JP6075774B2 - Heater and glow plug - Google Patents

Description

  The present invention relates to a heater used in various sensors or measuring devices such as a combustion-type in-vehicle heating device, a petroleum fan heater, a glow plug of an automobile engine, and an oxygen sensor, and a glow plug using the heater.

  For example, a heater described in Patent Document 1 is known as a heater used in various sensors or measuring devices such as a combustion-type in-vehicle heating device, an oil fan heater, a glow plug of an automobile engine, and an oxygen sensor. The heater described in Patent Document 1 includes a rod-shaped ceramic body provided with a tapered portion on one end side, a heating resistor embedded in the ceramic body, and a conductor layer provided on the tapered portion and connected to the heating resistor. And. Electric power can be supplied to the heater by connecting an external electrode to the conductor layer.

International Publication No. 2008/105327

  However, when the heater described in Patent Document 1 is used in an environment in which a greater vibration is generated than in the prior art, the crack is generated in the conductor layer due to the vibration, resulting in a poor connection between the conductor layer and the external electrode. There was a possibility. For this reason, it may be difficult to make the heater function effectively in an environment with large vibrations.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a heater that can maintain a good connection between a conductor layer and an external electrode even when used in an environment where vibration is large. There is to do.

  A heater according to an aspect of the present invention includes a rod-shaped ceramic body provided with a tapered portion on one end side, a heat generating resistor embedded in the ceramic body, and provided in the tapered portion to electrically connect the heat generating resistor. And a conductor layer connected to the groove, wherein the tapered portion is provided with a groove.

  According to the heater of one aspect of the present invention, since the groove is provided in the tapered portion, stress due to vibration transmitted from the external environment to the ceramic body is concentrated on the boundary between the conductor layer and the tapered portion. Can be suppressed. Specifically, the stress is applied not only to the boundary between the conductor layer and the tapered portion but also to the portion where the groove is formed. Thereby, the stress concerning the boundary of a conductor layer and a taper part can be reduced. Therefore, it can suppress that a crack arises in a conductor layer by vibration. As a result, the long-term reliability of the heater can be improved.

It is sectional drawing of one Embodiment of the heater of this invention. It is an enlarged view of the conductor layer vicinity of the heater shown in FIG. It is sectional drawing of the groove vicinity of the heater shown in FIG.

  Hereinafter, a heater 10 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a heater 10 of the present invention. As shown in FIG. 1, the heater 10 includes a ceramic body 1, a heating resistor 2 embedded in the ceramic body 1, and a conductor layer 3 provided on one end side of the ceramic body 1. The heating resistor 2 and the conductor layer 3 are electrically connected via the lead-out part 4.

  The ceramic body 1 is a member formed in, for example, a rod shape or a plate shape. The ceramic body 1 is provided with a tapered portion 11 on one end side. The tapered portion 11 is provided with a plurality of grooves 12 as shown in FIG. The ceramic body 1 is made of a ceramic sintered body. Examples of the ceramic sintered body include ceramics having electrical insulation properties such as oxide ceramics, nitride ceramics, and carbide ceramics. Specifically, alumina ceramics, silicon nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics, or the like can be used. In particular, the ceramic body 1 is preferably made of silicon nitride ceramics. Silicon nitride ceramics are excellent in that silicon nitride as a main component has high strength, high toughness, high insulation, and high heat resistance.

The ceramic body 1 made of silicon nitride ceramic is, for example, 5 to 15% by mass of a rare earth such as Y ₂ O ₃ , Yb ₂ O ₃ or Er ₂ O ₃ as a sintering aid with respect to silicon nitride as a main component. Element oxide, 0.5-5% by mass of Al ₂ O ₃ , and SiO ₂ are mixed so that the amount of SiO ₂ contained in the sintered body is 1.5-5% by mass, and formed into a predetermined shape Then, it can be obtained by hot press firing at 1650 to 1780 ° C. The length of the ceramic body 1 is set to 20 to 50 mm, for example, and the diameter of the ceramic body 1 is set to 3 to 5 mm, for example.

When the ceramic body 1 is made of silicon nitride ceramics and the heating resistor 2 is made of molybdenum (Mo) or tungsten (W), the ceramic body 1 includes MoSi ₂ and WSi. It is preferable to mix and disperse ₂ etc. Thereby, the thermal expansion coefficient of the silicon nitride ceramics which is a base material can be brought close to the thermal expansion coefficient of the heating resistor 2, and the durability of the heater 10 can be improved.

  The heating resistor 2 is a resistor for generating heat, and generates heat when a current flows. The heating resistor 2 is embedded in the ceramic body 1. The heating resistor 2 is provided on the other end side of the ceramic body 1. The heating resistor 2 has a folded shape, and each end portion is connected to the lead-out portion 4. The heating resistor 2 is the portion that generates the most heat near the center of the folded portion in the folded shape. The length from the front end of the heating resistor 2 to the rear end of the heating resistor 2 in the length direction of the ceramic body 1 is set to 2 to 10 mm, for example.

  The lead-out portion 4 is a member for electrically connecting the heating resistor 2 and an external power source, and one end is connected to the heating resistor 2 and the other end is drawn to the surface of the ceramic body 1. ing. The lead-out portions 4 are separately provided at both ends of the heating resistor 2. One lead-out portion 4 is drawn out to a tapered portion 11 provided on one end side of the ceramic body 1 and connected to the conductor layer 3. The other lead-out portion 4 is drawn out to the outer peripheral surface of the region on one end side of the ceramic body 1.

As the heating resistor 2 and the lead-out portion 4, a material mainly composed of carbides such as W, Mo or titanium (Ti), nitrides or silicides can be used. Further, the heating resistor 2 may contain the same material as the ceramic body 1 in order to bring the coefficient of thermal expansion close to that of the ceramic body 1. The heating resistor 2 is set to have a high resistance value, and generates heat most particularly near the turning point. On the other hand, the lead-out part 4 reduces the resistance value per unit length by making the content of the forming material of the ceramic body 1 smaller than that of the heating resistor 2 or making the cross-sectional area larger than that of the heating resistor 2. Is lower than the heating resistor 2.

  The conductor layer 3 is a member for electrically connecting the heating resistor 2 and an external electrode. The conductor layer 3 is provided on the tapered portion 11 of the ceramic body 1. The conductor layer 3 is electrically connected to the heating resistor 2 via the lead-out part 4. As shown in FIG. 3, the conductor layer 3 includes a metallized layer 31 and a plating layer 32 laminated on the metallized layer 31. As the metallized layer 31, for example, a metallized layer containing silver, copper and titanium or a metallized layer containing gold, nickel and palladium can be used. As the plating layer 32, for example, nickel boron plating or gold plating can be used. The thickness of the metallized layer 31 can be set to about 20 to 40 μm, for example. Moreover, it is preferable that the thickness of the plating layer 32 is 1 micrometer or more, for example.

  As shown in FIG. 2, the heater 10 of the present embodiment is provided with a groove 12 in a tapered portion 11 in which the conductor layer 3 is provided. Thereby, when the conductor layer 3 and the external electrode are connected, the vibration transmitted from the outside to the ceramic body 1 can be absorbed by the groove 12. Thereby, it can suppress that a crack arises in conductor layer 3 by vibration. As a result, the long-term reliability of the heater 10 can be improved. In addition, the dimension of the groove | channel 12 can set the width to 10-100 micrometers, the depth 10-200 micrometers, and length to 1-3 mm, for example. The dimensions of each groove 12 are preferably the same. Thereby, it can suppress that stress concentrates partially.

  Further, the groove 12 provided in the tapered portion 11 is preferably provided along the inclination direction of the tapered portion 11. When the groove 12 is not provided in the taper portion, or when the groove 12 is provided in the circumferential direction of the taper portion 11, resonance may occur in the taper portion 11 due to transmission of external vibration. . On the other hand, by providing the groove 12 along the inclination direction of the taper portion, it is possible to prevent resonance from occurring in the taper portion 11, so that vibration transmitted from the outside can be easily stopped. .

  As shown in FIG. 3, the conductor layer 3 includes a metallized layer 31 and a plating layer 32 laminated on the metallized layer 31, and a part of the metallized layer 31 enters the groove 12. Thereby, the joint strength between the metallized layer 31 and the ceramic body 1 can be improved. As a result, the durability of the heater 10 can be improved.

  Moreover, the groove | channel 12 provided in the taper part 11 is plural. By providing a plurality of grooves 12, vibrations can be more easily absorbed. Furthermore, since the conductor layer 3 enters the plurality of grooves 12, the bonding strength between the conductor layer 3 and the ceramic body 1 can be further improved.

  When the ceramic body 1 is viewed from one end side, the grooves 12 are provided radially in the tapered portion 11 of the ceramic body 1. Since the groove 12 is radial and the conductor layer 3 is provided in the groove 12, the thermal conductivity in the tapered portion 11 can be improved. That is, it is possible to suppress the partial heat generation at the one end side of the ceramic body 1. As a result, it is possible to suppress thermal stress from being partially concentrated on the ceramic body 1.

  The shape of the inner surface of the groove 12 is arcuate. Since the shape of the inner surface of the groove 12 is an arc, the groove 12 does not have a corner. Therefore, it can suppress that a thermal stress concentrates partially. The arc shape here includes, for example, a U-shape.

Returning to FIG. 1, the glow plug 100 of the present embodiment includes the above-described heater 10 and the heater 10.
The cylindrical metal member 5 attached to the taper part 11 side, and the electrode metal fitting 6 disposed on the inner side of the metal member 5 and connected to the conductor layer 3 are provided.

  The metal member 5 is a member for holding the ceramic body 1. The metal member 5 is a cylindrical member and is provided so as to surround one end side of the ceramic body 1. In other words, the ceramic body 1 is inserted inside the metal member 5. The metal member 5 is electrically connected to the other lead-out portion 4 drawn to one end side of the ceramic body 1. The metal member 5 is made of, for example, stainless steel or iron (Fe) -nickel (Ni) -cobalt (Co) alloy.

  The metal member 5 and the ceramic body 1 are joined by a brazing material. The brazing material is provided so as to surround the end of the ceramic body 1. In other words, the brazing material is provided in layers on the entire circumference of the end of the ceramic body 1. Thereby, the metal member 5 and the ceramic body 1 are firmly fixed.

  In order to provide the brazing material on the ceramic body 1, the glass component may be baked on the inner surface of the ceramic body 1 before brazing. Thereby, a brazing material can be provided satisfactorily. Here, in order for the metal member 5 to function as an electrode, it is preferable to mix a metal such as Ni with the above glass component. Thereby, the derivation | leading-out part 4, the brazing material, and the metal member 5 can be electrically connected.

  As the brazing material, silver (Ag) -copper (Cu) brazing, Ag brazing, Cu brazing or the like containing 5 to 20% by mass of a glass component can be used. Since the glass component has good wettability with ceramics and has a large coefficient of friction, the bonding strength between the brazing material and the ceramic body 1 or the bonding strength between the brazing material and the metal member 5 can be improved.

  The electrode fitting 6 is located inside the metal member 5. The electrode fitting 6 is located away from the inner peripheral surface of the metal member 5 so as not to cause a short circuit with the metal member 5. The electrode fitting 6 is a metal wire having a spiral portion provided for stress relaxation. The electrode fitting 6 is in contact with the conductor layer 3. The electrode fitting 6 is electrically connected to the conductor layer 3 and is electrically connected to an external power source (not shown). By applying a voltage between the metal member 5 and the electrode fitting 6 from an external power supply, a current can be passed through the heating resistor 2 via the metal member 5 and the electrode fitting 6. The electrode fitting 6 is made of nickel or stainless steel, for example.

  The glow plug 100 of the present embodiment includes the above-described heater 10 that can absorb vibrations, so that the electrode fitting 6 and the conductor layer 3 can be connected to each other even when used in an environment with large vibrations. Can keep in touch. For example, a joining member containing silver, copper, and titanium can be used to connect the electrode fitting 6 and the conductor layer 3.

  The heater 10 and the glow plug 100 of the example of the present invention were manufactured as follows.

First, as a raw material of the ceramic body 1, 85% by mass of silicon nitride powder, 10% by mass of Yb ₂ O ₃ powder as a sintering aid, 3.5% by mass of MoSi ₂ powder, and 1.5% by mass of aluminum oxide powder % To prepare a raw material powder. Then, the half of the molded object which becomes the ceramic body 1 after baking was produced by press molding using this raw material powder.

Next, as a conductive paste that becomes a part of the heating resistor 2 and the lead-out portion 4 located near the surface of the ceramic body 1, tungsten carbide (WC) powder 70 mass% silicon nitride powder 29.95 mass%, A metal compound Cr ₃ C ₂ 0.05% by mass as an additive was mixed and an appropriate organic solvent was added. Here, the silicon nitride powder mixed with the tungsten carbide powder was mixed with 0.1% by mass of Yb ₂ O ₃ powder as a sintering aid.

  Next, a lead pin serving as the remaining part of the lead-out portion 4 was provided on one of the half-shaped molded bodies. Then, the other molded body was overlapped with the molded body provided with the lead pins to obtain a molded body in which the heating resistor 2 and the lead-out portion 4 were embedded. As the lead pin, a W lead pin mainly composed of tungsten was used.

  Next, after putting the obtained molding into a cylindrical carbon mold, hot press firing was performed in a reducing atmosphere at 1700 ° C. and 35 MPa.

  Next, the sintered body was polished to obtain a heater 10 having a diameter of 4 mm and a total length of 40 mm. Furthermore, the heater 10 which formed the taper part 11 and the groove | channel 12 part was prepared as the sample 1 by grind | polishing the edge part of the obtained cylindrical heater 10 with a grindstone. Moreover, the heater which formed only the taper part 11 was prepared as the sample 2 which is a comparative example. After forming the tapered portion 11 in both the sample 1 and the sample 2, the metallized layer 31 and the plating layer 32 were formed. As the metallized layer 31, a metallized layer containing silver, copper and titanium was formed with a thickness of 20 μm, and as the plated layer 32, a nickel boron plated layer was formed with a thickness of 2 μm.

  Finally, the metal member 5 and the electrode fitting 6 were attached to the obtained heater 10. The metal member 5 and the lead-out part 4 were joined by a brazing material so as to be electrically connected. Moreover, the metal member 5 and the conductor layer 3 were joined by the brazing material.

  Then, a cycle test was performed in which a voltage was applied to the heater 10 of each prepared sample to raise and lower the temperature of the surface of the ceramic body 1 up to 1500 ° C. Specifically, after the energization of the heating resistor 2 is continued for 1 minute while the surface temperature of the ceramic body 1 is 1500 ° C., the energization is stopped and natural cooling is performed for 1 minute, which is defined as one cycle. The energization was performed for 10,000 cycles. During energization, each sample was vibrated at a predetermined frequency. And the resistance value between the electrode metal fitting 6 and the metal fitting member 5 before a test was measured in a 25 degreeC thermostat. After the test, the resistance value was measured under the same conditions as before the test, and the resistance change rate was obtained by comparison with the resistance value before the test.

  As a result, the resistance change rate after the test for the heater of the sample 2 was 12%, but the resistance change rate after the test for the heater 10 of the sample 1 was 0.5%. Moreover, when the conductor layer 3 was observed by SEM, it was confirmed that cracks occurred in the metallized layer of the heater of the sample 2, but no cracks occurred in the metallized layer 31 of the heater 10 of the sample 1. It was.

  From the above results, it was confirmed that the heater 10 of the present invention has improved durability under vibration as compared with the heater of the comparative example.

1: Ceramic body 11: Tapered portion 12: Groove 2: Heating resistor 3: Conductor layer 31: Metallized layer 32: Plating layer 4: Derived portion 5: Metal member 6: Electrode fitting 10: Heater 100: Glow plug

Claims (7)

  A rod-shaped ceramic body provided with a tapered portion on one end side, a heating resistor embedded in the ceramic body, and a conductor layer provided on the tapered portion and electrically connected to the heating resistor. The heater is characterized in that a groove is provided in the tapered portion.   The heater according to claim 1, wherein the groove is provided along an inclination direction of the tapered portion.   3. The heater according to claim 1, wherein the conductor layer includes a metallized layer and a plating layer laminated on the metallized layer, and a part of the metallized layer enters the groove. .   The heater according to any one of claims 1 to 3, wherein a plurality of the grooves are provided.   The heater according to claim 3 or 4, wherein the groove is provided radially in the tapered portion of the ceramic body when the ceramic body is viewed from the one end side.   The heater according to any one of claims 1 to 5, wherein the inner surface of the groove has an arc shape.   A glow plug comprising: the heater according to any one of claims 1 to 6; and a cylindrical metal member attached to the tapered portion of the heater.

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