JPS6180785A - Ceramic heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to ceramic heaters.

(Prior Art) It is known to use an arch-shaped ceramic heater such as a flat U-shape or V-shape as a regeneration heater of a device for collecting and purifying particulates contained in exhaust gas of a diesel engine, etc. From the viewpoint of reproducibility, it is preferable that the heat generating parts are uniformly distributed. Therefore, one of the possible external shapes is an arch shape with the legs widening toward the end and openings appropriately distributed.

(Problem to be Solved by the Invention) However, in a ceramic heater element having this type of shape, heat is generally first generated at the inner and peripheral portions of the apex bent portion of the shape, so the heat generation property is not uniform throughout the shape. , problems such as deterioration of the heat resistance of the heater itself and cracking due to differences in thermal stress occur.

(Means for Solving the Problems) The present invention has an arch-like flat plate shape made of conductive ceramic and consisting of an apex bent portion and two flaring leg portions extending to both ends thereof, and A ceramic heater in which electricity is supplied in the longitudinal direction using the leg ends of both legs as electric bridge parts,
With respect to the cross-sectional area of each heat-generating region of the leg section separated by the opening in the direction perpendicular to the direction of current flow, the cross-sectional area of the heat-generating portion is made larger at the outer periphery of the arch shape than at the inner periphery.

(Example) An example of the present invention will be described in detail with reference to FIG. The ceramic and the heater have an arch shape, and the open end portions are electrode portions 2 and 3, and the other portions are heat generating portions 1.

The electrode part 2.3, the heat generating part 1, and the ceramic heat generating resistor material are made of titanium nitride and silicon nitride. The electrode parts 2 and 3 are coated with PT, Ni, or Mo on the front and back surfaces of the terminal part 21.31.
It is constructed by fixing metals such as by paste baking or vapor deposition. The heat generating part 1 has two openings 4, 5, 6.7 in each case on the side near the electrode part 2.3, and one opening 8.9 in each case at the arch tips. The openings 4, 5.8 and 6.7.9 open the heating parts 10, 11, 12° 16.17 and 13. 14.
15. 18. It is branched into 19. Furthermore, the presence of the openings forms gathering portions 22.23 and tip portions 2o.

In this example, to list specific numerical values, the thickness of the heat generating part 1 is 2 mm, and the width of each heat generating part (in the direction perpendicular to the current flow; the same applies hereinafter) is as follows at 1o, tt, and 12. They are 3mm and 2mm, respectively, and the heat generating part 1
6.17 are 4.5 mm and 3.5 mm, respectively, so that the cross-sectional area of the heat generating part is large wherever it is in the arch-shaped outer periphery.

Of course, since the openings 4.5, 8.6° and 7.9 of the heat generating section 1 are line-symmetrical, the heat generating section 13 on the right side of FIG.
The width dimensions of 14.15 and 18.19 are also the same as above.

In this state, when a metal electric wire (not shown) is fixed to the electrode part 2.3 and electricity is passed between the electrode parts 2.3, the current flows: electrode part 2 - heat generating part 10, 11.12 = gathering part 21 - heat generating part 16
．． 17-Tip part 20-Branch part 18.19-Collecting part 22-
It flows from the heat generating parts 13, 14, 15 to the electrode part 3. In this case, since the gathering parts 22 and 23 have no openings and have a larger cross-sectional area than other parts, they do not generate heat (((). Therefore, the heat generation temperature is higher in each of the heat generation parts 10 to 15 and 16 to 19.
! and a tip portion 20. The electrode portion 2.3 does not generate heat because its cross-sectional area is larger than the cross-sectional area of each of the heat generating portions and the tip portion. By adopting such a structure, the effect of dispersing the heat generating parts is obtained, and the ceramic heater for ignition is effective as having many ignition sources over a wide area.

By the way, FIG. 3 shows a comparison of this heater shape with the heater shape shown in FIG. 2 from the viewpoint of heat uniformity of the heater. In the heater shape shown in Fig. 2, the heat generating part is 10°, 1
1", 12', 13", 14", and 15", the widths are 2 mm, 2 mm, and 2 mm, respectively, and the heating part 16',
17', 18'.

At 19°, the cross-sectional area of each heat generating portion is set to be equal to 4 mm and 4 mm, respectively, for both the inner and outer circumferential portions of the arch shape. Moreover, the thickness is constant at <2 mm, which is the same as that in FIG. Figure 3 shows the surface temperature of each part of the heater heat generating part measured with a radiant temperature needle when 400W of current is applied to these two heater shapes in a steady state with no wind. The shape of the heater in FIG. 1 is plotted with the X mark, which corresponds to the shape of the heater in FIG. From this, it is clear that the first model has better thermal uniformity, and the overall temperature difference is reduced from 110°C in the model shown in Figure 2 to 55°C in the model shown in Figure 1. became. This is because, in general, in a heater formed in an arch shape, current flows most easily in the inner periphery, and the outer periphery is easily cooled, so the temperature at the outer periphery inevitably becomes low, as in the case of Figure 2. . On the other hand, if you increase the cross-sectional area of the outer periphery as shown in Figure 1,
Current flows easily to the outer periphery (as a result, an overall uniform temperature distribution is obtained).

Note that this ceramic heater was manufactured as described below. That is, 35 wt% TiN (titanium nitride) with an average particle size of 1 μm and Si3N4 (
Silicon nitride>55wt% was wet mixed, and after drying, a small amount of polyvinyl alcohol was added as a binder to obtain a powder for molding. This was pressed into a heater shape using a die press and fired at 1800°C for 2 hours in an N2 atmosphere. The PT paste was baked on the terminal portion of the obtained ceramic heater at 1200°C for 1 hour in an H2 atmosphere.

As a second embodiment, the planar shape of the heater is the same as that in Fig. 2, but the thickness is not uniform (the cross section A-A in Fig. 2 is like that in Fig. 4, However, the same effect can be obtained with a thicker shape.

Further, in the above example, the basic shape of the heater shown in FIG. 1 was used, but it may have a U-arch shape as shown in FIG. 5. Furthermore, although two openings are provided in each of the electrode sections 2 and 3, there may be only one opening.

Next, application examples of the ceramic heater of the present invention will be explained.

FIG. 6 is a front view of a heating device 40 using six ceramic heaters according to the embodiment described above, with a portion of the presser ring 42 removed. This device 40 is for regenerating a filter for collecting particulates in the exhaust gas of a diesel engine vehicle. In FIG. 6, the ceramic heaters 41 are left radially so that their electrode portions are placed on the outer periphery. Each ceramic and kuhita 41 are A-A in FIG.
As shown in FIG. 7, which is a cross-sectional view, it is left on the plasma-sprayed surface 44 of a metal case 43, and is fixed by a retaining ring 42 screwed into the case 43 via a ceramic insulating ring 45. .

Each electrode part of the ceramic heater 41 is provided with an electrode fitting 4.
6.47 is brazed, and the positive side electrode fitting 46
is connected to a lead 48 made of nickel, and this linide is taken out to the outside through an electrode terminal portion (49 in FIG. 6) embedded and sealed in an insulating ring 45 so that it can be energized.

Note that the negative side electrode fitting 47 is connected to the metal case 43 and grounded.

FIG. 8 shows a schematic cross-sectional view of the above-mentioned heating device attached to the particulate collector.

The heating device 40 is housed within a casting case 50 with a sealing material 51 and John materials 52 and 53 interposed therebetween.
! The inlet 54 is held in an upstream portion of a cylindrical particulate collection structure 54 (hereinafter referred to as a filter) by flanges 55 and 56 while being sandwiched between the inlet 54 and the inlet 54 . Further, the flanges 57 and 58 are connected to an exhaust pipe of an engine (not shown). Note that arrows 59 and 60 indicate the gas flow direction.

The reason why there are a plurality of ceramic heaters 24 is that the power consumption of the battery cannot be unnecessarily increased. That is, in order to regenerate the filter 54 by heating the ceramic heater 41, a method is adopted in which the heaters 41 of a plurality of ceramic heaters are sequentially and intermittently energized.

The ceramic heater of the purification device of this example has excellent heat uniformity, so there is little deterioration of heat resistance due to local overheating, and there is no problem of cracking due to differences in thermal stress, making it extremely reliable. ing.

Therefore, the ceramic heater of the present invention is extremely suitable for application as a heater for regenerating a filter for collecting particulates contained in automatic military exhaust gas.

It goes without saying that the present invention can be applied to various other uses in addition to regenerating particulate filters and heating heaters.

(Effects of the Invention) According to the present invention, it is possible to reduce the temperature difference between the arch outer peripheral portion and the arch inner peripheral portion of the heater, and therefore, it is possible to obtain a heater with good heat uniformity.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, FIG. 2 is a plan view of a heater used to explain the operation of the present invention, FIG. 3 is a characteristic diagram used to explain the operation of the present invention, and FIG. 5 is a sectional view corresponding to the A-A cross section of FIG. 2, FIG. 5 is a plan view showing still another embodiment of the invention, and FIG.
The figure is a plan view showing an example of application of the present invention, and Figure 7 is A of Figure 6.
-A sectional view and FIG. 8 are sectional side views showing an example of application of the present invention. 4-9...Opening part, 10-19...Heating part, 21°31...Terminal part.

Claims (1)

[Claims] It comprises terminal parts spaced apart from each other and an arch-shaped heat generating part connected between the terminal parts, the heat generating part is made of a ceramic resistance material that generates heat when electricity is passed between the terminal parts, and the heat generating part 1. A ceramic heater in which a plurality of openings are provided to separate heat generating areas, the ceramic heater being characterized in that the cross-sectional area of the outer periphery of the arch is larger than the cross-sectional area of the inner periphery of the arch.