JP2003074849A - Glow plug and method for producing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug and a method for producing it in which a metallic lead part is simply attached to a ceramic heater and the attaching strength of the metallic lead part and the electric conduction can be assuredly ensured. SOLUTION: The glow plug 50 has a rod shape and the ceramic heater 1 in which a heating resistor 11 is embedded. In the ceramic heater 1, a heater terminal 12a for energizing the heating resistor 11 is exposed on an outer peripheral surface. A metallic terminal ring 14 electrically connected to the heater terminal is fastened and fitted to the heater terminal so as to cover the heater terminal. Then, on the surface of the terminal ring 14, the metallic lead part 17 is connected by an ultrasonic welding part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow plug for preheating a diesel engine and a method for manufacturing the glow plug.

[0002]

2. Description of the Related Art Heretofore, as the glow plug as described above, a glow plug having a rod-shaped ceramic heater disposed so as to protrude from the inside thereof is widely used. To energize the ceramic heater, a metal shaft (connected to the power supply) provided at the rear end of the metal shell,
It is performed through a metal lead portion that connects the metal shaft and the ceramic heater. In the conventional glow plug, the connection between the ceramic heater and the metal lead is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Unexamined Patent Publication No. 0-205753, the front end of the metal lead portion is formed into a coil shape, and the rear end portion of the ceramic heater having the heater terminal formed exposed is inserted into the inside thereof to braze them. It has been done by attaching.

[0003]

However, the joining form by brazing has a drawback that it is inefficient because it requires many steps such as a step of assembling the materials to be joined by sandwiching the brazing material and a heating step of melting the brazing material. . In addition, since the ceramic is joined to a metal member such as a metal lead portion or a metal ring, an expensive active brazing material must be used, and the heating temperature and atmosphere for brazing are slightly adjusted. Combined with the problem of increased man-hours described above, the manufacturing cost is likely to increase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a glow plug which is easy to assemble the metal lead portion to the ceramic heater, and can surely secure the metal lead portion assembling strength and continuity, and a manufacturing method thereof. And to provide a method.

[0005]

In order to solve the above-mentioned problems, the first structure of the glow plug of the present invention has a rod-shaped form, and a resistance heating element is embedded in the glow plug. A ceramic heater having a heater terminal for energizing a heating element exposed on the outer peripheral surface, and a metal heater that is electrically fitted to the heater terminal by being fitted onto the outer peripheral surface of the ceramic heater in an interference fit manner so as to cover the heater terminal. And a metal lead portion welded to the surface of the terminal ring via an ultrasonic welding portion.

The glow plug manufacturing method of the present invention is a ceramic heater having a rod-like shape, a resistance heating element embedded therein, and a heater terminal for energizing the resistance heating element formed on the outer peripheral surface. And a metal terminal ring that is electrically fitted to the outer peripheral surface of the ceramic heater so as to cover the heater terminal and is electrically connected to the heater terminal, and a metal lead portion welded to the surface of the terminal ring. In order to manufacture the glow plug, the welded joint between the metal lead portion and the terminal ring is formed by ultrasonic welding.

In the structure of the glow plug of the present invention, the metal terminal ring is arranged by interference fitting so as to cover the terminal ring formed on the outer peripheral surface of the ceramic heater, and the metal lead portion is ultrasonically welded thereto. I did it. As a result, the metal / ceramic brazing structure that requires man-hours can be eliminated from the assembly portion of the metal lead portion to the ceramic heater, and as a result, the metal lead portion can be easily assembled to the ceramic heater. Further, since the amount of heat input at the time of welding is limited due to the adoption of ultrasonic welding, residual thermal stress at the welded joint obtained or in the vicinity thereof is reduced. Therefore, defects such as welding cracks are less likely to occur, and it is possible to realize a glow plug having high assembly strength of the metal lead portion to the ceramic heater.

The assembling order of the assembling of the terminal ring to the ceramic heater and the welding of the metal lead portion to the terminal ring is either of the following two. After fitting the terminal ring onto the ceramic heater by interference fit, the metal lead is welded to the terminal ring. After welding the metal lead portion to the terminal ring, the terminal ring is tightly fitted to the ceramic heater.

According to the structure of the present invention, when the method (1) is adopted, since the amount of heat input at the time of welding is small due to the adoption of ultrasonic welding, the stress of fitting generated in the terminal ring is difficult to be released, and by extension, fitting is performed. The tight binding force can be maintained high even after welding. As a result, even if the terminal ring thermally expands and loosens easily due to the temperature rise when using the glow plug,
Since the margin of the tight binding force is increased, the conduction state between the terminal ring and the heater side terminal can be maintained at a higher temperature. On the other hand, when adopting method (2), since the terminal ring is fitted to the ceramic heater after welding, the effect of welding does not essentially affect the tight binding force of the fitting, and a high tight binding force is secured. it can. Further, as described above, since thermal stress is unlikely to remain in the joint portion by ultrasonic welding, even if a stress is newly added when the terminal ring is fitted, it is unlikely that a defect such as a crack occurs in the weld joint portion. . In any case, as a result of adopting the structure of the present invention, it is possible to reliably ensure conduction between the metal lead portion and the heater terminal via the terminal ring.

In the above method employing ultrasonic welding, high-speed minute mechanical vibration (hereinafter referred to as ultrasonic mechanical vibration) is applied by ultrasonic waves while the metal lead portion and the terminal ring are in pressure contact with each other, and the metal lead portion is pressed. Between the terminal ring and the metal /
A metal contact state (or an alloyed state due to plastic flow) is formed to join the two. In the ultrasonic welding, unlike friction pressure welding or the like in which members to be joined are rotated at high speed in a contact state, friction heat generation during joining is extremely small. In addition, the metal lead portion and the terminal ring are brought into pressure contact with each other and ultrasonic mechanical vibration is applied to instantaneously destroy the oxide or dirt layer on the contact surface, resulting in contact between clean metal layers and plastic flow. As a result, the solid state of joining can be realized.

The welded joint obtained by ultrasonic welding is
It is considered to be formed by alloying based on plastic flow due to mechanical vibration. Therefore, the component distribution of the welded joint is also clearly different from that of the welded portion such as resistance welding whose main component is thermal diffusion. The second configuration of the glow plug of the present invention recaptures the characteristic part from this point of view. Specifically, the glow plug has a rod-like shape and the resistance heating element is embedded, and the resistance heating element is energized. A ceramic heater having a heater terminal for exposing the outer peripheral surface is formed, and a metal terminal ring that is electrically connected to the heater terminal by being fitted onto the outer peripheral surface of the ceramic heater in an interference fit state so as to cover the heater terminal. , A metal lead portion welded to the surface of the terminal ring, and a welded joint portion between the metal lead portion and the terminal ring is provided with a metal lead portion from the joint interface between the metal lead portion and the terminal ring to the metal lead portion An alloyed layer of the constituent metal component of the lead portion and the constituent metal component of the terminal ring (ring constituent component) is formed, and the concentration of the ring constituent component is close to the bonding interface. Concentration inversion region is relatively lower than the side farther in the side is characterized in that it is formed so as to be identified.

FIG. 3 is a schematic view showing the concentration distribution profile of the ring constituents measured at the welded joint between the metal lead portion and the terminal ring in the direction intersecting the joint interface. This figure illustrates, for example, the case of Fe, which is the main element of the ring-constituting metal, but is not limited to this. In the case of resistance welding, which generates a large amount of heat, component movement from the terminal ring side to the metal lead portion side proceeds mainly by the heat diffusion mechanism, so the component diffusion generally follows Fick's law. Therefore, the ring constituent component of the alloyed layer on the metal lead portion side exhibits a profile shape that monotonically decreases with distance from the bonding interface, as indicated by the alternate long and short dash line in FIG. On the other hand, when ultrasonic welding is used, the progress of heat diffusion is slower than in resistance welding or the like. However, plastic flow of the material occurs due to the addition of mechanical vibration in the vicinity of the contact interface between the metal lead portion and the terminal ring, and alloying due to the plastic flow mainly occurs. As a result, as shown by the solid line in FIG. 3, the second region S in which the concentration of the ring constituent is relatively lower on the side closer to the bonding interface than in the first region P in which the concentration of the ring constituent is relatively high. Are formed in the form of density reversal regions.

The above profile is peculiar to the case where the alloying based on the above plastic flow is the main, and the high speed mechanical vibration peculiar to ultrasonic waves causes the formation of oxide and dirt layers on the contact surface. It means that the destruction instantly occurs, and the contact between the clean metal layers and the plastic flow proceed. As a result, a strong joining state can be realized between the terminal ring and the metal lead portion.

In the case of forming the alloyed layer as described above, it is preferable that the constituent metal of the metal lead portion is softer than the constituent metal of the terminal ring so that the plastic flow and the alloying due to the ultrasonic vibration are caused. Desirable to promote. As an example, a combination in which the terminal ring is made of a metal containing Fe as a main component and the metal lead portion is made of a metal containing Ni as a main component can be exemplified.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the glow plug of the present invention together with its internal structure. Also,
FIG. 2 is an enlarged view of the main part. The glow plug 50 has a ceramic heater 1 and a metal shell 4 that holds the ceramic heater 1. The ceramic heater 1 has a rod-like shape, and the resistance heating element 11 is embedded in the tip portion 2 of the ceramic heater 1. A first heater terminal 12a for energizing the resistance heating element 11 is formed on the outer peripheral surface of the rear end portion of itself. Further, the metal shell 4 is formed in a cylindrical shape that coaxially covers the outside of the ceramic heater 1, and the front end portion of the inner peripheral surface in the direction of the axis O is the heater holding surface 4a. Then, the ceramic heater 1 is held by the heater holding surface 4a indirectly via the cylindrical second terminal ring 3 which is another member, and in a form in which the tip portion 2 is projected (hence,
It is the inner peripheral surface of the second terminal ring 3 that directly holds the ceramic heater 1). Further, a ring arrangement gap G is formed between the outer peripheral surface of the rear end portion of the ceramic heater 1 and the inner peripheral surface of the metal shell 4 on the rear side of the heater holding surface 4a.

Next, on the outer peripheral surface of the metal shell 4, a screw portion 5 is formed as an attachment portion for fixing the glow plug 50 to an engine block (not shown), and a metal shaft 6 is attached to the rear end portion. Has been. The outer metal shaft 6 has a rod-like shape, is inserted in the rear end portion of the metal shell 4 in the direction of the axis O, and has its front end surface 6 in the direction of the axis O.
f is arranged so as to face the rear end surface 2r of the ceramic heater 1. On the other hand, in the ring arrangement gap G, the first heater terminal 12 is provided on the outer peripheral surface of the rear end portion of the ceramic heater 1.
A first terminal ring 14 made of metal and electrically connected to a is attached so as to cover the first heater terminal 12a in an interference fit state. Then, the metal shaft 6 and the first heater terminal 12
It is electrically connected to a by a metal lead portion 17 having one end coupled to the first terminal ring 14 and the other end coupled to the metal shaft 6.

An axis O is formed on the outer peripheral surface of the ceramic heater 1.
A second heater terminal 12b for energizing the resistance heating element 11 is exposed and formed on the front side of the first heater terminal 12a in the direction. Then, the second heater terminal 12b
A cylindrical second terminal ring 3 that covers and is electrically connected to the ceramic heater 1 with the rear end portion of the ceramic heater 1 projecting to the rear side of the ceramic heater 1 in an interference fit state on the outer peripheral surface of the ceramic heater 1. It is installed. The metal shell 4 is attached to the outer peripheral surface of the second terminal ring 3 at the cylindrical heater holding surface 4a.

By using the second terminal ring 3 interposed between the heater holding surface 4a of the metal shell 4 and the outer peripheral surface of the ceramic heater 1 as a spacer, the second terminal ring 3 projects rearward from the second terminal ring 3. An appropriate amount of the ring arrangement gap G can be formed between the outer peripheral surface of the rear end portion of the ceramic heater 1 and the inner peripheral surface of the metal shell 4 on the rear side of the heater holding surface 4a. By using the ring arrangement gap G, the first terminal ring 14 can be arranged at the rear end portion of the ceramic heater 1. Since the metal lead portion 17 may be attached to the first terminal ring 14 by metal / metal joining, a metal / ceramic brazing structure or a buried joining of the metal lead portion 17 to the ceramic heater 1 is required.
A complicated structure that requires man-hours is eliminated, and it can be manufactured at low cost. In addition, the first terminal ring 14 is connected to the ceramic heater 1.
Since the fitting is performed by interference fitting, the brazing material layer is not present unlike the conventional structure by brazing, and the coaxiality between the metal shaft 6 and the first terminal ring 14 can be easily secured. This allows
The joining surface between the metal lead portion 17 and the metal shaft 6 or the first terminal ring 14 is less likely to be displaced, and thus a good and high-strength joining portion can be formed.

In the present embodiment, the metal shell 4 is also attached to the outer peripheral surface of the second terminal ring 3 in a tight fit state on the heater holding surface 4a. Thereby, the assembly process of the glow plug 50 can be further simplified. Further, since the fitting surface (heater holding surface 4a) of the metal shell 4 to the second terminal ring 3 overlaps with the fitting surface of the second terminal ring 3 and the ceramic heater 1, the second surface to the ceramic heater 1 The tight binding force of the metal shell 4 is superimposed on the tight binding force of the terminal ring 3, and the airtightness of the fitting between the second terminal ring 3 and the ceramic heater 1 can be further enhanced.

Each terminal ring 1 to the ceramic heater 1
As shown in FIG. 6, each of the terminal rings 14 and 3 can be assembled into the ceramic heater 1 by inserting the terminal rings 14 and 3 into the ceramic heater 1 while inserting the terminal rings 14 and 3 in the axial direction. Note that shrink fitting may be used instead of press fitting. Of these, the first terminal ring 14 only needs to have a tight binding force enough to ensure conduction with the first heater terminal 12a. On the other hand, the second terminal ring 3 is required to have a tighter binding force than the first terminal ring 14 because it is necessary to secure the airtightness on the fitting surface in addition to ensuring the conduction with the second heater terminal 12b. To be In any case, it is important to secure a necessary and sufficient cohesive force not only at room temperature but also when the temperature of the ceramic heater 1 in which thermal expansion occurs in each part rises. Generally, when comparing ceramic and metal, except for special alloys such as Invar,
Metal has a higher coefficient of linear expansion, and the binding force of the terminal rings 14 and 3 tends to loosen more easily when the temperature rises.

In this case, the level of the tight binding force secured at the time of temperature rise also depends on the material of the ring and the wall thickness t.
As shown in FIG. 3, in the disassembled state in which the first terminal ring 14 or the second terminal ring 3 is removed from the ceramic heater 1, the inner diameter of the first terminal ring 14 is d1, and the formation position of the first heater terminal 12a in the disassembled state is also the same. And the outer diameter of the ceramic heater 1 is d2-d1 (hereinafter, referred to as a tightening margin after disassembly of the first terminal ring 14: in the present specification, a value at room temperature) is 8 μm or more. It is desirable that the outer diameter of the ceramic heater 1 at the mounting position of the first terminal ring 14 is adjusted to 2% or less. Further, in the disassembled state in which the second terminal ring 3 is removed from the ceramic heater 1, the inner diameter of the second terminal ring 3 is d1 ′ and the outer diameter of the ceramic heater 1 is d2 ′, and d2′−d1 ′ (hereinafter, referred to as (Tightening margin after disassembly of the two terminal ring 3: In the present specification, it means a value at room temperature). Similarly, the outer diameter of the ceramic heater 1 at the mounting position of the second terminal ring 3 is 8 μm or more. It is desirable that the range is adjusted to 2% or less.

After the disassembly, the tightening margin is the ceramic heater 1
It can be regarded as a parameter that reflects the elastic return amount of the rings 14 and 3 when removed from the substrate, that is, the elastic binding force of the rings 14 and 3 to the ceramic heater 1. If the tightening margin after disassembly is less than 8 μm, the necessary binding force cannot be secured when the temperature of the ring 3 or 4 rises within the above temperature range. For example, in the first terminal ring 14, an increase in the contact resistance with the first heater terminal 12a, and in the second terminal ring 3 an increase in the contact resistance with the first heater terminal 12b and a decrease in airtightness are concrete. It will lead to the occurrence of a malfunction. On the other hand, if the tightening margin after disassembly exceeds 100 μm, an excessive binding force acts on the ceramic heater 1, which may lead to cracks or cracks. When the thickness of the rings 3 and 14 is small, the amount of plastic deformation of the rings itself increases, and it may be essentially impossible to set the post-disassembly tightening margin to 100 μm or more. In addition,
Tightening allowance after disassembly d2-d1 or d2'-d1 '
Is more preferably adjusted in the range of 15 to 40 μm. Further, even if the value of the tightening margin after disassembly is the same, it is more advantageous that the thickness of the ring is larger from the viewpoint of increasing the value of the elastic binding force.

First terminal ring 14 and second terminal ring 3
As a material for the above, it is desirable to use an Fe-based alloy having hardness and heat resistance above a certain level in consideration of the balance between high temperature strength and material cost. In particular, in order to increase the tightening margin after disassembly and ensure a sufficient elastic binding force, the Vickers hardness (value measured at a load of 10 N by the method prescribed in JIS: Z2244 (1998)) Hv is 170 or more ( The use of Fe-based alloys of 350 or more) is recommended. As such an Fe-based alloy, stainless steel, for example, precipitation hardening stainless steel such as SUS630 or SUS631 can be preferably used. SUS630 is JI
H900, H1 specified in SG4303 (1988)
Aging precipitation hardening can be performed by heat treatment of any one of 025, H1075, and H1105.
Those subjected to 0 treatment can secure Hv350 or higher. On the other hand, SUS631 is TH1050 or RH of the same standard.
It can be aged precipitation hardened by the heat treatment of 950,
Both can secure Hv350 or higher. Further, although it is slightly inferior in hardness, ferritic stainless steel such as SUS430 can also be used.

Next, as shown in FIG. 2, the metal lead portion 1
7 is arranged in a bent shape between the metal shaft 6 and the first terminal ring 14. As a result, the ceramic heater 1
Even if a heating / cooling cycle is added due to the heat generated by
The metal lead portion 17 can absorb the expansion / contraction at its bent portion, and excessive stress is concentrated on the joint portion between the metal lead portion 17 and the first terminal ring 14, resulting in defects such as contact failure and disconnection. Can be prevented. Further, in order to easily and firmly join the metal lead portion 17 and the metal shaft 6, the joining end portion of the metal lead portion 17 with the metal shaft 6 is formed into a planar shape with respect to the outer peripheral surface tip end portion of the metal shaft 6. Are joined with the joint surface of. For example, when the metal lead portion 17 and the metal shaft 6 are joined by resistance welding, making the joint surface planar makes it possible to evenly apply a pressing force during resistance welding and form a welded joint portion with few defects. It is also advantageous in the above.

On the other hand, the metal lead portion 17 is welded to the outer peripheral surface of the first terminal ring 14 at its front end portion. In the present invention, for example, ultrasonic welding, which will be described later, is adopted as a welding method in which the temperature rise during joining is small. Thereby, as shown in FIG. 3, at the welded joint between the metal lead portion 17 and the terminal ring 14, from the joint interface between the metal lead portion 17 and the terminal ring 14 to the metal lead portion 17 side,
An alloyed layer of the constituent metal component of the metal lead portion 17 and the constituent metal component of the terminal ring 14 (ring constituent component) is formed, and the alloyed layer has a concentration of the ring constituent component close to the bonding interface. A density inversion region S that is relatively higher than that on the far side is formed to be distinguishable. In other words, in the cross section that crosses the bonding interface, the first regions P in which the concentration of the ring constituent component has the maximum value and the second regions (concentration inversion region) S in which the concentration has the minimum value are alternately formed in the bonding direction. A concentrated concentration distribution is formed.

The metal lead portion 17 is welded to the first terminal ring 14 as shown in FIG. 7 (a).
It is possible to adopt a process of welding the metal lead portion 17 to the first terminal ring 14 of the ceramic heater 1 after press-fitting the ceramic heater 4 into the ceramic heater 1 so as to be fitted. Metal first terminal ring 1
In No. 4, when the heat input during welding is large, the yield point of the material decreases due to the temperature rise, and the elastic strain of the ring generated during the interference fitting is converted into plastic deformation strain, and the elastic binding force is impaired. There is. However, by suppressing the heat input at the time of welding by adopting ultrasonic welding, it is possible to effectively suppress the above-mentioned decrease in elastic binding force.

On the other hand, as shown in FIG. 7B, after the metal lead portion 17 is welded to the first terminal ring 14, the step of fitting the first terminal ring 14 into the ceramic heater 1 by interference fit is used. You can also In this case, the effect of welding essentially does not affect the tight binding force of the fitting. Further, as a result of suppressing residual thermal stress in the welded joint, even if a new stress is applied when the terminal ring is fitted, the welded joint is unlikely to have a defect such as cracking.

Next, the ceramic heater 1 has a resistance heating element 11 in a ceramic base 13 made of an insulating ceramic.
Is embedded as a rod-shaped ceramic heater element. In this embodiment, the ceramic heater 1
Is configured such that a ceramic resistor 10 made of a conductive ceramic is embedded in a ceramic base 13 made of an insulating ceramic. Ceramic resistor 1
Reference numeral 0 indicates a first resistor portion 11 which is made of a first conductive ceramic and is disposed at the tip of the ceramic heater 1, and which functions as a resistance heating element, and a ceramic heater on the rear side of each first resistor portion 11. No. 1 is arranged so as to extend in the direction of the axis O, and the tip end is joined to both ends of the first resistor portion 11 in the energization direction, and the second conductivity is lower in resistivity than the first conductive ceramic. And a pair of second resistor portions 12 and 12 made of ceramic. Then, branch portions are formed in the pair of second resistor portions 12, 12 of the ceramic resistor 10 at different positions in the direction of the axis O, and the exposed portions of the branch portions on the surface of the ceramic heater 1. , Respectively, forming a first heater terminal 12a and a second heater terminal 12b.

The resistance heating element 11 is energized by, for example, as shown in FIG. 10, the embedded lead wires 18, 1 made of a high melting point metal wire material such as W embedded in the ceramic substrate 13.
It can also be done via 9. In this case, the first heater terminal is formed of the embedded lead wire 18, and the second heater terminal is formed of the embedded lead wire 19 as the exposed portions 18a and 19a.

Next, in this embodiment, a silicon nitride ceramic is used as an insulating ceramic forming the ceramic base 13. The structure of the silicon nitride ceramic is such that main phase particles containing silicon nitride (Si ₃ N ₄ ) as a main component are bonded by a grain boundary phase derived from a sintering aid component described later. The main phase may be one in which a part of Si or N is replaced with Al or O, and further, one in which metal atoms such as Li, Ca, Mg, and Y are solid-dissolved in the phase. .

For silicon nitride ceramics, 3 of the periodic table is used.
At least one selected from the group of elements of each group of A, 4A, 5A, 3B (for example, Al) and 4B (for example, Si) and Mg is used as the cation element, and the oxide is contained in the whole sintered body. It can be contained in an amount of 1 to 10 mass% in terms of conversion. These components are added mainly in the form of oxides,
In the sintered body, it is contained mainly in the form of oxide or complex oxide such as silicate. If the sintering additive component is less than 1% by mass, it is difficult to obtain a dense sintered body, and if it exceeds 10% by mass, the strength, toughness, or heat resistance becomes insufficient. The content of the sintering aid component is preferably 2 to 8% by mass.
It is good to say When a rare earth component is used as the sintering aid component, Sc, Y, La, Ce, Pr, Nd, Sm,
Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
u can be used. Among these, Tb, D
y, Ho, Er, Tm, and Yb have the effect of promoting crystallization of the grain boundary phase and improving high-temperature strength, and thus can be preferably used.

Next, the first resistor portion 11 and the second resistor portions 12, 12 constituting the ceramic resistor 10 are made of conductive ceramics having different electric resistivities as described above. The method of making the electric resistances of both conductive ceramics different from each other is not particularly limited, and, for example, a method of making the contents different from each other while using the same kind of conductive ceramic phase; Various methods can be exemplified, such as a method in which a characteristic ceramic phase is adopted; a method in combination with, and the like, but the method in this embodiment is adopted.

Examples of the conductive ceramic phase include tungsten carbide (WC) and molybdenum disilicide (MoSi).
₂ ) and tungsten disilicide (WSi ₂ ) can be used. In this embodiment, WC is adopted.
In order to reduce the difference in linear expansion coefficient from the ceramic base 13 and improve the thermal shock resistance, an insulating ceramic phase, which is the main component of the ceramic base 13, here a silicon nitride ceramic phase can be blended. Therefore, by changing the content ratio of the insulating ceramic phase and the conductive ceramic phase, the electric resistivity of the conductive ceramic forming the resistor portion can be adjusted to a desired value.

Concretely, the first conductive ceramics, which is the material of the first resistor portion 11 forming the resistance heating portion, has a conductive ceramic phase content of 10 to 25% by volume, and the remaining insulating ceramic phase. It is good to say If the content rate of the conductive ceramic phase exceeds 25% by volume, the electrical conductivity becomes too high and a sufficient calorific value cannot be expected, and if it is less than 10% by volume, the electrical conductivity becomes too low and the calorific value becomes the same. Can not be secured enough.

On the other hand, the second resistor portions 12 and 12 serve as conduction paths to the first resistor portion 11, and the second conductive ceramic, which is the material thereof, has a conductive ceramic phase content of 15%. ˜30% by volume, and the balance is preferably an insulating ceramic phase. If the content rate of the conductive ceramic phase exceeds 30% by volume, it becomes difficult to densify it by firing, resulting in insufficient strength, and even if the temperature range normally used for engine preheating is reached, the electrical resistivity The rise may be insufficient, and the self-saturation function for stabilizing the current density may not be realized. On the other hand, if it is less than 15% by volume, the heat generation in the second resistor portions 12 and 12 becomes too large, which leads to deterioration in heat generation efficiency of the first resistor portion 11. In the present embodiment, the content ratio of WC in the first conductive ceramic is 16% by volume (55 mass%), and the content ratio of WC in the second conductive ceramic is 20% by volume (7%).
0% by mass) (the rest are all silicon nitride ceramics (including a sintering aid)).

In this embodiment, the ceramic resistor 10
Is arranged such that the first resistor portion 11 has a U-shape, and the U-shaped bottom portion is located on the tip side of the ceramic heater 1, and the second resistor portions 12 and 12 have the U-shaped first portion. It is a rod-shaped portion that extends rearward from both ends of the one resistor portion 11 along the axis O direction and is substantially parallel to each other.

In the ceramic resistor 10, the first resistor portion 11 has a tip portion 11a which should have the highest temperature during operation.
In order to concentrate the electric current, the tip portion 11a has a smaller diameter than the both end portions 11b and 11b. The joint surface 15 with the second resistor portions 12 and 12 has a tip portion 1
It is formed on both ends 11b, 11b having a diameter larger than that of 1a.

As shown in FIG. 10, the embedded lead wire 1
In the structure in which 8 and 19 are arranged in the ceramic, when the voltage for driving the heater is applied at high temperature, the embedded lead wire 1
In some cases, the metal atoms forming 12 are consumed by the so-called electromigration effect of being forcibly diffused to the ceramic side by receiving an electrochemical driving force due to the electric field gradient, and thus wire breakage or the like is likely to occur. However, FIG.
Since the embedded lead wire is abolished in the above configuration, there is an advantage that it is essentially not affected by the electromigration effect.

Next, as shown in FIG. 1, inside the rear end portion of the metal shell 4, the metal shaft 6 for supplying electric power to the ceramic heater 1 is insulated from the metal shell 4 as described above. It is arranged. In this embodiment, the ceramic ring 3 is provided between the outer peripheral surface of the metal shaft 6 on the rear end side and the inner peripheral surface of the metal shell 4.
1 is arranged, and a glass filling layer 32 is formed on the rear side of the No. 1 and fixed. A ring-side engagement portion 31a is formed on the outer peripheral surface of the ceramic ring 31 in the form of a large diameter portion, and a metal fitting formed in the shape of a circumferential step portion near the rear end of the inner peripheral surface of the metal shell 4. By engaging with the side engaging portion 4e, the retaining to the front side in the axial direction is prevented. Further, the outer peripheral surface portion of the metal shaft 6 which is in contact with the glass filling layer 32 is provided with unevenness by knurling or the like (a shaded area in the drawing). Further, the rear end portion of the metal shaft 6 extends rearward of the metal shell 4, and the terminal metal fitting 7 is fitted into the extending portion via an insulating bush 8. The terminal fitting 7 is fixed to the outer peripheral surface of the metal shaft 6 in a conductive state by a caulking portion 9 in the circumferential direction.

The glow plug 50 is attached to the diesel engine so that the tip portion 2 of the ceramic heater 1 is located in the combustion chamber in the attachment portion 5 of the metal shell 4. Then, by connecting the terminal metal fitting 7 to a power source, the metal shaft 6 → the metal lead portion 17 → the first terminal ring 14 → the ceramic heater 1 → the second terminal ring 3 → the metal shell 4 → (grounded through the engine block) In this order, a current flows, the tip portion 2 of the ceramic heater 1 generates heat, and the inside of the combustion chamber can be preheated.

The method of manufacturing the glow plug 50 will be described below. First, as shown in FIG. 5A, a resistor powder molding portion 34 to be the ceramic resistor 10 is formed by injection molding. Further, the raw material powder for forming the ceramic base 13 is press-molded in advance with a die to prepare divided preforms 36 and 37 as separate base upper and lower bodies. A concave portion 37a having a shape corresponding to the resistor powder molding portion 34 (a concave portion on the divided preliminary molded body 36 side is not shown in the drawing) is formed on the mating surface of each of the divided preliminary molded bodies 36 and 37. , The resistor powder molding part 34 is housed therein, and the divided preform 3
As shown in FIG. 5 (b), by fitting 6, 37 on the mating surface, and further pressing and compressing,
A composite molded body 39 in which these are integrated is produced.

The composite molded body 39 thus obtained is subjected to binder removal processing, and is then fired at 1700 ° C. or higher, for example, about 1800 ° C. by a hot press or the like to obtain a fired body, and the outer peripheral surface is polished into a cylindrical shape. For example, the ceramic heater 1 is obtained. Then, as shown in FIG. 6, the first terminal ring 14 and the second terminal ring 3 are tightly fitted to the ceramic heater 1 by, for example, press fitting.

The metal lead portion 17 is joined to the first terminal ring 14 by ultrasonic welding. As described above, the order of this joining may be either after the first terminal ring 14 is assembled to the ceramic heater 1 or before it is assembled. The ultrasonic welding can be performed using, for example, a commercially available ultrasonic welder (for example, trade name: USW-610Z20S (Ultrasonic Industrial Co., Ltd.).
Shows the outline of the process. That is, the first terminal ring 14, which is a member to be welded, is placed on a pedestal (not shown), and the metal lead portion 17 is superposed on the outer peripheral surface thereof. On the other hand, a vibrating arm 5 connected to an ultrasonic oscillator (not shown)
The vibrator 51 is attached to the tip of 0. Then, the vibrator 51 is pressed against the metal lead portion 17 with a constant load P,
By ultrasonically vibrating the vibrating arm 50 at the amplitude A and the frequency Q in that state, the joint surfaces of the first terminal ring 14 and the metal lead portion 17 are firmly joined by solid-phase joining via plastic flow. It

Then, in the region on the metal lead side of the welded joint, based on the plastic flow due to mechanical vibration at this time,
As shown in FIG. 3, an alloy having a concentration distribution structure in which a first region P in which the concentration of the ring constituent component has a maximum value and a second region (concentration inversion region) S in which the concentration has a minimum value are alternately formed. A layer is formed. As a result, a strong joined state is formed between the terminal ring 14 and the metal lead portion 7. It is desirable that the thickness of the alloyed layer be 10 μm or more at the position where the thickness is maximum, from the viewpoint of ensuring sufficient bonding strength.

In order to obtain a good joining state, it is necessary that the kinetic energy of ultrasonic vibration is efficiently converted into the energy of relative kinematics along the joining surface between the first terminal ring 14 and the metal lead portion 17. Is. For that purpose, the follow-up mobility of the metal lead portion 17 accompanying the vibration of the vibrator 51 is enhanced, and more specifically, a concavo-convex portion such as a knurl pattern is formed on the tip end surface of the vibrator 51, and the concavo-convex portion is formed with It is effective to perform welding while the lead portion 17 is pressed into the lead portion. In this case, the metal lead portion 1 after welding
As shown in FIG. 9, the biting pattern 17a of the concave and convex portion is transferred to 7.

For example, when the first terminal ring 14 is made of an Fe-based material such as stainless steel, the metal lead portion 17 is a metal containing Ni as a main component (50 mass% or more), or the Ni content. When a Fe-based alloy having a relatively high value (for example, Invar or the like containing Ni in an amount of 20 to 50 mass%: the above are collectively referred to as Ni-containing metal) is adopted, Fe in the stainless steel and the metal lead portion 17 N
Since the affinity with i is high, the strength of the obtained ultrasonic welded joint can be increased. In this case, the pressing force P during ultrasonic welding is suitably 5 to 50 kg. Also,
It is suitable that the frequency Q of ultrasonic vibration is 19 to 100 kHz and the amplitude A is 10 to 25 μm. The vibration time is 0.0
About 2 to 2 seconds is suitable.

[0047]

EXAMPLES The results of experiments conducted to confirm the effects of the present invention will be described below. First, the ceramic heater 1 having the form shown in FIG. 1 was produced by the method described above. However, the length of the ceramic heater 1 is 40 mm, the outer diameter is 3.5 mm, the thickness of the second resistor portions 12 and 12 is 1 mm, and the first heater terminal 12a and the second heater terminal 12b are each a diameter. The circular area was 0.8 mm.

On the other hand, the first terminal ring 14 and the second terminal ring 3 were produced using the above-mentioned SUS630 (H900 age hardening treated product: Hv = about 400). The wall thickness of the first terminal ring 14 is 0.5 mm, and the inner diameter d1i is 50 μ in the initial tightening margin defined by d2i-d1i, where d2i is the outer diameter before assembly to the ceramic heater 1.
What was adjusted to be m was prepared. On the other hand, the wall thickness of the second terminal ring 3 is 0.85 mm, and its inner diameter d1
i ′ was fixedly set so that the initial tightening margin defined similarly to the first terminal ring 14 was 50 μm.

Then, the above-mentioned first terminal ring 14 and second terminal ring 3 were assembled into the ceramic heater 1 at predetermined positions by press fitting. At the time of press fitting, an appropriate amount of lubricant (Paskin M30 (trade name: Kyoeisha Chemical Co., Ltd.)) is applied to the inner surface of each ring, and after press fitting, the lubricant is decomposed at 300 ° C. In the first terminal ring, as the metal lead portion 17, pure Ni having a wire diameter of 0.8 mm is used.
The wire (the end of the joint was flattened by pressing) was ultrasonically welded under the following conditions: -Ultrasonic frequency: 19 kHz-Ultrasonic output: 600 W-Excitation time: 0.1 seconds-Amplitude: 25 μm- Pressing force: 25 kg. On the other hand, for comparison, a test product in which the above-mentioned metal lead portion 17 was joined to the first terminal ring 14 by resistance welding was similarly prepared.

Using the above test product, the first terminal ring 14 at various temperatures from room temperature (20 ° C.) to 400 ° C.
And the series resistance value between the second terminal ring 3 was measured. The result is shown in FIG. According to this, the resistance value of the comparative example product using resistance welding sharply increases in the temperature range of 300 ° C. or higher, whereas that of ultrasonic welding does not show such a sharp increase in resistance value. It can be seen that good conduction is maintained even at high temperatures. Further, after the above resistance measurement was completed, the first terminal ring 14 was removed from the ceramic heater 1, and the above-described disassembled interference was measured. As a result, the comparative example product using resistance welding had a tightening margin after disassembly close to zero, whereas the product using ultrasonic welding had a friction coefficient of 17μ.
It was found that the tightening allowance was secured after the disassembly of m.

In FIG. 12, the welded joint portion between the first terminal ring 14 and the metal lead portion 17 is cut and polished in a direction orthogonal to the joint interface, and the Fe concentration distribution is measured by a scanning electron microscope (SEM). Built-in EPMA (Electron Probe Micro
(A) is an ultrasonic welded product, and (b) is a resistance welded product. In the image, the whiter area is F
e means high concentration. In each case, an alloyed layer having a reduced Fe concentration is formed in the direction away from the bonding interface toward the metal lead portion. However, in the ultrasonic welded product of (a), the Fe concentration is decreased in the direction away from the bonding interface. As a result of a large fluctuation, a striped shading pattern is seen. It is considered that this is caused by plastic flow due to ultrasonic vibration, and in the direction away from the bonding interface, the first region where the Fe concentration is maximum (the white region) and the second region where the Fe concentration is minimum ( The density inversion area: the part that appears in black) is clearly identified. On the other hand, in the resistance welded product (b), a uniform gradation pattern in which the Fe concentration monotonically decreases is formed on the metal lead portion side from the bonding interface, and the above-mentioned first region and second region are not distinguished. It is considered that this is because the Fe component of the first terminal ring 14 thermally diffused toward the metal lead portion 17 side according to Fick's law.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a glow plug of the present invention.

FIG. 2 is a vertical sectional view showing a main part of FIG.

FIG. 3 is a conceptual explanatory view of an alloyed layer formed in a welded joint.

FIG. 4 is a diagram illustrating a part used for calculating a post-disassembly tightening margin.

FIG. 5 is an explanatory view of a manufacturing process of the glow plug of FIG.

FIG. 6 is an explanatory diagram following FIG. 5;

FIG. 7 is an explanatory diagram following FIG. 6;

FIG. 8 is a process explanatory diagram of ultrasonic welding.

FIG. 9 is a diagram for explaining the external characteristics of the ultrasonic welded portion.

10 is a longitudinal cross-sectional view of a main part showing a modified example of the glow plug of FIG.

FIG. 11 is a graph showing the experimental results of the examples.

FIG. 12 is a two-dimensional mapping image of Fe concentration when an EPMA surface analysis is performed on a cross section of a joint between a terminal ring and a metal lead portion by ultrasonic welding and resistance welding.

[Explanation of symbols]

1 Ceramic heater 2 Tip 3 Second terminal ring 4 metal shell 4a Heater holding surface 10 Ceramic resistor 11 First resistor part (resistance heating element) 12,12 Second resistor part 12a First heater terminal 12b Second heater terminal 14 First terminal ring (terminal ring) 17 Metal lead part 50 glow plug

Continued front page    (72) Inventor Hiroyuki Suzuki             14-18 Takatsuji-cho, Mizuho-ku, Nagoya City, Aichi Prefecture             Inside this special ceramics company (72) Inventor Masaya Ito             14-18 Takatsuji-cho, Mizuho-ku, Nagoya City, Aichi Prefecture             Inside this special ceramics company

Claims (7)

[Claims] 1. A ceramic heater (1) having a rod-like shape, in which a resistance heating element (11) is embedded, and a heater terminal (12a) for energizing the resistance heating element is exposed and formed on the outer peripheral surface. And a metal terminal ring (14) that is electrically connected to the heater terminal (12a) by being fitted onto the outer peripheral surface of the ceramic heater (1) in an interference fit state so as to cover the heater terminal (12a). A glow plug comprising: a metal lead portion (17) welded to the surface of the terminal ring (14) through an ultrasonic welding portion. 2. A ceramic heater (1) having a rod-like shape, in which a resistance heating element (11) is embedded, and a heater terminal (12a) for energizing the resistance heating element is exposed and formed on the outer peripheral surface. And a metal terminal ring (14) that is electrically connected to the heater terminal (12a) by being fitted onto the outer peripheral surface of the ceramic heater (1) in an interference fit state so as to cover the heater terminal (12a). A metal lead portion (17) welded to the surface of the terminal ring (14), and the metal lead portion (17) at a welded joint portion between the metal lead portion (17) and the terminal ring (14). ) And the terminal ring (14) from the joint interface to the metal lead portion (17) side, the metal component of the metal lead portion (17) and the metal component of the terminal ring (14) (hereinafter, ring). (Hereinafter referred to as a component) is formed, and the alloyed layer has a concentration inversion region in which the concentration of the ring constituent component is relatively lower on the side closer to the bonding interface than on the far side. A glow plug characterized by being formed to be distinguishable. 3. The glow plug (50) according to claim 2, wherein the thickness of the alloying layer at the thickest position in the cross section is 10 μm or more. 4. The terminal ring (14) is made of stainless steel, and the metal lead portion (17) is made of a metal containing Ni as a main component.
The glow plug (50) according to any one of items 1. 5. A ceramic heater (1) having a rod-like shape, in which a resistance heating element (11) is embedded, and a heater terminal (12a) for energizing the resistance heating element is formed exposed on the outer peripheral surface. And a metal terminal ring (14) that is electrically connected to the heater terminal (12a) by being fitted onto the outer peripheral surface of the ceramic heater (1) in an interference fit state so as to cover the heater terminal (12a). A welded joint between the metal lead portion (17) and the terminal ring (14) for producing a glow plug comprising: a metal lead portion (17) welded to the surface of the terminal ring (14); A method for manufacturing a glow plug (50), characterized in that the portion is formed by ultrasonic welding. 6. The metal lead portion (17) is ultrasonically welded to the terminal ring (14) after the terminal ring (14) is press-fit and fitted to the ceramic heater (1). A method for manufacturing the glow plug (50). 7. The terminal ring (1) is formed by ultrasonically welding the metal lead portion (17) to the terminal ring (14).
The method for manufacturing a glow plug (50) according to claim 5, wherein 4) is fitted into the ceramic heater by interference fit.