JP6199951B2 - Heater and glow plug equipped with the same - Google Patents

Description

  The present invention is, for example, for a heater for ignition or flame detection in a combustion-type in-vehicle heating device, a heater for ignition of various combustion devices such as an oil fan heater, a heater for a glow plug of an automobile engine, and various sensors such as an oxygen sensor. In particular, the present invention relates to a heater used for a heater, a heater for heating a measuring instrument, and a glow plug including the heater.

  A heater used for a glow plug or the like of an automobile engine includes a resistor having a heat generating portion, a lead connected to the resistor, and an insulating base in which the resistor and the lead are embedded. These materials are selected and the shape is designed so that the resistance of the lead is smaller than the resistance of the resistor.

  Here, the connection portion between the resistor and the lead is a shape change point for connecting the resistor and the lead having different shapes or a material composition change point for connecting the resistor and the lead having different material compositions. Therefore, a contrivance has been made such as increasing the bonding area so as to reduce the influence of thermal stress during heat generation and cooling due to differences in thermal expansion of the resistor, the lead, and the insulating base. For example, as shown in FIG. 13A, when the cross section parallel to the axial direction of the lead 8 is viewed, the boundary surface between the resistor 3 and the lead 8 is symmetrically inclined at a pair of joint portions. Is known (see Patent Documents 1 and 2). Moreover, the heat generating part of the resistor is designed to have a high resistance locally among the resistors, for example, by reducing the wire diameter so that it can be rapidly heated.

JP 2002-334768 A JP 2003-22889 A

  In recent years, electric power with a sharper rise and higher voltage than in the past has been introduced into the heater. The technological development of fuel-efficient engines and combustion systems has progressed, and with the advancement of technologies such as idling stop and lean burn engine, the ignition drive with glow plugs, which was used at the time of startup, corresponds to idling stop. Glow plugs, such as afterglow technology that ignites even when the engine is running, are used because the engine temperature drops in an engine that has been drastically increased and the fuel efficiency has improved. The environment used has changed greatly. That is, in order to cope with idling stop, a higher temperature increase is required, or in order to optimize the combustion state of the engine that has been lowered, the control signal from the in-vehicle ECU is pulsed, and the temperature is changed with the duty ratio of the pulse. A method such as driving with a controlled heater has been adopted. As the pulse, a rectangular wave voltage by low-loss control using an IC is often used. In such a driving method, the current overshoots when the voltage rises, and the problem that high power including high-frequency components enters the heater becomes significant.

  In such a use environment, in the heater with the conventional design, current overshoot occurs at the moment when the pulse voltage rises, and the heat generating part of the resistor suddenly generates heat and instantaneously occurs in the insulating base near the heat generating part. There is a risk that microcracks may enter the insulating substrate and the resistor due to the tensile stress. Further, cracks may develop while the heater is repeatedly used with a pulse voltage for a long period of time, and the resistance value of the heater may change, leading to the destruction of the heater.

  The present invention has been devised in view of the problems of the heater according to the above-described conventional design, and its purpose is that even if a high-frequency high current that overshoots the heater when the heater is driven by a pulse voltage enters the heater. Another object of the present invention is to provide a highly reliable heater in which microcracks are prevented from occurring in a heat generating portion of a resistor, and a glow plug including the heater.

The heater of the present invention includes an insulating base, a resistor embedded in the insulating base and having a folded shape, and embedded in the insulating base and connected to both ends of the resistor on the front end side, and a rear end A heater having a pair of leads led out to the surface of the insulating base on the side, wherein two joints between the resistor and the pair of leads are longitudinal sections including both shafts of the pair of leads. Each of the two joints has a boundary surface perpendicular to the axis of the pair of leads. When there is only one boundary line between the resistor and the lead when viewed in FIG. 1 and has an uneven shape, the uneven shape at the joint changes toward the tip side, and the boundary line Place of There wherein the moving toward the distal side.

  In the heater of the present invention, the boundary line between the resistor and the lead is uneven when the cathode-side junction of the two junctions is viewed in the cross section. It is characterized by.

  Further, in the heater of the present invention, in the above configuration, when both of the two joints are viewed in the cross section, the boundary line between the resistor and the lead is uneven. Features.

  Further, in the heater of the present invention, in the above configuration, when both of the two joint portions are viewed in the cross section, the uneven shape of the boundary line between the resistor and the lead is the two joint portions. It is characterized by being symmetrical with respect to a straight line connecting equidistant positions.

  The heater according to the present invention is characterized in that, in the above configuration, the uneven shape is a shape having a corner.

  According to another aspect of the present invention, there is provided a glow plug comprising: the heater according to any one of the above configurations; and a metal holding member that is electrically connected to the lead and holds the heater.

  According to the heater of the present invention, the boundary line between the resistor and the lead when the boundary between the resistor and the lead has an inclined boundary surface and the joint portion is viewed in a cross section perpendicular to the lead axis. Because of the uneven shape, even if current overshoot occurs at the rising edge of the pulse voltage, the overshoot current is reduced to flow into the resistor and the heat generation part suddenly generates heat. Generation of cracks is suppressed, and a stable resistance value can be obtained over a long period of time. Thereby, the reliability and durability of the heater are improved.

It is a longitudinal section showing an example of an embodiment of a heater of the present invention. (A) is the expanded sectional view which expanded the area | region A containing the junction part of the resistor shown in FIG. 1, and (b) is a cross-sectional view in the XX line shown to (a). It is a longitudinal cross-sectional view which shows the other example of embodiment of the heater of this invention. (A) is the expanded sectional view which expanded the area | region A containing the junction part of the resistor and lead shown in FIG. 3, (b) is a cross-sectional view in the XX line shown to (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the X1-X1 line | wire shown to (a), (c) Is a cross-sectional view taken along line X2-X2 shown in (a), and (d) is a cross-sectional view taken along line X3-X3 shown in (a). (A) is an expanded sectional view which shows the principal part of the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the X1-X1 line | wire shown to (a), (c) Is a cross-sectional view taken along line X2-X2 shown in (a), and (d) is a cross-sectional view taken along line X3-X3 shown in (a). (A) is a longitudinal cross-sectional view which shows the principal part of the conventional heater, (b) is a cross-sectional view in the XX line | wire shown to (a).

  Hereinafter, examples of embodiments of the heater of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing an example of an embodiment of a heater according to the present invention, and FIG. 2A is an enlarged sectional view in which a region A including a joint portion between a resistor and a lead shown in FIG. 1 is enlarged. FIG. 2B is a cross-sectional view taken along line XX shown in FIG.

  The heater 1 of the present embodiment includes an insulating base 9, a resistor 3 embedded in the insulating base 9, and a lead 8 embedded in the insulating base 9 and connected to one end of the resistor 3 on the distal end side. The joint 2 between the resistor 3 and the lead 8 has a boundary surface on which the boundary line between the resistor 3 and the lead 8 is inclined when viewed in a longitudinal section including the axis of the lead 8. When the junction 2 is viewed in a cross section perpendicular to the lead axis, the boundary line between the resistor 3 and the lead 8 is uneven.

The insulating base 9 in the heater 1 of the present embodiment is formed in a rod shape, for example. The insulating substrate 9 covers the resistor 3 and the lead 8. In other words, the resistor 3 and the lead 8 are embedded in the insulating substrate 9. Here, it is preferable that the insulating base 9 is made of ceramics, which can withstand temperatures higher than that of metal, so that it is possible to provide the heater 1 with improved reliability at the time of rapid temperature rise. become. In particular,
Examples thereof include ceramics having electrical insulation properties such as oxide ceramics, nitride ceramics, and carbide ceramics. In particular, the insulating substrate 9 is preferably made of silicon nitride ceramics. This is because silicon nitride ceramics is excellent in terms of high strength, high toughness, high insulating properties, and heat resistance. This silicon nitride ceramic is, for example, 3 to 12% by mass of a rare earth element oxide such as Y ₂ O ₃ , Yb ₂ O ₃ , Er ₂ O ₃ as a sintering aid with respect to silicon nitride as a main component, 0.5 to 3% by mass of Al ₂ O ₃ and further SiO _{2 are} mixed so that the amount of SiO ₂ contained in the sintered body is 1.5 to 5% by mass and molded into a predetermined shape. Thereafter, for example, 1650 to 1780 It can be obtained by hot press firing at 0 ° C.

In the case of using a made of silicon nitride ceramics as the insulating substrate _9, it is preferable to mixing MoSi 2, WSi _2, etc. dispersed. In this case, the coefficient of thermal expansion of the silicon nitride ceramic that is the base material can be brought close to the coefficient of thermal expansion of the resistor 3, and the durability of the heater 1 can be improved.

  The resistor 3 has a heat generating portion 4 that is a region that generates heat. For example, by providing a region having a partially reduced cross-sectional area or a spiral region, this region can be used as the heat generating portion 4.

  As this resistor 3, the thing which has a carbide | carbonized_material, nitride, silicide, etc., such as W, Mo, Ti, etc. as a main component can be used. In the case where the insulating base 9 is made of the above-described material, tungsten carbide (WC) is one of the above materials because it has a small difference in thermal expansion coefficient from the insulating base 9, high heat resistance, and low specific resistance. It is excellent as a material for the resistor 3. Furthermore, when the insulating substrate 9 is made of silicon nitride ceramics, the resistor 3 is preferably composed mainly of WC of an inorganic conductor, and the content of silicon nitride added thereto is 20% by mass or more. For example, in the insulating substrate 9 made of silicon nitride ceramics, the conductor component serving as the resistor 3 has a higher coefficient of thermal expansion than silicon nitride, so that the insulating substrate 9 is in a state of tensile stress in the driving state. . On the other hand, by adding silicon nitride into the resistor 3, the thermal expansion coefficient of the resistor 3 is brought close to the thermal expansion coefficient of the insulating base 9, and the thermal expansion coefficient when the heater 1 is heated and lowered. The stress due to the difference can be relaxed.

  When the content of silicon nitride contained in the resistor 3 is 40% by mass or less, the resistance value of the resistor 3 can be made relatively low and stabilized. Therefore, the content of silicon nitride contained in the resistor 3 is preferably 20% by mass to 40% by mass. More preferably, the content of silicon nitride is 25% by mass to 35% by mass. Further, as a similar additive to the resistor 3, boron nitride can be added in an amount of 4% by mass to 12% by mass instead of silicon nitride.

  The thickness of the resistor 3 is preferably about 0.5 mm to 1.5 mm, and the width of the resistor 3 is preferably about 0.3 mm to 1.3 mm. By setting it within this range, the resistance of the resistor 3 is reduced and heat is efficiently generated, and the adhesion at the laminated interface of the insulating substrate 9 having a laminated structure can be maintained.

For the lead 8 connected to one end of the resistor 3 on the distal end side, the same material as that of the resistor 3 whose main component is a carbide such as W, Mo, Ti, nitride, silicide, or the like can be used. In particular, WC is suitable as a material for the lead 8 in that the difference in coefficient of thermal expansion from the insulating base 9 is small, the heat resistance is high, and the specific resistance is low. When the insulating substrate 9 is made of silicon nitride ceramic, the lead 8 is preferably composed mainly of WC, which is an inorganic conductor, and silicon nitride is added to the lead 8 so that the content is 15% by mass or more. . As the silicon nitride content increases, the thermal expansion coefficient of the lead 8 can be made closer to the thermal expansion coefficient of the insulating substrate 9. When the silicon nitride content is 40% by mass or less, the resistance value of the lead 8 is kept low and stable. Therefore, the content of silicon nitride is preferably 15% by mass to 40% by mass. More preferably,
The silicon nitride content is preferably 20% by mass to 35% by mass. The lead 8 may have a resistance value per unit length lower than that of the resistor 3 by making the content of the forming material of the insulating base 9 smaller than that of the resistor 3. The resistance value per unit length may be lower than that of the resistor 3 by increasing the cross-sectional area.

  As shown in FIG. 2, the joint portion 2 between the resistor 3 and the lead 8 is a boundary surface where the boundary line between the resistor 3 and the lead 8 is inclined when viewed in a longitudinal section including the axis of the lead 8. When the junction 2 is viewed in a cross section perpendicular to the axis of the lead 8, the boundary line between the resistor 3 and the lead 8 is uneven. The inclination angle of the boundary surface with respect to the surface perpendicular to the axial direction is, for example, 10 to 80 degrees. The inclination angle of the boundary surface with respect to the plane perpendicular to the axial direction here means an angle at which a line connecting the front end portion and the rear end portion of the boundary surface is inclined with respect to the XX line. At this time, if the resistor 3 is convex, the lead 8 is concave, and if the resistor 3 is uneven, the lead 8 is uneven so as to match the unevenness of the resistor 3.

  The junction 2 between the resistor 3 and the lead 8 having a different composition is a surface where the resistance value of the conductor line (the resistor 3 and the lead 8) is rapidly increased due to the interface resistance, and a barrier against the overshooting high-frequency current. become. By making the joining part 2 into a concavo-convex shape, the joining area of the joining part 2 can be increased. As a result, it is possible to increase the barrier effect against the overshooted high-frequency current while expanding the area of the junction 2 and lowering the bulk resistance with respect to the normal current, so that the heating start of the heating portion 4 of the resistor 3 is delayed. Thus, thermal stress generated instantaneously can be reduced, and generation of microcracks can be suppressed.

  Further, since the boundary surface at the joint portion 2 between the lead 8 and the resistor 3 is slanted, the portion where the resistance value changes continuously in the traveling direction with respect to the traveling direction of the current, and Since the cross section is uneven, the effect as a scattering barrier against high-frequency current is also increased.

  In the example shown in FIGS. 1 and 2, the conductor layer 11 is provided on the surface of the insulating base 9, and the other end of the resistor 3 is electrically connected to the conductor layer 11. As shown in FIG. 3, the conductor layer 11 may not be provided on the surface of the insulating base 9, and the resistor 3 may have a folded shape.

  In addition, when the resistor 3 has a folded shape as shown in FIG. 3, the heat generating portion 4 that generates the most heat near the middle point of the folding is a region having a partially reduced cross-sectional area or a spiral-shaped region. May be provided to form the heat generating portion 4.

  At this time, as shown in FIG. 4, the pair of leads 8 are respectively connected to both ends of the resistor 3 having a folded shape on the front end side and led out to the surface of the insulating base 9 on the rear end side. . The two joint portions 2 between the resistor 3 and the pair of leads 8 have boundary surfaces whose tip ends are inclined inward or outward when viewed in a longitudinal section including both axes of the pair of leads 8. And the boundary line between the resistor 3 and the lead 8 has an uneven shape when at least one of the two joints 2 is viewed in a cross section perpendicular to the axis of the pair of leads 8. It has become.

  By setting it as such a structure, the junction area of the junction part 2 can be enlarged. As a result, it is possible to increase the barrier effect against the overshooted high-frequency current while expanding the area of the junction 2 and lowering the bulk resistance with respect to the normal current. Thermal stress can be reduced and generation of microcracks can be suppressed.

Here, it is preferable that the boundary line between the resistor 3 and the lead 8 has an uneven shape when the cathode-side junction 2 of the two junctions 2 is viewed in a cross section. Although the movement of electrons starts in the entire region of the conductor line at the moment of applying the pulse voltage, the electrons are likely to enter the junction 2 from the lead 8 side having a particularly low resistance. Therefore, by providing unevenness in the junction 2 on the cathode side with respect to the heat generating part 4 to increase the effect of the barrier against high-frequency current, the movement of the overshooting electrons is suppressed, and the heat generation start of the heat generating part 4 is delayed to instantaneously. This is because the thermal stress can be reduced.

  In addition, the inclination angle of the boundary surface of the cathode-side bonding portion 2 with respect to the surface perpendicular to the lead axis direction is larger than the inclination angle of the boundary surface of the anode-side bonding portion 2 to the surface perpendicular to the lead axis direction. Is preferred. For example, it is preferable that the inclination angle of the boundary surface in the cathode-side bonding portion 2 is larger than the inclination angle of the boundary surface in the anode-side bonding portion 2 by 5 degrees or more. Thereby, the area of the boundary surface (contact area between the resistor 3 and the lead 8) in the junction 2 on the cathode side can be increased. Here, the inclination angle of the boundary surface with respect to the plane perpendicular to the lead axis direction means an angle at which a line connecting the front end portion and the rear end portion of the boundary surface is inclined with respect to the XX line.

  Moreover, it is preferable that the diameter of the junction part 2 on the cathode side is larger than the diameter of the junction part 2 on the anode side. Thereby, the area of the boundary surface (contact area between the resistor 3 and the lead 8) in the junction 2 on the cathode side can be increased.

  At this time, as shown in FIGS. 5 to 12, it is preferable that the boundary line between each resistor 3 and the lead 8 has an uneven shape when both of the two joint portions 2 are viewed in cross section. . It is because generation | occurrence | production of the electric current which overshoots can further be suppressed because the two junction parts 2 become a barrier area | region with respect to a high frequency current.

  The heater 1 shown in FIGS. 5, 6, 8, and 10 is viewed in a longitudinal section in which the two joint portions 2 between the resistor 3 and the pair of leads 8 include both shafts of the pair of leads 8. Each of the two joints 2 is seen in a cross section perpendicular to the axis of the pair of leads 8. The boundary line between the resistor 3 and the lead 8 has an uneven shape. On the other hand, in the heater 1 shown in FIGS. 7, 9, 11, and 12, the two joint portions 2 of the resistor 3 and the pair of leads 8 are viewed in a longitudinal section including both shafts of the pair of leads 8. Each of the two joints 2 is seen in a cross section perpendicular to the axis of the pair of leads 8. The boundary line between the resistor 3 and the lead 8 has an uneven shape.

  Further, FIG. 11 shows a configuration in which the uneven shape at the joint 2 is substantially the same at the front end side and the rear end side, and only the position of the boundary line moves outward as it goes to the front end side. On the other hand, FIG. 12 shows a configuration in which the uneven shape in the joint portion 2 changes as it goes to the tip side, and the boundary line moves outward as it goes to the tip side. According to the configuration shown in FIG. 12, the effect of electron scattering at the junction as a barrier against high-frequency current can be further increased, so that the occurrence of microcracks in the heat generating portion 4 can be suppressed.

  Moreover, as shown in FIGS. 6 to 12, when both the two joint portions 2 are viewed in cross section, the uneven shape of the boundary line between each resistor 3 and the lead 8 is equidistant from the two joint portions 2. It is preferable that it is symmetric with respect to a straight line connecting the positions. As a result, the distribution of heat generated from the entire resistor is symmetric on the anode side and cathode side, and the thermal expansion of the heater can also be symmetric. Therefore, the concentration of tensile stress on the heater surface that occurs due to asymmetric deformation is concentrated. It is because it can avoid.

Further, the uneven shape is preferably a shape having a corner, and this increases the effect of scattering of electrons at the junction as a barrier against high-frequency current. It is possible to reduce the thermal stress generated in.

  Further, the heater 1 of the present embodiment is a metal holding member that holds the heater 1 by being electrically connected to the heater 1 according to any of the above-described configurations and a terminal portion (not shown) of the lead 8. It is preferable to use as a glow plug provided with. Specifically, in the heater 1, a resistor 3 having a folded shape is embedded in a rod-shaped insulating base 9, and a pair of leads 8 are electrically connected to both ends of the resistor 3, respectively. The glow plug includes a metal holding member (sheath fitting) electrically connected to one lead 8 and a wire electrically connected to the other lead 8. preferable.

  The metal holding member (sheath fitting) is a metal cylindrical body that holds the heater 1, and is joined to one lead 8 drawn to the side surface of the ceramic base 9 with a brazing material or the like. Further, the wire is joined to the other lead 8 drawn out to the rear end of the other ceramic base 9 with a brazing material or the like. As a result, the resistance of the heater 1 does not change even if it is used for a long time while being repeatedly turned on and off in a high-temperature engine.

  Next, the manufacturing method of the heater 1 of this Embodiment is demonstrated.

  The heater 1 of the present embodiment can be formed by, for example, an injection molding method using a die having the shape of the resistor 3, the lead 8, and the insulating base 9.

  First, a conductive paste to be the resistor 3 and the lead 8 including the conductive ceramic powder and the resin binder is manufactured, and a ceramic paste to be the insulating base 9 including the insulating ceramic powder and the resin binder is manufactured.

  Next, a conductive paste molded body (molded body a) having a predetermined pattern to be the resistor 3 is formed by an injection molding method or the like using the conductive paste. At this time, a shape to be the joint 2 may be formed at the end of the molded body a.

  Next, with the molded body a held in the mold, the conductive paste is filled in the mold to form a conductive paste molded body (molded body b) having a predetermined pattern to be the leads 8. Thereby, the molded product a and the molded product b connected to the molded product a are held in the mold.

  Next, in a state where the molded body a and the molded body b are held in the mold, a part of the mold is replaced with one for molding the insulating base 9, and then the ceramic paste that becomes the insulating base 9 in the mold Fill. Thereby, the molded body (molded body d) of the heater 1 in which the molded body a and the molded body b are covered with the molded body of the ceramic paste (molded body c) is obtained.

  Next, the obtained molded body d is fired at, for example, a temperature of 1650 ° C. to 1780 ° C. and a pressure of 30 MPa to 50 MPa, whereby the heater 1 can be manufactured. The firing is preferably performed in a non-oxidizing gas atmosphere such as hydrogen gas.

  The heater of the Example of this invention was produced as follows.

First, a conductive paste containing 50% by mass of tungsten carbide (WC) powder, 35% by mass of silicon nitride (Si ₃ N ₄ ) powder, and 15% by mass of a resin binder is injection-molded into a mold to form a resistor. A formed product a was produced.

  Next, with the molded body a held in the mold, the conductive paste to be the lead is filled in the mold to form the molded body b to be connected to the molded body a. did. At this time, as shown in Tables 1 and 2, joints of four types of resistors and leads were formed using dies having various shapes.

Next, 85% by mass of silicon nitride (Si ₃ N ₄ ) powder and ytterbium (Yb) oxide (Yb ₂ ) as a sintering aid while the molded product a and the molded product b are held in the mold. A ceramic paste containing 10% by mass of O ₃ ) and 5% by mass of tungsten carbide (WC) for bringing the coefficient of thermal expansion close to the resistor and the lead was injection molded into a mold. As a result, a molded body d having a configuration in which the molded body a and the molded body b were embedded in the molded body c serving as an insulating base was formed.

  Next, after putting the obtained compact d in a cylindrical carbon mold, hot pressing is performed in a non-oxidizing gas atmosphere made of nitrogen gas at a pressure of 1700 ° C. and 35 MPa to sinter the heater. Was made. A glow plug was produced by brazing a cylindrical metal holding member (sheath fitting) to the lead end portion (terminal portion) exposed on the surface of the obtained sintered body.

  A pulse pattern generator was connected to the electrode of the glow plug, and a rectangular pulse having an applied voltage of 7 V, a pulse width of 10 μs, and a pulse interval of 1 μs was continuously energized. After 1000 hours, the rate of change in resistance value before and after energization ((resistance value after energization−resistance value before energization) / resistance value before energization) was measured. The results are shown in Table 1.

  As shown in Table 1, in the heater of Sample No. 1, which is a comparative example, the most heat generating portion was the heat generating portion of the resistor. Then, in order to confirm the energization state, the current waveform flowing through the heater of sample number 1 was confirmed using an oscilloscope, and as a result, the current suddenly rose and overshooted immediately after the rise of the pulse voltage. It took about 1 μs to reach a stable current. From this, it is considered that the sample No. 1 heater generated instantaneous heat generation in the heat generating portion.

  Furthermore, since the resistance change before and after the energization of Sample No. 1 was as large as 55%, when the heating portion of Sample No. 1 was observed with a scanning electron microscope after applying the pulse, a microcrack occurred in the heating portion. It was confirmed.

  On the other hand, also in the heaters of Sample Nos. 2 to 4 which are the embodiments of the present invention, the most heat generating portion was the heating portion of the resistor at the tip of the heater. Then, in order to confirm the energization state, the current waveform flowing through the heater was confirmed using an oscilloscope. As a result, the waveform did not overshoot and the rise was delayed with respect to the input pulse voltage. This is considered to indicate that the effect as a barrier against the high-frequency current at the interface between the lead and the resistor is affected.

  In addition, the resistance change before and after the energization of the heaters of sample numbers 2 to 4 was as small as 5% or less. After the pulse energization, the heating part of the resistors of these sample numbers was observed with a scanning electron microscope. It was.

1: Heater 2: Joint part 3: Resistor 4: Heat generating part 8: Lead 9: Insulating substrate 11: Conductor layer

Claims (6)

An insulating substrate;
A resistor embedded in the insulating substrate and having a folded shape;
A heater embedded in the insulating base and connected to both ends of the resistor on the front end side and a pair of leads led to the surface of the insulating base on the rear end side;
The two joint portions between the resistor and the pair of leads each have a boundary surface whose tip side is inclined inward or outward when viewed in a longitudinal section including both axes of the pair of leads. When at least one of the two joints is viewed in a cross section perpendicular to the axis of the pair of leads, there is only one boundary line between the resistor and the lead and the unevenness It has a shape
The heater according to claim 1, wherein the uneven shape at the joint changes as it goes toward the tip side, and the position of the boundary line moves as it goes toward the tip side.   The boundary line of the said resistor and the said lead is uneven | corrugated shape when the junction part by the side of the cathode of the said two junction parts is seen in the said cross section. heater.   2. The heater according to claim 1, wherein a boundary line between each of the resistor and the lead has an uneven shape when both of the two joints are viewed in the cross section.   When both of the two joints are viewed in the cross section, the concavo-convex shape of the boundary line between each of the resistors and the leads is symmetrical with respect to a straight line connecting the equidistant positions from the two joints. The heater according to claim 3, wherein   The heater according to any one of claims 1 to 4, wherein the uneven shape is a shape having a corner.   A glow plug comprising: the heater according to any one of claims 1 to 5; and a metal member that is electrically connected to the lead and holds the heater.

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