JP3813234B2 - Porous electric resistance heater - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an electrical resistance heater made of a porous material that has high total resistance and excellent structure strength, and that efficiently transfers heat to a gas or liquid passing through the inside.
[0002]
[Prior art and problems]
In a catalyst system for purifying automobile exhaust gas, a relatively large heater may be used for efficient heating for early ignition of the catalyst. For this reason, development of materials having higher specific resistance and excellent heat resistance, corrosion resistance and the like is underway. For example, Japanese Patent Laid-Open No. 7-31038 introduces an Fe—Cr heater alloy containing 8 to 20% by weight of Al. However, when a large block heater is made of a metal material, the electric resistance of the heater is reduced, and it is necessary to supply a large current in order to obtain a desired power, which is not practical.
It is also known to form slits in the honeycomb structure in order to increase electric resistance. However, since the strength of the honeycomb structure decreases due to the formation of the slits, the actual situation is that a large heater suitable for efficient heating has not been obtained.
[0003]
[Means for Solving the Problems]
The present invention has been devised to solve such problems, and the porous body block previously proposed in Japanese Patent Application No. 6-181818 has a large contact area with respect to the substrate or liquid and also has heat transfer characteristics. By paying attention to the excellent point and using this porous body block as a heater, an object is to provide a large-sized electric resistance heater having high total resistance and excellent structure strength and heating efficiency.
In order to achieve the object, the porous electrical resistance heater according to the present invention is formed in a corrugated or concavo-convex shape so that adjacent surfaces of a metal plate or foil material whose surfaces are insulated are insulated from each other. A through-hole having a structure that is laminated in a fold-like shape and having a yoke-like protrusion or burr on the periphery is formed in the corrugated or uneven peak or valley. The metal plate or foil material can also be wound in a spiral shape so that adjacent surfaces are insulated from each other . It is preferable to incline the wavefront direction of the corrugations or irregularities with respect to the direction of the fold or the spiral winding direction.
Examples of the material of the metal plate or foil material include an Fe alloy containing Cr: 8 to 30% by weight, Al: 8% by weight or less, Ti: 1% by weight or less, and Mo: 3% by weight or less.
[0004]
Embodiment
The surface of the metal plate or foil material 10 used in the present invention is insulated, and the corrugations or irregularities 11 are regularly and periodically formed as shown in FIG.
It is preferable that the corrugations or irregularities 11 have undulations that periodically change the cross-sectional shape in the wavefront direction. A through-hole 13 having a yoke-like protrusion or burr 12 is formed in a peak portion, valley portion, or middle of the corrugated or uneven portion 11.
The metal plate or foil material 10 provided with the corrugations or irregularities 11 is laminated as shown in FIG. 2 or is wound in a spiral shape as shown in FIG. Thereby, a gap 14 through which liquid or gas passes is formed between adjacent metal plates or foil members 10. In the laminated body of FIG. 2, a liquid or gas can be flowed along any direction of the left-right direction, the depth method, and the up-down direction. In the entrainment structure of FIG. 3, a liquid or gas flows along the vertical direction.
[0005]
As shown in FIG. 4, the yoke-like protrusions or burrs 12 of the adjacent metal plate or foil material 10 are engaged with each other to ensure shape stability as a laminated or rolled porous body. The yoke-like protrusions or burrs 12 thus secure the gap 14 for passing the liquid or gas and promote heat exchange with the passing liquid or gas.
The porous body is formed by folding the metal plate or the foil material 10 into a spiral fold shape. In this case, it is preferable to reinforce the bent portion, which tends to be mechanically weak or partially broken and whose electric resistance tends to increase locally, by spot welding or the like. Moreover, the metal plate or foil material 10 cut | judged can be overlap | superposed, and it can also be set as a spiral fold-shaped porous body by welding the other side alternately. In this case, the formed porous body is a rectangular parallelepiped block. Moreover, when making it into a spiral shape, as shown in FIG. 5, it is preferable to first fold the metal plate or foil material 10 provided with the corrugations or irregularities 11 and the through-holes 13 into a spiral shape, and then wind it in a spiral shape.
[0006]
It is preferable that the wavefront direction of the corrugation or unevenness 11 attached to the metal plate or the foil material 10 is inclined with respect to the direction of the fold or the winding direction. As shown in FIG. 6, for example, when the metal plate or the foil material 10 is folded in a spiral fold shape, the corrugation or unevenness 11 positioned along the inclined wavefront has the inclination direction as shown in FIG. Reverse direction. Therefore, the space | gap distribution between both surfaces becomes uniform, without the A surface and B surface of the folded metal plate or foil material 10 contact | adhering. Similarly, when the folded metal plate or foil material 10 is spirally wound (FIG. 5), the corrugation or unevenness 11 is inclined in the opposite direction between the adjacent surfaces, so that the air gap distribution between both surfaces is uniform. become.
It is necessary to form an insulating film on the surface of the metal plate or foil material 10 before being fixed in a block shape as a porous body so that adjacent surfaces are insulated from each other. The insulating film is formed by a method of heating the metal plate or foil material 10 in an oxidizing atmosphere, a method of coating an insulating material such as ceramics, or the like. In some cases, an insulating spacer may be interposed. When the electrodes are attached to both ends in the longitudinal direction of the metal plate or foil material 10 in which the adjacent surfaces are insulated in this way, a long resistance heater is formed as a whole, and the entire resistance necessary as an electric resistance heating element can be secured, Heat exchange with the liquid or gas passing through the gap 14 is promoted. Further, when the corrugations or the uneven shapes are stacked in a spiral fold shape or wound in a spiral shape with an inclination, a honeycomb structure is obtained as a whole, and an excellent structure strength is obtained.
[0007]
As the metal plate or foil material 10, Cr: 8 to 30% by weight, Si: 5% by weight or less, Al: 8% by weight or less, Ti forming a passive film excellent in heat resistance, oxidation resistance and denseness, Ti Stainless steel containing 1% by weight or less and Mo: 3% by weight or less is used. Cr is an alloy element necessary for heat resistance and oxidation resistance, and the effect of addition of Cr becomes remarkable when the content is 8% by weight or more. However, if a large amount of Cr exceeding 30% by weight is contained, manufacturability and workability due to embrittlement deteriorate, which is not preferable.
Si is effective in improving heat resistance and oxidation resistance, but if a large amount of Si exceeding 5% by weight is contained, the steel is hardened and the workability is deteriorated. Al is an alloy element that is effective in improving heat resistance, oxidation resistance and the denseness of the passive film. However, if a large amount of Al exceeding 5% by weight is contained, productivity is deteriorated. Ti is an alloy element that is effective in improving heat resistance, oxidation resistance and denseness of the passive film. However, if a large amount of Ti exceeding 1% by weight is contained, productivity deteriorates. Mo is effective in improving heat resistance and oxidation resistance, but if a large amount of Mo exceeding 3% by weight is contained, workability deteriorates.
[0008]
[Action]
Although stainless steel has a high resistance among steel materials, it is difficult to use as a heater material because it has a lower electrical resistance than nichrome. However, in the heater according to the present invention, since the metal plate or the foil material 10 is processed into a corrugated or uneven shape, the apparent specific resistance with respect to the length direction is increased, and further, laminated or spirally in a spiral fold shape. By entraining, it is possible to further increase the current flowing distance. Therefore, the resistance value as a whole of the heater is increased, and processing such as cutting is not required like a porous body made by sintering or the like, and a honeycomb structure is formed by stacking or winding. Obtainable. As a result, the degree of freedom in material selection is high in design.
[0009]
When an electrode is connected to both ends of a porous body block wound in a stack (FIG. 2) or a spiral shape (FIGS. 3 and 5) and an electric current is passed, the porous body is uniformly heated as a whole. When a liquid or gas is allowed to flow inside the porous body under these conditions, heat exchange is efficiently performed between the heated porous body and the liquid or gas. As a result, the liquid or gas is heated in a short time. In this porous body, since the gaps 14 can be formed uniformly, the amount of heat generated is also uniform. However, in some cases, the amount of heat generated can be changed intentionally, for example, between the peripheral portion and the central portion by changing a part of the material and the waveform pattern.
The porous body block can be incorporated as an electric heater in an electric warm air machine, a hair dryer or the like. In this case, since it is not necessary to heat the heater red as in the prior art, it becomes a safe electric device, and since it is not necessary to use an expensive material such as nichrome as a material, the heater itself is also inexpensive. Moreover, it can also be used for applications such as an afterburner for exhaust gas treatment. By passing the exhaust gas through a suitably heated porous body, the lean unburned exhaust gas is completely burned and becomes clean exhaust gas.
[0010]
【Example】
Example 1:
A stainless steel plate having a thickness of 100 μm, a width of 40 mm and a length of 2000 mm including Cr: 11% by weight, Si: 0.6% by weight, Al: 0.05% by weight, Ti: 0.3% by weight, and a corrugated pitch of 1.8 mm. , And press-molded into a waveform shape (FIG. 1) having an amplitude (wave depth) of 0.6 mm. A through-hole 13 having a burr 12 having a height of 0.2 mm at the periphery was formed at the top of the waveform 11. Next, bead blasting was applied to the stainless steel plate so that the sharp part of the burr 12 did not scratch the oxide film.
The treated stainless steel plate was cut to a length of 20 mm, and 32 strip-shaped plates were superposed. The both ends of each plate were spot welded alternately to form a spiral fold. The folds of the crane were folded lightly to make a block. This block was heat-oxidized at 1000 ° C. for 45 minutes in a wet hydrogen atmosphere to form a good insulating film on the stainless steel surface.
[0011]
A part of the oxide film at both ends in the longitudinal direction of the stainless steel plate in a fold-like shape was removed, and a nickel plate was spot welded to attach an electrode. Thus, a rectangular parallelepiped porous heater having a width of 40 mm, a thickness of 40 mm, and a length of 20 mm was obtained. The electrical resistance of this porous heater was about 3Ω. When a porous heater was fixed in the quartz tube and a voltage of 10 V was applied to the electrode, a current of about 3 A flowed and the temperature was raised to about 100 ° C. in 40 seconds.
[0012]
Example 2:
Corrugated pitch of 1.8 mm by press forming on stainless steel foil with thickness of 50 μm and width of 40 mm including Cr: 18 wt%, Si: 0.4 wt%, Al: 3.2 wt%, Ti: 0.14 wt% A waveform shape (FIG. 1) having an amplitude (wave depth) of 0.6 mm was applied. In this example, the wavefront direction of the wave is inclined by 5 degrees. A through-hole 13 having a burr 12 having a height of 0.2 mm at the periphery was formed at the top of the waveform 11. Next, bead blasting was applied to the stainless steel plate so that the sharp part of the burr 12 did not scratch the oxide film.
Next, the stainless steel foil was folded in half and wound into a double spiral shape (FIG. 5) to form a cylindrical porous body having a diameter of 60 mm in a tightly wound state. The cylindrical porous body was slightly loosened and subjected to a heat oxidation treatment at 1000 ° C. for 45 minutes in a wet hydrogen atmosphere. Even after the oxidation treatment, even when the cylindrical porous body was tightly wound, the electrical resistance between both ends in the longitudinal direction showed a constant value of about 8Ω at room temperature, and it was confirmed that a good insulating film was formed.
[0013]
Electrodes were attached to both ends of the stainless steel foil in the longitudinal direction by spot welding of nickel foil. The obtained cylindrical porous body was inserted into a fixing quartz tube having an outer diameter of 65 mm. The opening ratio of the cylindrical porous body in this state was 93% when measured by a weight method.
When a voltage of 10 V was applied to the cylindrical porous body electrode and a current of about 1 A was applied, the temperature was raised to about 100 ° C. in 1 minute. In addition, when a current of about 10 A was applied at a voltage of 100 V, it heated red in about 15 seconds. This cylindrical porous body also exhibited excellent heat exchange performance, similar to the porous heater of Example 1.
[0014]
【The invention's effect】
As described above, the electric resistance heater of the present invention uses a porous body in which a metal plate or a foil material whose surface is insulated is laminated or spirally wound. This porous body has good heat transfer efficiency, heats a liquid or gas passing through the inside in a short time, and easily burns even a gas containing a lean gas or an unburned component. It is also used as an afterburner. And since it can manufacture easily compared with the conventional sintered compact, it is used in various fields as various heaters.
[Brief description of the drawings]
[Fig. 1] Press-formed metal plate or foil material [Fig. 2] Laminated metal plate or foil material [Fig. 3] Metal plate or foil material wound in a spiral shape [Fig. 4] Metal plate or adjacent burrs intertwined Foil material [Fig. 5] Metal plate or foil material wound in a double spiral shape [Fig. 6] Metal plate or foil material in a fold-like shape [Fig. 7] With adjacent surfaces (A) and (B) folded in a vine shape Waveform or unevenness with reversed wavefront direction [Explanation of symbols]
10: Metal plate or foil material 11: Corrugated or uneven 12: Yoke-shaped protrusion or burr 13: Through hole 14: Gap

Claims (4)

It has a structure in which a corrugated or uneven press-molded metal plate or foil material is laminated in a spiral fold so that adjacent surfaces are insulated from each other, with yoke-like protrusions or burrs on the periphery A porous electrical resistance heater in which through holes are formed in the corrugated or uneven peaks or valleys. It has a structure in which corrugated or irregularly pressed metal plate or foil material is wound in a spiral shape so that adjacent surfaces are insulated from each other, and has a yoke-like protrusion or burr on the periphery A porous electric resistance heater in which a through hole is formed in the corrugated or uneven peak or valley.   The electric resistance heater according to claim 1 or 2, wherein a corrugated or uneven wave front direction formed on the metal plate or the foil material is inclined with respect to the direction of spiral folding or the spiral winding direction.   An Fe alloy containing Cr: 8 to 30 wt%, Al: 8 wt% or less, Ti: 1 wt% or less, and Mo: 3 wt% or less as the metal plate or foil material according to any one of claims 1 to 3 An electrical resistance heater made of porous material.

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