JP4559671B2 - Glow plug and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glow plug for preheating a diesel engine and a manufacturing method thereof.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, glow plugs such as those described above are widely used in which the tip portion of a rod-shaped ceramic heater protrudes inside the tip portion of a cylindrical metal shell. Energization of the ceramic heater is performed through a metal shaft (connected to a power source) provided at the rear end portion of the metallic shell and a metal lead portion connecting the metal shaft and the ceramic heater. In the conventional glow plug, the connection between the ceramic heater and the metal lead portion is formed by, for example, forming the tip portion of the metal lead portion in a coil shape and exposing the heater terminal as disclosed in Japanese Patent Laid-Open No. 10-205753. This has been done by inserting the rear end of the ceramic heater into the inside and brazing the two.
[0003]
[Problems to be solved by the invention]
However, the joining form by brazing has a drawback that the efficiency is poor due to a large number of man-hours such as a process for assembling the materials to be joined by sandwiching the brazing material and a heating process for melting the brazing material. In addition, since it is the joining of ceramic and metal members such as metal leads or metal rings, expensive active brazing materials must be used, and the heating temperature and atmosphere for brazing are also delicately adjusted. In combination with the above-described problem of increasing man-hours, the manufacturing cost is likely to increase.
[0004]
An object of the present invention is to provide a glow plug capable of easily assembling a metal lead portion to a ceramic heater and ensuring the assembly strength and conduction of the metal lead portion, and a method for manufacturing the same. It is to provide.
[0005]
[Means for solving the problems and actions / effects]
In order to solve the above problems, the first configuration of the glow plug of the present invention is:
A ceramic heater having a rod-like shape and embedded with a resistance heating element, and a heater terminal for energizing the resistance heating element is exposed on the outer peripheral surface;
A metal terminal ring that is electrically connected to the heater terminal by being attached to the outer peripheral surface of the ceramic heater so as to cover the heater terminal,
A metal lead welded to the surface of the terminal ring via an ultrasonic weld;
It is provided with.
[0006]
In addition, the method for manufacturing the glow plug of the present invention includes:
A ceramic heater having a rod-like shape and embedded with a resistance heating element, and a heater terminal for energizing the resistance heating element is exposed on the outer peripheral surface;
A metal terminal ring that is electrically connected to the heater terminal by being attached to the outer peripheral surface of the ceramic heater so as to cover the heater terminal,
To manufacture a glow plug with a metal lead welded to the surface of the terminal ring,
A weld joint between the metal lead and the terminal ring is formed by ultrasonic welding.
[0007]
In the above-described glow plug configuration of the present invention, a metal terminal ring is disposed 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. . As a result, the metal / ceramic brazing structure requiring man-hours can be eliminated from the part where the metal lead part is attached to the ceramic heater, and as a result, the metal lead part can be easily attached to the ceramic heater. Further, since the amount of heat input at the time of welding is limited by adopting ultrasonic welding, residual thermal stress is reduced in the welded joint obtained or in the vicinity thereof. Therefore, defects such as weld cracks are less likely to occur, and a glow plug having a high assembly strength of the metal lead portion to the ceramic heater can be realized.
[0008]
The order of assembly of the terminal ring to the ceramic heater and welding of the metal lead portion to the terminal ring is one of the following two.
(1) After the terminal ring is tightly fitted and fitted to the ceramic heater, the metal lead portion is welded to the terminal ring.
(2) After welding the metal lead part to the terminal ring, the terminal ring is tightly fitted to the ceramic heater.
[0009]
When the method of (1) is adopted, according to the structure of the present invention, the amount of heat input at the time of welding is small due to the adoption of ultrasonic welding, so that the fitting stress generated in the terminal ring is difficult to be released, and as a result The tight binding force can be maintained high after welding. As a result, even when the terminal ring thermally expands due to temperature rise when using a glow plug, the tightness margin is increased, so the continuity between the terminal ring and the heater side terminal is increased to a higher temperature. Can be maintained. On the other hand, when the method (2) is adopted, since the terminal ring is fitted to the ceramic heater after welding, the influence of the welding does not substantially affect the tightness of the fit, and the tightness of the fit. Can be secured high. In addition, as described above, since the thermal stress hardly remains in the joint portion by ultrasonic welding, even if a stress at the time of fitting the terminal ring is newly added, a defect such as a crack is hardly generated in the weld joint portion. . In either case, as a result of adopting the structure of the present invention, it is possible to ensure the conduction between the metal lead portion and the heater terminal via the terminal ring.
[0010]
In the above method employing ultrasonic welding, the metal lead portion and the terminal ring are subjected to high-speed and fine mechanical vibration (hereinafter referred to as ultrasonic mechanical vibration) while being brought into pressure contact with the metal lead portion and the terminal ring. A metal / metal contact state (or an alloyed state by plastic flow) is formed between the two, and the two are joined. The ultrasonic welding, unlike the friction welding that joins the members to be joined by rotating them at high speed in a contact state, generates very little frictional heat during joining. In addition, by applying ultrasonic mechanical vibration by applying pressure contact between the metal lead part and the terminal ring, the oxide or dirt layer on the contact surface is instantaneously destroyed, and contact between the clean metal layers and plastic flow Therefore, a strong bonded state can be realized.
[0011]
A weld joint obtained by ultrasonic welding is considered to be formed by alloying based on plastic flow caused by mechanical vibration. Therefore, the component distribution of the welded joint is also clearly different from the welded part by resistance welding or the like mainly composed of thermal diffusion. The second configuration of the glow plug of the present invention is a recapture of the features from this point of view. Specifically, the glow plug has a rod-like form and a resistance heating element is embedded, and the resistance heating element is energized. A ceramic heater in which a heater terminal is exposed on the outer peripheral surface;
A metal terminal ring that is electrically connected to the heater terminal by being attached to the outer peripheral surface of the ceramic heater so as to cover the heater terminal,
A metal lead portion welded to the surface of the terminal ring, and the metal lead portion is connected to the metal lead portion side from the joint interface between the metal lead portion and the terminal ring. The first region in which the alloying layer of the constituent metal component of the part and the constituent metal component of the terminal ring (ring constituent component) is formed , and the concentration of the constituent component of the ring shows the maximum value in the cross section across the joining interface A concentration distribution is formed in which P and a second region (concentration inversion region) S exhibiting a minimum value are alternately formed in the direction of the welding joint .
[0012]
FIG. 3 is a schematic diagram in which the concentration distribution profile of the ring constituent components is measured in the direction intersecting the joint interface at the weld joint between the metal lead portion and the terminal ring. This figure illustrates the case of Fe, which is a main component element of the ring constituent metal, for example, but is not limited to this. In the case of resistance welding or the like that generates a large amount of heat, component movement from the terminal ring side to the metal lead portion side proceeds mainly by the thermal diffusion mechanism, so that component diffusion generally follows Fick's law. For this reason, the ring component of the alloying layer on the metal lead portion side exhibits a profile shape that monotonously decreases as the distance from the bonding interface increases, as indicated by a dashed line in FIG. On the other hand, when ultrasonic welding is used, the progress of thermal diffusion becomes dull compared to resistance welding or the like. However, plastic flow of the material accompanying mechanical vibration is generated near the contact interface between the metal lead portion and the terminal ring, and alloying by the material is mainly performed. As a result, as shown by a solid line in FIG. 3, the second region S in which the concentration of the ring component is relatively low is closer to the bonding interface than the first region P in which the concentration of the ring component is relatively high. Is formed in the form of a density inversion region.
[0013]
The above profile is unique when alloying based on plastic flow as described above is the main component, and the destruction of the oxide or dirt layer on the contact surface is instantaneous due to the high-speed mechanical vibration unique to ultrasonic waves. It means that contact between the clean metal layers and plastic flow proceed. As a result, a strong joined state can be realized between the terminal ring and the metal lead portion.
[0014]
When forming the alloying layer as described above, it is preferable to make the constituent metal of the metal lead portion softer than the constituent metal of the terminal ring in order to promote plastic flow by ultrasonic vibration, and thus alloying. Is desirable. As an example, a combination in which the terminal ring is a metal mainly composed of Fe and the metal lead portion is a metal mainly composed of Ni can be exemplified.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of the glow plug of the present invention together with its internal structure. FIG. 2 is an enlarged view of the main part. The glow plug 50 includes a ceramic heater 1 and a metal shell 4 that holds the ceramic heater 1. The ceramic heater 1 has a rod-like form, and a resistance heating element 11 is embedded in the front end portion 2 thereof.
Moreover, the 1st heater terminal 12a for supplying with electricity to the resistance heating element 11 is exposedly formed by the own rear end part outer peripheral surface. 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 serves as a heater holding surface 4 a. Then, the ceramic heater 1 is held by the heater holding surface 4a indirectly through the cylindrical second terminal ring 3 which is another member and in a form in which the tip portion 2 protrudes (accordingly, 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.
[0016]
Next, the outer peripheral surface of the metal shell 4 is formed with a screw portion 5 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. . The outer metal shaft 6 has a rod shape and is inserted in the direction of the axis O inside the rear end of the metal shell 4, and its front end surface 6 f faces the rear end surface 2 r of the ceramic heater 1 in the direction of the axis O. Are arranged in the form of On the other hand, on the outer peripheral surface of the rear end portion of the ceramic heater 1 in the ring arrangement gap G, a metal first terminal ring 14 electrically connected to the first heater terminal 12a covers the first heater terminal 12a in an interference fit state. It is attached as follows. The metal shaft 6 and the first heater terminal 12 a are electrically connected 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.
[0017]
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 in front of the first heater terminal 12a in the axis O direction. The cylindrical second terminal ring 3 that covers the second heater terminal 12b and is electrically connected to the second heater terminal 12b projects the rear end of the ceramic heater 1 toward the rear side of the ceramic heater 1. It is attached to the outer peripheral surface with an interference fit. The metal shell 4 is attached to the outer peripheral surface of the second terminal ring 3 on a cylindrical heater holding surface 4a.
[0018]
The ceramic protruded rearward from the second terminal ring 3 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 ring arrangement gap G can be formed in an appropriate amount between the outer peripheral surface of the rear end portion of the heater 1 and the inner peripheral surface on the rear side of the heater holding surface 4a of the metal shell 4. 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 bonding, the metal / ceramic brazing structure or the complicated bonding that requires man-hours such as embedded bonding of the metal lead portion 17 to the ceramic heater 1 is required. The structure is eliminated and it can be manufactured at low cost. Further, since the first terminal ring 14 is fitted to the ceramic heater 1 by interference fitting, the brazing material layer is not interposed as in the conventional structure by brazing, and the coaxiality between the metal shaft 6 and the first terminal ring 14 is increased. Easy to secure. Thereby, it becomes difficult to produce a shift | offset | difference etc. in the joining surface of the metal lead part 17, and the metal shaft 6 or the 1st terminal ring 14, and a favorable and high intensity | strength joining part can be formed by extension.
[0019]
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, the fitting surface (heater holding surface 4 a) of the metal shell 4 with respect to the second terminal ring 3 overlaps with the fitting surface of the second terminal ring 3 and the ceramic heater 1. The tightness of the metal shell 4 is superimposed on the tightness of the terminal ring 3, and the tightness of the fitting between the second terminal ring 3 and the ceramic heater 1 can be further enhanced.
[0020]
As shown in FIG. 6, the terminal rings 14 and 3 are assembled to the ceramic heater 1 by pressing the individual terminal rings 14 or 3 into the ceramic heater 1 while being inserted in the axial direction from the end portion. be able to. Note that shrink fitting may be used instead of press-fitting. Of these, the first terminal ring 14 only needs to have a binding force sufficient to ensure electrical continuity with the first heater terminal 12a. On the other hand, for the second terminal ring 3, in addition to ensuring conduction with the second heater terminal 12b, it is necessary to ensure airtightness on the fitting surface, and therefore a tighter binding force than that of the first terminal ring 14 is required. It is done. In any case, it is important that a necessary and sufficient binding force is secured not only at room temperature but also at the time of temperature rise of the ceramic heater 1 in which thermal expansion occurs in each part. In general, when ceramic and metal are compared, except for special alloys such as invar, metal has a higher coefficient of linear expansion, and terminal rings 14 and 3 tend to loosen tightly when the temperature rises.
[0021]
In this case, although the level of the binding force secured at the time of temperature rise varies depending on the material of the ring and the thickness t, as shown in FIG. 4, the first terminal ring 14 or the second terminal ring 3 is connected from the ceramic heater 1. In the disassembled state, the inner diameter of the first terminal ring 14 is d1, and the outer diameter of the ceramic heater 1 at the position where the first heater terminal 12a is formed in the disassembled state is d2. The post-decomposition fastening allowance of the ring 14 is a value at room temperature in this specification) is 8 μm or more and 2% or less of the outer diameter of the ceramic heater 1 at the mounting position of the first terminal ring 14. It is desirable that the range is adjusted. In the disassembled state in which the second terminal ring 3 is removed from the ceramic heater 1, d2′−d1 ′ (hereinafter referred to as the second terminal ring 3), where the inner diameter of the second terminal ring 3 is d1 ′ and the outer diameter of the ceramic heater 1 is d2 ′. Similarly, the tightening allowance after disassembly of the two-terminal ring 3 (which means a value in a room temperature state in this specification) is also 8 μm or more, and the outer diameter of the ceramic heater 1 at the mounting position of the second terminal ring 3 It is desirable to adjust to a range of 2% or less.
[0022]
The post-disassembly tightening allowance can be regarded as a parameter reflecting the elastic return amount of the rings 14 and 3 when removed from the ceramic heater 1, that is, the elastic binding force to the ceramic heater 1 by the rings 14 and 3. If the tightening allowance after decomposition is less than 8 μm, the required tight force cannot be secured when the temperature of the ring 3 or 4 rises to the above temperature range. For example, an increase in contact resistance with the first heater terminal 12a in the first terminal ring 14 and an increase in contact resistance with the first heater terminal 12b and a decrease in hermeticity are concrete in the second terminal ring 3. It will lead to occur as a malfunction. On the other hand, if the tightening allowance after disassembly exceeds 100 μm, an excessive tight force acts on the ceramic heater 1 and may lead to the occurrence of cracks, cracks, and the like. In addition, when the thickness of the rings 3 and 14 is small, the amount of plastic deformation of the rings themselves increases, so that it may be essentially impossible to set the allowance after disassembly to 100 μm or more. Note that the post-decomposition tightening allowance d2-d1 or d2′-d1 ′ is more preferably adjusted to a range of 15 to 40 μm. Further, even if the tightening value after disassembly is the same, it is more advantageous that the ring thickness is larger from the viewpoint of increasing the value of the elastic binding force.
[0023]
As a material for the first terminal ring 14 and the second terminal ring 3, it is desirable to use an Fe-based alloy having a certain level of hardness and heat resistance in consideration of the balance between high temperature strength and material cost. In particular, in order to increase the tightening allowance after disassembly and ensure a sufficient elastic binding force, the Vickers hardness (measured at a load of 10 N by a method prescribed in JIS: Z2244 (1998)) Hv is 170 or more ( The use of an Fe-based alloy (preferably 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 suitably used. SUS630 can be age-precipitated and hardened by heat treatment of any of H900, H1025, H1075 or H1105 specified in JIS G4303 (1988). On the other hand, SUS631 can be age precipitation hardened by heat treatment of TH1050 or RH950 of the same standard, and both can ensure Hv350 or more. Moreover, although it is slightly inferior in terms of hardness, ferritic stainless steel such as SUS430 can also be used.
[0024]
Next, as shown in FIG. 2, the metal lead portion 17 is arranged in a bent shape between the metal shaft 6 and the first terminal ring 14. Thereby, even when a heating / cooling cycle is applied due to heat generated by the ceramic heater 1, the metal lead portion 17 can absorb expansion / contraction at the bent portion, and thus the metal lead portion 17 and the first terminal ring 14. It is possible to prevent the occurrence of problems such as contact failure and disconnection due to excessive stress concentration at the joint portion. 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 planar with respect to the outer peripheral surface tip portion of the metal shaft 6. It is connected with the joint surface. For example, when the metal lead portion 17 and the metal shaft 6 are joined by resistance welding, making the joining surface flat makes it possible to apply a pressure force during resistance welding evenly and form a weld joint with few defects. This is also advantageous.
[0025]
On the other hand, the metal lead portion 17 is welded to the outer peripheral surface of the first terminal ring 14 at the front end portion thereof. In the present invention, for example, ultrasonic welding described later is employed as a welding method with a small temperature rise during joining. As a result, as shown in FIG. 3, the welded joint between the metal lead portion 17 and the terminal ring 14 is connected to the metal lead portion 17 side from the joint interface between the metal lead portion 17 and the terminal ring 14. An alloying layer of the constituent metal component 17 and the constituent metal component (ring constituent component) of the terminal ring 14 is formed. In the alloyed layer, the concentration of the ring constituent component is closer to the side closer to the bonding interface than the far side. Also, the density inversion region S that is relatively high is formed to be distinguishable. In other words, in the cross section crossing the bonding interface, the first region P in which the concentration of the ring component has a maximum value and the second region (concentration inversion region) S in which the concentration value is a minimum value are alternately formed in the bonding direction. A concentration distribution is formed.
[0026]
As shown in FIG. 7A, welding of the metal lead portion 17 to the first terminal ring 14 is performed by press-fitting the first terminal ring 14 into the ceramic heater 1 and then fitting the first terminal ring 14 to the first terminal ring 14. The process of welding the metal lead part 17 to 14 can be adopted.
If the metal first terminal ring 14 has a large amount of heat input during welding, the yield point of the material is lowered due to the temperature rise, and the elastic strain of the ring generated at the time of interference fitting is converted into a plastic deformation strain. Power may be lost. However, by suppressing the heat input during welding by adopting ultrasonic welding, it is possible to effectively suppress the decrease in the elastic binding force as described above.
[0027]
On the other hand, as shown in FIG. 7B, after the metal lead portion 17 is welded to the first terminal ring 14, a process of fitting the first terminal ring 14 to the ceramic heater 1 can be used. In this case, the influence of welding is essentially not exerted on the tight binding force. In addition, as a result of suppressing the thermal stress remaining in the welded joint, even if a new stress is applied when the terminal ring is fitted, defects such as cracks are unlikely to occur in the welded joint.
[0028]
Next, the ceramic heater 1 is configured as a rod-shaped ceramic heater element in which a resistance heating element 11 is embedded in a ceramic base 13 made of an insulating ceramic. In this embodiment, the ceramic heater 1 is configured such that a ceramic resistor 10 made of conductive ceramic is embedded in a ceramic base 13 made of insulating ceramic. The ceramic resistor 10 is made of a first conductive ceramic disposed at the tip portion of the ceramic heater 1, and a first resistor portion 11 that functions as a resistance heating element and a rear side of the first resistor portion 11, respectively. The ceramic heater 1 is arranged so as to extend in the direction of the axis O, and the tip portion is joined to both end portions in the energizing direction of the first resistor portion 11 and has a lower resistivity than the first conductive ceramic. And a pair of second resistor portions 12 and 12 made of two conductive ceramics. The pair of second resistor portions 12 and 12 of the ceramic resistor 10 are formed with branch portions at different positions in the axis O direction, and these branch portions are exposed to the surface of the ceramic heater 1. However, the first heater terminal 12a and the second heater terminal 12b are respectively formed.
[0029]
Note that the energization of the resistance heating element 11 can also be performed through embedded lead wires 18 and 19 made of a refractory metal wire such as W embedded in the ceramic substrate 13 as shown in FIG. In this case, the first heater terminal is formed as the exposed lead 18 and the second heater terminal is formed as the exposed portions 18 a and 19 a of the embedded lead 19.
[0030]
Next, in this embodiment, a silicon nitride ceramic is adopted as the insulating ceramic constituting the ceramic base 13. The structure of the silicon nitride ceramic is such that main phase particles mainly composed of silicon nitride (Si ₃ N ₄ ) 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 substituted with Al or O, or may be one in which metal atoms such as Li, Ca, Mg, and Y are dissolved in the phase. .
[0031]
In the silicon nitride ceramic, at least one selected from the group of elements 3A, 4A, 5A, 3B (for example Al) and 4B (for example Si) in the periodic table and Mg is used as the cation element. It can be made to contain 1-10 mass% in conversion of an oxide in content in the whole body. These components are mainly added in the form of oxides, and are contained in the sintered body mainly in the form of complex oxides such as oxides or silicates. When the sintering aid component is less than 1% by mass, it is difficult to obtain a dense sintered body, and when it exceeds 10% by mass, the strength, toughness or heat resistance is insufficient. The content of the sintering aid component is desirably 2 to 8% by mass. 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, and Lu can be used. Among these, Tb, Dy, Ho, Er, Tm, and Yb can be suitably used because they promote the crystallization of the grain boundary phase and improve the high temperature strength.
[0032]
Next, the first resistor portion 11 and the second resistor portions 12 and 12 constituting the ceramic resistor 10 are made of conductive ceramics having different electric resistivity as described above. The method for making the electrical resistivity of the two conductive ceramics different from each other is not particularly limited. For example,
(1) A method in which the same kind of conductive ceramic phase is used and the contents thereof are different from each other;
(2) A method of using different types of conductive ceramic phases having different electric resistivity;
Method by combination of (3) (1) and (2);
In this embodiment, the method (1) is adopted.
[0033]
As the conductive ceramic phase, for example, well-known materials such as tungsten carbide (WC), molybdenum disilicide (MoSi ₂ ), and tungsten disilicide (WSi ₂ ) can be employed. In this embodiment, WC is adopted. In order to reduce the difference in coefficient of linear expansion from the ceramic substrate 13 and increase the thermal shock resistance, an insulating ceramic phase, which is the main component of the ceramic substrate 13, here, a silicon nitride ceramic phase can be blended. Therefore, by changing the content ratio between the insulating ceramic phase and the conductive ceramic phase, the electrical resistivity of the conductive ceramic constituting the resistor portion can be adjusted to a desired value.
[0034]
Specifically, in the first conductive ceramic that is the material of the first resistor portion 11 that forms the resistance heating portion, the content of the conductive ceramic phase is 10 to 25% by volume, and the remainder is the insulating ceramic phase. Is good. If the content of the conductive ceramic phase exceeds 25% by volume, the conductivity becomes too high and a sufficient calorific value cannot be expected. If the content is less than 10% by volume, the conductivity becomes too low, and similarly the calorific value. Cannot be secured sufficiently.
[0035]
On the other hand, the second resistor parts 12 and 12 serve as a conduction path to the first resistor part 11, and the second conductive ceramic as the material has a content of the conductive ceramic phase of 15 to 30 volumes. %, The balance should be an insulating ceramic phase. If the content of the conductive ceramic phase exceeds 30% by volume, densification by firing becomes difficult and the strength tends to be insufficient, and even if the temperature reaches the normal temperature range for preheating the engine, the electrical resistivity is reduced. In some cases, the rise is insufficient, and the self-saturation function for stabilizing the current density cannot be realized. On the other hand, if it is less than 15% by volume, heat generation in the second resistor portions 12 and 12 becomes too large, leading to deterioration in heat generation efficiency of the first resistor portion 11. In the present embodiment, the content of WC in the first conductive ceramic is 16% by volume (55% by mass), and the content of WC in the second conductive ceramic is 20% by volume (70% by mass) (the balance). Both are silicon nitride ceramics (including sintering aids).
[0036]
In the present embodiment, the ceramic resistor 10 is arranged such that the first resistor portion 11 is U-shaped and the bottom of the U-shape is located on the tip side of the ceramic heater 1. These are rod-like portions that are substantially parallel to each other and extend backward from the both end portions of the U-shaped first resistor portion 11 along the direction of the axis O, respectively.
[0037]
In the ceramic resistor 10, the first resistor portion 11 has a diameter smaller than that of both end portions 11 b and 11 b in order to concentrate current on the end portion 11 a that should be at the highest temperature during operation. And the joining surface 15 with the 2nd resistor part 12 and 12 is formed in the both ends 11b and 11b which became larger diameter than the front-end | tip part 11a.
[0038]
As shown in FIG. 10, in the structure in which the buried lead wires 18 and 19 are arranged in the ceramic, when a heater driving voltage is applied at a high temperature, the metal atoms constituting the buried lead wire 112 are subjected to the electric field. In some cases, it is consumed by a so-called electromigration effect that is forcedly diffused to the ceramic side under the electrochemical driving force due to the gradient, and breakage or the like is likely to occur. However, since the embedded lead wire is abolished in the configuration of FIG. 2, there is an advantage that it is hardly affected by the electromigration effect.
[0039]
Next, as shown in FIG. 1, the metal shaft 6 for supplying electric power to the ceramic heater 1 is disposed in an insulated state from the metal shell 4 inside the rear end portion of the metal shell 4 as described above. Yes. In the present embodiment, the ceramic ring 31 is disposed between the rear end side outer peripheral surface of the metal shaft 6 and the inner peripheral surface of the metal shell 4, and the glass filling layer 32 is formed and fixed on the rear side thereof. . 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 near the rear end of the inner peripheral surface of the metal shell 4 By engaging with the side engaging portion 4e, it is prevented from slipping forward in the axial direction. Moreover, the outer peripheral surface part which contacts the glass filling layer 32 of the metal axis | shaft 6 is uneven | corrugated by knurling etc. (area | region which shaded in the figure). 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 extended portion via an insulating bush 8. The terminal fitting 7 is fixed in a conductive state to the outer peripheral surface of the metal shaft 6 by a caulking portion 9 in the circumferential direction.
[0040]
The glow plug 50 is attached to the diesel engine so that the tip 2 of the ceramic heater 1 is positioned in the combustion chamber at the attachment 5 of the metal shell 4. And by connecting the terminal fitting 7 to the 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 fitting 4 → (grounded through the engine block) In this order, current flows, the tip 2 of the ceramic heater 1 generates heat, and the combustion chamber can be preheated.
[0041]
Hereinafter, a method for manufacturing the glow plug 50 will be described.
First, as shown in FIG. 5A, a resistor powder molding portion 34 to be the ceramic resistor 10 is formed by injection molding. Moreover, the division | segmentation preforming bodies 36 and 37 as a base-molding body formed in the upper-lower separate body are prepared by carrying out the die press molding of the raw material powder for forming the ceramic base | substrate 13 previously. A concave portion 37a having a shape corresponding to the resistor powder molding portion 34 (a concave portion on the side of the divided preform body 36 is not shown in the drawing) is formed on the mating surfaces of the divided preforms 36 and 37. The resistor powder molding portion 34 is accommodated here, and the divided preforms 36 and 37 are fitted on the mating surfaces, and further pressed and compressed to integrate them as shown in FIG. 5 (b). A composite molded body 39 is produced.
[0042]
The composite molded body 39 thus obtained is subjected to a binder removal treatment, and then fired at 1700 ° C. or higher, for example, around 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. 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 press fitting, for example.
[0043]
Further, the metal lead portion 17 is joined to the first terminal ring 14 by ultrasonic welding. As described above, this joining sequence may be either after assembly of the first terminal ring 14 to the ceramic heater 1 or before assembly. Ultrasonic welding can be performed using, for example, a commercially available ultrasonic welding machine (for example, trade name: USW-610Z20S, etc. (Ultrasonic Industry Co., Ltd.). The first terminal ring 14 as a welded joining member is placed on a cradle (not shown), and the metal lead portion 17 is overlaid on the outer peripheral surface of the first terminal ring 14. On the other hand, the tip of the vibration arm 50 connected to an ultrasonic oscillator (not shown). Then, the vibrator 51 is attached to the metal lead portion 17 with a constant load P, and the vibrating arm 50 is ultrasonically vibrated with an amplitude A and a frequency Q in this state, thereby The joint surfaces of the terminal ring 14 and the metal lead part 17 are firmly joined by solid phase joining via plastic flow.
[0044]
Then, in the region on the metal lead portion side of the welded joint, based on the plastic flow due to the mechanical vibration at this time, as shown in FIG. 3, the first region P in which the concentration of the ring constituent component shows the maximum value, and the minimum An alloyed layer having a concentration distribution structure in which second regions (concentration inversion regions) S showing values are alternately formed is formed. As a result, a strong bonding state is formed between the terminal ring 14 and the metal lead portion 7. The thickness of the alloying layer is preferably 10 μm or more at the position where the thickness is maximum, from the viewpoint of sufficiently securing the bonding strength.
[0045]
In order to obtain a good bonding state, it is necessary that the kinetic energy of the ultrasonic vibration is efficiently converted into the energy of relative movement along the bonding surface between the first terminal ring 14 and the metal lead portion 17. For this purpose, the follow-up mobility of the metal lead portion 17 accompanying the vibration of the vibrator 51 is improved. Specifically, an uneven portion such as a knurled pattern is formed on the tip surface of the vibrator 51, and the uneven portion is made of metal. It is effective to perform welding in a state where the lead portion 17 is bitten by pressurization. In this case, as shown in FIG. 9, the biting pattern 17a of the uneven portion is transferred to the metal lead portion 17 after welding.
[0046]
For example, when the first terminal ring 14 is made of an Fe-based material, for example, stainless steel, the metal lead portion 17 has a relatively high Ni content or a relatively high Ni content. When a high Fe-based alloy (for example, Invar or the like containing 20 to 50% by mass of Ni: the above is collectively referred to as Ni-containing metal), Fe in stainless steel and Ni in the metal lead portion 17 are used. Since the affinity is high, the strength of the obtained ultrasonic welded joint can be increased. In this case, the pressing force P at the time of ultrasonic welding is suitably 5 to 50 kg. Further, the frequency Q of the ultrasonic vibration is suitably 19 to 100 kHz, and the amplitude A is suitably 10 to 25 μm. The excitation time is suitably about 0.02 to 2 seconds.
[0047]
【Example】
Hereinafter, experimental results performed to confirm the effects of the present invention will be described.
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 of a diameter. A circular area of 0.8 mm was used.
[0048]
On the other hand, the 1st terminal ring 14 and the 2nd terminal ring 3 were produced using above-mentioned SUS630 (H900 age-hardening processed goods: Hv = about 400). The wall thickness of the first terminal ring 14 is 0.5 mm, and its inner diameter d1i is such that the outer diameter before assembly to the ceramic heater 1 is d2i and the initial tightening allowance defined by d2i-d1i is 50 μm. I prepared the adjusted one. On the other hand, the wall thickness of the second terminal ring 3 was 0.85 mm, and the inner diameter d1i ′ was fixedly set so that the initial tightening margin defined in the same manner as the first terminal ring 14 was 50 μm.
[0049]
And said 1st terminal ring 14 and 2nd terminal ring 3 were assembled | attached to the predetermined position of the ceramic heater 1 by press injection. 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 the press-fitting, the lubricant is decomposed at 300 ° C. The first terminal ring was ultrasonically welded as a metal lead portion 17 with a pure Ni wire having a wire diameter of 0.8 mm (the joining end portion was flattened by pressing) under the following conditions;
・ Ultrasonic frequency: 19 kHz
・ Ultrasonic output: 600W
・ Excitation time: 0.1 second ・ Amplitude: 25 μm
-Pushing force: 25 kg.
On the other hand, for comparison, a test product in which the metal lead portion 17 was joined to the first terminal ring 14 by resistance welding was also produced.
[0050]
The series resistance value between the first terminal ring 14 and the second terminal ring 3 at various temperatures from room temperature (20 ° C.) to 400 ° C. was measured using the above-described test product. The result is shown in FIG. According to this, the resistance value of the comparative example product using resistance welding rapidly increases in the temperature range of 300 ° C. or higher, while that of the ultrasonic welding method does not show such a rapid increase in resistance value. It can be seen that a good conduction state is maintained even at high temperatures. Moreover, after said resistance measurement was complete | finished, the 1st terminal ring 14 was removed from the ceramic heater 1, and the above-mentioned after-disassembly interference was measured. As a result, the comparative product using resistance welding had a post-decomposition tightening margin close to zero, while that using ultrasonic welding was able to secure a post-decomposition tightening margin of 17 μm. all right.
[0051]
FIG. 12 shows an EPMA in which a weld joint portion between the first terminal ring 14 and the metal lead portion 17 is cut and polished in a direction perpendicular to the joint interface, and the Fe concentration distribution is incorporated in a scanning electron microscope (SEM). The two-dimensional mapping image which was surface-analyzed by (Electron Probe Micro Analyzer) is shown, (a) is an ultrasonic welded product, (b) is a resistance welded product. The white area in the image means that the Fe concentration is higher. In either case, an alloying layer in which the Fe concentration decreases in a direction away from the joint interface toward the metal lead portion side is formed. In the ultrasonic welded product of (a), the Fe concentration in the direction away from the joint interface. As a result of a large fluctuation, a striped shading pattern is seen. This is considered to be 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 maximized (the white portion) and the second region where it is minimized The density inversion area: the black part) is clearly identified. On the other hand, in the resistance welded product (b), a uniform gradation pattern in which the Fe concentration monotonously decreases is formed on the metal lead portion side from the joint interface, and the first region and the second region are not distinguished. This is considered to be because the Fe component of the first terminal ring 14 was thermally diffused toward the metal lead portion 17 side according to Fick's law.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a glow plug of the present invention.
FIG. 2 is a longitudinal sectional view showing the main part of FIG.
FIG. 3 is a conceptual explanatory diagram of an alloying layer formed in a welded joint.
FIG. 4 is a diagram for explaining a part used for calculating a post-disassembly tightening allowance.
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 an explanatory diagram of ultrasonic welding processes.
FIG. 9 is a view for explaining the external features of an ultrasonic weld.
10 is a longitudinal sectional view of an essential part showing a modification of the glow plug of FIG. 1. FIG.
FIG. 11 is a graph showing experimental results of 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 by ultrasonic welding and resistance welding.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ceramic heater 2 Front-end | tip part 3 Second terminal ring 4 Main metal fitting 4a Heater holding surface 10 Ceramic resistor 11 First resistor part (resistance heating element)
12, 12 Second resistor portion 12a First heater terminal 12b Second heater terminal 14 First terminal ring (terminal ring)
17 Metal lead 50 Glow plug

Claims (7)

A ceramic heater (1) having a rod-like shape and having a resistance heating element (11) embedded therein, and a heater terminal (12a) for energizing the resistance heating element exposed on the outer peripheral surface;
A metal terminal ring (14) that is electrically connected to the heater terminal (12a) by being attached to the outer peripheral surface of the ceramic heater (1) so as to cover the heater terminal (12a).
A metal lead (17) welded to the surface of the terminal ring (14) via an ultrasonic weld;
Glow plug characterized by having. A ceramic heater (1) having a rod-like shape and having a resistance heating element (11) embedded therein, and a heater terminal (12a) for energizing the resistance heating element exposed on the outer peripheral surface;
A metal terminal ring (14) that is electrically connected to the heater terminal (12a) by being attached to the outer peripheral surface of the ceramic heater (1) 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 between the metal lead portion (17) and the terminal ring (14). From the joint interface between the terminal ring (14) and the metal lead portion (17), the metal component of the metal lead portion (17) and the metal component of the terminal ring (14) (hereinafter referred to as ring component) And a second region (concentration reversal region) in which the concentration of the constituent components of the ring exhibits a maximum value and a second region (concentration inversion region) in which the concentration is minimum. A glow plug characterized in that a concentration distribution is formed in which S and C are alternately formed in the direction of the welding joint . 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. The glow plug (50) according to any one of claims 1 to 3, wherein the terminal ring (14) is made of stainless steel, and the metal lead portion (17) is made of a metal mainly composed of Ni. ). A ceramic heater (1) having a rod-like shape and having a resistance heating element (11) embedded therein, and a heater terminal (12a) for energizing the resistance heating element exposed on the outer peripheral surface;
A metal terminal ring (14) that is electrically connected to the heater terminal (12a) by being attached to the outer peripheral surface of the ceramic heater (1) so as to cover the heater terminal (12a).
A metal lead portion (17) welded to the surface of the terminal ring (14);
To manufacture glow plugs with
A method for manufacturing a glow plug (50), wherein a weld joint between the metal lead portion (17) and the terminal ring (14) is formed by ultrasonic welding. The glow plug (50) according to claim 5, wherein after the terminal ring (14) is tightly fitted to the ceramic heater (1), the metal lead portion (17) is ultrasonically welded to the terminal ring (14). ) Manufacturing method. The glow plug (50) according to claim 5, wherein after the metal lead portion (17) is ultrasonically welded to the terminal ring (14), the terminal ring (14) is tightly fitted to the ceramic heater (1). Manufacturing method.

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