preferably made of a fluororesin having excellent heat resistance.

<Configuration of ceramic cylinder>
The ceramic cylinder 4 is a member for protecting the conductor layer 3 and the lead terminal 6 together with the sealing material 5. Specifically, it is a member provided to prevent the combustion gas from contacting the conductor layer 3 and the lead terminal 6 when the tip of the ceramic body 1 is disposed in the combustion gas atmosphere. The ceramic cylinder 4 is a cylindrical member such as a cylindrical or square cylinder. The rear end of the ceramic body 1 is inserted into the ceramic cylinder 4. The ceramic cylinder 4 surrounds the rear end of the ceramic body 1 together with the conductor layer 3 and the lead terminal 6. The ceramic cylinder 4 is made of a ceramic material such as alumina or silica. When the ceramic cylinder 4 is cylindrical, the dimensions can be set to 42 mm in length, 8 mm in inner diameter, and 10 mm in outer diameter, for example.

<Configuration of sealing material>
The sealing material 5 is a member for protecting the conductor layer 3 and the lead terminal 6 together with the ceramic cylinder 4. The sealing material 5 is provided at the end of the ceramic cylinder 4 where the ceramic body 1 is inserted. The sealing material 5 seals the end of the ceramic cylinder 4 together with the ceramic body 1. Thereby, when the front-end | tip of the ceramic body 1 is arrange | positioned in combustion gas atmosphere, this combustion gas can prevent entering the inside of the ceramic cylinder 4. FIG. The sealing material 5 is made of an insulating material such as ceramics such as alumina or silica. The sealing material 5 is provided so as to close the opening surface of the ceramic cylinder 4 in which the ceramic body 1 is inserted. Of the sealing material 5, the thickness of the ceramic body 1 in the length direction can be set to 10 mm, for example.

  The sealing material 5 can be provided by the following method. Specifically, in a state where the ceramic body 1 is inserted into the ceramic cylinder 4, a raw material to be the sealing material 5 is poured into the end portion on the side where the ceramic body 1 is inserted. As a raw material used as the sealing material 5, the thing which disperse | distributed the alumina or the silica in the inorganic binder etc. can be used. After pouring the raw material used as the sealing material 5 in the ceramic cylinder 4, the sealing material 5 can be provided by heating at the temperature of 200 degrees C or less.

  In the heater 10 of the present embodiment, the conductor layer 3 is provided on the surface of one end (rear end) of the ceramic body 1, and the ceramic cylinder 4 into which one end of the ceramic body 1 is inserted and the ceramic cylinder 4 A sealing material 5 made of an insulating material that seals the end portion into which the ceramic body 1 is inserted together with the ceramic body 1 is provided. Thereby, even if the heater 10 is heated to a temperature higher than the conventional temperature, the ceramic cylinder 4 does not cause a large thermal expansion unlike the metal fitting, so that one end of the ceramic body 1 can be kept airtight. . Therefore, the possibility that the conductor layer 3 reacts with the combustion gas can be reduced. As a result, the durability of the heater 10 can be improved.

<Modification 1>
In the heater 10 of the above-described embodiment, the sealing material 5 is provided only in the vicinity of the opening surface of the ceramic cylinder 4, but is not limited thereto. As shown in FIG. 2, in the heater 10 of the first modification, the sealing material 5 may cover the ceramic body 1 together with the connection portion between the conductor layer 3 and the lead terminal 6. In this way, by covering the connecting portion between the conductor layer 3 and the lead terminal 6 with the sealing material 5, the conductor layer 3 can be hermetically sealed. As a result, the durability of the heater 10 can be improved.

<Modification 2>
In the heater 10 of the above-described embodiment, the inner diameter of the ceramic cylinder 4 is constant, but is not limited thereto. As shown in FIG. 3, the ceramic cylinder 4 may have an overhanging portion 41 that protrudes toward the ceramic body 1 on the entire circumference of the end portion into which the ceramic body 1 is inserted. Thereby, since a part of sealing material 5 can be covered with the overhang | projection part 41, the sealing material 5 can be protected. Further, the sealing material 5 is also provided between the overhanging portion 41 and the ceramic body 1. Thus, the durability of the sealing material 5 is improved by increasing the thickness in the length direction of the ceramic body 1 in the portion of the sealing material 5 that is not protected by the overhanging portion 41 of the ceramic cylinder 4. Can do. As a result, the durability of the heater 10 can be improved.

  The overhanging portion 41 can be projected from the inner peripheral surface of the ceramic cylinder 4 by 3 mm, for example. Moreover, the thickness of the ceramic body 1 in the length direction of the overhanging portion 41 can be set to about 1 mm. The overhang portion 41 can be formed by, for example, injection molding.

<Modification 3>
In the heater 10 according to the second modification, the surface of the sealing material 5 and the surface of the overhang portion 41 are flush with each other, but the present invention is not limited to this. As shown in FIG. 4, the sealing material 5 may wrap around the outer surface of the overhang portion 41. As a result, even if the ceramic body 1 and the sealing material 5 are displaced as a result of the expansion and contraction of the ceramic body 1 and the sealing material 5 in the length direction under the heat cycle, the overhanging portion 41 and the ceramic body 1 The sealing material 5 can always be interposed therebetween. Thereby, possibility that a clearance gap will be made between the overhang | projection part 41 of the ceramic cylinder 4 and the sealing material 5 can be reduced. As a result, the durability of the heater 10 can be improved.

1: Ceramic body 2: Heating resistor 3: Conductor layer 4: Ceramic cylinder 41: Overhang portion 5: Sealing material 6: Lead terminal 10: Heater

Claims (4)

  A rod-shaped ceramic body; a heating resistor embedded in the ceramic body; a conductor layer provided on a surface of one end of the ceramic body and electrically connected to the heating resistor; and the one end of the ceramic body A heater comprising: a ceramic cylinder into which the ceramic body is inserted; and a sealing material made of an insulating material that seals an end of the ceramic cylinder in which the ceramic body is inserted together with the ceramic body.   A lead terminal connected to the conductor layer and drawn out of the ceramic cylinder is further provided, and the sealing material covers the ceramic body to the one end together with a connection portion between the conductor layer and the lead terminal. The heater according to claim 1.   The ceramic cylinder has a projecting portion projecting toward the ceramic body on the entire circumference of the end portion, and the sealing material seals between the projecting portion and the ceramic body. The heater according to claim 1 or 2, characterized by the above.   The heater according to claim 3, wherein the sealing material wraps around an outer surface of the overhanging portion.

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