2. Description of the Related Art Generally, since an internal combustion engine for a vehicle bolws off a great quantity of harmful exhaust gas by burning a fuel, a catalyst is used for reducing the amount of harmful exhaust gas.

The catalyst is usually coated on a ceramic-based substrate, and acts to convert the harmful exhaust gas into harmless carbon dioxide or the like. Ho wever, the ceramic-based substrate is vulnerable to a thermal impact caused b y the exothermic reaction accompanied with catalyst activation and oxidation and to a vibration of the vehicle. Moreover, physical or chemical damage to the ceramic-based substrate, such as poisoning by sulfur compounds or the lik e contained in the fuel, frequently occurs.

In order to solve these problems, there has been suggested a metal subs trate coated with a catalyst therefore, instead of the ceramic (mainly, Codierite ) substrate coated with a noble metal for the catalyst. The metal substrate is

manufactured by alternately laminating a corrugated strip and a flat strip, each being made of a thin metal plate, winding the laminated metal strips, applyin g a paste-type filler metal or a sheet-type brazing foil to the wound metal strip s for increasing a binding force therebetween, and brazing the metal strips in a vacuum furnace.

The metal strips are bonded to each other by brazing the flat/corrugate d strips, which are previously wound as an integral component and inserted in a can. As with the conventional ceramic substrate, the metal substrate prod uced by brazing is formed with minute cell structures, and may be used after c oating with the catalyst thereon.

While the metal substrate basically has a similar structure to that of the ceramic substrate, it has very strong thermal and mechanical durability, com pared with the conventional ceramic substrate. Accordingly, the metal substr ate has been primarily applied to two-wheel vehicles, which has a very high te mperature exhaust gas with a high flux.

In particular, according to a recent trend of strengthening regulations ai med at reduction of exhaust gas emissions, in case of a gasoline engine, there is a method, in which the three-way catalyst is located adjacent to the engine i n order to reduce the amount of unburned hydrocarbons discharged during a c old start or idling of the engine. Alternatively, there is a method using an ele ctric heater based on the principle of the metal substrate, which activates the c atalyst in a short period of time by heating the electric heater during the cold s tart.

Meanwhile, in case of a diesel engine, a diesel particulate filter trap is used to reduce smoke of the diesel engine. As for a technology available for the diesel particulate filter trap, there are trapping technology using a ceramic filter, and regeneration technology for periodically oxidizing or burning trapp ed smoke. Recently, the electric heater having the metal substrate has been e mployed for the regeneration technology.

Here, the electrical heater for the regeneration technology generally ha s several sheets of thin plates laminated to each other, which are used when m anufacturing the metal substrate, as described above. Meanwhile, in the elec trical heater with the metal substrate, corrugated strips having different cell si zes are alternately laminated and bonded to each other. Accordingly, the cor

rugated strips form a non-uniform bonding surface, causing deterioration in b onding force after being brazed. Moreover, it is difficult to apply the above method in practice, not only due to the difficulty of winding the heating line w ith the strips laminated to each other, but also due to non-uniformity of specifi c resistance, the structure, and the electrical properties of the heating line.

The non-uniform specific resistance of the heating line causes a relativ ely large amount of current to be applied to one side of the heating line, comp ared with the other side thereof, resulting in a non-uniform temperature in the heating line or a local increase of the temperature therein. As a result, therm al endurance is reduced at a specific portion of the heating line.

Meanwhile, considering the role of the existing electrode and mantle of the electric heater, the electrode connects the internal heating line to a power supply. Accordingly, it must be appropriately insulated from the surround gs and have good thermal/mechanical endurance. Moreover, since the mantl e enables current to be applied between the heating line and the ground of the surrounding power source, sufficient thermal and mechanical endurances mus t be also ensured.

The structure of the electrode of the conventional electric heater is vuln erable to impact or vibration, compared with a case where a ceramic material i s used as an insulation material. Further, since the electrode is bonded to the internal mantle, there is an inconvenience in that even though only the electr ode is spoiled or broken, the entire electric heater must be replaced with a ne w one. The mantle acts to enable current to be applied between the heating 1 ine and the outside, and is bonded to the heating line by brazing.

With regard to this, since a bonding surface between the flat mantle an d the corrugated strips of the heating line is not uniform, the conventional elec tric heater has very weak mechanical and thermal structures, and does not allo w a free variation of the specific resistance of the mantle according to the amo unt of current in the heating line.

Moreover, in a case where, with the heater and the radiantaion heat pre vention means or the metal substrate provided as described above, an insulatio n pin is mounted at a final assembly stage for the purpose of electrically insul ating the units while maintaining the mechanical strength thereof, there are pr oblems in that the insulation pin complicates the configuration and a manufact

uring process of the electric heater, and in that even though the manufacturing process is commercialized, manufacturing costs are increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is one object of the present invention to provide a method of manufacturing an electric heater, which comprises the step of maintaining the shape of a heat ing line using a jig, thereby preventing a decrease of yield according to variati on of the length and the shape of the heating line caused by brazing.

It is another object of the present invention to provide an electrical heat er, which allows a free variation of the specific resistance of a mantle while ha ving an excellent mechanical strength, at a connected portion between the ma ntle and the heating line, an excellent radiantion heat shield, and an excellent i nsulation property.

In accordance with one aspect of the present invention, the above and o ther objects can be accomplished by the provision of a method of manufacturi ng an electric heater for purifying exhaust gas of a vehicle, comprising the ste p of laminating strips to form a heating line, wherein strips are laminated in a jig with a heating line insertion groove of a predetermined shape formed there in.

The jig may be made of metal or a ceramic material. The jig may be f urther formed with at least one mantle insertion groove therein for mounting a mantle for supplying power to the heating line. Further, the jig may be furt her formed with a chamfer at an edge of a wall of the heating line insertion gr oove or at an edge of a wall of the mantle insertion groove.

In accordance with another aspect of the present invention, there is pro vided an electric heater for purifying exhaust gas of a vehicle, comprising inn er and outer mantles separating the electric heater into inner and outer portion s and supplied with power from electrodes, respectively, a heating line having strips laminated to each other while being provided such that the heating line can be separately located at inner and outer portions of the electric heater and such that the strips of the heating line are connected to the inner and outer ma ntles, respectively, and a radiantion heat shield integrally mounted on an asse

mbly of the mantles and the heating line, wherein each of the mantles is divid ed into at least two parts.

The heating line may have flat-shaped strips having a predetermined le ngth at the end of the heating line connected to the mantles by means of a fast ening means. The strips of the heating line may be connected to the mantles at different heights of the mantles to remove interference between the electrod e and the heating line and to widen a specific surface area of the mantle. Eac h of the electrodes may comprise an electrode rod provided at one end of the e lectrode rod with a bolt tap to be fastened to the mantle, a ceramic layer surro unding the electrode rod at a portion of the electrode rod, and an electrode rin g fitted around the electrode rod such that the electrode ring can surround the ceramic layer. The mantles and the strips of the heating line may be bonded to each other by brazing. Further, the mantles and the strips of the heating li ne may be fastened to each other by means of a socket support located at a pre determined portion of the heating line and a socket fitted into the socket supp ort while contacting the mantles. The mantles and the strips of the heating li ne may be fastened to each other by means of a fastening pin. The radiantion heat shield is mounted on the assembly of the heating line and the mantles usi ng an insulation pin assembly, such that the radiantion heat shield is electricall y insulated from the heating line and the mantles.

The mantle of an anode of the electrode may have a length shorter than that of the mantle of a cathode of the electrode. The electrode rod is forme d with at least one recess on an outer periphery of the electrode rod where the electrode ring is mounted thereon. The insulation pin assembly may compris e a ceramic member having a penetration hole, and an insulation pin inserted i nto the penetration hole of the ceramic member. The insulation pin may be d ivided into two parts in the insulation pin assembly such that a predetermined gap is provided between the two parts of the insulation pin in the ceramic me mber.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and other advantages of the prese nt invention will be more clearly understood from the following detailed descr

iption taken in conjunction with the accompanying drawings, in which: Fig. 1 is a diagram illustrating a heating line and a jig separated from e ach other for a separated electric heater according to an embodiment of the pr esent invention; Fig. 2 is a diagram illustrating the heating line inserted into the jig for t he separated electric heater according to the embodiment of the present invent ion; Fig. 3 is a partially enlarged view of the jig; Fig. 4 is a partially enlarged view of the heating line of Fig. 1 ; Fig. 5 is a view illustrating a heating line inserted into a jig for an one- piece electric heater according to another embodiment of the present inventio n; Fig. 6 is a diagram illustrating a heating line inserted into a jig in a case of a separated electric heater according to another embodiment of the present invention; Fig. 7 is an enlarged view illustrating a portion"C"in Fig. 6; Fig. 8 is an enlarged view illustrating a portion"D"in Fig. 7; Fig. 9 is a diagram illustrating the end of the heating line and the mantl e connected to each other; Fig. 10 is a diagram illustrating an inner mantle and an outer mantle in an assembled state; Fig. 11 is a perspective view of an electrode rod of the present inventio n; Fig. 12 is a diagram of a first embodiment of an electrode, in which the electrode rod and an electrode ring are assembled; Fig. 13 is a cross sectional view of the electrode of Fig. 12; Fig. 14 is a cross sectional view of a second embodiment of an electrod e of the present invention; Fig. 15 is a diagram illustrating a state wherein the heating line and an assembly of the mantles and the electrode are separated from each other; Fig. 16 is a diagram illustrating the laminated heating line, the mantles, and the electrode, in an assembled state; Fig. 17 is a diagram illustrating fastening pins for connecting the inner and outer mantles to the heating line;

Fig. 18 is a diagram illustrating a state wherein the inner and outer man tles are connected to the heating line by the fastening pins; Fig. 19 is a perspective view of a socket and a socket support; Fig. 20 is a diagram illustrating the socket and the socket support conn ecting the mantle and the heating line in an assembled state.

Fig. 21 is a view illustrating a first embodiment of an insulation pin ass embly according to the present invention; Fig. 22 is a view illustrating a second embodiment of an insulation pin assembly according to the present invention; Fig. 23 is a view illustrating a third embodiment of an insulation pin as sembly according to the present invention; Fig. 24 is a view illustrating a forth embodiment of an insulation pin as sembly according to the present invention; Fig. 25 is a view illustrating a fifth embodiment of an insulation pin ass embly according to the present invention; Fig. 26 is a view illustrating a sixth embodiment of an insulation pin as sembly according to the present invention; Fig. 27 is a diagram illustrating an electric heater assembly and a radia nt heat prevention film in a separated state; Fig. 28 is a diagram illustrating the electric heater assembly and the rad iant heat prevention film in an assembled state; Fig. 29 is a diagram illustrating the electric heater and an outer canning in a separated state; and Fig. 30 is a diagram illustrating the electric heater and the outer cannin g in an assembled state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily understand and repeat the present invention.

The electric heater for vehicles of the present invention is applied to an apparatus for purifying exhaust gas. The electric heater of the present inve ntion is manufactured by a process comprising the steps of laminating a corru

gated strip and a flat strip, each being made of a thin metal plate, to form a he ating line, applying a paste-type filler metal or a sheet-type brazing foil to the heating line, mounting a radiantion heat shield on the heating line, and brazin g the heating line in a vacuum furnace.

For a separated electric heater, the heater is divided into at least two po rtions, such as an inner electric heater portion and an outer electric heater port ion, and thus heat capacities of the inner and outer electric heater portions can be independently controlled thereby. Specifically, the separated electric hea ter is divided into the inner electric heater portion and the outer electric heater portion by mantles, in which electrodes and the mantles are used to supply p ower to the heating line and then to flow current through the heating line.

The number of the electrodes and mantles is provided in correspondenc e to the number of the divided portions of the electric heater. The electrodes and the mantles are connected to the heating line and an outer canning, and ac t to increase the overall mechanical/thermal strengths of the electric heater.

A method of manufacturing the electric heater as described above will be described in detail as follows. The method of manufacturing the electric heater comprises the steps of alternately laminating a flat strip and a corrugate d strip or laminating strips alternately formed with corrugations thereon, form ing a heating line of a desired shape using the laminated strips, connecting ma ntles and electrodes to the strips of the heating line having the desired shape, a pplying a bonding agent to an assembly of the heating line and the mantles, m ounting a radiantion heat shield on the assembly of the heating line and the m antles, and brazing the assembly of the heating line and the mantles mounted with the radiantion heat shield.

In the mean time, at the step of forming the heating line of the desired s hape using the laminated strips, it is difficult to form the heating line of the de sired shape while maintaining spaces between the strips. Accordingly, the pr esent invention uses a jig formed with heating line insertion groove having a p redetermined shape therein.

Since the jig must be repetitiously used, the jig is preferably made of m etal or a ceramic material.

In a case where the jig is made of the metal, the jig may be coated with the ceramic material in order to prevent the mantles and the jig or the heating

line and the jig from being bonded to each other.

The jig is formed with at least one mantle insertion groove in the jig fo r mounting the mantles thereon, which are electrically connected to the heatin g line to supply power thereto. Further, the jig may be further formed with a chamfer at an edge of a wall of the heating line insertion groove or at an edge of a wall of the mantle insertion groove.

The mantle insertion groove is formed in the jig such that the mantle in sertion groove can be immediately adjacent to the outer surface of the strip of the heating line and the mantles can be located in the mantle insertion groove to provide a slight adhering force to the strips.

Further, when forming the heating line having the desired shape using t he jig with the strips or the mantles inserted thereto, there is inconvenience in operation since the strips or the mantles can collide with the edge of the wall of the heating line insertion groove or the edge of the wall of the mantle insert ion groove. Accordingly, the heating line insertion groove or the mantle inse rtion groove is preferably formed with the chamfer at the edge of the wall ther eof.

In a case where the electric heater is manufactured by the method as de scribed above, each of the mantles is divided into at least two parts.

The mantle of an anode of the electrode has a length shorter than that o f the mantle of a cathode of the electrode.

The heating line has flat-shaped strips having a predetermined length at the end of the heating line fastened to the mantles by means of a fastening m eans. Meanwhile, in the conventional electric heater, the strips of the heatin g line are bonded to the mantles in a corrugated state of the end of the heating line, causing a decrease of a fastening force between the mantles and the strip s of the heating line after frequent operations of the electric heater.

According to the present invention, when manufacturing the heating lin e with the strips, the strips are not corrugated at their ends for forming the flat - shaped strips at the end of the heating line to be connected to the mantles as a n attempt to enhance the fastening force between the mantle and the strips of t he heating line. As a result, fastening between the mantle and the strips of th e heating line is easy and secure, thereby preventing the fastened strips of the heating line and the mantles from being loosened or released by the vibration

of the vehicle.

The electrodes are connected to the mantles to supply power. Each of the electrodes comprises an electrode rod provided at one end of the electrod e rod with a bolt tap to be fastened to the mantle, and an electrode ring mount ed around the outer periphery of the electrode rod.

The electrode rod is connected to the mantle, and acts to connect the he ater and power supply. The electrode rod is required to electrically insulate t he heating line from the ground of the power supply of the engine, and must h ave an excellent thermal characteristic since the heat is repetitiously applied t hereto.

The electrode rod is provided with the ceramic layer on a portion of the electrode rod, and formed with a groove on the outer surface of the electrode rod where the electrode ring is mounted and the ceramic layer is provided, th ereby providing enhanced thermal and electrical properties to the electrode rin g.

In order to reduce contact resistance between the mantles and the heati ng line, the mantles are increased in their surface areas, and structured such th at a connected portion between the mantles and the electrode can be freely var ied. Moreover, structural variation of the mantles accompanied with variatio ns in capacity of the electric heater is achieved by variation of the height of th e mantles.

Further, the strips of the heating line are connected to the mantles at dif ferent heights of the mantles in order to widen a specific surface area by remo ving interference between the electrode and the heating line. As a result, the number of the heating lines wound per unit area can be further increased.

Further, the mantles and the strips of the heating line are fixed to each other by means of brazing, a socket, or a fastening pin.

Brazing is performed in a vacuum furnace, with a brazing filler applied onto the assembly of the mantles and the heating line.

Moreover, it is possible to fasten the mantles and the strips of the heati ng line to each other using a socket support located at a predetermined portion of the heating line and the socket, which is fitted into the socket support whil e contacting the mantle.

The radiantion heat shield is mounted on the assembly of the heating li ne and the mantles using an insulation pin assembly. The insulation pin asse

mbly comprises a ceramic member having a typical penetration hole, and an i nsulation pin inserted into the penetration hole of the ceramic member. The i nsulation pin is divided into two parts such that a predetermined gap is provid ed between the two parts thereof in the ceramic member.

The insulation pin assembly is located between the radiantion heat shie ld and the mantles, for maintaining mechanical strength between these two co mponents and for insulating the radiantion heat shield and the mantles from ea ch other. The insulation pin assembly is provided for maintaining the overall shape of the radiantion heat shield, and consists of metal and a ceramic mate rial. In addition to the role of maintaining mechanical strength between thes e two components, the insulation pin assembly of the present invention may al so act to maintain spaces between the components.

An embodiment of the present invention will be described in detail wit h reference to the drawings as follows.

Fig. 1 shows a heating line for an inner heater 1 and an outer heater 2, and a jig 10 according to one embodiment of the present invention, which can be used when manufacturing a separated electric heater.

As shown by circles A and B in Fig. 1, the heating line of the embodim ent may have a structure wherein one or more strips having different cell dens ities are laminated in the heating line, or a structure wherein one or more strip s respectively having a predetermined period are laminated therein.

The jig 10 according to the present embodiment may be formed with a heating line insertion groove, an inner mantle insertion groove 4 and an outer mantle insertion groove 3, so that mantles and electrodes can be integrally ass embled together.

Moreover, the jig may be further formed with a maintenance portion 5 for maintaining a gap between the inner mantle insertion groove 4 and the out er mantle insertion groove 3 in order to prevent portions of the heating line fro m being shortened after practically mounting the electric heater to the engine.

Fig. 2 is a diagram illustrating the heating line of the electric heater ins erted into the jig.

Fig. 3 is a partially enlarged view of the jig 10. As shown in Fig. 3, t he jig is formed with a chamfer 6 of a predetermined angle at an upper edge o f a wall of the heating line insertion groove or at an upper edge of a wall of th

e mantle insertion groove. The chamfer is provided for easy insertion of the heating line.

Fig. 4 is a partially enlarged view of the heating line, showing an exam ple of a method of laminating the strips, which can be employed in the present invention.

As for strips for the heating line, there can be used strips having differe nt cell densities, strips having different oscillations, and strips having different periods of corrugation. Specifically, in the case where the heating line is fo rmed by laminating the strips having the different cell densities, a method of a lternately laminating a low cell density corrugation strip 11 and a high cell de nsity corrugation strip 12 is used as the method of laminating the strips, and in the case where the heating line is formed by laminating the strips having the different periods, a method of laminating the strips of an identical shape such that a corrugated portion of one strip can be located on a flat portion of anothe r strip is used as a method of laminating the strips. For the heating lines, diff erent types of metallic contact portion 13 are provided, respectively.

Fig. 5 is a view illustrating a heating line inserted into a jig for an one- piece electric heater in an assembled state according to another embodiment o f the present invention. In case of the one-piece electric heater, the manufact uring process is similar to that of the separated electric heater except for the n umber of the mantles.

Fig. 6 is a diagram illustrating a heating line inserted into a jig for a sep arated electric heater in an assembled state according to another embodiment of the present invention. Fig. 7 is an enlarged view illustrating a portion"C" in Fig. 6, Fig. 8 is an enlarged view illustrating a portion"D"in Fig. 7, and F ig. 9 is a diagram illustrating the distal end of the heating line and a mantle of an outer heater connected to each other.

Generally, the heating line of the corrugated strips 11 and 12 is directly bonded to the mantles. However, in accordance with the present invention, with the heating line formed with flat-shaped strips 14 at the end thereof, the heating line is connected at the end thereof to the mantle by a bolt 27.

Fig. 10 is a diagram illustrating inner and outer mantles of the present i nvention. The inner mantle at the center portion is divided into an anode inn er mantle 20 and a cathode inner mantle 21, and in the case of the separated el

ectric heater, the anode part is smaller than the cathode part. The anode inne r mantle 20 is provided with a portion into which an electrode connected to a power supply is to be inserted, and the cathode inner mantle 21 is provided wi th a portion to be connected to the heating line.

The outer mantle 22 comprises one or a plurality of mantles, each of w hich are connected to the electrodes.

Figs. 11 to 14 are diagrams showing an electrode rod used in the prese nt embodiment. As shown in Fig. 11, the electrode rod is formed with recess es 31 where a ceramic layer 33 surrounds the electrode rod 30 as shown in Fig . 12, thereby causing an increase in thermal and electrical properties, which is resulted from a ceramic material, and is formed with a bolt tap 32 at a portion to be connected to the mantle, thereby minimizing contact resistance between the mantle and the electrode rod.

As shown in Fig. 12, the electrode rod 30 is provided with an electrode ring 36 on the insulative ceramic layer 33 surrounding the electrode rod in or der to connect the mantle to an outer canning. The inner electrode rod 30 act s to allow current to flow thereon, while the outer electrode ring 36 acts to con nect the mantle to the outer canning. The ceramic layer between these two metal elements serves to insulate the electrode rod 30 and the electrode ring 3 6 from each other.

Fig. 13 is a cross-sectional view of the electrode rod of Fig. 12. Fig.

14 is a cross-sectional view of an electrode rod according to another embodim ent of the present invention, in which an insulative ceramic layer 33 is extend ed to a portion fixed or assembled to the mantle for breakage of insulation dur ing an assembly process or a fixing process.

Figs. 15 and 16 are diagrams illustrating the components of the electric heater of the present invention in assembled states, respectively, according to processes from Fig. 1 to Fig. 14. When the mantles 20,21 and 22 are moun ted on the jig 10, it is necessary that the mantles 20,21 and 22 be always conn ected to the jig 10 at a constant position of the jig. For this purpose, first, a s shown in Fig. 10, the inner and outer mantles or the inner mantles 20 and 21 are provided, and the electrode rod as shown in Fig. 12 is connected to the m antle by means of bonding or the bolt 32.

Specifically, the electrode is connected to the inner mantle such the inn

er mantle can be electrically insulated from the outer mantle 22.

Further, the electrode rod and the connected portion of the heating line and the mantles are located at different positions, thereby increasing the specif ic surface area of the mantle and freely adjusting a width of the heating line w ithout a large variation of the mantle.

Figs. 17 and 18 are diagrams illustrating a method of fixing the heating line and the mantles. An inner portion of the heating line, located inside th e inner mantle, is bonded to the inner mantles 20 and 21 in such a manner that after being directly contacted to the inner mantles 20 and 21, the heating line is bonded to the inner mantles 20 and 21 by brazing. An outer portion there of, located between the inner mantle and the outer mantle, is connected to the inner and outer mantles, respectively, by a plurality of fastening pins 15. He re, the fastening pins 15 connect the inner mantle and the outer portion of the heating line as well as the outer mantle and the outer portion of the heating lin e.

Moreover, as an example of using the method of connecting the mantle s and the heating line, in the case where the heating line must be replaced with a new one, due to the heating line having been cut, as shown in Figs. 19 and 20, a socket 40 and a socket support 41 may be used for connecting the heatin g line and the mantles to each other. Here, the socket 40 is supported by the socket support 41.

To enable the use of the socket, the socket is structured so as to minimi ze a contact resistance between the socket and the mantle, most of all in consi deration of the metallic properties of the socket and the mantle.

After assembling the mantles and the heating line, a radiant heat preve ntion film 73 is mounted on the assembly thereof. In this case, it should be e nsured that the radiant heat prevention film 73 has a sufficient mechanical stre ngth, and that the radiant heat prevention film 73 and the heating line are elect rically insulated from each other.

Figs. 21 to 26 show embodiments of an insulation pin assembly applie d to the present invention.

In Fig. 21, hexahedral insulation pins 62 having a square cross section are inserted into a cylindrical ceramic member 60. In Fig. 22, cylindrical ins ulation pins are inserted into a cylindrical ceramic member.

These two insulation assemblies commonly have a structure in which t wo insulation pins are inserted into one cylindrical ceramic member with a pr edetermined gap 64 of 2-3 mm provided between them. In view of the bon ding strength between the ceramic material of the ceramic member and metal of the insulation pin, the hexahedral insulation pin is prefer to the cylindrical i nsulation pin. However, in view of ease of manufacturing, the cylindrical in sulation pin is more advantageous than the hexahedral insulation pin. Accor dingly, the insulation pin assembly may be manufactured appropriately accord ing to the application environment.

In Fig. 23, cylindrical insulation pins are inserted into a hexahedral cer amic member. In Fig. 24, gap holding plates 69 are used to increase the bon ding strength. Fig. 25 shows a gap holder 70 of a predetermined size inserte d into the insulation pin assembly for more securely and rapidly maintaining t he gap between the insulation pins during the process of forming the insulatio n pin assembly. Fig. 26 shows an example of an offset type ceramic member 72, which can be used in the case where the insulation pin assembly is not str ucturally restricted in size while being increased in bonding strength. In this case, since many metallic pins are inserted into the ceramic member, there is a n advantageous effect of an increase in strength thereof.

In the present invention, these insulation pin assemblies are adequately used according to application, price and restriction.

Figs. 27 and 28 show a method of using the insulation pin assembly for the radiantion heat shield 73. First, prior to forming the radiantion heat shi eld 73, a minimal number of insulation pin assemblies are inserted into the rad iantion heat shield 73 at locations of the insulation pin in the radiantion heat s hield, where the mechanical strength of the electric heater can be maintained.

The insulation pin assemblies are inserted to the radiantion heat shield 73 using an inserting apparatus, while in correspondence to the locations and t he number of the insulation pin assemblies. The radiantion heat shield 73 ha ving the insulation pin assemblies is mounted on the assembled heating line a nd mantles, using a predetermined force carefully applied from the outside to the heating line. The mounting operation must be conducted such that the ra diantion heat shield can be mounted thereon while being maintained at a right angle to the mantles.

Figs. 29 and 30 show the electric heater according to the present invent ion in a completely assembled state. Here, a can 100 for the electric heater i s connected thereto, so that the overall mechanical strength of the electric heat er can be maintained.

The present invention is designed to solve deterioration of thermal dura bility of the heating line itself due to local differences in the specific resistanc e caused by structural non-uniformity in forming and winding the conventiona 1 corrugated heating line for the electric heater using the metal substrate. Ac cording to the present invention, the above problems can be solved by the met hod of manufacturing the heating line using the jig of the metal or the ceramic material, which is different from the conventional winding method for formi ng the corrugated heating line.

As apparent from the above description, according to the present inven tion, the mantle is fixed to the jig and the jig applies a predetermined force to the mantles upon brazing, so that the operation of connecting the heating line and the mantles can be conveniently performed. Moreover, since the mantle has a structure, which can be easily varied in size, contact resistance, which ca n occur between the heating line and the mantles, can be reduced, thereby rem arkably reducing loss of electric energy.

Further, in addition to brazing, for directly bonding the mantles and he ating line or the heating line and the heating line, since the socket is used for t he connection thereof, thermally and mechanically excellent endurance can be ensured.

Further, the electrode according to the present invention is improved in its structure at the contact portion between the ceramic material and the meta 1 therein, and the electrode rod is provided with the ceramic material at a pred etermined space from each other on the grooves formed on the electrode rod, t hereby remarkably preventing the electrode rod from being broken due to a th ermal expansion between the ceramic material and the metal. Moreover, the insulation pin assembly may have various embodiments in accordance with a variety of applications, and is sufficiently enhanced in its structural and electri cal properties, thereby providing excellent endurance.

It should be understood that the embodiments and the accompanying dr awings as described above have been described for illustrative purposes and t he present invention is limited by the following claims. Further, those skille d in the art will appreciate that various modifications, additions and substituti ons are allowed without departing from the scope and spirit of the invention a s set forth in the accompanying claims.