WO2018199229A1

WO2018199229A1 - Heater and glow plug provided therewith

Info

Publication number: WO2018199229A1
Application number: PCT/JP2018/016973
Authority: WO
Inventors: 孝太郎田井村
Original assignee: 京セラ株式会社
Priority date: 2017-04-27
Filing date: 2018-04-26
Publication date: 2018-11-01
Also published as: JP6970188B2; JPWO2018199229A1

Abstract

This heater 10 comprises: a rod-shaped ceramic body 1; and a heating resistor 2 provided inside the ceramic body 1. The heating resistor 2 includes a first linear section 211, a second linear section 212 opposing the first linear section 211, and an arc-shaped section 22 having an apex and connecting the first linear section 211 and the second linear section 212. When a first cross section passing through the apex and perpendicular to the axial direction of the arc-shaped section 22 is viewed, the arc-shaped section 22 has a long axis and a short axis, and the long axis and short axis are inclined with respect to a plane containing the axes of the first linear section 211 and the second linear section 212.

Description

Heater and glow plug equipped with the same

The present disclosure is, for example, 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 a petroleum fan heater, a heater for a glow plug of a diesel engine, and various sensors such as an oxygen sensor. In particular, the present invention relates to a heater used for a heater or a heater for heating a measuring instrument, and a glow plug including the heater.

As a ceramic heater, for example, a ceramic heater disclosed in JP 2012-99373 A (hereinafter referred to as Patent Document 1) is known. The ceramic heater disclosed in Patent Document 1 includes a round bar-shaped base body having an insulating ceramic and a heating element embedded therein. Moreover, the heat generating element has two lead portions facing each other and a U-shaped heat generating portion that connects the two lead portions.

The heater of the present disclosure includes a rod-shaped ceramic body and a heating resistor provided inside the ceramic body, and the heating resistor is opposed to the first straight portion and the first straight portion. When the first cross section perpendicular to the axial direction of the arc-shaped portion passing through the top portion and the arc-shaped portion connecting the first straight portion and the second straight portion has the second straight portion and the top straight portion. In addition, the arcuate portion has a major axis and a minor axis, and the major axis and the minor axis are inclined with respect to a plane including the respective axes of the first linear portion and the second linear portion.

The heater of the present disclosure can improve the durability of the heater.

It is sectional drawing which shows an example of the heater of this indication. (A) is the expanded sectional view which expanded the vicinity of the heating resistor of the heater shown in FIG. 1, (b) is sectional drawing in the XX line shown in (a). (A) And (b) is sectional drawing of the top part of the arc-shaped part in the heater of another example, respectively. (A) is the expanded sectional view which expanded the vicinity of the heating resistor of the heater of another example, (b) is a sectional view in the YY line shown in (a). (A) is the expanded sectional view which expanded the vicinity of the heating resistor of the heater of another example, (b) is a sectional view in the XX line shown in (a), (c) is (a) FIG. 6 is a sectional view taken along line YY shown in FIG. (A) is the expanded sectional view which expanded the vicinity of the heating resistor of the heater of another example, (b) is a sectional view in the XX line shown in (a), (c) is (a) FIG. 6 is a sectional view taken along line YY shown in FIG. (A) is the expanded sectional view which expanded the vicinity of the heating resistor of the heater of another example, (b) is a sectional view in the XX line shown in (a), (c) is (a) FIG. 6 is a sectional view taken along line YY shown in FIG. It is sectional drawing which shows an example of the glow plug provided with the heater of this indication.

An example of the heater 10 of the present disclosure will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing a heater 10 as an example of the disclosure. As shown in FIG. 1, the heater 10 includes a rod-shaped ceramic body 1 and a heating resistor 2.

The ceramic body 1 is a member for protecting the heating resistor 2. The ceramic body 1 has, for example, a rod shape such as a column shape or a prism shape. Further, the ceramic body 1 may have a rounded shape on the tip side. Here, the tip side means one when the ceramic body 1 is divided in half in the longitudinal direction, and the end on the tip side of the ceramic body 1 is the tip. The ceramic body 1 includes electrically insulating ceramics such as oxide ceramics, nitride ceramics, or carbide ceramics. Thereby, the heater 10 with high reliability at the time of rapid temperature rise can be provided.

In particular, the ceramic body 1 is preferably formed from silicon nitride ceramics. This is because silicon nitride ceramics is excellent in terms of high strength, high toughness, high insulating properties, and heat resistance. The ceramic body 1 having a silicon nitride ceramic is, for example, 3 to 12% by mass of a rare earth 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. Element oxide, 0.5 to 3% 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 to 5% by mass, and formed into a predetermined shape Then, it can be obtained by hot press firing at 1650 to 1780 ° C. The dimensions of the ceramic body 1 can be, for example, 20 to 50 mm in length. When the ceramic body 1 is cylindrical, the diameter can be 3 to 5 mm, for example.

The heating resistor 2 is a member that generates heat when an electric current flows. The heating resistor 2 is provided inside the ceramic body 1. Further, the heating resistor 2 is provided, for example, on the tip side of the ceramic body 1. As shown in FIG. 1, the heating resistor 2 includes a first straight portion 211 and a second straight portion 212 that face each other, and an arcuate portion 22 that connects one end of each of the first straight portion 211 and the second straight portion 212. Have. The first straight part 211 and the second straight part 212 are the first straight part 211 and the second straight part 212. The arcuate portion 22 has a top. Here, the top portion means a portion of the arc-shaped portion 22 that is closest to the tip of the ceramic body 1.

As the straight portion 21 and the arc-shaped portion 22, for example, a material mainly composed of a ceramic having a carbide, nitride, or silicide such as W, Mo, or Ti can be used. In the case where the ceramic body 1 has a silicon nitride ceramic, tungsten carbide (WC) is a conductive ceramic material among the above materials in that the difference in coefficient of thermal expansion from the ceramic body 1 is small and the heat resistance is high. As excellent. The straight portion 21 and the arc-shaped portion 22 may be integrally formed from the same material, or may be separately formed from different materials.

As a dimension of the heating resistor 2, for example, the length of the linear portion 21 can be set to 0.1 to 50 mm. Further, the inner length of the arc-shaped portion 22 can be 0.1 to 10 mm, and the outer length can be 0.2 to 12 mm. The dimensions of the heating resistor 2 can be, for example, the cross-sectional area of the straight portion 21 can be 0.01 to 5 mm ² and the cross-sectional area of the arc-shaped portion 22 can be 0.01 to 5 mm ² . Further, the linear portion 21 may have a larger cross-sectional area than the arc-shaped portion 22. Thereby, the resistance value per unit length of the linear portion 21 can be made lower than that of the arc-shaped portion 22. For this reason, the amount of heat generated in the straight portion 21 can be suppressed.

Further, the first straight portion 211 and the second straight portion 212 may be connected to the lead 3 at the other end. One end of the lead 3 is connected to the other end of the linear portion 21, and the other end is drawn out to the side surface on the rear end side of the ceramic body 1 or the rear end of the ceramic body 1. Here, the rear end side means the other when the ceramic body 1 is divided in half in the longitudinal direction, and the end of the ceramic body 1 on the rear end side is defined as the rear end. The lead 3 is formed using the same material as the heating resistor 2. For example, the lead 3 has a larger cross-sectional area than the heating resistor 2, and the content of the forming material of the ceramic body 1 is less than that of the heating resistor 2. By doing so, the resistance value per unit length may be low.

As the material of the lead 3, WC can be used in that the difference in coefficient of thermal expansion from the ceramic body 1 is small, the heat resistance is high, and the specific resistance is small. Furthermore, the lead 3 is preferably composed mainly of WC that is an inorganic conductor, and silicon nitride is added to the lead 3 so that the content is 15 mass% or more. Thereby, the thermal expansion coefficient of the lead 3 can be brought close to the thermal expansion coefficient of the silicon nitride constituting the ceramic body 1. Further, when the content of silicon nitride is 40% by mass or less, the resistance value of the lead 3 is reduced and stabilized. Therefore, the silicon nitride content is preferably 15% by mass to 40% by mass. More preferably, the silicon nitride content is 20 mass% to 35 mass%.

In the heater 10 of the present disclosure, when the cross section perpendicular to the extending direction of the folded portion 22 is viewed at the top of the arc-shaped portion 22, the cross-sectional shape of the arc-shaped portion 22 is a shape having a major axis and a minor axis. The short axis is inclined with respect to the plane including the respective axes of the first straight portion 211 and the second straight portion 212. In other words, in the heater 10 of the present disclosure, when the first cross section passing through the top and perpendicular to the axial direction of the arc-shaped portion 22 is viewed, the arc-shaped portion 22 has a major axis and a minor axis, and the major axis and the minor axis are It inclines with respect to the plane containing each axis | shaft of the 1st linear part 211 and the 2nd linear part 212. FIG. For example, in the heater 10 shown in FIG. 2, the long axis when the top of the arc-shaped portion 22 is viewed in a cross section perpendicular to the extending direction of the arc-shaped portion 22 (cross section taken along line XX shown in FIG. 2A). Further, the minor axis is inclined with respect to a plane (AA line shown in FIG. 2B) including the respective axes of the first linear portion 211 and the second linear portion 212.

When the cross-sectional shape of the top portion of the arc-shaped portion 22 is a shape having a major axis and a minor axis, the portion of the ceramic body 1 that is in contact with the major axis is the portion that is farthest from the minor axis, and the short portion of the ceramic body 1 is short. The part in contact with the axis is the part farthest from the long axis. Therefore, under the heat cycle, the amount of thermal expansion on the major axis and the minor axis tends to be larger than the vicinity of the major axis and the minor axis. Thereby, in the vicinity of the major axis and minor axis of the ceramic body 1, thermal stress tends to be easily generated.

According to the heater 10 of the present disclosure, when the first cross section is viewed, the major axis and the minor axis are inclined with respect to the plane including the respective axes of the first linear portion 211 and the second linear portion 212. Thereby, the axial directions of the major axis and the minor axis of the top of the arc-shaped part 22 can be shifted with respect to the plane including the axes of the first linear part 211 and the second linear part 212. Therefore, it is possible to reduce the possibility of thermal stress concentrating on the ceramic body 1 on the plane including the respective axes of the first straight portion 211 and the second straight portion 212. Thereby, it is possible to reduce the possibility of cracks occurring in the ceramic body 1 on the plane including the respective axes of the first straight portion 211 and the second straight portion 212. As a result, the durability of the heater 10 can be improved. Specifically, the major axis of the apex is inclined by, for example, about 0.1 to 30 degrees with respect to the plane including the respective axes of the linear portions 21, and the minor axis of the apex is set to each of the linear portions 21. For example, it may be inclined by about 0.1 to 30 degrees with respect to the plane including the axis.

Further, as shown in FIG. 2B, the cross-sectional shape at the top of the arcuate portion 22 may be elliptical. Thereby, the surface of the top part of the arc-shaped part 22 can be made smooth. Therefore, in the heat cycle, the thermal stress generated in the vicinity of the major axis and the minor axis of the top portion of the ceramic body 1 can be dispersed. Thereby, the possibility that thermal stress concentrates on the ceramic body 1 in the vicinity of the major axis and minor axis of the top can be reduced. Therefore, it is possible to reduce the possibility of cracks occurring in the ceramic body 1 in the vicinity of the major axis and the minor axis at the top. As a result, the long-term reliability of the heater 10 can be improved.

Further, the shape having the major axis and the minor axis is not limited to the elliptical shape as shown in FIG. For example, as shown in FIG. 3 (a), two ellipses having the same length of either the long axis or the short axis are divided in half by the same length, and the axes are overlapped. The shape may be different. In this case, the axis of the semicircle and the axis perpendicular to the axis of the semicircle can be a major axis or a minor axis, respectively.

Further, as shown in FIG. 3B, the cross-sectional shape may be a shape having a recess in a part of the ellipse. In this case, the major axis and the minor axis of the ellipse having the smallest area among the ellipses circumscribing a shape having a depression in a part of the ellipse can be set as the major axis and the minor axis, respectively. Thus, when there is a dent on the outer peripheral surface of the top of the arcuate portion 22, the thermal stress generated in the vicinity of the dent in the ceramic body 1 can be distributed to both side portions forming the dent. Therefore, the possibility that thermal stress concentrates on a part of the ceramic body 1 can be reduced. As a result, the long-term reliability of the heater 10 can be improved. In the cross-sectional shape, there may be a plurality of dents. When the cross-sectional shape of the top is a shape with a dent in a part of the ellipse, for example, when compared with an elliptical shape without a dent, it is recessed by about 0.05 to 0.5 mm toward the center of the ellipse. It only has to be.

Further, as shown in FIG. 4, when a cross section perpendicular to the extending direction of the arc-shaped portion 22 is viewed at a portion other than the top of the arc-shaped portion 22, the cross-sectional shape of the arc-shaped portion 22 is a shape having a major axis and a minor axis. In addition, the long axis and the short axis may be inclined with respect to a plane including the respective axes of the first straight line portion 211 and the second straight line portion 212. In other words, the heater 10 has a major axis and a minor axis when the second cross section passing through a portion other than the top of the arc-shaped portion 22 and perpendicular to the axial direction of the arc-shaped portion 22 has a major axis and a minor axis. The minor axis may be inclined with respect to a plane including the respective axes of the first straight line portion 211 and the second straight line portion 212. For example, in the heater 10 shown in FIG. 4, when a portion other than the top of the arc-shaped portion 22 is viewed in a cross section perpendicular to the extending direction of the arc-shaped portion 22 (cross section taken along line YY shown in FIG. 4A). The major axis and the minor axis are inclined with respect to a plane (AA line shown in FIG. 4B) including the respective axes of the first linear portion 211 and the second linear portion 212.

Thereby, the axial directions of the long axis and the short axis in the portion other than the top of the arc-shaped portion 22 can be shifted with respect to the plane including the respective axes of the first straight portion 211 and the second straight portion 212. Therefore, under the heat cycle, the vicinity of the major axis and the minor axis, which are parts where the thermal stress is likely to occur, in the ceramic body 1 with respect to the plane including the respective axes of the first linear portion 211 and the second linear portion 212. Can be shifted. Therefore, it is possible to reduce the risk of thermal stress concentrating on the plane including the respective axes of the first straight portion 211 and the second straight portion 212 in the ceramic body 1. As a result, the durability of the heater 10 can be further improved. Specifically, the major axis of the part other than the top part is inclined by, for example, about 0.1 to 30 degrees with respect to the plane including the respective axes of the linear part 21, and the minor axis of the part other than the top part is What is necessary is just to incline about 0.1 to 30 degree | times with respect to the plane containing each axis | shaft of the linear part 21, for example.

In addition, in FIG.4 (b), in order to help an understanding, the ceramic body 1 is abbreviate | omitted and only sectional drawing of the arc-shaped part 22 is shown. 5, 6, and 7, which will be described later, similarly, the ceramic body 1 is omitted and only a cross-sectional view of the arc-shaped portion 22 is shown.

Further, as shown in FIG. 5, the inclination of the short axis at the top of the arcuate part 22 may be larger than the inclination of the short axis at a part other than the top of the arcuate part 22. Thereby, the major axis and minor axis of the top part of the arcuate part 22 and the major axis and minor axis of parts other than the apex part of the arcuate part 22 do not intersect when viewed in three dimensions on the respective extension lines. Can do. Therefore, it is possible to disperse portions of the ceramic body 1 where thermal stress is likely to occur. As a result, the durability of the heater 10 can be further improved. Specifically, the short axis of the top portion is inclined by, for example, about 2 to 30 degrees with respect to the plane including the respective axes of the straight portion 21, and the short axis of the portion other than the top portion is set to each of the straight portion 21. For example, it may be inclined by about 0.1 to 5 degrees with respect to the plane including the axis.

Further, the cross-sectional area may be constant in the arc-shaped portion 22. Specifically, when the respective cross sections when the arc-shaped portion 22 is divided into four equal parts perpendicular to the extending direction of the arc-shaped portion 22 using CT or the like, the difference between the respective cross-sectional areas and the cross-sectional area of the top portion are obtained. However, if it is in the range of 5% of the cross-sectional area of the top part, it can be considered that the cross-sectional area of the arc-shaped part 22 is constant. Since the cross-sectional area of the arc-shaped part 22 is constant, the possibility that the resistance value per unit length varies in the entire arc-shaped part 22 due to the cross-sectional area can be reduced. Therefore, the calorific value in the whole arcuate part 22 can be made constant. As a result, the heat uniformity of the heater 10 can be improved.

In addition, as shown in FIG. 6, the arc-shaped portion 22 may have a smaller cross-sectional area at the top than at portions other than the top. In other words, the arcuate portion 22 may have a smaller cross-sectional area in the first cross section than in the second cross section. Thereby, compared with the case where the whole cross-sectional area of the arc-shaped part 22 is constant, the amount of thermal expansion of the top part of the arc-shaped part 22 under a heat cycle can be reduced while improving the durability of parts other than the top part. it can. Therefore, thermal stress generated in the ceramic body 1 in the vicinity of the top of the arc-shaped portion 22 can be reduced. Thereby, in the vicinity of the top portion of the arc-shaped portion 22, it is possible to reduce the possibility of cracks occurring in the ceramic body 1. As a result, the durability of the heater 10 can be improved. In this case, the cross-sectional area of the top of the arcuate portion 22 can be 0.01 to 2 mm ² , and the cross-sectional area of the portion other than the top can be 0.03 to 5 mm ² . In addition, the arc-shaped part 22 may have the smallest cross-sectional area at the top, or may continuously have a small cross-sectional area near the top.

In addition, as shown in FIG. 7, the arc-shaped portion 22 may have a larger cross-sectional area at the top than at a portion other than the top. In other words, the arcuate portion 22 may have a larger cross-sectional area in the first cross section than in the second cross section. Thereby, compared with the case where the whole cross-sectional area of the arc-shaped part 22 is constant, durability of the top part of the arc-shaped part 22 can be improved, raising the emitted-heat amount of the arc-shaped part 22 whole. Therefore, it is possible to reduce the possibility of cracks occurring at the top of the arc-shaped portion 22 under a heat cycle. As a result, the durability of the heater 10 can be improved. In this case, the cross-sectional area of the top of the arcuate portion 22 can be 0.03 to 5 mm ² , and the cross-sectional area of the portion other than the top can be 0.01 to 2 mm ² . In addition, the arc-shaped part 22 may have the largest cross-sectional area in the top part, and the cross-sectional area may become large continuously in the vicinity of the top part.

As shown in FIG. 8, the glow plug 100 is the heater 10 described above, and includes the heater 10 and the metal cylinder 4 that covers the ceramic body 1. According to the glow plug 100, since the above-described heater 10 is used, the durability of the heater 10 can be improved, so that the durability can be improved.

The metal cylinder 4 is a metal cylinder that holds the heater 10. For example, the metal cylinder 4 is joined to one lead 3 drawn out to the side surface of the ceramic body 1 with a brazing material or the like and electrically connected thereto. The glow plug 100 is used by connecting external electrodes to the metal cylinder 4 and the other lead 3.

1: Ceramic body 2: Heating resistor 21: Linear portion 211: First linear portion 212: Second linear portion 22: Arc-shaped portion 3: Lead 4: Metal cylinder 10: Heater 100: Glow plug

Claims

A rod-shaped ceramic body, and a heating resistor provided inside the ceramic body,
The heating resistor includes a first straight portion, a second straight portion facing the first straight portion, an arc-shaped portion having a top and connecting the first straight portion and the second straight portion,
When looking at the first cross section passing through the top and perpendicular to the axial direction of the arcuate portion,
The arcuate portion has a major axis and a minor axis, and the major axis and the minor axis are inclined with respect to a plane including the respective axes of the first linear portion and the second linear portion.
When looking at a second cross section perpendicular to the axial direction of the arcuate part through the part other than the top part of the arcuate part,
The arcuate portion has a major axis and a minor axis, and the major axis and the minor axis are inclined with respect to a plane including the respective axes of the first linear portion and the second linear portion. Heater.
The heater according to claim 2, wherein the inclination of the short axis in the first cross section is larger than the inclination of the short axis in the second cross section.
The heater according to any one of claims 1 to 3, wherein the arc-shaped portion has a constant cross-sectional area.
The heater according to any one of claims 1 to 3, wherein the arcuate portion has a smaller cross-sectional area in the first cross section than in the second cross section.
The heater according to any one of claims 1 to 3, wherein the arc-shaped portion has a larger cross-sectional area in the first cross section than in the second cross section.
The heater according to any one of claims 1 to 6, wherein the first cross section is elliptical.
The heater according to any one of claims 1 to 6, wherein the top surface has a recess.
A heater according to any one of claims 1 to 8,
A glow plug comprising a metal tube covering the heater.