JP2002134251A - Ceramic heater equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of electric connection of ceramic heater equipment and to aim reduction of a cost of the equipment by miniaturizing the ceramic heater. SOLUTION: The ceramic heater equipment has a ceramic heater 2 in a metallic main body 4, which is attached through a metallic pipe-like body 3 so that its tip 2a side may be projected and covered in its perimeter surface. This heater 2 has a ceramic-heating element 6, which consists of conductive ceramics in a ceramic base body 5, which consists of insulating ceramics and has a shape of a stick, is laid underground as a returning shape by the tip side. Grinding the back end 6c of the ceramic-heating element 6 to a planer shape exposes the both ends of the ceramic-heating element 6. The exposed ceramic-heating element surface is made as a terminal 11 for a lead connection, and the metal leads 15, 16 are attached by brazing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater device, and more particularly, to a ceramic heater device used for a glow plug used for accelerating a start of a diesel engine or an ignition heater for an oil fan heater.

[0002]

2. Description of the Related Art FIGS. 13 and 14 show a ceramic glow plug 71 for a diesel engine as an example of this type of ceramic heater device. This is composed of a rod-shaped ceramic heater 72 and a cylindrical main body 74 holding the ceramic heater 72 and forming a mounting portion to the engine. The ceramic heater 72 forming the glow plug 71 is a ceramic heating element (hereinafter simply referred to as a heating element) formed of a conductive ceramic and formed in a folded shape (U-shape) at a position near a tip 72a of a ceramic base 75 made of an insulating ceramic. (Also referred to as) 76. One ends of relay wires 78 and 79 for connecting to the metal leads 15 and 16 for energization are respectively connected to both ends (ends of both legs) 76c of the U-shape of the heating element. Buried in

The other end of each of the relay wires 78 and 79 is exposed to a side surface near the rear end 72c of the ceramic heater 72 to serve as a connection terminal (hereinafter, simply referred to as a terminal). 15 and 16 are connected by brazing. Such a ceramic heater device 7
Numeral 1 is configured to generate heat by heating the heating element 76 by applying current through the metal leads 15 and 16.

[0004]

The glow plug 71 is mounted in a space such as the sub-combustion chamber of the engine head so that the tip 72a of the ceramic heater 72 is exposed. Besides, during combustion of the engine, it is constantly exposed to remarkable temperature changes and blast (thermal shock). On the other hand, the connecting wires 78 and 79 for connecting the heating element 76 and the metal leads 15 and 16 are usually thin, having a wire diameter of 1 mm or less, and therefore, the metal connected (brazed) to the terminal formed at the end of the connecting wire. Lead 1
The connection (junction) area with 5 and 16 is extremely small. Moreover, such relay wires 78 and 79 are generally made of a high melting point metal such as W (tungsten).

In addition, the ceramic heater constituting the glow plug having the above structure is manufactured by firing the relay wires 78 and 79 connected to the ceramic heating element 76 in a state of being embedded in the ceramic base 75. . Therefore, based on the remarkable difference in the coefficient of thermal expansion between the metal (tungsten) and the ceramic forming the relay wire, the relay wire 7 is fired during the firing process.
8, 79 generate residual (tensile) stress. Therefore, there is a high risk of disconnection due to the above-mentioned thermal shock or the like received during the subsequent use process.

Further, such a conventional ceramic heater forming a glow plug is usually set (fixed) to a main body 74 after a metal cylindrical body (hereinafter simply referred to as a cylindrical body) 73 is inserted through the inside thereof. ) Is done. Therefore, of the ceramic base 75 in which the ceramic heating element 76 is embedded, the rear end of the ceramic heating element 76 opposite to the front end 72a side, that is, the connection portion of the metal lead, It must protrude from the end of the body. Because the end of the relay wire exposed on the side surface of the ceramic base is used as a terminal, and a metal lead is connected to the terminal,
This is because if the rear end 75c side of the ceramic base 75 where the terminal is located does not protrude from the metal cylindrical body 73, the connection is difficult. Therefore, such a ceramic heater has a longer protruding portion at its rear end, and thus has a longer length, and requires an extra ceramic material.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of a conventional ceramic heater device such as a glow plug and the like. It is an object of the invention to reduce the amount.

[0008]

According to a first aspect of the present invention, a ceramic heating element made of a conductive ceramic is folded back into a ceramic base made of an insulating ceramic at a tip end. A ceramic heater device provided with a rod-shaped ceramic heater embedded in a shape, wherein a side surface (outer peripheral surface) near a rear end of the ceramic heater is ground into a flat shape to expose both ends of the ceramic heating element. The exposed surface of the ceramic heating element is used as a lead connection terminal, and a conductive metal lead is brazed to the lead connection terminal.

According to a second aspect of the present invention, there is provided a ceramic heater device comprising a rod-shaped ceramic heater fixed to a cylindrical metal body with its tip protruding, wherein the ceramic heater is made of a conductive material. A ceramic heating element made of ceramic is embedded in a ceramic base made of insulating ceramic as a folded shape on the tip side,
The side surface (outer peripheral surface) near the rear end of the ceramic heater is ground to expose both ends of the ceramic heating element, and the exposed surface of the ceramic heating element is used as a lead connection terminal, and the lead connection is performed. The present invention is characterized in that a current-carrying metal lead is brazed to the terminal.

As described above, according to the present invention, both ends of the ceramic heating element are exposed on the side near the rear end of the ceramic heater without using the high melting point metal for the relay wire, and the exposed surface of the ceramic heating element is exposed. Lead connection terminal,
Since the lead connection terminal has a connection structure in which a metal lead for conduction (hereinafter also simply referred to as a lead) is directly brazed, the lead connection terminal is formed (exposed) in the axial direction of the ceramic heater, for example. For example, the connection area with the lead can be easily increased. In addition, there is no danger of breakage of the relay wire since no relay wire made of a high melting point metal having a significantly different coefficient of thermal expansion from ceramic is used. Therefore, a ceramic heater device having high reliability of electrical connection can be provided. Since the ceramic heating element is exposed by grinding in a planar shape, a decrease in strength in the ground portion can be suppressed as compared with the case of grinding in a round shape. Then, by grinding and exposing, the manufacturing process is simplified.
It is preferable that the lead connection terminal be a plane that is substantially parallel to the axis of the ceramic heater, both in terms of its formation and connection of metal leads. Furthermore, since the ceramic heating element is exposed by grinding the ceramic base into a planar shape, the distance between the lead and the metal body can be increased. Therefore, it is possible to prevent the lead from being short-circuited to the metal body.

The invention according to claim 3 of the present invention provides a rod-shaped ceramic heater in a metal cylindrical body.
The heater tip is fixed so as to protrude from the tip of the metal tubular body, and the metal tubular body is fixed in the tubular metal body such that the tip protrudes from the tip of the metal body. A ceramic heater device comprising: a ceramic heater in which a ceramic heating element made of conductive ceramic is embedded in a ceramic base made of insulative ceramic in a folded shape at a front end side; The opposite side surface is ground into a flat shape to expose both ends of the ceramic heating element, and the exposed surface of the ceramic heating element is used as a lead connection terminal. And the lead connection terminal is arranged inside the metal tubular body so as not to protrude from the rear end of the metal tubular body. And wherein the door.

That is, as in the third aspect of the present invention, the lead connection terminal is arranged inside the metal tubular body so as not to protrude from the rear end of the metal tubular body. In this case, since the length of the ceramic heater itself can be reduced, the size can be reduced or the cost of the device can be reduced. Further, since the ceramic heater is shortened, the contact area with the metal cylindrical body is reduced, and the heat escape is reduced, which contributes to the improvement of the temperature rising characteristics.

[0013] Further, as in the fourth aspect of the present invention, in the third aspect, the ceramic heater is arranged such that the ceramic heater is located on the inner peripheral surface of the metal cylindrical body from the tip of the metal main body (hereinafter also simply referred to as the main body). Those not in contact at the site near the rear end are preferred. If the ceramic heater device is used as a glow plug, the ceramic heater
External forces such as blast also act in the lateral direction. On the other hand, since the metal body constituting the ceramic heater device is firmly fixed to the engine head, such external force causes a bending force to act on the ceramic heater with the front end of the metal body being a fixed end. In this case, in the invention described in claim 4, the ceramic heater is not in contact with the fixed end, that is, the portion closer to the rear end than the front end of the metal main body, on the inner peripheral surface of the metal cylindrical body. This is effective in preventing the ceramic heater from cracking.

In any of the first to fifth aspects, it is preferable that the metal lead is soldered to the lead connection terminal with an active solder. When brazing with a normal brazing such as silver brazing, vapor deposition is applied to the lead connection terminals,
It is sufficient that the wax used is metallized by a plating method or the like so as to be wet.

It is preferable that the ceramic heating element constituting the ceramic heater is formed of ceramic having a conductive property with a large resistance value at the front end and a small resistance value at the rear end. This is because the tip side can be quickly heated to a high temperature.

[0016]

FIG. 1 shows a first embodiment of the present invention.
This will be described in detail with reference to FIG. In the figure, reference numeral 1 denotes a ceramic heater device (in this example, a glow plug for a diesel engine), and a substantially cylindrical ceramic heater 2;
The metal cylindrical body 3 that projects the hemispherical tip 2a side of the ceramic heater 2 to cover the outer peripheral surface 2b, and further covers the outer peripheral surface 3b of the metal cylindrical body 3 so as to hold the ceramic heater 2. It is composed of the formed main body 4 and the like, and is configured as follows.

That is, the ceramic heater 2 has a ceramic heating element 6 made of a conductive ceramic formed substantially in a U-shape in a ceramic base 5 made of an insulating ceramic, and a U-shaped folded portion 7a at the front end. And is buried in a cast-in shape. The ceramic heating element 6 is formed so as to extend from the folded portion 7a near the front end 2a of the ceramic heater 2 to a portion near the rear end 2c. However, in the present embodiment, the ceramic heating element 7 having a composition having a high resistance value is provided on the tip 2a side including the folded portion 7a.
Are arranged, and a ceramic heating element 6 having a composite structure in which a ceramic heating element 8 having a low resistance value is arranged on the rear end 2c side not including the folded portion 7a. The cross section of each leg 9 of the ceramic heating element 6 has an elliptical shape, as described later, because the cross section of the leg 9 is circular at the unfired stage, This is because hot pressing is performed in a direction to narrow the distance between the two legs and simultaneous firing is performed.

In this embodiment, such a ceramic heater 2 is made of a cylindrical metal (for example, made of Incoloy 903) so as to cover the outer peripheral surface 2b except for both ends 2a and 2c.
Is externally fitted. However, the metal cylindrical body 3
Although not shown, the space between the inner peripheral surface 3d of the ceramic heater 2 and the outer peripheral surface 2b of the ceramic heater 2 is shrink-fitted with, for example, silver brazing. The metal tubular body 3 is inserted and fixed inside one end (a part near the front end) of the main body 4 via an outer peripheral surface 3b near the rear end 3c of the metal cylindrical body 3. That is, the ceramic heater 2 has a metal tubular body 3 fitted externally thereto.
Of the cylindrical portion of the main body 4 (lower side in FIG. 1) is inserted into and fixed to a reduced diameter portion 14 in which the inner peripheral surface 4d of the cylindrical portion of the main body 4 is slightly reduced in diameter. . The outer peripheral surface 3b of the metal tubular body 3 and the inner peripheral surface 4d of the reduced diameter portion 14 of the main body 4 are used.
Is fixed between the inner peripheral surface 3d of the metal cylindrical body 3 and the outer peripheral surface 2b of the ceramic heater 2 by brazing with a lower melting point than the brazing material (material) used. And such a ceramic heater 2 has a tip 2a
Is protruded from the tip 4a of the main body 4 outwardly (downward in FIG. 1) by a suitable amount, and the metal cylindrical body 3 has its tip 3a protruded from the main body 4 by an appropriate amount. It covers up to more than a part.

Next, the connection structure between the ceramic heating element 6 and the metal leads 15 and 16 in the ceramic heater 2 which forms the gist of the present invention will be described in detail. 2 c (upper end in FIG. 1) is disposed so as to protrude into the main body 4. In the present embodiment, the opposite outer surfaces of the portions of the ceramic heating element 6 near the ends (rear ends) 6c of both legs 9 are exposed in parallel with the axis G of the ceramic heater 2 and in the same direction over a certain length. The ceramic base 5 and the ceramic heating element 6 are ground in a planar shape, and the surfaces of both legs of the ceramic heating element 6 that have been ground and exposed are used as lead connection terminals 11. The length of the lead connection terminal 11 along the direction of the axis G may be set in consideration of the width of the leads 15 and 16 so as to obtain appropriate strength for connection with the metal leads 15 and 16. Good. In this embodiment, both lead connection terminals 11 are planes parallel to each other.

The exposed surfaces of both legs of the ceramic heating element 6 constituting the ceramic heater 2 are connected to the lead connection terminals 1.
1 and metal leads (width 2 mm, thickness 0.5 mm) 15 and 16 each made of a nickel strip, and each end 15 a and 16 a of which is, for example, an active wax (for example, 70 Ag-
28Cu-2Ti). The other end 16b of one of the leads 16 is welded to the end of a metal shaft 17 for electric current penetrated inside and outside of the upper end of the main body 4 along the axis G in a penetrating manner. The other end 15b of the lead 15 is externally fitted to the outside of the metal shaft 17 while maintaining insulation with a glass seal material.
(See FIG. 1).

In addition, on the outer peripheral surface of the main body 4, a screw portion 12 for mounting to a mounting portion (screw hole) of a cylinder head (not shown) is provided, and a hexagonal portion 13 for screwing is provided on the screw portion 12. ing. And a metal shaft 1 for energization
The metal lead tube 18 in which the metal tube 7 is fitted has a ring 19 fixed to the outside thereof via a glass seal material.
Is arranged so as to fit into the enlarged diameter portion formed on the inner peripheral surface side of the hexagonal portion 13 for screwing of the main body 4, and the metal shaft and the like are positioned. The metal shaft and the like are connected to the rear end 4c of the main body 4.
Is fixed by caulking so as to be bent inward, and a fixing ring 21 is further connected to the lead tube 1 via an insulating ring 20.
8 is press-fitted into the outer peripheral surface from above and assembled as a ceramic heater device 1. In the present embodiment, the glow plug is a non-grounding type (both insulated type). However, when the glow plug is a grounding type, the other end 15b of the metal lead 15 of the cathode is connected to the rear end of the metal cylindrical body 3, for example. It may be welded or brazed to the end 3c.

The ceramic heater device 1 of the present embodiment generates electric resistance by energizing the ceramic heating element 6 made of conductive ceramic through the metal leads 15 and 16. In order to connect the metal leads 15 and 16 with each other, a thin high melting point metal is not used as a relay wire as in the related art. That is, since the metal leads 15 and 16 are directly connected to the ceramic heating element 6, a large lead connection area of the metal leads 15 and 16 in the lead connection terminals 11 can be secured. Further, since there is no relay wire buried in the ceramic base 5, there is no problem of danger of disconnection due to residual stress of the relay wire in the process of manufacturing the ceramic heater 2. Therefore, even when used as a glow plug in a severe thermal shock environment, the ceramic heater device 1 is hardly disconnected and has high reliability of electrical connection. In this embodiment, since the two lead connection terminals 11 are flat and arranged in parallel with each other, the lead connection terminals 11 can be easily formed by grinding, and the lead connection with the metal leads 15 and 16 can be made. A large area can be secured. In addition, since the rear-side ceramic heating element 8 has a lower resistance than the front-side ceramic heating element 7, rapid resistance heating is expected.

Here, a method of manufacturing the ceramic heater 2 forming such a glow plug will be described with reference to FIGS. Unfired ceramic heating elements (having a circular cross section) 26 having different resistance values are formed before and after so as to form a U-shape. On the other hand, an insulating surface of a shape divided into two so as to form a ceramic heater by sandwiching the unfired ceramic heating element with an imaginary plane including the respective axes of both legs of the unfired ceramic heating element 26 as a mating surface. An unfired ceramic (unfired split mold of ceramic substrate 5) 25 made of ceramic is separately press-molded. As shown in FIG. 6, the U-shaped recess 2 on the mating surface side of the two unfired split molds 25
7, an unfired ceramic heating element 26 is arranged and sandwiched therebetween, and integrated as shown in FIG. Next, as shown in FIG. 8, the ceramic heating element 6 is hot-pressed in a direction to narrow the space between both legs and fired simultaneously. The fired body thus obtained is cylindrical except for the hemispherical portion at the tip.
b is polished, and the ceramic substrate 5 and the ceramic heating element 6 at the portions indicated by the two-dot chain lines in FIG. Expose the heating element.

The ceramic heater 2 thus formed
In this embodiment, after the exposed surfaces of both legs of the ceramic heating element 6 are used as the lead connection terminals 11, the metal cylindrical body 3 is shrink-fitted with pure silver brazing at 1100 ° C. in a nitrogen gas atmosphere using a brazing material. Before brazing to the main body 4, two metal leads made of nickel (width 2 mm, thickness 0.5 mm) 1
5 and 16, one end of which is an active wax (for example, 70 Ag-2).
8Cu-2Ti) in a vacuum at 900 ° C.
Then, the other end of one of them 16 is welded to the end of the metal shaft 17 for energization, and the other end of another one 15 is welded to the metal shaft 1.
7 is welded to a metal lead tube 18 for terminal connection, which is externally fitted while holding insulation with a glass seal material. The main parts including the ceramic heater 2 and the metal shaft 17 and the like having the metal tubular body 3 fitted outside are set in the main body 4 as described above, and a wax having a lower melting point than the wax used so far (for example, 56Ag-22Cu-17Zn-5S
In n), the main body 4 and the metal cylindrical body 3 are brazed. Finally, the rear end 4c of the main body 4 is crimped, and the fixing ring 21 is press-fitted via the insulating ring 20 to assemble the ceramic heater device 1.

Next, a second embodiment will be described in detail with reference to FIG. However, the ceramic heater device 31 of the present embodiment can be said to be an improvement of the above-described first embodiment, and there is no essential difference. Therefore, the difference will be mainly described, and the same reference numerals will be used for the same portions. And description thereof will be omitted as appropriate.

That is, in the present embodiment, both outer surfaces of both legs of the ceramic heating element 6 formed in a U-shape are formed on the side surface near the rear end of the ceramic heater 32 so as to be connected to the lead connection terminal 11. And the metal cylinder 3
, That is, the rear end 2c of the ceramic heater 32 on which the lead connection terminals 11 are formed does not protrude from the rear end 3c of the metal tubular body 3, but is retracted.
As described above, in the present embodiment, the lead connection terminal 11 is provided so as to be present inside the metal tubular body 3 and the metal leads 15 and 16 are connected thereto, so that the ceramic heater 32 is shortened by, for example, about 20 mm. it can. In this case, it is preferable from the viewpoint of assembly that the metal tubular body 3 is fitted after the leads 15 and 16 are brazed, and the ceramic heater 32 is shrink-fitted to the tubular body 3 with a brazing material. In this case, the brazing between the ceramic heater 32 and the metal tubular body 3 is performed using a lower melting point brazing than the brazing used for brazing the metal leads 15 and 16 to the lead connection terminals 11. For example, an active solder (for example, 91Cu-3Si-3Pd-3T) is used for brazing the metal leads 15 and 16 to the lead connection terminals 11.
When the brazing is performed at 1080 ° C. in a vacuum using i), the ceramic heater 32 and the metal tubular body 3 are brazed at 900 ° C. by using, for example, a silver-copper eutectic brazing material having a lower melting point. Do with.

In the present embodiment, however, the length of the ceramic heater 32 can be reduced, so that the amount of ceramic material can be reduced, and the cost of the ceramic heater device 31 can be reduced, and further, the ceramic heater device can be downsized. Is also planned. And ceramic heater 3
By making 2 smaller, the contact area with the metal cylindrical body 3 can be reduced, so that the escape of heat is reduced, so that the temperature rise characteristics are improved and power saving is achieved. Note that the ceramic heating element 6 may be an integrated one having the same composition, or a composite structure in which the rear end side has a low resistance as in the above-described embodiment.

Next, a third embodiment of the present invention will be described in detail with reference to FIGS. However, the ceramic heater device 41 of this embodiment can also be said to be an improvement of the above-described first embodiment, and there is no essential difference. Therefore, the difference will be mainly described, and the same portions will be denoted by the same reference numerals. The description is omitted as appropriate.

That is, also in the present embodiment, the rear end 2c of the ceramic heater 42 is configured not to protrude from the rear end 3c of the metal tubular body 3. Then, the metal cylindrical member 3 is formed so that the ceramic heater 42 is not in contact with the inner peripheral surface 3 d of the metal cylindrical body 3 at a position closer to the rear end than the front end 4 a of the metal main body 4 (upper in FIG. 10). Inner peripheral surface 3 of body 3
Of d, the inner diameter of the upper part is increased from a position slightly below the tip 4a of the main body 4. In other words, the inner diameter above the PP line in the figure is made slightly larger than the inner diameter below it (see FIG. 11), so that not only the portions corresponding to the lead connection terminals 11 but also between the lead connection terminals 11 are provided. The outer peripheral surface 5s of the continuous ceramic base 5 is also the inner peripheral surface 3 of the metal cylindrical body 3.
d is not contacted.

In this embodiment, however, the ceramic
The length of the motor 42 is longer than that of the second embodiment.
It can be further reduced (for example, 5 mm). On top of that, the ceramic
An external force such as a blast acts on the
The tip 4a of the metal body 4 is fixed to the
Even if a bending force acts on the tip 4a of the main body 4
Responsible for the displacement based on the external force in the metal cylindrical body 3
Becomes possible. That is, in this embodiment, the ceramic heater 4
2 is a fixed end of the inner peripheral surface 3d of the metal cylindrical body 3
That is, at a position closer to the rear end than the front end 4a of the metal body 4
The ceramic heater 42
This is effective in preventing occurrence of disconnection or disconnection. This form
Now, the diameter expansion of the ceramic heater 42 and the metal cylindrical body 3
The space formed by the part is hollow, but it is insulated.
Filled with a heat-resistant material or glass material
It may be fixed. By fixing with such a material,
The ceramic heater 42 falls into the engine.
And can be prevented. Epoxy resin is used as the insulating material
Fat, silicone resin, Teflon (registered trademark) resin,
Lumina, magnesia, and the like.
SiO₂-B₂O₃-R₂O, SiO ₂-B₂O₃-A
l₂O₃And the like. Note that R is an alkali metal (L
i, Na, Ba). When using glass materials
Means that the heat treatment temperature (melting point) of the glass is
Ceramic heater higher than the brazing temperature with body 3
42 and the shrink-fit temperature of the metal cylindrical body 3 with the brazing material.
It is desirable to lower the

Here, the three types of glow plugs of the first to third embodiments (sample Nos. 1 to 3) were tested for durability, that is, the number of disconnections by using a vibration tester. 1 to 10). However, the test conditions were such that a 300 G acceleration was applied to the entire region of 0 to 1000 Hz, and the durability test was performed for 5000 cycles. However, the comparative example has a conventional structure shown in FIGS. 13 and 14, and a relay wire (a tungsten wire having a diameter of 0.4 mm) for connecting a ceramic heating element and a metal lead is provided inside a ceramic base (insulating ceramic). A nickel lead is soldered to a terminal having the end of the relay wire exposed on the side surface of the rear end of the ceramic heater with a silver solder. The results are as shown in Table 1.

Each of the ceramic heaters has an outer diameter of 3.5 mm and a length of 40 mm. Among these, the insulating ceramic constituting the ceramic base is, for example, one containing silicon nitride as a main component (Si ₃ N ₄ :
85% by mass, rare earth oxide: 10% by mass, SiO ₂ : 5
Mass%), and the ceramic heating element is mainly composed of, for example, silicon nitride and tungsten carbide (WC). However, in the first embodiment, the ceramic heating element on the front end side is WC: 50% by mass, Si ₃ N ₄ : 44% by mass, rare earth oxide: 4% by mass, SiO ₂ : 2% by mass, and the rear end side WC: 60% by mass,
Si ₃ N ₄ : 35% by mass, rare earth oxide: 3% by mass, S
iO ₂ : 2% by mass. In the second and third embodiments, the ceramic heating element is composed of WC: 55% by mass, Si
₃ N ₄ : 40% by mass, rare earth oxide: 3% by mass, SiO
₂ : 2% by mass.

[0033]

[Table 1]

According to Table 1, in the comparative example, 4 out of 10 samples
While the wire was broken, the product of the present invention (Sample No. 1)
In (3), the occurrence of such a disconnection was zero. In addition,
The disconnection includes three peelings (separation) between the metal lead and the lead connection terminal.

Next, the same sample as in the above test was subjected to a thermal cycling evaluation. However, each sample was subjected to a gas phase cooling / heating test machine, and a durability test was performed at −65 ° C. (1 hour) / + 500 ° C. (1 hour) for 5000 cycles.
A current test was conducted to check the current characteristics. The results are as shown in Table 2.

[0036]

[Table 2]

As shown in Table 2, in the comparative example, 8 out of 10 samples
Disconnection was seen in the individual. Then, in the test of the current-carrying characteristics of the two pieces without disconnection, the resistance values of both two pieces increased, and the danger of disconnection or peeling of the connection portion was predicted. On the other hand, in the product of the present invention (samples Nos. 1 to 3), no disconnection was observed, and no problem was observed in the electric conduction characteristics.

FIG. 12 shows a fourth embodiment according to the present invention. Ceramic heater device 51 of the present embodiment
Is the lead connection terminal 1 in the ceramic heater 2
1 is a plane, but its two lead connection terminals 1
1 is such that the rear end 2c of the ceramic heater 2 is formed in a wedge shape, that is, the two lead connection terminals 11 are tapered with respect to an imaginary plane including the axis G of the ceramic heater 2. Then, the metal lead 15,
In the brazing of the metal lead 15, for example, a ring-shaped jig (temporary fixing tool) 61 as shown in the drawing is attached to the metal lead 15, 16 while the metal leads 15, 16 are in contact with the lead connection terminals 11. 16 so as to be pressed against the connection end to the lead connection terminal 11. By doing this,
Since it is possible to make a temporary fixing when brazing the metal leads 15 and 16, the brazing operation becomes easy.

In the present invention, the lead connection terminals made of a ceramic heating element are not exposed when the ceramic heater is fired, but are preferably exposed by grinding (polishing). It may be formed in advance, and only grinding (or polishing) finishing may be performed. Further, the lead connection terminals of the ceramic heating element may be provided on the side surface near the rear end of the ceramic base, but need not be on the outer sides of both legs of the ceramic heating element. In the case where the metal lead is a flat plate (or a strip), it is preferable that the lead connection terminal be flat in accordance with the flatness from the viewpoint of brazing.

The ceramic heating element constituting the ceramic heater according to the present invention is not limited to the above-mentioned composition, but may be made of a conductive ceramic having an appropriate composition according to the use of the ceramic heater device. Good. Similarly, the insulating ceramic forming the ceramic base may be formed of an insulating ceramic having an appropriate composition according to the use of the ceramic heater device.
That is, the ceramic heater according to the present invention may be formed by selecting an appropriate material and composition according to the use of the ceramic heater device.

In each of the above embodiments, the glow plug is exemplified as the ceramic heater device. However, the application example is not limited to the glow plug. It can be embodied as a device.

[0042]

As is clear from the above description and the test results, according to the ceramic heater device according to the first aspect of the present invention, the rear end of the ceramic heater is located near the rear end of the ceramic heater without using the high melting point metal for the relay wire. A connection structure in which both ends of the ceramic heating element are exposed on the side surfaces of the ceramic heating element, and the exposed surface of the ceramic heating element is used as a lead connection terminal, and a metal lead for conduction is directly brazed to the lead connection terminal. Therefore, by forming the lead connection terminals long in the axial direction of the ceramic heater, for example, the connection area with the leads can be easily increased. In addition, there is no danger of breakage of the relay wire since no relay wire made of a high melting point metal having a significantly different coefficient of thermal expansion from ceramic is used. Therefore, a ceramic heater device having high reliability of electrical connection can be provided.

In the ceramic heater device according to the present invention, a rod-shaped ceramic heater is fixed in a metal main body via a metal cylindrical body attached so as to cover the outer peripheral surface thereof. I have. In this device, in addition to the same effect as the ceramic heater device according to the first aspect, the lead connection terminal is provided inside the metal cylindrical body as in the ceramic heater device according to the third and fourth aspects. It can be arranged so as not to protrude from the rear end of the tubular body. Therefore, even if the ceramic heater is fixed in the main body via the metal cylindrical body, the length of the ceramic heater itself can be shortened, so that the size can be reduced or the cost of the device can be reduced. . Further, since the ceramic heater is shortened, the contact area with the metal cylindrical body is reduced, and the heat escape is reduced, which contributes to the improvement of the temperature rising characteristics.

[Brief description of the drawings]

FIG. 1 is a front vertical sectional view of a first embodiment of a ceramic heater device according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 2;

FIG. 5 is a side view taken along line CC of FIG. 2;

FIG. 6 is an exploded perspective view illustrating a manufacturing process of the ceramic heater used in the first embodiment.

FIG. 7 is a cross-sectional view of an integrated unfired ceramic heater.

FIG. 8 is an explanatory view of a hot pressed state of the unfired ceramic heater.

FIG. 9 is an enlarged front longitudinal sectional view of a main part of a second embodiment according to the present invention.

FIG. 10 is an enlarged front longitudinal sectional view of a main part of a third embodiment according to the present invention.

FIG. 11 is an enlarged sectional view taken along line DD of FIG. 10;

FIG. 12 is an enlarged front longitudinal sectional view of a main part of a fourth embodiment according to the present invention.

FIG. 13 is a front vertical sectional view of a conventional ceramic heater device.

FIG. 14 is an enlarged view of a main part of FIG. 13;

[Explanation of symbols]

 1, 31, 41 Ceramic heater device 2 Ceramic heater 2a Tip of ceramic heater 2b Peripheral surface (side surface) of ceramic heater 2c Rear end of ceramic heater 3 Metal tubular body 3a Tip of metallic tubular body 3c Metal tubular Rear end of body 3d Inner peripheral surface of metal cylindrical body 4 Metal body 4a Tip of metal body 5 Ceramic base 6, 7, 8 Ceramic heating element 6c End of ceramic heating element 11 Lead connection terminals 15, 16 Metal lead G Axis of ceramic heater

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) H05B 3/18 H05B 3/18 F term (reference) 3K092 PP15 PP16 PP20 QA01 QB02 QB03 QB13 QB24 QB74 QC02 QC16 QC42 QC52 RA02 RB02 RB22 RD04 RD46 TT08 TT13 TT37 VV04 VV28

Claims (5)

[Claims] 1. A ceramic heater device comprising a rod-shaped ceramic heater in which a ceramic heating element made of a conductive ceramic is embedded in a ceramic base made of an insulative ceramic in a folded shape at the tip end side, The side face near the rear end of the ceramic heater is ground into a flat shape to expose both ends of the ceramic heating element, and the exposed surface of the ceramic heating element is used as a lead connection terminal. Ceramic heater device, characterized by brazing metal leads for use. 2. A ceramic heater device comprising a rod-shaped ceramic heater fixed in a cylindrical metal body with its tip protruding, said ceramic heater comprising: a ceramic heating element made of conductive ceramic; The ceramic heater is embedded in a ceramic base made of an insulating ceramic in a folded shape on the front end side, and the side surface near the rear end of the ceramic heater is ground flat to expose both end portions of the ceramic heating element. The surface of the ceramic heating element
A ceramic heater device, characterized in that a metal lead for conduction is brazed to the lead connection terminal. 3. A rod-shaped ceramic heater is fixed in a metal tubular body so that a heater tip projects from the tip of the metal tubular body.
What is claimed is: 1. A ceramic heater device comprising: a metal tubular body fixedly attached so that a tip thereof protrudes from a tip of the metal body; wherein the ceramic heater comprises: a ceramic heating element made of conductive ceramic; The ceramic heater is buried in a folded shape at the front end side, and the side near the rear end of the ceramic heater is ground into a flat shape to expose both ends of the ceramic heating element. Use the body surface as a lead connection terminal,
A metal lead for conduction is brazed to the lead connection terminal, and the lead connection terminal is arranged so as not to protrude from the rear end of the metal tubular body inside the metal tubular body. A ceramic heater device characterized by being made. 4. The ceramic heater device according to claim 3, wherein the ceramic heater is not in contact with a portion of the inner peripheral surface of the metal cylindrical body closer to the rear end than the front end of the metal main body. 5. The lead connection terminal is a flat surface substantially parallel to an axis of a ceramic heater.
The ceramic heater device according to any one of the above.