JP2016015342A - Heater and glow plug equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater having high reliability and durability obtained by suppressing generation of micro cracks in a joint part between a resistor and a lead and change in product resistance even if a large current flows through the resistor during pulse driving, DC drive and rapid temperature rise or the like, and to provide a glow plug equipped with the heater.SOLUTION: A heater 1 includes: an insulating base material 9; a resistor 3 buried in the insulating base material 9 and forms a folded shape; and a pair of leads 8 which are buried in the insulating base material 9, connected to the resistor 3 on the tip side, and led out to the surface of the insulating base material 9 on the rear end side. The resistor 3 and the pair of the leads 8 are overlapped in the direction perpendicular to the axial direction and connected to each other, and at least one of two boundary surfaces between the resistor and the pair of the leads 8 is inclined in the direction perpendicular to the plane including both of respective axes of the pair of the leads 8.

Description

  The present invention is, for example, for ignition or flame detection heaters in combustion-type in-vehicle heating devices, ignition heaters for various combustion devices such as oil fan heaters, heaters for glow plugs of automobile engines, and various sensors such as oxygen sensors. 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 of an automobile engine includes a resistor having a heat generating portion, a lead, and an insulating base. These materials are selected and designed so that the resistance of the lead is smaller than the resistance of the resistor.

  Here, the joint between the resistor and the lead is a point of change in shape or a point of change in material composition, so that it is not affected by the difference in thermal expansion during heat generation or cooling during use. For the purpose of increasing the bonding area, as shown in FIG. 11A, 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 inclined. Known (for example, see Patent Documents 1 and 2).

JP 2002-334768 A JP 2003-22889 A

  In recent years, in order to optimize the combustion state of an engine, a driving method in which a control signal from the ECU is pulsed has been adopted as a heater driving method.

  Here, a rectangular wave is often used as the pulse. There is a high frequency component at the rising edge of the pulse, and this high frequency component is transmitted on the surface of the lead. However, if the seam portion (boundary surface) is formed so that the end surface of the lead having a different impedance and the end surface of the resistor face each other, part of the high-frequency component that cannot be matched in impedance is Or the boundary surface functions as an antenna and dissipates from the lead surface through the surrounding dielectric. In particular, it dissipates in a direction perpendicular to the boundary surface and in a direction on the extension of the surface along the boundary surface.

  The conventional two boundary surfaces are arranged so as to be diagonally opposed so as not to be twisted, so that two planar antennas are arranged so that the phases of transmitted and received signals are exactly the same. An interference phenomenon (crosstalk phenomenon) occurs from the boundary surface on the power input side to the boundary surface on the power output side.

  For this reason, the signal is transmitted to the boundary surface on the power output side while the pulse waveform is distorted, impedance matching is not achieved at this boundary surface, it is dissipated as Joule heat, and the boundary surface generates heat locally. At this time, due to the difference between the thermal expansion coefficient of the lead and the thermal expansion coefficient of the resistor, microcracks are generated at the interface between the lead and the resistor, and along the interface between the lead and the resistor. The crack has progressed all at once, causing a problem that the resistance value changes.

Similar problems have arisen when DC driving is employed instead of pulse driving. That is, since there is no circuit loss in recent ECUs, a large current flows through the resistor at the start of engine operation for the purpose of rapid temperature rise. Therefore, since the rising of the power inrush becomes steep as in the case of the rectangular wave of the pulse and the high power containing the high frequency component has entered the heater, the same problem has arisen.

  The present invention has been devised in view of the above-mentioned conventional problems, and its purpose is to achieve high-frequency cross-over even when a large current flows through a resistor during pulse driving, DC driving, or rapid temperature rise. By suppressing the talk phenomenon, a highly reliable and durable heater in which the occurrence of microcracks at the boundary surface between the resistor and the lead, the progress of cracks at the boundary surface, and changes in product resistance are suppressed, and the heater Is to provide a glow plug with

  The present invention provides an insulating base, a resistor embedded in the insulating base and having a folded shape, and embedded in the insulating base, connected to the resistor on the front end side, and the insulating base on the rear end side A heater including a pair of leads led to a surface of the resistor, wherein the resistor and the pair of leads are connected to overlap each other in a direction perpendicular to an axial direction, and the resistor and the pair of leads At least one of the two boundary surfaces is inclined with respect to a direction perpendicular to a plane including both axes of the pair of leads.

  Moreover, the heater of the present invention is characterized in that, in the above configuration, the two boundary surfaces are inclined with respect to a direction perpendicular to a plane including both axes of the pair of leads. .

  The heater of the present invention is characterized in that, in the above configuration, the two boundary surfaces are inclined to opposite sides.

  In addition, the heater of the present invention has an inclination of a boundary line between the resistor and the pair of leads when viewed in a cross section perpendicular to a plane including both axes of the pair of leads in the above configuration. Is gradually changing from the front end side toward the rear end side.

  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 phase of the high frequency propagating from the power input side interface and the phase of the high frequency reaching the power output interface are difficult to coincide with each other, so that the crosstalk phenomenon in which high frequency signals interfere with each other is suppressed. can do. As a result, it is possible to suppress abnormal heat generation at the boundary surface and generation of microcracks due to abnormal heat generation. Therefore, regardless of pulse driving or DC driving, even if the rising of the power inrush becomes steep, the generation of microcracks at the boundary surface between the resistor and the lead and the progress of cracks at the boundary surface are suppressed, and the long-term Resistance is stable. 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 interface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the XX line shown to (a). (A) is the expanded sectional view which expanded the area | region A containing the boundary surface of the resistor shown in FIG. 1, (b) is a cross-sectional view in the YY line shown to (a), c) is a cross-sectional view taken along line ZZ shown in FIG. (A) is an expanded sectional view of the other example which expanded the area | region A containing the boundary surface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the XX line shown to (a). It is. (A) is an expanded sectional view of the other example which expanded the area | region A containing the boundary surface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the YY line shown to (a). (C) is a cross-sectional view taken along line ZZ shown in (a). (A) is an expanded sectional view of the other example which expanded the area | region A containing the boundary surface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the XX line shown to (a). It is. (A) is an expanded sectional view of the other example which expanded the area | region A containing the boundary surface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the XX line shown to (a). It is. (A) is an expanded sectional view of the other example which expanded the area | region A containing the boundary surface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the XX line shown to (a). It is. (A) is an expanded sectional view of the other example which expanded the area | region A containing the boundary surface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the YY line shown to (a). (C) is a cross-sectional view taken along line ZZ shown in (a). (A) is an expanded sectional view of the other example which expanded the area | region A containing the boundary surface of a resistor and a lead shown in FIG. 1, (b) is a cross-sectional view in the YY line shown to (a). (C) is a cross-sectional view taken along line ZZ 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 the heater of the present invention, and FIG. 2 is a transverse sectional view taken along line XX shown in FIG.

  The heater 1 according to the present embodiment includes an insulating base 9, a resistor 3 embedded in the insulating base 9 and having a folded shape, and embedded in the insulating base 9 and connected to the resistor 3 on the front end side and the rear. A heater having a pair of leads 8 led to the surface of the insulating base 9 on the end side, wherein the resistor 3 and the pair of leads 8 are connected to each other in a direction perpendicular to the axial direction. At least one of the two boundary surfaces 2 between the pair 3 and the pair of leads 8 is inclined with respect to a direction perpendicular to a plane including both axes of the pair of leads 8.

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. Specifically, ceramics having electrical insulation properties such as oxide ceramics, nitride ceramics, carbide ceramics can be given. 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 addition, when using an insulating substrate 9 made of silicon nitride ceramics, MoSi
₂ , WSi _{2 and the} like are preferably mixed and 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 in particular, and this region can be used as the heat generating portion 4 by providing a region having a partially reduced cross-sectional area or a spiral region. In the case where the resistor 3 has a folded shape as shown in FIG. 1, the vicinity of the middle point of the folding is the heat generating portion 4 that generates the most heat.

  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, and thus is usually in a state where tensile stress is applied. 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.

  Further, 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 small 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. By setting the thickness 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.

  The width of the resistor 3 is preferably about 0.3 mm to 1.3 mm. By setting the width 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 base 9 having a laminated structure can be maintained.

  The lead 8 whose tip side is connected to the end of the resistor 3 can use the same material as that of the resistor 3 mainly composed of carbide, nitride, silicide, etc. such as W, Mo, Ti. 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 small. When the insulating substrate 9 is made of silicon nitride ceramics, the lead 8 is preferably composed mainly of WC, which is an inorganic conductor, and silicon nitride is added thereto 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. Further, when the content of silicon nitride is 40% by mass or less, the resistance value of the lead 8 becomes small and stable. Therefore, the content of silicon nitride is preferably 15% by mass to 40% by mass. More preferably, the content of silicon nitride is 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 resistor 3 and the pair of leads 8 are connected so as to overlap each other in a direction perpendicular to the axial direction, and the two boundary surfaces 2 between the resistor 3 and the pair of leads 8 are connected. Is inclined with respect to a direction perpendicular to a plane including both axes of the pair of leads 8.

  For example, as shown in FIG. 2, in order to increase the bonding area between the end face of the resistor 3 and the end face of the lead 8, the end face of the resistor 3 and the lead are viewed in a longitudinal section parallel to the axial direction of the lead 8. The boundary surface 2 is provided so that the boundary line with the end surface of 8 is inclined with respect to the axial direction of the lead 8. The tilt angle of the boundary line with respect to the axial direction is, for example, 10 to 80 degrees.

  With such a configuration, a part of the high frequency component whose impedance is not matched at the boundary surface 2 between the resistor 3 and the lead 8 causes the boundary surface 2 to function as an antenna, Even if it is dissipated from the lead surface, the planes (boundary surfaces) of the two planar antennas are placed in a twisted position. Interference phenomenon (crosstalk phenomenon) can be suppressed from the boundary surface 2 on the side to the boundary surface 2 on the power output side. As a result, abnormal heat generation at the boundary surface and generation of microcracks due to abnormal heat generation can be suppressed.

  In other words, regardless of whether the control signal from the ECU is pulse drive or DC drive, the occurrence of microcracks at the boundary surface between the resistor and the lead and the progress of cracks at the boundary surface, even if the rise of power entry becomes steep Is suppressed, and the resistance is stabilized for a long time. Thereby, the reliability and durability of the heater are improved.

  Further, as shown in FIG. 3, by arranging the boundary surface 2 between the resistor 3 and the lead 8 as a flat surface over the entire region in a torsional position relationship, the high-frequency wave propagating in the direction perpendicular to the boundary surface 2 and the boundary surface The crosstalk phenomenon caused by the high frequency propagating along the two planes can be suppressed. As a result, it is preferable because abnormal heat generation at the boundary surface 2 and generation of microcracks due to abnormal heat generation can be suppressed.

  Further, as shown in FIG. 4, when the resistor 3 and the lead 8 are two pairs of heaters, at least two of the four boundary surfaces 2 have both axes of the leads 8. Inclined with respect to the direction perpendicular to the plane containing the surface, and the at least two boundary surfaces 2 are arranged so as to be diagonal, so that the crosstalk phenomenon can be suppressed and abnormalities at the boundary surface can be prevented. This is preferable because generation of microcracks caused by heat generation and abnormal heat generation can be suppressed. It is most preferable that all four boundary surfaces are inclined with respect to a direction perpendicular to a plane including both axes of the leads 8.

  Further, as shown in FIG. 5, the two boundary surfaces 2 are inclined with respect to a direction perpendicular to a plane including both axes of the pair of leads 8, so that the boundary surface 2 functions as an antenna. Arranged so that the planes of the two planar antennas are twisted, and even when high-frequency waves propagated from one antenna surface reach the other antenna surface, they reach all positions on the antenna surface. Since the time is different, an abnormal waveform of the pulse is not generated by being included in the background noise of the pulse that arrives via the resistor 3. As a result, abnormal heat generation at the boundary surface and generation of microcracks due to abnormal heat generation can be suppressed.

  In particular, as shown in FIGS. 6 to 8, the two boundary surfaces 2 are inclined opposite to each other, so that the transmission direction from the antenna does not coincide with the reception direction at all, and the crosstalk phenomenon is further suppressed. This is preferable because abnormal heat generation at the boundary surface 2 and generation of microcracks due to abnormal heat generation can be suppressed.

Then, as shown in FIG. 9, when viewed in a cross section perpendicular to the plane including both axes of the pair of leads 8, the inclination of the boundary line between the resistor 3 and the pair of leads 8 is rearward from the front end side. Even if it gradually changes toward the end side, the phase of the transmitted and received high-frequency signals can be prevented from matching, and the crosstalk phenomenon can be further suppressed. Note that the inclination of the boundary line between the resistor 3 and the pair of leads 8 gradually changes from the front end side toward the rear end side means that the boundary surface 2 is a curved surface.

  This is because even if the boundary surface 2 functions as an antenna, one of the two antennas is configured as a curved antenna and the antenna surfaces are arranged in a twisted position. Even if the high-frequency wave propagated from the antenna surface reaches the other antenna surface, the arrival time is different at all positions on the antenna surface, so it is included in the background noise of the pulses that arrive via the resistor 3 This is because no abnormal pulse waveform occurs. As a result, abnormal heat generation at the boundary surface 2 and generation of microcracks due to abnormal heat generation can be suppressed.

  In particular, as shown in FIG. 10, the inclination of the two boundary lines 2 between the resistor 3 and the pair of leads 8 gradually changes from the front end side toward the rear end side. Inclination with respect to the direction perpendicular to the plane including both axes of the pair of leads 8 completely prevents the phases of the transmitted and received high-frequency signals from matching. As a result, it is possible to suppress abnormal heat generation at the boundary surface 2 and generation of microcracks due to the abnormal heat generation.

  Further, the heater 1 of the present embodiment is a metal holding that holds the heater 1 while 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 it as a glow plug provided with a member. 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. Then, in a state where the molded body a is 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 Table 1 and Table 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 Sample No. 1, the most heat-generating portion was the boundary surface between the lead and the resistor. In order to confirm the energization state, the pulse waveform flowing through the heater of sample number 1 was confirmed using an oscilloscope. Unlike the input waveform, the rise of the pulse did not become steep, and it took 1 μs to reach 7V. Waving while overshooting.

  This is considered to be because the waveform of the high frequency component included in the rising portion of the pulse is synthesized by the crosstalk phenomenon in the heater of sample number 1. Also, regarding the fact that the most heat-generating part of the heater is on the cathode side particularly at the interface between the lead and the resistor, the interface between the cathode-side lead and the resistor is caused by an abnormal pulse caused by crosstalk. It is considered that local heat generation was caused by the fact that impedance matching could not be achieved.

  Furthermore, the resistance change before and after energization of sample No. 1 was very large at 55%. After pulse energization, the boundary surface between the lead and resistor of sample No. 1 was observed with a scanning electron microscope. It was confirmed that microcracks were generated from the outer peripheral direction to the inner side.

  On the other hand, with respect to sample numbers 2 to 4, the most heat generating portion was the resistor heating portion at the tip of the heater. Then, in order to confirm the energization state, the pulse waveform flowing through the heater was confirmed using an oscilloscope, and the waveform was almost the same as the input waveform. This indicates that energization was possible without abnormal heating at the interface between the lead and the resistor.

  In addition, the resistance change before and after the energization of sample numbers 2 to 4 was as small as 5% or less. After the pulse energization, the interface between the lead of these sample numbers and the resistor was observed with a scanning electron microscope. There was no.

  Next, connect the DC power supply to the heater and set the applied voltage so that the temperature of the resistor is 1400 ° C. 1) Energize for 5 minutes and 2) Deenergize for 2 minutes 1), 2) 10,000 cycles were repeated. The rate of change in the resistance value of the heater before and after energization was measured.

  As shown in Table 2, since the resistance change before and after the energization of Sample No. 1 was as large as 55%, the interface between the lead and the resistor of Sample No. 1 was observed with a scanning electron microscope after the DC energization. However, it was confirmed that microcracks were generated on the boundary surface from the outer peripheral direction toward the inner side.

  On the other hand, with respect to sample numbers 2 to 4, the resistance change before and after energization was as small as 5% or less, and the interface between the lead of these sample numbers and the resistor was observed with a scanning electron microscope after DC energization. There was no.

1: Heater 2: Boundary surface 3: Resistor 4: Heat generating part 8: Lead 9: Insulating substrate

The present invention includes an insulating base, a resistor embedded in the insulating base and having a folded shape,
A heater comprising a pair of leads embedded in the insulating base, connected to the resistor on the front end side and led to the surface of the insulating base on the rear end side, the resistor and the pair of leads The leads are connected to overlap with each other in a direction perpendicular to the axial direction, and when viewed in a cross section perpendicular to a plane including both axes of the pair of leads, at least the resistor and the pair of leads The inclination of the boundary line with one side is different between the front end side and the rear end side .

Claims (5)

An insulating substrate;
A resistor embedded in the insulating substrate and having a folded shape;
A heater comprising a pair of leads embedded in the insulating base, connected to the resistor on the front end side and led to the surface of the insulating base on the rear end side,
The resistor and the pair of leads are connected so as to overlap in a direction perpendicular to the axial direction, and at least one of the two boundary surfaces of the resistor and the pair of leads is connected to the pair of leads. A heater which is inclined with respect to a direction perpendicular to a plane including both of the respective axes.   The heater according to claim 1, wherein the two boundary surfaces are inclined with respect to a direction perpendicular to a plane including both axes of the pair of leads.   The heater according to claim 2, wherein the two boundary surfaces are inclined opposite to each other.   When viewed in a cross section perpendicular to a plane including both axes of the pair of leads, the inclination of the boundary line between the resistor and the pair of leads gradually changes from the front end side to the rear end side. The heater according to claim 1, wherein:   A glow plug comprising: the heater according to claim 1; and a metal holding member that is electrically connected to one of the pair of leads and holds the heater.

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