JP2020183703A - Ceramic heater and exhaust emission control device using the same - Google Patents

Abstract

To provide a ceramic heater which is excellent in durability, and can equally heat an exhaust gas, and an exhaust emission control device having the ceramic heater.SOLUTION: A ceramic heater 1 comprises a heat generation resistance body 10, an electrode 20, a terminal 30 and a lead wire 40. The heat generation resistance body 10 has a bulkhead 12 for partitioning a plurality of spaces which extend in an internal space of a peripheral wall 11 in an axial line direction. The bulkhead 12 also comprises end faces 13 and side faces 14 at both ends in the axial line direction. The electrode 20 is located over the end faces 13 and the side faces 14 at both the sides continuing to the end faces 13.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a ceramic heater and an exhaust gas purification device provided with the ceramic heater.

Exhaust gas from internal combustion engines such as automobile engines contains harmful substances such as HC, CO, and NOx that cause environmental pollution, and in recent years, emission regulations for these harmful substances have been tightened. Generally, these harmful substances are purified by a method using a so-called three-way catalyst. In that case, the catalyst needs to be heated to 300 ° C. where the catalyst is activated by using the heat of the exhaust gas, but when the temperature of the exhaust gas is low such as when starting the engine, the catalyst is activated. It is not possible to purify the exhaust gas sufficiently. Further, in recent fuel-efficient automobiles, the temperature of the exhaust gas is lowered, so that the temperature of the catalyst cannot be heated to the temperature required for activation.

In order to deal with the above problems, an exhaust gas treatment device that heats a honeycomb structure made of a conductive material and heats the inflowing exhaust gas to a temperature at which the catalyst is activated is used. Recently, a honeycomb structure in which electrodes are formed on the entire surfaces of both ends has been proposed. For example, Patent Document 1 includes a large number of through holes made of a conductive material and partitioned by a partition wall substantially parallel to the gas flow direction, and both end surfaces on the gas inflow side and the gas outflow side, and energizes the partition wall. It is a honeycomb body for energization heat generation that controls heat generation by controlling the flow of electric current at the time of operation. It is provided with an electrode portion having a low volume resistivity and a heat generating portion having a high volume resistivity, and the electrode portions are both end surfaces. It is formed on the entire surface, the volume resistivity of the heat generating part is 0.1 to 10 Ω · cm, the volume resistivity of the electrode part is 1/10 or less of the resistivity of the heat generating part, and at least the heat generating part is a composite of metal and ceramic. A honeycomb body for energizing heat generation made of a material is disclosed.

Japanese Unexamined Patent Publication No. 2010-229976

As a method of forming electrodes on both end faces of a honeycomb structure made of a ceramic material, methods such as firing, plating, vapor deposition, and sputtering are generally used. However, in the honeycomb structure in which the electrodes are formed on the end faces by these methods, the entire electrode may not be uniformly energized and the honeycomb structure may be partially energized. In that case, the honeycomb structure generates abnormal heat. Therefore, there is a problem that cracks are likely to occur. Further, by forming the electrode on the end face of the honeycomb structure, there is a problem that the pressure loss increases and the purification efficiency decreases.

This disclosure is
A heating resistor made of a ceramic material, which has a tubular peripheral wall and a partition wall that divides the internal space of the peripheral wall into a plurality of spaces extending in the axial direction.
Electrodes provided at both ends in the axial direction of the heat generation resistor are provided.
An object of the electrode is to provide a ceramic heater characterized in that it is located over an end face of the partition wall and both side surfaces connected to the end face.

Another object of the present disclosure is to provide an exhaust gas purification device including the ceramic heater.

In the ceramic heater of the present disclosure, since the electrodes are formed over the end face of the partition wall of the heat generation resistor and both side surfaces connected to the end faces, the resistance of the electrodes is smaller than that when the electrodes are located only on the end faces. , The entire electrode can be uniformly energized. As a result, the occurrence of cracks in the heat generating resistor can be reduced, and a ceramic heater having excellent durability can be provided.

According to the exhaust gas treatment apparatus of the present disclosure, by providing the ceramic heater of the present disclosure, the exhaust gas can be efficiently heated and the pressure loss can be reduced, so that the purification efficiency of the exhaust gas can be improved. ..

It is a perspective view in 1st Embodiment of the ceramic heater of this disclosure. It is sectional drawing which follows the AA line of FIG. 1 in the 1st Embodiment of this disclosure. It is sectional drawing of the part corresponding to line AA of FIG. 1 in the 2nd Embodiment of this disclosure. An exhaust gas purification device including the ceramic heater of the present disclosure.

<First Embodiment>
Hereinafter, the ceramic heater according to the first embodiment of the present disclosure will be described with reference to the drawings, taking as an example a heater for purifying exhaust gas. FIG. 1 is a perspective view of the ceramic heater 1 of the present embodiment. FIG. 2 is a cross-sectional view of a part of the ceramic heater 1. The ceramic heater 1 includes a heat generating resistor 10, an electrode 20, a terminal 30, and a lead wire 40.

<Heat resistor>
The heat generation resistor 10 is a tubular member, and includes a peripheral wall 11 and a partition wall 12. In the present embodiment, the heat generating resistor 10 has a cylindrical shape, but if it has a tubular shape, it may have other shapes including a triangular tubular shape, a square tubular shape, and an elliptical tubular shape.

The heat generation resistor 10 has a partition wall 12 that divides the internal space of the peripheral wall 11 into a plurality of spaces extending in the axial direction. The partition wall 12 further includes end faces 13 and side surfaces 14 at both ends in the axial direction. The space surrounded by the side surface 14 defines a plurality of distribution holes 15. The exhaust gas generated by the internal combustion engine flows in from one end face of the heat generation resistor 10, passes through the flow hole 15, and is discharged from the other end face of the heat generation resistor 10.

In the present embodiment, the cross section of the flow hole 15 is a quadrangle as shown in FIG. 1, but may have other shapes including a circle, an ellipse, and a polygon. The thickness of the partition wall of the flow hole 15 is preferably 0.05 to 0.30 mm.

The heat generation resistor 10 is made of a conductive ceramic material. Examples of the ceramic material used in the heat generating resistor 10 include ceramics containing lanthanum manganese light (LaMnO ₃ ) and lanthanum chromite (LaCrO ₃ ) having a perovskite-type crystal structure as main components. A part of La may be replaced with an element of Periodic Table 2A such as Ca, Sr and Ba, and a part of Mn and Cr may be replaced with an element such as Co, Fe, Ni, Ce and Zr. By adjusting these substitution amounts, it is possible to form a heat generating resistor 10 having various volume resistivitys.

<Electrode>
The electrodes 20a and 20b (hereinafter, collectively referred to as "electrode 20") are located over the end faces 13 at both ends of the heat generating resistor 10 and the side surfaces 14 on both sides connected to the end faces 13, respectively. .. In the conventional heater having a honeycomb structure, for example, the electrode 20 is located only on the end face 13, but in the ceramic heater 1 of the present embodiment, as shown in FIG. 2, the electrode 20 is from the end face 13. It is formed with a thickness so as to wrap around the side surface 14. In the present embodiment, the width of the electrode 20 in the thickness direction of the partition wall 12 is larger than the thickness of the portion of the partition wall 12 where the electrode 20 is not provided. Further, as shown in FIG. 2, the thickness of the electrode 20 located on the side surface 14 may be constant.

The material of the electrode 20 is not particularly limited, but a material having a volume resistivity lower than that of the ceramic material constituting the heat generating resistor 10 is used. Examples of the method for forming the electrode 20 include, but are not limited to, methods such as firing, plating, vapor deposition, and sputtering.

The volume resistivity of the conductive ceramic material used in the heat generation resistor 10 is preferably 0.1 to 500 Ω · cm. When the volume resistivity is 0.1 Ω · cm or less, the heating resistor 10 is overheated, causing problems such as cracks. On the other hand, when the volume resistivity exceeds 500 Ω · cm, the heat generating resistance Since it becomes difficult for the current to flow through the body 10 and the heat generation resistor 10 cannot be sufficiently heated, the purification efficiency of the exhaust gas is lowered.

In the present embodiment, the electrodes 20 are formed so as to wrap around not only the end surface 13 of the partition wall 12 but also the side surface 14. Therefore, since the electric resistance value of the electrode 20 is smaller than that when the electrode 20 is formed only on the end face 13, it becomes easier to energize the entire electrode 20, and the entire heating resistor 10 is also energized, so that the heating resistor is energized. 10 uniformly generates heat. As a result, partial energization of the heat generation resistor 10 and abnormal heat generation of the heat generation resistor 10 due to this can be suppressed, and the occurrence of cracks in the heat generation resistor 10 can be reduced, thereby providing a ceramic heater having excellent durability. be able to. Further, when the heat generating resistor 10 generates heat uniformly, the catalytic action can be promoted and the exhaust gas can be efficiently heated.

<Catalyst>
The catalyst for purifying the exhaust gas can be supported on a carrier different from the heat generation resistor 10, or can be supported on the partition wall 12 of the heat generation resistor 10.

Precious metals such as platinum (Pt), rhodium (Rh), and palladium (Pd) are used as the catalyst to be supported on the partition wall 12, but any material that can purify harmful substances contained in the exhaust gas is used. Not limited to these.

The exhaust gas flowing in from one end surface 13 of the heat generation resistor 10 passes through the flow hole 15 and is heated by the heat generation resistor 10 that generates heat uniformly, and is purified by the catalyst supported on the partition wall 12 to generate heat resistance. It is ejected from the other end face 13 of the body 10.

<Second Embodiment>
Next, the ceramic heater according to the second embodiment of the present disclosure will be described with reference to FIG. 3 by taking a heater for purifying exhaust gas as an example, as in the description of the first embodiment. Further, in the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted.

In the present embodiment, as shown in FIG. 3, the electrode 20 is formed so as to include the end surface 13 of the partition wall 12 as in the first embodiment.

In the present embodiment, the electrode 20 is further such that the distance in the thickness direction of the partition wall 12 between the surface of the electrode 20 and the side surface 14 of the partition wall 12 is the axis of the heat generating resistor 10 at least a part of the side surface 14. It is formed so as to become shorter in the direction, that is, toward the inside of the flow hole 15 into which the exhaust gas flows. As shown in FIG. 3, at the end of the portion located on the side surface 14 of the electrode 20, as the distance between the surface of the electrode 20 and the side surface 14 of the partition wall 12 goes inward in the axial direction of the heat generating resistor 10. The electrode 20 may be formed so as to be gradually shortened.

According to the present embodiment, the distance in the thickness direction of the partition wall 12 between the surface of the electrode 20 and the side surface 14 of the partition wall 12 is inward in the axial direction of the heat generating resistor 10 at least a part of the side surface 14. By forming the electrode 20 so as to be gradually shortened toward the direction, it is possible to reduce the occurrence of cracks in the portion of the electrode 20 where the exhaust gas from the internal combustion engine collides.

Further, according to the present embodiment, the distance between the surface of the electrode 20 and the side surface 14 of the partition wall 12 in the thickness direction of the partition wall 12 is the side surface 14 toward the inside of the flow hole 15 into which the exhaust gas flows. By forming the electrode 20 so as to be gradually shortened at least in a part thereof, it is possible to reduce the pressure loss due to clogging or the like due to the particulate matter in the exhaust gas.

<Exhaust gas purification device>
FIG. 4 is a cross-sectional view showing an example of an embodiment of the exhaust gas purification device provided with the ceramic heater of the present disclosure.

As shown in FIG. 4, in the exhaust gas purification device 100, the ceramic heater 1 of the present disclosure is housed in the case 101 with its outer periphery held by the heat insulating material layer 105. The exhaust gas purification device 100 includes an exhaust gas inlet 102 and an exhaust gas outlet 103, and exhaust pipes 104a and 104b are connected to each of the exhaust gas purification device 100.

The case 101 is made of, for example, stainless steel such as SUS303, SUS304, and SUS316, and the central portion thereof is formed in a cylindrical shape and both ends thereof are formed in a truncated cone shape. The insulation layer 105 is formed from, for example, at least one of ceramic fiber, glass fiber, carbon fiber and ceramic whiskers.

An internal combustion engine such as a gasoline engine is connected to the exhaust gas inflow side of the exhaust gas purification device 100 through an exhaust pipe 104a. The exhaust gas generated by the internal combustion engine is supplied to the case 101 through the exhaust pipe 104a and the inflow port 102, passes through the flow hole 15 of the ceramic heater 1, and is heated by the heat generating resistor 10. In the present embodiment, a catalyst is supported on the ceramic heater 1, and the exhaust gas heated by the heat generating resistor 10 is purified by the catalyst and discharged to the outside from the outlet 103 through the exhaust pipe 104b. To.

As described above, the exhaust gas purification device 100 is provided with the ceramic heater 1 of the present disclosure, so that the exhaust gas can be efficiently heated and the pressure loss can be reduced. Therefore, the exhaust gas containing harmful substances from the internal combustion engine can be exhausted. The gas purification efficiency can be improved.

In the above, the ceramic heater has been described for purifying exhaust gas, but the invention of the present disclosure is not limited to this, as long as it is an application in which a fluid such as gas or liquid is circulated in the flow hole to heat the fluid. , Applicable to anything.

1 Ceramic heater 10 Heat generation resistor 11 Peripheral wall 12 Partition wall 13 End face 14 Side surface 15 Flow holes 20, 20a, 20b Electrodes 30 Terminal 40 Lead wire 100 Exhaust gas purification device 101 Case 102 Inflow port 103 Outlet 104, 104a, 104b Exhaust pipe 105 Insulation layer

Claims (4)

A heating resistor made of a ceramic material, which has a tubular peripheral wall and a partition wall that divides the internal space of the peripheral wall into a plurality of spaces extending in the axial direction.
Electrodes provided at both ends in the axial direction of the heat generation resistor are provided.
A ceramic heater characterized in that the electrodes are located over an end face of the partition wall and both side surfaces connected to the end face. The ceramic heater according to claim 1, wherein the width of the electrode in the thickness direction of the partition wall is larger than the thickness of the portion of the partition wall where the electrode is not provided. A claim characterized in that the distance in the thickness direction of the partition wall between the surface of the electrode and the side surface of the partition wall becomes shorter toward inward in the axial direction at least a part of the side surface. Item 2. The ceramic heater according to item 2. An exhaust gas purification device including the ceramic heater according to any one of claims 1 to 3.

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