JPH0416000B2 - - Google Patents

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to ceramic heater elements.

[Prior art]

A flat U-shaped or V-shaped ceramic heater element is used in a regeneration heater of a device for collecting and purifying particulates contained in the exhaust gas of a diesel engine or the like. The ceramic heater element has the following features: (1) The electrode part and the fixing point can be placed on the outer periphery (cantilevered), (2) the thermal expansion at the fixing point of the heater element can be reduced, and (3) the filter end face can be made evenly. It has features such as being divisible. These features are:
This is extremely advantageous in purification devices (particularly those related to automobiles) in which exhaust gas flows through the center of the device and a particulate-collecting filter is also placed in the center.

However, in the conventional flat U-shaped or V-shaped ceramic heater element, heat is first generated at the inner periphery of the apex bend of the shape, which lacks uniform heat generation over the entire shape, causing problems in filter regeneration. arise. Usually, metal leads and metal electrode plates are often used to supply electricity to the electrode portions of ceramic heater elements. However, in the conventional ceramic heater element, the electrode portion thereof is often exposed to high temperatures, so oxidation deterioration of the metal lead and electrode plate has been a problem. Furthermore, in cantilever support, the most stress is applied to the fixed portion at the end of the leg during vibration. In the above-mentioned conventional ceramic heater element, the width or thickness of the fixing portion is relatively small, so there was also a problem in the vibration resistance of the ceramic heater element.

[Purpose of the invention]

The present invention overcomes the above problems,
It is an object of the present invention to provide a ceramic heater element that maintains the features of a U-shape or V-shape while improving uniform heat generation properties, oxidation deterioration prevention properties of metal leads, vibration resistance, etc.

[Structure of the invention]

The ceramic heater element of the present invention is made of conductive ceramic and has a U- or V-shaped flat plate shape consisting of an apex bent portion and two legs extending to both ends thereof. In a ceramic heater element in which current is applied in the longitudinal direction using the leg ends of the legs as electrodes, the cross-sectional area (hereinafter simply referred to as the vertical direction) of at least all or most of the upper parts of both legs in the direction perpendicular to the current flow (hereinafter simply referred to as the vertical direction) is , simply called "cross-sectional area")
is smaller than the cross-sectional area of the apex bend.

The U- or V-shaped ceramic heater element of the present invention, for example, as shown in FIG. 1, is composed of a vertex bent portion 1 and two leg portions 2 extending to both ends thereof. The leg portion 2 consists of a leg end portion 3 which is mainly an electrode portion and constitutes a fixing portion, and a leg upper portion 4 located above the leg end portion toward the apex bending portion. A portion of the leg end 3 is connected to a metal lead via an electrode plate.

In the above, "most part of the upper part of the leg" does not refer to the entire upper part of the leg, but refers to the part excluding a part with a large cross-sectional area. For example, the "most part of the upper leg"
As shown in Figure 1, there are two
When the above-mentioned slits are provided, it refers to the part between the two vertical slits and the part (hatched part) 6 excluding the horizontal part (dotted part) 5.
As another example, even if there is no slit, there is a part that additionally has a large cross-sectional area, and this refers to the part excluding that part.

The overall shape of the ceramic heater element, which is the subject of the present invention, may have a U-shaped or V-shaped planar shape, a modification thereof, or a combination of the two, and its thickness is not particularly limited. That is, the overall planar shape is not particularly limited in terms of the width of the legs, whether or not the legs widen toward the end, the extent of the spread, and the angular angle of both legs. However, the planar shape or the thickness must satisfy the condition that at least the cross-sectional area of all or most of the upper portions of both legs is smaller than the cross-sectional area of the vertex bending portion.

For example, the overall planar shape of the ceramic heater element of the present invention may be U-shaped as shown in FIG. 1, or V-shaped as shown in FIGS. 2 and 3. The overall planar shape may be such that one leg 51 of a V-shape is flared toward the end as shown in FIG. It may be wider. Fifth
As shown in the figure, the apex 59 of the V-shaped apex bent portion 55
may be more protruding than the one 54 in FIG. 4, or both V-shaped legs 66, 66 as shown in FIG.
1 may be wider than that in FIG. 4. The upper part 74 of the V-shaped leg as shown in FIG.
may have the same width, and the lower part 75 may be widened toward the end. Further, the shapes of the legs of both legs may be different, but are usually the same.

The ceramic heater element of the present invention is characterized in that the cross-sectional area of at least all or most of the upper portions of both legs is smaller than the cross-sectional area of the vertex bent portion. There are two methods for reducing the cross-sectional area. One of them is a method (A) in which the overall shape is simply changed without providing a slit. This method includes a method of narrowing the width of the planar shape of the leg in the direction perpendicular to the current flow (hereinafter simply referred to as width) (a ₁ ), and a method of reducing the thickness of the shape (a ₂ ). There are two.
Of course, a combination of these methods a ₁ and a ₂ may be used. Another method is to provide slits in the legs (B); these two methods (A) and (B)
can also be combined.

In the ceramic heater element of the present invention, the width of the planar shape of the legs, especially the upper part of the legs, is reduced by the above method (a ₁ ), so that the cross-sectional area of the legs, etc. is made smaller than the cross-sectional area of the vertex bending part. Can be made smaller. That is, if the leg portions are not provided with slits and the overall thickness is the same, the width of the leg portions 41 is greater than the width of the apex bent portion 40, as shown in FIG.
The width can be narrowed. In FIG. 2, the width of the leg end portion 43 and the width of the upper leg portion 42 are the same, but in this ceramic heater element, the width of the leg end portion can be made larger; Preferable for preventing heat generation.

In the ceramic heater element of the present invention, the cross-sectional area of the legs, etc. is reduced by the above method ( _a2 ), that is, by making the thickness of the legs, especially the upper part of the legs, thinner than the thickness of the apex bending part. can be made smaller than the cross-sectional area of Further, it is preferable that the wall thickness on the inner circumferential side of the apex bent portion is thicker than the wall thickness on the outer circumferential side. It is further preferable that the thickness of the leg end is thicker than the thickness of the upper part of the leg. The degree of the wall thickness is
It can be changed depending on the width of the planar shape, purpose, etc. The thickness may be the same for the entire leg portion or the entire upper portion of the leg, or may be changed as appropriate. When changing the wall thickness, it may be changed discontinuously or continuously. The above-mentioned thickness depends on the relative relationship between the two parts.
The wall thickness is determined in consideration of the desired degree of uniform heat generation, degree of heat generation area, difference in overall planar shape, required mechanical strength, ease of manufacture, and the like.

The ceramic heater element of the present invention can be obtained by the above method (B).
For example, as shown in FIGS. 1, 3 to 10, the upper legs 4, 47, 52, 57, 6
7, 72, 82, 92, 97 (shown in the order of these figures. The same applies to the following), and leg ends 3, 48, 53, 58, 68, 73, 83, 9
Legs 2, 46, 51, 56, 6 consisting of 3,98
6, 71, 81, 91, 96 In particular, by having at least one slit in the upper part of the leg, the cross-sectional area of at least a large part of the upper part of the leg can be reduced to the vertex bending part 1,
45, 50, 55, 65, 70, 80, 90, 9
The cross-sectional area can be made smaller than that of No. 5. In this case, slits 7, 8, 9, 10, 60, 6
1,69,76,84,85,11,94,1
The planar shape, number, and installation position of the slits 2,99 are not particularly limited, but the planar shape of the slits varies depending on the planar shape of the leg, the degree of its wall thickness, the desired degree of uniform heat generation, and the like.

For example, the planar shape of the slit is a rectangular shape 7 with rounded ends as shown in FIG. 1, a long rectangular shape 8 as shown in FIG. A pointed shape with a rounded end at the other end 9, a flared shape with rounded ends at both ends 1 as shown in the same figure
0, 101, round shape 11 as shown in FIG. 9, etc. Then, if necessary, change the width and length of the above shape.
The degree of divergence, diameter, etc. can be changed. Note that the shape can also be a rectangle, another square shape, or the like. Those with the same width (for example, slit 7 in FIG. 1 and slit 8 in FIG. 3) are U
It is mainly used when the widths of the legs of a letter or V-shape are the same (for example, Fig. 1 and Fig. 3). If the planar shape of the leg part is a shape that widens towards the end, for example, the fourth
As shown in the figure, the slits 9, 10,
It is preferable from the viewpoint of uniform heat generation that the planar shape of 101 is also a similar shape that widens toward the end. Also round,
Simple shapes such as rectangles and squares are convenient for manufacturing.

The number of slits is not particularly limited, and can be changed depending on the desired degree of uniform heating properties, strength, etc., the size of the planar shape of the legs, etc. For example, the number of slits provided on one leg is the third
Whether it's one as shown in the figure or four as shown in Figure 1,
There may be three as shown in Fig. 4, 11 as shown in Fig. 8, or any other number. Normally, when the planar shape of the leg is large, especially when the width is wide, the number of slits is large, and when the leg is small and narrow, the number of slits is large.
The number of slits is small. Generally, from the viewpoint of uniform heat generation property and heat generation intensity, it is preferable to provide a large number of small-shaped slits within the range permitted by manufacturing or strength considerations.

The installation location of the slit is not particularly limited as long as the cross-sectional area of at least all or most of the upper part of the leg is smaller than the cross-sectional area of the apex bend. Usually the slit is placed in the upper part of the leg. The slit installed in the upper part of the leg can be installed so that the cross-sectional area of the apex bend and the majority of the upper part of the leg are equal. That is, for example, in the ceramic heater element shown in FIG.
-The cross-sectional areas of A, B-B, and C-C are equal to each other.

Further, as shown in FIG. 5, for example, the slit has a cross-sectional area of most of the vertex bent portion 55 and the upper leg portion 57, which gradually decreases from the vertex bent portion 55 side to the lower side of the leg upper portion 57. It can be set up as desired. The ceramic heater element shown in FIG. 5 has a cross-sectional area ratio of 1:0.8:0.7 between cross-sections DD, EE, and FF. In this way, even if heat escapes to the leg end portion 58 side, the temperature of the upper leg portion 57 can be prevented from decreasing. That is, as shown in FIG. 4, for example, the inner peripheral part 501 of the vertex bending part 54 generates heat intensively, and in the upper part of the leg (shaded part) near the leg end 53, heat moves in the direction of the arrow. , the temperature of the upper part of the leg does not easily rise. Therefore, as shown in FIG.
When the cross-sectional areas of A, B-B, and C-C are equal to each other, the heat generation gradually increases from the top to the base, and it takes a long time of nearly one minute to reach saturation. However, in the case shown in FIG.
All parts except the 1st part generate heat almost simultaneously, and it takes only about 20 seconds to reach saturation.

Also, if the slits are not installed in parallel,
Usually the slit is placed approximately in the center. This means that even if the legs have the same width, as in the case of the slit 7 in FIG. 1 and the slit 8 in FIG. 3, for example,
The same applies even if the legs are flared at the end like the slit 9 in FIG. However, for example, the 10th
Even if the slit 12 is not installed substantially in the center as shown in the figure, the width of the planar shape divided by the slit may be about 1:5 or less. This is because it does not particularly impede uniform heating properties in practical use.

On the other hand, if the slits are installed in parallel,
It is preferable that the widths of each plane shape divided by the slits (for example, h, i, j in FIG. 4) are substantially the same. Furthermore, when the leg portion has a shape that widens toward the end, it is preferable to install a plurality of slits in parallel. In addition, in order to further improve uniform heat generation, small-shaped slits 8 are provided as shown in Figure 8.
It is more preferable to install a large number of 4,85 in series or in parallel.

Note that the slit can be provided not only at the upper part of the leg but also at the upper part of the leg end or the apex bend. However, in this case, it is necessary that each cross-sectional area of the leg end portion or vertex bent portion provided with the slit be larger than the cross-sectional area of the upper leg portion.

For example, as shown in FIG. 7, a slit 77 that can be used as a fixing hole can be provided at the end of the leg, or a slit can be provided along the outer peripheral surface of the apex bend. This latter case is particularly effective when the apex of the apex bend protrudes more or the width of the apex bend is wide.

In summary, the main ways to make the cross-sectional area of all or most of the upper part of the leg smaller than the cross-sectional area of the apex bend are to (1) reduce the planar shape of the leg, especially its width, and (2) reduce the width of the leg. (3) slits may be provided in the legs. When the wall thickness is constant, the above (1) and (3) are effective, and 1
In order to increase the heat generating area of one ceramic heater element, the above (3) is effective when the leg part has a relatively wide width and a shape that flares out towards the end, as in the case of the ceramic heater element shown in Fig. 6, for example. It is preferable to provide a plurality of slits. Furthermore, the above (2), (1), and (3) can be combined as appropriate.
The optimal shape of the ceramic heater element depends on the purpose (uniform heat generation or localized heat generation, extent of heating area of one ceramic heater element, heating when multiple ceramic heater elements are combined in a circular shape) Various shapes can be set depending on efficiency, energization time, power consumption, strength, etc.

In the ceramic heater element of the present invention, it is sufficient that the cross-sectional area of at least all or most of the upper part of the leg is smaller than the cross-sectional area of the apex bent portion. Therefore, the cross-sectional area of the leg end can be the same as the cross-sectional area of the upper leg, or it can be larger. The former is convenient from the viewpoint of ease of manufacture, but the latter is preferable from the viewpoint of preventing heat generation at the end of the leg. Therefore, at the end of the leg, for example, as shown in FIGS.
It is preferable not to provide a slit as shown in the figures, or for example, it is preferable that the leg end portions 53 have a shape that widens toward the end, as shown in FIG. 4, for example. Further, even if the planar widths of the upper leg portion 42 and the leg end portion 43 are the same as shown in FIG. 2, for example, the wall thickness of the leg end portion can be made thicker. Further, as described above, a slit 77 which can be used as a fixing hole may be provided at the end of the leg, as shown in FIG. 7, for example.

〔Effect of the invention〕

The ceramic heater element of the present invention has a U-shape or a V-shape.
It is characterized in that the cross-sectional area of at least all or most of the upper part of the leg is smaller than the cross-sectional area of the vertex bending part.

Therefore, the ceramic heater element of the present invention can simultaneously generate heat not only at the apex bend but also at both legs, particularly at the upper portions of both legs. Therefore, the present ceramic heater element can uniformly and easily regenerate the filter while maintaining the features derived from the U-shaped or V-shaped shape, and the energization time can be shortened, thereby reducing power consumption.

In the ceramic heater element of the present invention, the cross-sectional area of all or most of the upper part of the leg can be made smaller than the cross-sectional area of the vertex bending part, and the cross-sectional area of the leg end can be made smaller than the cross-sectional area of the upper leg or the conventional leg. It can be made larger than the cross-sectional area of the upper part. Therefore, the ceramic heater element of the present invention can reduce heat generation at the leg ends, thereby preventing oxidation deterioration of the metal leads that persist at the leg ends. Therefore, the regeneration device using the present ceramic heater element has a long life. Furthermore, the present ceramic heater element has a large cross-sectional area at the end of the leg, where stress is applied the most during vibration when the element is supported on a cantilever. Therefore, the present ceramic heater element has excellent vibration resistance. This effect is particularly great when the planar shape of each of the legs is widened from the apex bend side to the leg end side.

In the ceramic heater element of the present invention, the thickness of the shape of the ceramic heater element can be freely changed, and arbitrary slits can be provided in the upper part of the legs of the ceramic heater element.
Therefore, while maintaining the above-mentioned effects, this ceramic heater element has the following advantages compared to conventional ceramic heater elements:
The shape of this ceramic heater element can be freely designed according to the purpose. Therefore, in the present ceramic heater element, the planar shape of the heat generating part can be changed arbitrarily, and it is easy to increase the area of the heat generating part or to make the shape suitable for the device in which it is used.

In particular, the ceramic heater element of the present invention, in which both legs are flared toward each other, fits extremely well into the circular cross section of the exhaust system by combining them radially. Therefore, the ceramic heater element of the present invention is particularly suitable for application as a heater for regenerating filters for collecting particulates contained in automobile exhaust gas.

In the ceramic heater element of the present invention, the cross-sectional area of most of the bent apex portion and the upper part of the leg can be made almost the same; If the temperature is set to gradually decrease to , even if the generated heat flows slightly toward the end of the leg, the temperature at the lower part of the upper part of the leg can be prevented from decreasing. Therefore, in the present ceramic heater element, the parts other than the leg ends generate heat almost simultaneously, and the time until saturation is shortened. Therefore, the present ceramic heater element can raise the temperature of the entire heat generating part at the same time, has extremely excellent heat uniformity over the entire heat generating part, can extremely reduce power consumption, and has extremely good ignitability of the collected particulates.

〔Example〕

Embodiment Each leg 51 shown in FIG.
A ceramic heater element in the shape of a letter was manufactured by the following method. The planar lengths of the flat V-shape are a=9, b=8.8, c=20, and d=
45 mm, and its thickness is 2 mm uniform. Slit 9 has a maximum length of 10.9 mm and a width of 2 at the center.
mm, the slit 10 has a maximum length of 14.6 mm and a center width of 3 mm, and the slit 101 has a maximum length of 14.6 mm and a width of 3 mm at the center.
It has the same shape as . Cross section A-A in Fig. 4,
The cross-sectional areas of B-B and C-C are the same, and the widths (h, i, j) divided by the slits 10 and 101 are the same.

The flat ceramic heater element was manufactured as described below.

30% by weight of titanium nitride (average particle size 1μ) and 70% by weight of silicon nitride were mixed and dried in a wet process, and granulated with a small amount of polyvinyl alcohol added as a binder. This powder was pressed into a heater shape using a die press and fired at 1800° C. for 2 hours in a nitrogen atmosphere to obtain the heater element.

A heating device was set up using each of the six ceramic heater elements manufactured as described above, and a plan view of the device is shown in FIG. The heating device 13 is for regenerating a filter for collecting particulates in the exhaust gas of a diesel engine vehicle. In the figure, six ceramic heater elements are arranged radially such that the leg ends of the ceramic heater elements 14 are placed on the outer periphery. Note that the ceramic heater element 14 is fixed with fixing screws 15 via a metal case. The ceramic heater element 14 is
It is connected to the electrode terminal section 16 via a metal lead.

The GG sectional view of the device in FIG.
Shown in Figure 2. According to the figure, the heater element 14 is surrounded by insulating rings 17 and 18 made of fired alumina from above and below.
are sandwiched between a cushion material 19 entwined with ceramic fibers and a nickel electrode plate 20, which is further sandwiched between a metal case 21
It is contained in The insulating ring 17 is fixed to the case 21 by tightening the insulating ring 17 to the case 21 using fixing screws (15 in FIG. 11). The electrode plate 19 is connected to a nickel lead 22 at a part not shown, and the lead 22 is taken out to the outside through an electrode terminal part (16 in FIG. 11) embedded in the insulating ring 17 and sealed, and energized. I'm starting to be able to do it. The negative side is also connected to the metal case by a lead (not shown) and grounded.

FIG. 13 shows a schematic cross-section of the above-mentioned heating device attached to the particulate collector. Heating device 1
31 is sandwiched between an inlet 30 and an upstream part of a cylindrical particulate collection structure 29 (hereinafter referred to as a filter) housed in a cast case 23 via a sealing material 24 and cushioning materials 25 and 26. and is held by flanges 27 and 28. Further, the flanges 31, 311 are connected to an exhaust pipe of an engine (not shown). arrow 32,3
21 indicates the flow direction of exhaust gas.

The reason why there is a plurality of heater elements is because the power consumption of the heater element 14 cannot be unnecessarily increased. That is, in order to regenerate the filter 29 by heating the ceramic heater, a method is adopted in which a plurality of heater elements 14 are sequentially and intermittently energized.

In the ceramic heater element used in the above embodiment, each of the legs of the ceramic heater element has a shape that widens toward the end, and has a plurality of slits in the upper part of the leg, and the cross-sectional area of the upper part of the leg is equal to smaller than the cross-sectional area. Therefore, the ceramic heater element can expand the heating area and uniformly heat the area. Therefore, according to the heating device using the present ceramic heater element, the upstream end face of the filter can be uniformly heated, and the filter can be regenerated efficiently. In addition, this ceramic heater element has the following features:
By combining the pieces, they fit extremely well into the circular cross-section of the exhaust system. Therefore, the present ceramic heater element is extremely suitable for application as a heater for regenerating filters for collecting particulates contained in automobile exhaust gas.

Furthermore, since the width of the leg end of the present ceramic heater element is wide, the cross-sectional area thereof is larger than the cross-sectional area of the upper part of the leg. Therefore, the heat generated at the end of the leg can be reduced. Therefore, the ceramic heater element of the present invention can prevent oxidation deterioration of the metal leads, and has high durability and reliability in energization.

[Brief explanation of drawings]

1 to 10 are plan views of the ceramic heater element of the present invention. In addition, Fig. 1 shows a U-shape,
FIGS. 2 to 10 are plan views of a device having a V-shape, and FIGS. 4 to 10 a V-shape with legs widening toward the end, both of which have slits in the legs.
FIG. 11 is a plan view of a heating device combining six ceramic heater elements. FIG. 12 is a GG sectional view of the heating device in FIG. 11. 13th
The figure is a schematic cross-sectional view of the heating device attached to the particulate collector. 1, 40, 45, 50, 55, 65, 70, 8
0,90,95...Vertex bending part, 2,41,4
6,51,56,66,661,71,81,9
1,96...leg, 3,43,48,53,5
8, 68, 73, 83, 93, 98... leg end,
4, 42, 47, 52, 57, 67, 72, 8
2, 92, 97... Upper part of the leg, 5... Part of the upper leg, 6... Most part of the upper leg, 54, 59... Vertex of the apex bending part, 501... Inner circumference of the apex bending part,
74... Upper part of the upper leg, 75... Lower part of the upper leg,
7-12, 60, 61, 69, 76, 77, 8
4, 85, 94, 99...slit, 13, 13
DESCRIPTION OF SYMBOLS 1... Heating device, 14, 141... Ceramic heater element, 15... Fixing screw, 16... Electrode terminal part, 17, 18... Insulating ring, 19... Cushion material, 20... Electrode plate, 21... ...Metal case, 22...Lead, 23...Cast case, 2
4... Sealing material, 25, 26... Cushion material,
27, 28...flange, 29...filter, 3
0...Inlet, 31,311...Flange,
32, 321...Flow direction of exhaust gas.

Claims (1)

[Scope of Claims] 1. It is made of conductive ceramic and has a U- or V-shaped flat plate shape consisting of an apex bent part and two legs extending to both ends thereof, and both of the legs In a ceramic heater element in which current is passed in the longitudinal direction using the leg end portions as electrodes, the cross-sectional area of at least all or most of the upper portions of both legs in the direction perpendicular to the current flow is larger than the cross-sectional area of the vertex bent portion. A ceramic heater element characterized by its small size. 2. The ceramic heater element according to claim 1, wherein the width of the planar shape of both legs in the direction perpendicular to the current flow is narrower than the width of the planar shape of the vertex bent portion. 3 The wall thickness on the inner circumferential side of the apex bent portion is thicker than the wall thickness on the outer circumferential side thereof, and the wall thickness at the upper part of the leg is thinner than the wall thickness on the inner circumferential side of the apex bent portion, and the leg The ceramic heater element according to claim 1, wherein the thickness of the end portion is thicker than the thickness of the upper portion of the leg. 4. The ceramic heater element according to claim 1, wherein each of the upper legs has at least one slit. 5. The ceramic heater element according to claim 4, wherein the planar shape of each of the legs gradually increases from the apex bend side to the leg end side, and widens toward the end. 6.Claim 5: The cross-sectional area of most of the apex bend and the upper part of the leg in the direction perpendicular to the current flow gradually decreases from the side of the apex bend to the lower part of the upper leg. The ceramic heater element described above.