JP2017004613A - heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the residual stress while increasing the bonding strength between an electrode layer and a lead terminal.SOLUTION: A heater 10 of the present invention includes a ceramic body 1, a heating resistor 2 provided inside the ceramic body 1, an electrode layer 3 provided on the surface of the ceramic body 1 and connected to the heating resistor 2, and a lead terminal 4 bonded to the electrode layer 3 with a bonding material 5. The lead terminal 4 includes a first portion 41 rising from the electrode layer 3 and a second portion 42 extending along the longitudinal direction of the ceramic body 1. The bonding material 5 includes a meniscus portion 50 for bonding the electrode layer 3 to the first portion 41, and a coating portion 51 having a constant thickness and spreading from the meniscus portion 50 to a side of the second portion 42.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heater used for a liquid heating heater, a powder heating heater, a gas heating heater, an oxygen sensor heater, and the like.

  As a heater used in a liquid heating heater, a powder heating heater, a gas heating heater, an oxygen sensor heater, and the like, for example, a heater disclosed in Patent Document 1 is known. The heater device disclosed in Patent Document 1 includes a ceramic body in which a heating resistor is embedded, an electrode pad provided on the surface of the ceramic body, and a terminal member joined to the electrode pad.

JP 2011-60712 A

  The heater device disclosed in Patent Document 1 is provided such that the terminal member rises from the ceramic body. The terminal member is joined to the electrode pad by a brazing material. In the heater device having such a configuration, although it is easy to improve the bonding strength against vibration in the direction perpendicular to the length direction of the ceramic body, the bonding is performed against vibration in a direction parallel to the length direction of the ceramic body. It was difficult to improve the strength.

  In order to improve the bonding strength, a method of increasing the amount of brazing material applied to the terminal member is conceivable. However, if the amount of brazing material applied simply to the terminal member is increased, the bonding strength against vibration can be increased, but high residual stress may be generated in the brazing material. For this reason, there is a risk that cracks or the like may occur in the brazing material or the like located between the ceramic body and the electrode pad or between the electrode pad and the lead terminal. As a result, it has been difficult to improve the long-term reliability of the heater.

  The present invention has been made in view of such problems, and an object thereof is to reduce the residual stress generated in the heater while increasing the bonding strength between the electrode layer (electrode pad) and the lead terminal (terminal member) in the heater. is there.

  The heater according to one aspect of the present invention includes a rod-shaped or cylindrical ceramic body, a heating resistor provided inside the ceramic body, and an electrode provided on a surface of the ceramic body and connected to the heating resistor. A lead terminal joined to the electrode layer by a joining material, the lead terminal rising from the electrode layer, and a second part extending along the length direction of the ceramic body. The bonding material has a meniscus portion for bonding the electrode layer and the first portion, and a coating portion having a constant thickness extending from the meniscus portion to the second portion side. It is characterized by.

  According to the heater of one aspect of the present invention, the residual stress generated in the heater can be reduced while increasing the bonding strength between the electrode layer and the lead terminal in the heater.

It is a longitudinal cross-sectional view which shows one Embodiment of the heater of this invention. FIG. 2 is an enlarged sectional view showing the vicinity of a lead terminal in FIG. 1.

  The heater 10 according to an embodiment of the present invention will be described in detail.

  FIG. 1 is a longitudinal sectional view showing an example of an embodiment of a heater 10 of the present invention. As shown in FIG. 1, the heater 10 includes a rod-shaped or cylindrical ceramic body 1, a heating resistor 2 provided inside the ceramic body 1, and an electrode layer 3 provided on the surface of the ceramic body 1. And a lead terminal 4 joined to the electrode layer 3.

  The ceramic body 1 is a member provided to protect the heating resistor 2. The shape of the ceramic body 1 is rod-shaped or cylindrical. Examples of the rod shape include a column shape such as a column shape or a prism shape. In addition, the column shape here includes, for example, a plate shape extending long in a specific direction. Examples of the cylindrical shape include a cylindrical shape and a rectangular tube shape. In the heater 10 shown in FIG. 1, the ceramic body 1 has a cylindrical shape.

  The ceramic body 1 is made of an insulating ceramic material. Examples of the insulating ceramic material include alumina, silicon nitride, and aluminum nitride. From the viewpoint of excellent thermal conductivity, it is preferable to use aluminum nitride. In particular, when aluminum nitride is used, the thermal conductivity of the ceramic body 1 can be increased to 150 W / (m · K), so the heat generated by the heating resistor 2 formed inside the ceramic body 1 Can communicate efficiently to the surface. Accordingly, the heater 10 can be rapidly heated.

  From the viewpoint of ease of production, it is preferable to use alumina. When the ceramic body 1 is cylindrical, the dimensions of the ceramic body 1 can be set, for example, to a length of 100 mm and an outer diameter of 20 mm. When the ceramic body 1 is plate-shaped, the dimensions of the ceramic body 1 can be set, for example, to a length of 80 mm, a width of 50 mm, and a thickness of 2 mm. When the ceramic body 1 is cylindrical, the dimensions of the ceramic body 1 can be set, for example, to a length of 100 mm, an outer diameter of 20 mm, and an inner diameter of 14 mm.

  The heating resistor 2 is a resistor that generates heat when a current flows. The heating resistor 2 is provided inside the ceramic body 1. That is, the heating resistor 2 is embedded in the ceramic body 1. The heating resistor 2 in the heater 10 of the present embodiment has a folded shape. Both ends of the heating resistor 2 are connected to the extraction electrode 21. The extraction electrode 21 is extracted to one end portion of the ceramic body 1, and is extracted to the outer peripheral surface of the ceramic body 1 at the end portion.

  A folded portion of the heating resistor 2 is provided at the other end of the ceramic body 1. That is, the extraction electrode 21 is provided in a region of the ceramic body 1 opposite to the folded portion of the heating resistor 2. Both ends of the heating resistor 2 are electrically connected to the electrode layer 3 provided on the outer peripheral surface of the ceramic body 1 through the extraction electrode 21.

  The heating resistor 2 is made of a metal material. Examples of the metal material include tungsten, molybdenum, rhenium, and the like. The dimensions of the heating resistor 2 can be set, for example, to a width of 1 mm, a total length of 3000 mm, and a thickness of 0.02 mm. The extraction electrode 21 can be formed simultaneously with the heating resistor 2 by using the same metal material as that of the heating resistor 2. The extraction electrode 21 can also be formed separately using a material different from that of the heating resistor 2.

  The electrode layer 3 is provided on the surface of the ceramic body 1. The electrode layer 3 is connected to the heating resistor 2 via the extraction electrode 21. The electrode layer 3 is made of a metal material. Examples of the metal material include tungsten, molybdenum, rhenium, and the like. The dimensions of the electrode layer 3 can be set, for example, to a length of 9 mm, a width of 5 mm, and a thickness of 0.02 mm. In the present embodiment, the electrode layer 3 is connected to the heating resistor 2 via the extraction electrode 21, but the present invention is not limited to this. Specifically, the heater 10 does not have the extraction electrode 21, and the electrode layer 3 and the heating resistor 2 may be directly connected.

  The lead terminal 4 is a member for supplying power to the heating resistor 2. The lead terminal 4 is used by being connected to an external power source (not shown). As the lead terminal 4, a wire or plate made of nickel or copper metal can be used. The lead terminal 4 can be attached on the surface of the electrode layer 3 using the bonding material 5. As the bonding material 5, for example, a brazing material can be used.

  The lead terminal 4 includes a first portion 41 rising from the electrode layer 3, a second portion 42 extending along the length direction from the outer periphery to the outside of the ceramic body 1, and the second portion 42 via the outer side. A curved portion 43 that connects the first portion 41 and the second portion 42 is provided. Thereby, when a vibration is generated in a direction parallel to the length direction of the ceramic body 1, the bending portion 43 bends, whereby this vibration can be reduced. For this reason, the stress which arises in the junction part of the 1st part 41 and the electrode layer 3 can be reduced. As a result, the strength against vibration in a direction parallel to the length direction of the ceramic body 1 can be improved.

  In the present embodiment, the cross section of the lead terminal 4 (the cross section of the first portion 41, the second portion 42, and the curved portion 43) is circular. In particular, since the cross section of the bending portion 43 is circular, the possibility that the bending portion 43 is damaged when the bending portion 43 is bent can be reduced. Examples of other shapes of the cross section of the lead terminal 4 include a rectangular shape, a U-shape, and a hollow shape. In particular, when the cross-sectional shape of the curved portion 43 is a U-shape, the open side of the U-shape is located on the side opposite to the ceramic body 1 (that is, the outer peripheral side of the curved portion 43). Preferably it is. Thereby, the bending part 43 can be made easy to bend. In addition, as a U-shape here, the case where a corner is round like a so-called C shape etc. is included, for example.

  Moreover, in this embodiment, although the shape and magnitude | size of the cross section of the 1st part 41, the 2nd part 42, and the curved part 43 are the same among the lead terminals 4, it is not restricted to this. Specifically, the shape and size of each part may be different. In particular, the curved portion 43 is preferably thinner than the first portion 41 and the second portion 42. Thereby, the bending part 43 can be easily bent while ensuring the strength of the lead terminal 4.

  The dimension of the lead terminal 4 can be set as follows, for example. In the case of the heater 10 shown in FIG. 1, the length of the first portion 41 can be set to 2.3 mm. The length of the second portion 42 can be set to 1.5 mm in the direction perpendicular to the length direction of the ceramic body 1 and 2.5 mm in the direction parallel to the length direction of the ceramic body 1. . Further, the length of the bending portion 43 can be set to 6.5 mm. Moreover, each cross section of the 1st part 41, the 2nd part 42, and the curved part 43 can be set to the circular shape whose diameter is (phi) 0.8mm.

  As shown in FIG. 2, in the heater 10 of the present embodiment, the bonding material 5 spreads from the meniscus portion 50 to the second portion 42 side, which joins the electrode layer 3 and the first portion 41. And a coating portion 51 having a constant thickness. More specifically, the coating portion 51 extends from the end portion of the meniscus portion 50 toward the second portion 42 with a constant thickness. Thereby, compared with the case where only the meniscus portion 50 is simply formed by the bonding material 5, the bonding material 5 can be provided over a wide range of the first portion 41 with a small amount of the bonding material 5. Thereby, generation | occurrence | production of a residual stress can be reduced, raising the joining strength of the 1st part 41 and the electrode layer 3. FIG. As a result, the long-term reliability of the heater 10 can be improved while ensuring the bonding strength.

  The meniscus part 50 here is a part having a meniscus shape and a thickness that decreases toward the tip. The coating portion 51 is a portion having a constant thickness provided adjacent to the meniscus portion 50. That is, when the bonding material 5 is viewed, the portion of the meniscus portion 50 that is wet and spreads in the first portion 41 and continues to decrease in thickness is the meniscus portion 50, and the second thickness is further kept constant from the end portion of the meniscus portion 50. The portion wetted and spread on the portion 42 side is the coating portion 51. In addition, the 2nd part 42 side here means only the direction approaching the 2nd part 42 seeing from the edge part of the meniscus part 50. FIG. That is, the bonding material 5 (coating part 51) does not necessarily have to extend to the second portion 42.

  In addition, the terms “thickness continues to decrease” and “thickness is constant” as used herein do not need to be “thickness continues to decrease” and “thickness is constant” in a strict sense. Specifically, an error of a fine bubble level generated on the surface of the bonding material 5 can be ignored.

  Examples of the method for forming the coating portion 51 include the following methods. Specifically, when the bonding material 5 is made of a brazing material, a sheet-like brazing material or the like is wound around a portion where the coating portion 51 is formed, separately from the brazing material for forming the meniscus portion 50. What is necessary is just to heat. At this time, a flux composed of an organic acid such as carboxylic acid and an activator is applied to a portion of the first portion 41 where the coating portion 51 is to be formed, and a sheet-like brazing material is wound around. Thereby, since it can reduce that the sheet-like brazing material wound around the part which wants to form the coating part 51 flows, the coating part 51 can be formed easily.

  Moreover, the part in which the coating part 51 is provided may be longer than the part in which the meniscus part 50 is provided in the first part 41. As a result, most (at least half or more) of the portion of the first portion 41 that is covered with the bonding material 5 is covered with the coating portion 50, thereby further reducing the occurrence of residual stress while increasing the bonding strength. it can.

  Further, the coating part 51 may cover a part of the bending part 43. Since the bonding material 5 covers a part of the curved portion 43, the bonding strength against forces from various directions can be improved. This is because when the coating portion 51 is spread only in the first portion 41 and spreads over the entire circumference of the first portion, the coating portion 51 spreads in a cylindrical shape having a linear central axis. Become. Here, when the coating part 51 spreads also to a part of the curved part 41, the coating part 51 will spread in the cylinder shape extended in the shape of a curve in the direction different from this linear center axis | shaft mentioned above. . Thereby, since the coating part 51 has the cylindrical part on the curve extended in the direction different from a linear center axis | shaft, the intensity | strength with respect to the force from various directions can be improved. In the above example, in order to help understanding, the example in which the coating portion 51 is provided on the entire circumference of the first portion 41 has been described, but the present invention is not limited thereto. Specifically, the coating part 51 may be provided partially.

Moreover, the part by which the coating part 51 is provided in the inner peripheral side rather than the outer peripheral side among the curved parts 43 may become long. When external vibration is transmitted to the lead terminal 4, the bending portion 43 is likely to vibrate so as to bend. Therefore, in the bonding material 5, stress tends to concentrate particularly on the inner peripheral side rather than the outer peripheral side of the curved portion 43. On the other hand, since the coating 51 is spread toward the inner peripheral side of the curved portion 43, the stress generated by the vibration can be absorbed by a wide range of the bonding material 5 (meniscus portion 50 and coating portion 51). 50 can reduce the occurrence of cracks.

1: Ceramic body 2: Heating resistor 21: Lead electrode 3: Electrode layer 4: Lead terminal 41: First part 42: Second part 43: Curved part 5: Bonding material 50: Meniscus part 51: Coating part 10: Heater

Claims (4)

A rod-shaped or cylindrical ceramic body, a heating resistor provided inside the ceramic body, an electrode layer provided on the surface of the ceramic body and connected to the heating resistor, and a bonding material to the electrode layer With lead terminals joined at
The lead terminal includes a first portion rising from the electrode layer, and a second portion extending along the length direction of the ceramic body,
The bonding material includes a meniscus portion for bonding the electrode layer and the first portion, and a coating portion having a constant thickness extending from the meniscus portion to the second portion side. heater.   2. The heater according to claim 1, wherein a portion of the first portion where the coating portion is provided is longer than a portion where the meniscus portion is provided.   The lead terminal includes a curved portion that connects the first portion and the second portion, and the coating portion covers a part of the curved portion. Item 3. The heater according to Item 2.   The heater according to claim 3, wherein a portion where the coating portion is provided is longer on the inner peripheral side than on the outer peripheral side in the curved portion.

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