KR20130137675A - Heater and glow plug provided with same - Google Patents

Abstract

DISCLOSURE OF THE INVENTION Provided is a heater having a high reliability and durability in which a large stress concentration is prevented from occurring at the end of a junction between a resistor and a lead even when a large current flows through the resistor during rapid temperature rise or the like, and a glow plug having the same.
[Measures] The heater 1 includes the resistor 3 having the heat generating portion 4, the leads 8 bonded to the ends of the resistor 3, the insulation covering the resistors 3 and the leads 8. The base body 9 is provided, and the junction part of the resistor 3 and the lead 8 is a shape where the lead 8 is thicker than the resistor 3, and the end part of the resistor 3 enters the front end of the lead 8. In addition, a recess is formed in the end surface of the resistor 3, and a part of the lead 8 enters the recess.

Description

HEATER AND GLOW PLUG PROVIDED WITH SAME}

The present invention is, for example, for ignition or flame detection heaters in combustion-type vehicle heating devices, ignition heaters for various combustion devices such as petroleum fan heaters, glow plug heaters for automobile engines, for various sensors such as oxygen sensors. The present invention relates to a heater used for a heater, a heater for heating a measuring device, and the like and a glow plug having the same.

The heater used for a glow plug of an automobile engine, etc. is comprised including the resistor, lead, and insulating gas which have a heat generating part. Then, these materials are selected or shaped so that the resistance of the lead becomes smaller than that of the resistor.

Here, since the junction between the resistor and the lead is a point of change in shape or a change in material composition, the joint is parallel to the axial direction of the lead in order to increase the junction area so as not to be affected by the difference in thermal expansion due to heat generation or cooling during use. It is known that the interface between the resistor and the lead is oblique when viewed from one cross section (see Patent Documents 1 and 2, for example).

Japanese Patent Publication No. 2002-334768 Japanese Patent Publication No. 2003-22889

In recent years, since rapid temperature rise is required more than conventionally, the necessity of flowing a large current to the resistor at the start of engine operation has arisen. In this way, when a large current flows through the heater, even if the interface between the resistor and the lead is oblique, the junction area is increased, and the thermal expansion difference between the resistor and the lead is large, and the thermal stress is concentrated at the junction (the end of the resistor or the end of the lead). There has been a problem that cracks occur.

The present invention has been devised in view of the above-mentioned conventional problems, and its object is a heater having high reliability and durability that prevents large thermal stress from concentrating on the junction between the resistor and the lead even when a large current flows through the resistor during rapid temperature increase. To provide.

The heater of the present invention includes an insulation gas, a resistor embedded in the insulation gas, and a lead embedded in the insulation gas and connected to the resistor at the front end side and led to the surface of the insulation gas at the rear end side. The lead is thicker than the resistor, and is connected to the leading end of the lead so that the end of the resistor enters, and a recess is formed in the end surface of the resistor, and a part of the lead enters the recess. It is.

Moreover, the heater of this invention can be used as a glow plug provided with the heater of the said structure and the metal holding member electrically connected with the said lead, and holding the said heater.

[Effects of the Invention]

According to the heater of the present invention, even when a large current flows at a rapid temperature increase, heat inside the resistor can be lost in a lead having a lower resistance value than the resistor. Therefore, the accumulation of heat at the junction can be suppressed and the load caused by heat generation can be reduced. As a result, cracks can be suppressed from occurring at the joint even if the temperature is repeatedly raised or lowered. This improves the reliability and durability of the heater.

(A) is a principal part enlarged longitudinal cross-sectional view which shows an example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a).
(A) is a principal part enlarged longitudinal cross-sectional view which shows 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 a principal part enlarged longitudinal cross-sectional view which shows the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a).
4: (a) is a principal part enlarged longitudinal cross-sectional view which shows the other example of embodiment of the heater of this invention, (b) is a cross-sectional view in the XX line shown to (a).
5 (a) and 5 (b) are enlarged longitudinal sectional views of main parts each showing another example of the embodiment of the heater of the present invention.
It is a schematic longitudinal cross-sectional view which shows an example of embodiment of the glow plug of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, the example of embodiment of the heater of this invention is described in detail with reference to drawings.

1: (a) is a longitudinal cross-sectional view which shows an example of embodiment of the heater of this invention, and FIG. 1 (b) is a cross-sectional view in the X-X line shown to FIG. 1 (a). 2 (a) is a longitudinal cross-sectional view which shows the other example of embodiment of the heater of this invention, and FIG. 2 (b) is a cross-sectional view in the X-X line shown to FIG. 2 (a).

The heater 1 of the present embodiment is connected to the resistor 3 embedded in the insulating base 9, the insulating base 9, the insulating base 9, and connected to the resistor 3 at the front end side, and the rear end. And a lead 8 drawn on the surface of the insulating base 9 from the side, and the lead 8 is thicker than the resistor 3 so that the end of the resistor 3 enters the leading end of the lead 8. While being connected, the recess 31 is formed in the end face of the resistor 3, and a part of the lead 8 enters the recess 31.

The insulating base 9 in the heater 1 of this embodiment is formed in rod shape, for example. The insulating base 9 covers the resistor 3 and the lead 8, in other words, the resistor 3 and the lead 8 are embedded in the insulating base 9. Here, it is preferable that the insulating base 9 consists of ceramics, and since this can endure to high temperature than a metal, it becomes possible to provide the heater 1 with the improved reliability at the time of rapid temperature rising. Specifically, ceramics having electrical insulation such as oxide ceramics, nitride ceramics, and carbide ceramics can be cited. In particular, the insulating substrate 9 is preferably made of silicon nitride ceramics. This is because silicon nitride, which is the main component, is excellent in terms of high strength, high toughness, high insulation and heat resistance. The silicon nitride ceramics is, for example, of 3-12% by weight as a sintering aid for the main component of silicon nitride _{Y 2 O 3, Yb 2 O} 3, Er 2 O 3 Of a rare earth element oxide and 0.5 to 3 mass% Al ₂ O such as a _3, and an SiO ₂ amount contained in the sintered body mixture of SiO ₂ such that 1.5 to 5% by weight and molded into a predetermined shape, and thereafter, 1650 It can obtain by hot press baking at -1780 degreeC.

In addition, when using the ceramic made of a silicon nitride as an insulating substrate _{(9), MoSi 2, WSi} 2 It is preferable to mix and disperse | distribute etc. In this case, the thermal expansion rate of the silicon nitride ceramics, which is the base material, can be approximated to the thermal expansion rate of the resistor 3, so that the durability of the heater 1 can be improved.

If the resistor 3 has a linear shape as shown in Fig. 1, the region between the leads 8 can be the heat generating portion 4, and in order to selectively form the heat generating portion 4, the area having a small cross-sectional area or a spiral shape can be used. It is good to form an area. In addition, in the case of having a folded shape as shown in FIG. 2, the region between the leads 8 of the resistor 3 can be used as the heat generating portion 4, and the heat generated in the vicinity of the folded middle point generates the most heat. It becomes part (4). As the resistor 3, those containing mainly carbides, nitrides, and silicides such as W, Mo, and Ti can be used. In the case where the insulating base 9 is the above-described material, tungsten carbide (WC) is selected from the material of the resistor 3 in that the difference in thermal expansion rate with the insulating base 9 is small, has high heat resistance, and has a small specific resistance. Excellent as a material In addition, when the insulating base 9 consists of silicon nitride ceramics, it is preferable that the resistor 3 has WC which is an inorganic conductor as a main component, and the content rate of the silicon nitride added to this is 20 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 large thermal expansion rate as compared with silicon nitride, and therefore is usually in a state where tensile stress is applied. On the other hand, by adding silicon nitride to the resistor 3, the thermal expansion rate of the resistor 3 is made close to the thermal expansion rate of the insulating substrate 9, and is caused by the difference in the thermal expansion rate of the heater 1 at the time of raising and lowering the temperature. It can relieve stress.

Moreover, when content of the silicon nitride contained in the resistor 3 is 40 mass% or less, the resistance value of the resistor 3 can be made comparatively small, and can be stabilized. Therefore, it is preferable that content of the silicon nitride contained in the resistor 3 is 20 mass%-40 mass%. More preferably, content of silicon nitride is 25 mass%-35 mass%. In addition, 4 mass%-12 mass% of boron nitride can also be added instead of the silicon nitride as the same additive to the resistor 3.

The thickness (thickness in the vertical direction shown in Fig. 2 (b)) of the resistor 3 is preferably 0.5 mm to 1.5 mm, and the width (the width in the horizontal direction shown in Fig. 2 (b)) of the resistor 3 is 0.3 mm. ~ 1.3 mm is good. By setting it in this range, the resistance value of the resistor 3 can be made small and it can fully generate heat. Moreover, in the case of the laminated structure in which the insulating base 9 is formed by laminating | stacking the molded object divided | segmented in half, for example, adhesiveness of the laminated interface of the insulating base 9 of a laminated structure can be maintained.

The lead 8 bonded to the end of the resistor 3 may be formed of carbide, nitride, silicide, or the like as W, Mo, Ti, or the like as a main component. For example, the material for forming the insulating base 9 may be formed of a resistor ( The resistance value per unit length is lower than that of the resistor 3, for example, to include more than 3) or to increase the cross-sectional area of the resistor 3.

This lead 8 can be formed using the same material as the resistor 3. In particular, WC is preferable as the material of the lead 8 in that the difference in thermal expansion rate with the insulating base 9 is small, the high heat resistance, and the small specific resistance are small. In addition, when the insulating base 9 consists of silicon nitride ceramics, it is preferable that the lead 8 has WC which is an inorganic conductor as a main component, and it adds silicon nitride so that content may be 15 mass% or more. As the content of silicon nitride increases, the thermal expansion rate of the lead 8 can be made closer to the thermal expansion rate of the insulating base 9. Moreover, when content of silicon nitride is 40 mass% or less, the resistance value of the lead 8 becomes small and it is stable. Therefore, as for content of silicon nitride, 15 mass%-40 mass% are preferable. More preferably, the content of silicon nitride is preferably 20% by mass to 35% by mass. In addition, the lead 8 may have a larger cross-sectional area than the resistor 3, and may have a lower resistance value per unit length by reducing the content of the material for forming the insulating base 9 than the resistor 3.

1 and 2, the lead 8 is thicker than the resistor 3, is connected to the tip of the lead 8 so that the end of the resistor 3 enters, and the resistor 3 A concave portion 31 is formed at the end surface of the crest), and a part of the lid 8 enters the concave portion 31. That is, the junction of the resistor 3 and the lead 8 firstly has an end portion of the resistor 3 in the tip end of the lead 8, and a recess formed in the end surface of the resistor 3 entering the tip end of the lead 8 ( A part of the lead 8 has entered into 31. In addition, the junction part here means the area | region in which the interface of the resistor 3 and the lead 8 exists when seen from the cross section parallel to the axial direction of the lead 8.

The end of the resistor 3 preferably enters, for example, 0.1 to 1.0 mm into the tip of the lead 8, and the depth of the recess 31 formed in the end face of the resistor 3 is the lead of the end of the resistor 3. Although it changes with the quantity which enters the front-end | tip part of (8), it is 0.01-0.3 mm, for example. As the shape of the recess 31, the cross-sectional shape (opening shape) may be circular, elliptical, polygonal or the like, but when the cross-sectional shape of the recess 31 is circular, the diameter is preferably 0.05 to 1.3 mm, for example. Do.

With such a configuration, even when a large current flows during rapid temperature increase, heat inside the resistor 3 can be lost in the lead 8 having a lower resistance value than the resistor 3. Therefore, the accumulation of heat at the junction can be suppressed and the load caused by heat generation can be reduced.

That is, since the inside of the recessed part 31 becomes the composition of the lead 8 which is low resistance compared with the resistor 3, a heat generation load can be reduced and a stress can be reduced.

As a result, it can suppress that a crack generate | occur | produces in a junction part even if a large electric current flows at the rapid temperature rising. In addition, cracks can be prevented from occurring at the junction even if the temperature is increased or decreased by flowing a current repeatedly, thereby improving the reliability and durability of the heater 1.

Here, in the heater 1 of this embodiment, as shown in FIG. 3 and FIG. 4, it is preferable that the recessed part 31 of the resistor 3 in a junction part is formed in the center part of the end surface of the resistor 3 here. Do. As a result, heat generated inside the resistor 3 that is hard to be lost even when the resistor 3 heats rapidly due to a large current flowing at a rapid temperature increase is substantially passed in the circumferential direction through the lead 8 inside the recess 31. It can be lost evenly. As a result, since stress concentration can be reduced, the product resistance can be configured not to change even in long-term use.

The heater 1 shown in Fig. 3 has such a shape that the end portion of the resistor 3 enters the substantially central portion of the cross section of the tip end portion of the lead 8, and the heater 1 shown in Fig. 4 is preferable because it has a long distance from the resistor 3 to the surface of the heater 1 so as to enter the inside of the transverse section of the tip end portion of the lead 8 and is excellent in insulation at the time of use.

As shown in Figs. 5A and 5B, it is preferable that the inner surface of the recess 31 of the resistor 3 in the joint portion does not have a corner portion. The inner surface of the concave portion 31 does not have an acute angle corner, that is, the inner surface is a secondary curved surface so that stress is not concentrated in the concave portion 31 and cracks do not occur. As a result, product resistance does not change with long term use. Therefore, the reliability and durability of the heater 1 are further improved. In addition, the heater 1 shown in FIG. 5 (a) has a shape in which the concave portion 31 is formed over almost the entire end surface of the resistor 3, and the heater 1 shown in FIG. 5 (b) is a resistor. The concave portion 31 is formed only in the vicinity of the center of the end face of (3). However, the shape shown in Fig. 5 (a) is preferable in that the heat generation load can be further reduced and the stress can be effectively reduced.

Moreover, it is preferable that the recessed part 31 of the resistor 3 in a junction part is formed in the end surface of both sides of the resistor 3. As a result, the load caused by the heat generation can be reduced regardless of the anode side or the negative electrode side, so that the product resistance does not change even if the anode side and the negative electrode side are set without worry. Therefore, the reliability and durability of the heater 1 can be improved more.

In addition, the heater 1 shown in FIGS. 1-5 is a shape in which the edge part of the resistor 3 is enclosed so that the tip part of the lead 8 may be enclosed. As the heater of the present invention, if the lead 8 is thicker than the resistor 3, and is connected so that the end of the resistor 3 enters the front end of the lead 8, the end of the resistor 3 must be connected to the entire circumference. Although it is not enclosed in the front-end | tip part of the lead 8 over, part or several places may be cut | disconnected, for example, Preferably it is good to enter so that the edge part of the resistor 3 may be enclosed in the front-end | tip part of the lead 8. As a result, the leads 8 covering the resistor 3 thermally expanding at the time of rapid temperature rise serve as cushioning materials for insulating ceramics having different linear expansion coefficients, so that stress concentration is reduced and no cracks are generated. As a result, product resistance does not change with long term use. Therefore, the reliability and durability of the heater 1 can be improved more.

As shown in FIG. 6, the heater 1 of the present embodiment is a glow plug having a metal holding member 7 that is electrically connected to the heater 1 and the lid 8 to hold the heater 1. It is preferable to use. The metal holding member 7 is a conventional body for holding the heater 1, and is joined to one lead 8 drawn out to the side of the ceramic base 9 with a solder or the like. Thereby, since the resistance of the heater 1 does not change even if it is used for a long time while ON / OFF is repeated in a high temperature engine, the glow plug which is excellent in ignition can be provided at any time.

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

The heater 1 of this embodiment can be formed by the injection molding method using the metal mold | die of the shape of the resistor 3, the lead 8, and the insulating base 9, etc., for example.

First, the conductive paste to be the resistor 3 containing the conductive ceramic powder, the resin binder and the like and the lead 8 is prepared, and the ceramic paste to be the insulating base 9 containing the insulating ceramic powder and the resin binder is prepared. To make.

Next, the molded object (molded object A) of the conductive paste of the predetermined pattern which becomes the resistor 3 by the injection molding method etc. is formed using an electrically conductive paste. The electrically conductive paste is filled in the metal mold | die in the state which hold | maintained the molded object A in the metal mold | die, and the molded object (molded body B) of the electrically conductive paste of the predetermined pattern used as the lead 8 is formed. Thereby, the molded object A and the molded object B connected to it are in the state hold | maintained in the metal mold | die.

Subsequently, after replacing a part of a metal mold | die with the thing for shaping | molding the insulating base 9 in the state which hold | maintained the molded object A and the molded object B in the metal mold | die, the ceramic paste used as the insulating base 9 is filled in a metal mold | die. Thereby, the molded object (molded object D) of the heater 1 in which the molded object A and the molded object B were covered with the molded object (molded object C) of the ceramic paste is obtained.

Next, the heater 1 can be produced by baking the obtained molded object D at the temperature of 1650 degreeC-1800 degreeC, and the pressure of 30 Mpa-50 Mpa, for example. It is preferable to perform baking in non-oxidizing gas atmosphere, such as hydrogen gas.

Example

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

First, 50% by weight of a tungsten carbide (WC) powder, silicon nitride (Si ₃ N ₄₎ powder to a shaped body (A) which is injection-molded to the resistor a conductive paste in a mold comprising 35 mass%, 15 mass% of a resin binder .

Subsequently, the said electrically conductive paste used as lead in the state which hold | maintained this molded object A in the metal mold was filled in the metal mold | die, it was connected with the molded object A, and the molded object B used as lead was formed. At this time, the junction part of a resistor and lead was formed using the metal mold | die which has a various shape.

Then, the silicon nitride in maintaining the molded body (A) and molded product (B) in a mold state (Si ₃ N ₄₎ powder of 85% by mass, an oxide of ytterbium (Yb) as a sintering aid (Yb ₂ O ₃₎ 10 parts by mass The ceramic paste containing 5 mass% of WC for making thermal expansion rate close to%, a resistor, and a lead was injection-molded in the metal mold | die. This formed the molded object D of the structure by which the molded object A and the molded object B were embedded in the molded object C used as an insulating base.

Subsequently, after putting the obtained molded object (D) in the cylindrical carbon mold, it hot-pressed at 1700 degreeC and 35 Mpa in the non-oxidizing gas atmosphere which consists of nitrogen gas, and sintered. The heater holding member was soldered to the lead edge part exposed to the surface of the obtained sintered compact, and the heater was produced.

Here, the embodiment shown in Fig. 2 was produced as an example. At this time, the resistor 3 had a thickness of 0.9 mm in the vertical direction and a width of 0.6 mm in the horizontal direction, and the end of the resistor 3 entered 0.5 mm in the distal end of the lead 8, and was formed in the end surface of the resistor 3. The heater of 0.05 mm in depth of the part 31, and 0.5 mm in diameter of the recessed part 31 was produced.

In addition, as a comparative example, the resistor 3 has a thickness of 0.9 mm in the vertical direction and a width of 0.6 mm in the horizontal direction, and the end of the resistor 3 does not enter the leading end portion of the lead 8. The heater without the recessed part 31 was produced.

The cold heat cycle test was done using these heaters. The conditions of the cold cycle test were first applied to the heater to set the applied voltage so that the temperature of the resistor was 1400 ° C, and then repeated 10,000 cycles using 1) energized for 5 minutes and 2) non-energized 1) and 2) for 1 cycle. did.

When the change in the resistance value of the heater before and after the cold cycle test was measured, the sample of the present invention had a resistance change of 1% or less. In addition, there was no trace of local heat generation and no micro cracks were observed at the connection portion between the resistor and the lead of this sample. In contrast, the sample of the comparative example had a resistance change of 5% or more, and microcracks were observed.

1 heater 3 resistor
31: recessed portion 4: heat generating portion
7 metal holding member 8 lead
9: insulation gas

Claims (6)

With insulation gas,
A resistor embedded in the insulating gas,
A lead embedded in the insulating base and connected to the resistor at the tip end side and led to the surface of the insulating base at the rear end side,
The lead is thicker than the resistor, and is connected to the leading end of the lead so that the end of the resistor enters, and a recess is formed in the end surface of the resistor, and a part of the lead enters the recess. Heater characterized by the above-mentioned. The method of claim 1,
And the recess is formed at the center of the end face of the resistor. 3. The method according to claim 1 or 2,
And the inner surface of the concave portion has no corner portion. The method according to any one of claims 1 to 3,
And the recess is formed on both end faces of the resistor. The method according to any one of claims 1 to 4,
An end of the resistor is inserted so as to be surrounded by the front end of the lead. A glow plug comprising a heater according to claim 1 and a metal holding member electrically connected to the lead to hold the heater.

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