JP6951126B2 - Ceramic heater and glow plug - Google Patents

Description

The present invention relates to ceramic heaters and glow plugs.

Conventionally, as a ceramic heater used for glow plugs and the like, a ceramic heater in which a folded resistor made of a conductive ceramic is embedded inside a rod-shaped substrate made of an insulating ceramic is known (for example, Patent Document 1). reference).

In the ceramic heater of Patent Document 1, the ratio of the cross-sectional area of a part (small diameter portion) of the resistor configured as the heat generating portion to the cross-sectional area of the lead portion (large diameter portion) connected to both ends of the small diameter portion. By defining the above within a predetermined range, it is possible to raise the temperature rapidly while suppressing power consumption.

Japanese Unexamined Patent Publication No. 2006-24394

By the way, in the conventional ceramic heater including the ceramic heater of Patent Document 1, power consumption is suppressed by reducing the cross-sectional area of the heat-generating portion, and simply reducing the cross-sectional area of the heat-generating portion increases the strength of the heat-generating portion. There was a problem that it caused a decline. Moreover, if the cross-sectional area of the heat generating portion is reduced, the volume of the heat generating portion is reduced, so that more heat must be generated in order to bring the surface of the ceramic heater to the target temperature. As a result, the thermal stress increases, and defects (disconnection, etc.) due to the thermal stress are likely to occur, so that the energization durability may decrease.

The present invention has been made to solve at least a part of the above-mentioned problems, and an object of the present invention is to provide a ceramic heater or glow plug capable of suppressing power consumption and having durability. Is.

The ceramic heater, which is one of the solutions of the present invention, is
A substrate made of insulating ceramic that extends along the axial direction from the rear end side to the front end side,
A resistor made of a conductive ceramic and embedded in the substrate. It is connected to a pair of conductive portions arranged on the rear end side of the substrate and extending along the axial direction, and connected to the pair of conductive portions. A resistor having a heat generating portion that generates heat when energized from the conductive portion is provided.
The heat generating portion has a first resistance portion whose rear end side is connected to the tip end side of one of the conductive portions and which extends from one of the conductive portions to the tip end side of the substrate, and the rear end side of itself is the other. A second resistance portion that is connected to the tip end side of the conductive portion and extends from the other conductive portion to the tip end side of the substrate, and a connecting portion that connects the first resistance portion and the tip end side of the second resistance portion. It is a ceramic heater equipped with
At least one of the first resistance portion and the second resistance portion has a proximal resistance portion extending in a predetermined direction and a direction different from the proximal resistance portion on the distal end side of the proximal resistance portion. A tip-side resistance portion extending to and a bending portion for connecting the base-end-side resistance portion and the tip-end-side resistance portion are formed.
The bent portion is located in a predetermined cross section of the ceramic heater, passing through a high temperature region having a surface having a temperature of 96% or more with respect to the maximum heat generation temperature of the surface, and orthogonal to the axial direction.

Since the ceramic heater has a bent portion formed in at least one of the first resistance portion and the second resistance portion, the current density in the vicinity of the bent portion can be locally increased in the heat generating portion. Moreover, the bent portion is located in a predetermined cross section of the ceramic heater, which passes through a high temperature region having a surface having a temperature of 96% or more with respect to the maximum heat generation temperature of the surface and is orthogonal to the axial direction. That is, the current density can be increased in the vicinity of the high temperature region of the ceramic heater, and the heat generation can be further increased in the high temperature region. Therefore, the temperature tends to rise more rapidly on the surface of the high temperature region, and the power consumption required to bring the surface temperature of the ceramic heater to the target temperature is suppressed. Moreover, since the above-mentioned effect can be produced without significantly reducing the cross-sectional area of the heat generating portion, it is unlikely that the durability will be lowered.

In the ceramic heater, the bent portion may be formed in the first resistance portion and the second resistance portion, respectively. Then, both the bent portions of the first resistance portion and the second resistance portion may be located in a predetermined cross section that passes through the high temperature region and is orthogonal to the axial direction.
Since the current density of this ceramic heater can be increased in each of the first resistance portion and the second resistance portion, the power consumption required to bring the surface temperature of the ceramic heater to the target temperature can be further suppressed. Moreover, since the above-mentioned effect can be produced without significantly reducing the cross-sectional areas of the first resistance portion and the second resistance portion, the durability is less likely to be lowered.
In addition, since this ceramic heater can increase the current density in each of the first resistance portion and the second resistance portion, the heat is equalized in the opposite direction in which the first resistance portion and the second resistance portion face each other. Be done.

In the ceramic heater, both the bent portions of the first resistance portion and the second resistance portion may be located in the same cross section that passes through the high temperature region and is orthogonal to the axial direction.
In this ceramic heater, both the bent portions of the first resistance portion and the second resistance portion are located in the same cross section orthogonal to the axial direction, so that the first resistance portion and the second resistance portion face each other in the opposite direction. Heat generation can be more concentrated in the vicinity of a predetermined position in the axial direction (near the same cross section) while trying to equalize the heat.

In the ceramic heater, the shortest distance between the surface of the substrate and the heat generating portion may be 0.2 mm or more.
This ceramic heater suppresses power consumption in a form that suppresses deterioration of durability, and secures a distance between the surface of the substrate and the heat generating part, so that the heat generating part is less likely to be exposed to the outside air and is resistant to corrosion. Can be enhanced.

In the ceramic heater, the tip end side resistance portion is inclined to one side in the vertical direction orthogonal to the axial direction and the opposite direction in which the first resistance portion and the second resistance portion face each other with respect to the base end side resistance portion. May be done.
If the tip side resistance part is inclined to one side of the opposite direction in which the first resistance part and the second resistance part face each other and the direction orthogonal to the axial direction (vertical direction), the bending angle (base end) of the bending part It is easy to increase the inclination angle of the tip side resistance part with respect to the side resistance part).

In the ceramic heater, the tip end side resistance portion may be configured to be inclined to one side in the opposite direction in which the first resistance portion and the second resistance portion face each other with respect to the base end side resistance portion.
If the tip side resistance portion is configured to be inclined to one side in the facing direction, the heat generating portion will not be bulky in the axial direction and the vertical direction orthogonal to the facing direction, and the tip side resistance portion will be bulky in the orthogonal direction. Since it is possible to reduce the labor or burden in manufacturing, it is an advantageous configuration in manufacturing a ceramic heater.

In the ceramic heater, the pair of conductive portions and the heat generating portion may be formed of the same material in the resistor, or the heat generating portion and the pair of conductive portions may be formed of different materials. When the pair of conductive parts and the heat generating part of the resistor are made of the same material, the part having a relatively small diameter on the tip side of the resistor is referred to as the "heating part", and the part having a relatively large diameter is defined as the "heat generating part". It can be a "conductive part". When the heat generating portion and the pair of conductive portions are made of different materials, the portion of the material on the tip end side of the resistor, that is, the portion of the material different from the base end side is referred to as the "heating portion" of the resistor. The portion of the material on the proximal end side can be the "conductive portion".

A glow plug according to another solution of the present invention is a glow plug including a ceramic heater and a metal fitting for holding the ceramic heater, and the ceramic heater includes any of the above ceramic heaters.
Since the glow plug also includes the ceramic heater described above, the power consumption required to bring the surface temperature of the ceramic heater to the target temperature can be suppressed. Moreover, since the above-mentioned effect can be produced without significantly reducing the cross-sectional area of the heat generating portion, it is unlikely that the durability will be lowered.

According to the present invention, it is possible to realize a ceramic heater or glow plug capable of suppressing power consumption and improving temperature rising performance.

It is sectional drawing which shows an example of the glow plug of 1st Embodiment. FIG. 5 is an enlarged cross-sectional view showing an enlarged portion of the glow plug of the first embodiment including the ceramic heater of the first aspect. FIG. 5 is an enlarged cross-sectional view showing a part of the ceramic heater shown in FIG. 2 in an enlarged manner. FIG. 4A is a side view partially showing the heat generating resistor in the ceramic heater of the first aspect, and FIG. 4B is a side view seen from a direction different from that of FIG. 4A. .. It is an enlarged cross-sectional view which shows the part of the ceramic heater of the 2nd aspect enlarged. It is a side view which partially shows the heat generation resistor in the ceramic heater of the 2nd aspect.

A. First Embodiment A1. Configuration of Glow Plugs FIG. 1 is a schematic view showing an example of glow plugs of the first embodiment. FIG. 2 is an enlarged cross-sectional view showing a portion of the glow plug 1 shown in FIG. 1 including a ceramic heater 40. The line CL illustrated in FIGS. 1 and 2 indicates the central axis of the glow plug 1. The cross section shown in FIG. 1 is a cross section including the central axis CL, and the resistor 120 is omitted. The cross section shown in FIG. 2 shows a cut surface cut along the resistor 120. In FIG. 2, the cross section on the rear end side of the bent portions 132 and 133 (described later) is a cross section including the central axis CL of the glow plug 1, and is the central axis of the first conductive portion 122 and the second conductive portion 123. The cross section is in the plane direction passing through the central axes of the base end side resistance portions 134A and 135A. In FIG. 2, the cross section on the tip side of the bent portions 132 and 133 is a cross section including the central axes C1 and C2 (FIG. 4) of the tip side resistance portions 134B and 135B, and passes through the central axes C1 and C2. It has a cross section in the plane direction.

Hereinafter, the central axis CL is also referred to as "axis CL", and the direction parallel to the central axis CL is also referred to as "axis direction". The radial direction of the circle centered on the central axis CL is also simply referred to as the "diameter direction", and the circumferential direction of the circle centered on the central axis CL is also referred to as the "circumferential direction". Of the directions parallel to the central axis CL, the downward direction in FIG. 1 is called the first direction D1. The first direction D1 is a direction from the terminal member 80, which will be described later, toward the ceramic heater 40. The second direction D2 and the third direction D3 in the figure are directions perpendicular to each other, and both are directions perpendicular to the first direction D1. Hereinafter, the first direction D1 is also referred to as a tip direction D1, and the direction opposite to the first direction D1 is also referred to as a rear end direction D1r. Further, the front end direction D1 side in FIG. 1 is referred to as the front end side of the glow plug 1, and the rear end direction Dr1 side in FIG. 1 is referred to as the rear end side of the glow plug 1.

As shown in FIG. 1, the glow plug 1 includes a main metal fitting 20, a center pole 30, a ceramic heater 40, an O-ring 50, an insulating member 60, and a metal outer cylinder 70 (hereinafter, also simply referred to as “outer cylinder 70”). ), The terminal member 80, and the connecting member 90.

The main metal fitting 20 is a cylindrical member having a through hole 20A extending along the central axis CL. The main metal fitting 20 includes a tool engaging portion 28 formed at an end portion on the Dr1 side in the rear end direction, and a male screw portion 22 provided on the D1 side in the distal end direction with respect to the tool engaging portion 28. The tool engaging portion 28 is a portion that engages with a tool (not shown) when the glow plug 1 is attached or detached. The male screw portion 22 includes a screw thread for screwing into a female screw formed in a mounting hole of an internal combustion engine (not shown). The main metal fitting 20 is made of a conductive material (for example, a metal such as carbon steel).

The center pole 30 is housed in the through hole 20A of the main metal fitting 20. The center pole 30 is a round bar-shaped member. The center pole 30 is made of a conductive material (for example, stainless steel). The rear end portion 39, which is the end portion on the rear end direction Dr1 side of the center pole 30, projects from the opening 20B on the rear end direction Dr1 side of the main metal fitting 20 toward the rear end direction Dr1.

An O-ring 50 is provided between the outer surface of the center pole 30 and the inner surface of the through hole 20A of the main metal fitting 20 in the vicinity of the opening 20B. The O-ring 50 is made of an elastic material (for example, rubber). A ring-shaped insulating member 60 is attached to the opening 20B of the main metal fitting 20. The insulating member 60 includes a cylindrical portion 62 and a flange portion 68 provided on the Dr1 side in the rear end direction of the tubular portion 62. The tubular portion 62 is sandwiched between the outer surface of the center pole 30 and the inner surface of the portion forming the opening 20B of the main metal fitting 20. The insulating member 60 is made of, for example, a resin. The main metal fitting 20 supports the center pole 30 via the O-ring 50 and the insulating member 60.

The terminal member 80 is arranged on the Dr1 side in the rear end direction of the insulating member 60. The terminal member 80 is a cap-shaped member and is made of a conductive material (for example, a metal such as nickel). A flange portion 68 of the insulating member 60 is sandwiched between the terminal member 80 and the main metal fitting 20. The rear end 39 of the center pole 30 is inserted into the terminal member 80. By crimping the terminal member 80, the terminal member 80 is fixed to the rear end portion 39. With such a structure, the terminal member 80 and the center pole 30 are electrically connected.

The outer cylinder 70 is fixed to the opening 20C on the D1 side in the tip direction of the main metal fitting 20. The outer cylinder 70 is fixed to the opening 20C by, for example, press fitting or welding. The outer cylinder 70 is a tubular member having a through hole 70A extending along the central axis CL. The outer cylinder 70 is made of a conductive material (for example, stainless steel).

A ceramic heater 40 that generates heat when energized is inserted into the through hole 70A of the outer cylinder 70. The ceramic heater 40 is a rod-shaped member arranged so as to extend along the central axis CL. The outer cylinder 70 holds the outer peripheral surface of the central portion of the ceramic heater 40 in a state where the tip portion 41 of the ceramic heater 40 is exposed. The rear end 49 of the ceramic heater 40 is housed in the through hole 20A of the main metal fitting 20.

A connecting member 90 is fixed to the rear end 49 of the ceramic heater 40. The connecting member 90 is a cylindrical member having a through hole extending along the central axis CL, and is made of a conductive material (for example, stainless steel). The rear end 49 of the ceramic heater 40 is press-fitted on the D1 side of the connecting member 90 in the tip direction. A tip portion 31 which is an end portion of the center pole 30 on the tip end direction D1 side is press-fitted to the rear end direction Dr1 side of the connecting member 90. With such a structure, the center pole 30 and the connecting member 90 are electrically connected.

A2. Configuration of ceramic heater 40 (first aspect)
Next, the ceramic heater 40 of the first aspect will be described with reference to FIGS. 2 and 3. 2 and 3 show the details of the ceramic heater 40 of the first aspect. FIG. 2 is a cross-sectional view showing the metal outer cylinder 70, the connecting member 90, the ceramic heater 40, and the like in more detail. FIG. 3 is an enlarged cross-sectional view obtained by further enlarging a part of the cross-sectional view shown in FIG. 2 m.

As shown in FIG. 2, the ceramic heater 40 has a round bar-shaped base 110 extending from the rear end side to the front end side along a direction parallel to the axis CL (axis direction), and a substantially U-shape embedded inside the base 110. The heat generating resistor 120 (hereinafter, simply referred to as “resistor 120”) is included. The ceramic heater 40 is formed by firing the material.

The substrate 110 is made of an insulating ceramic material. In the present embodiment, the ceramic material forming the substrate 110 is mainly composed of _{silicon nitride (Si 3} N _4). In another embodiment, of the silicon nitride (Si ₃ N ₄ ) constituting the substrate 110, at least a part of silicon (Si) is replaced with aluminum (Al), and at least a part of nitrogen (N) is oxygen. It may be replaced with (O).

The resistor 120 is made of a conductive ceramic material. The conductive ceramic material forming the resistor 120 may be a conductive substance capable of generating heat by energization, and in this embodiment, a mixture of tungsten carbide (WC) and silicon nitride is used. As another embodiment, a mixture of molybdenum dissilicate (MoSi ₂ ) and silicon nitride or the like may be used.

The tip of the substrate 110 (that is, the tip 41 of the ceramic heater 40) is gradually tapered toward the tip. The electrical conductivity of the resistor 120 is higher than the electrical conductivity of the substrate 110. The resistor 120 generates heat when energized.

As shown in FIG. 2, the resistor 120 has a first conductive portion 122 and a second conductive portion 123 formed as two lead portions, and a heat generating portion connected to the first conductive portion 122 and the second conductive portion 123. 121 and electrode extraction portions 124 and 125 are included. The first conductive portion 122 and the second conductive portion 123 are a pair of conductive portions that are partially arranged on the rear end 110A side of the substrate 110 and extend along the axial direction from the rear end 110A side toward the tip 110B side. .. Each of the first conductive portion 122 and the second conductive portion 123 extends parallel to the axis CL from the rear end portion 49 of the ceramic heater 40 to the vicinity of the front end portion 41. The first conductive portion 122 and the second conductive portion 123 are arranged at positions substantially symmetrical with respect to the central axis CL. The direction from the first conductive portion 122 to the second conductive portion 123 is the third direction D3.

As shown in FIG. 3, the heat generating portion 121 is a portion that generates heat when energized from the conductive portion described above, and includes a first resistance portion 121A, a second resistance portion 121B, and a connecting portion 121C. The rear end side of the first resistance portion 121A is connected to the tip end side of one of the conductive portions (first conductive portion 122), and extends from the first conductive portion 122 to the tip end side of the substrate 110. The rear end side of the second resistance portion 121B is connected to the tip end side of the other conductive portion (second conductive portion 123), and extends from the second conductive portion 123 to the tip end side of the substrate 110. The connecting portion 121C has a configuration in which the tip ends of the first resistance portion 121A and the second resistance portion 121B are connected to each other. In the resistor 120, the heat generating portion 121 and the pair of conductive portions (first conductive portion 122 and second conductive portion 123) are formed of the same material. In the example shown in FIG. 3 and the like, the portion having a relatively small diameter on the tip side of the resistor 120 is the heat generating portion 121, and the portion having a relatively large diameter is a pair of conductive portions (first conductive portion 122 and second conductive portion 122). Conductive portion 123).

As shown in FIGS. 3 and 4, in the heat generating portion 121, bending portions 132 and 133 are formed in the first resistance portion 121A and the second resistance portion 121B, respectively. Note that FIG. 4A is a side view of the ceramic heater 40 (FIG. 3, etc.) viewed from one side in a predetermined direction (direction in which the first resistance portion 121A and the second resistance portion 121B face each other). Only the outer shape of the substrate 110 is shown by a virtual line of a two-dot chain line. That is, FIG. 4A is a view showing a side view of a part of the resistor 120 (FIG. 3 and the like) viewed from one side together with the outer shape (virtual line) of the substrate 110. FIG. 4B is a side view of the ceramic heater 40 (FIG. 3 etc.) viewed from the other side in a predetermined direction (the side opposite to FIG. 4A), and the substrate 110 is a virtual two-dot chain line. Only the outer shape is shown by a line. FIG. 4B is a view showing a side view of a part of the resistor 120 (FIG. 3 and the like) viewed from the other side in a predetermined direction together with the outer shape (virtual line) of the substrate 110.

As shown in FIG. 4A, the first resistance portion 121A has a proximal side resistance portion 134A extending in a predetermined direction and a direction different from that of the proximal end side resistance portion 134A on the distal end side of the proximal end side resistance portion 134A. It has an extending tip-side resistance portion 134B. Then, the bent portion 132 is formed in a form of connecting the proximal end side resistance portion 134A and the distal end side resistance portion 134B. In the examples of FIGS. 3 and 4 (A), the proximal end side resistance portion 134A is formed in an axial shape and extends linearly in parallel with the central axis CL of the glow plug 1 (FIG. 1). The tip-side resistance portion 134B is configured to have a shaft shape, and is configured to be inclined to one side in a predetermined "vertical direction" with respect to the tip-side resistance portion 134B. The "vertical direction" referred to here is a direction orthogonal to the opposite direction in which the first resistance portion 121A and the second resistance portion 121B face each other and orthogonal to the axial direction, and is the front end direction D1 and the rear end direction D1r. The direction is along. Further, the tip end side resistance portion 134B is inclined by an angle θ1 with respect to the axis of the base end side resistance portion 134A (in the first aspect, the axis parallel to the central axis CL of the glow plug 1 (FIG. 1)). It extends in a straight line. In FIG. 4A, the angle θ1 is a central axis C1 which is a virtual line passing through the center of the distal end side resistance portion 134B and an axis of the proximal end side resistance portion 134A (in this first aspect, the glow plug 1 (FIG. 1). ) In a direction parallel to the central axis CL (axial direction)). The bent portion 132 is configured as a corner portion connecting the proximal end side resistance portion 134A and the distal end side resistance portion 134B, and has a shape in which the current density is locally increased when the heat generating portion 121 is energized. ..

As shown in FIG. 4B, the second resistance portion 121B has the same shape as the first resistance portion 121A. The second resistance portion 121B includes a proximal side resistance portion 135A extending in a predetermined direction and a distal end side resistance portion 135B extending in a direction different from the proximal end side resistance portion 135A on the distal end side of the proximal end side resistance portion 135A. Have. Then, the bent portion 133 is formed in a form of connecting the proximal end side resistance portion 135A and the distal end side resistance portion 135B. Also in the examples of FIGS. 3 and 4B, the proximal end side resistance portion 135A is configured in an axial shape and extends linearly in parallel with the central axis CL of the glow plug 1 (FIG. 1). The tip-side resistance portion 135B is configured to have a shaft shape, and is configured to be inclined to one side in the above-mentioned "vertical direction" with respect to the base-end-side resistance portion 135A. That is, the tip side resistance portion 135B is inclined to the same side as the side on which the tip side resistance portion 134B shown in FIG. 4A is inclined in the "vertical direction". Further, the tip end side resistance portion 135B is linear in a form inclined by an angle θ2 with respect to the axis of the base end side resistance portion 135A (in this first aspect, the axis parallel to the central axis CL of the glow plug 1 (FIG. 1)). It extends like a shape. In FIG. 4B, the angle θ2 is a central axis C2 which is a virtual line passing through the center of the distal end side resistance portion 134B and an axis of the proximal end side resistance portion 135A (in the first aspect, the glow plug 1 (FIG. 1). ) In a direction parallel to the central axis CL (axial direction)). The bent portion 133 is configured as a corner portion connecting the base end side resistance portion 135A and the tip end side resistance portion 135B, and has a shape in which the current density is locally increased when the heat generating portion 121 is energized. ..

In the example of FIG. 4, the angle θ1 shown in FIG. 4 (A) and the angle θ2 shown in FIG. 4 (B) are the same. That is, the inclination angle of the tip side resistance portion 134B with respect to the axial direction and the inclination angle of the tip side resistance portion 135B with respect to the axial direction are the same. It is more desirable that the angles θ1 and θ2 are, for example, in the range of 5 ° or more and 25 ° or less. The angle θ1 shown in FIG. 4 (A) and the angle θ2 shown in FIG. 4 (B) may be different.

As shown in FIG. 3, all of the bent portions 132 and 133 formed in the first resistance portion 121A and the second resistance portion 121B are located in the same cross section Cs orthogonal to the axial direction. The cross section Cs is a cross section that passes through a predetermined “high temperature region” in the ceramic heater 40 and is orthogonal to the axial direction. The “high temperature region” is a region having a surface having a temperature of 96% or more with respect to the maximum heat generation temperature of the surface of the ceramic heater 40 when the heat generating portion 121 is energized. In FIG. 3, a region in which the surface temperature of the ceramic heater 40 is 96% or more of the maximum heat generation temperature of the surface when the heat generating portion 121 is energized is conceptually indicated by reference numeral AR. That is, when the heat generating portion 121 is energized, the surface temperature is 96% or more of the maximum heating temperature in the range of the symbol AR in the axial direction, and in the ceramic heater 40, the vicinity of the surface portion in this range is in the “high temperature region”. Equivalent to. The cross section Cs is a cross section that passes through such a "high temperature region".

In the ceramic heater 40, the shortest distance t between the surface of the substrate 110 and the heat generating portion 121 is 0.2 mm or more. In this configuration, as shown in FIG. 4A, the shortest distance t is between the predetermined position of the heat generating portion 121 (specifically, the predetermined position P1 of the connecting portion 121C) and the predetermined position P2 near the tip end portion of the substrate 110. By setting this shortest distance t to 0.2 mm or more, the corrosion resistance is improved. The shortest distance t can be, for example, 1.5 mm or less.

A3. Modification example (second aspect)
Next, with reference to FIGS. 5 and 6, the ceramic heater 240 and the glow plug 201 of the second aspect, in which a part of the ceramic heater 40 of the first aspect is modified, will be described. The cross section shown in FIG. 5 partially shows a cut surface obtained by cutting the glow plug 201 along the resistor 220. FIG. 5 shows the central shaft CL of the glow plug 1, the central shafts of the first conductive portion 122 and the second conductive portion 123, the central shafts of the proximal end side resistance portions 234A and 235A, and the distal end side resistance portions 234B and 235B. It is a cross section including each central axis, and is a cross section in the plane direction passing through these central axes. FIG. 6 is a side view of the ceramic heater 240 (FIG. 5) when viewed from one side in a predetermined direction (the direction in which the first resistance portion 221A and the second resistance portion 221B face each other). Only the outer shape is shown by the virtual line of the dotted chain line. That is, FIG. 6 is a view showing a side view of a part of the resistor 220 (FIG. 5, etc.) viewed from one side together with the outer shape (virtual line) of the substrate 210.

The glow plug 201 and the ceramic heater 240 shown in FIG. 5 have the same configuration as the glow plug 1 and the ceramic heater 40 of the first aspect shown in FIGS. 1 and 2 except for the ceramic heater 240. The ceramic heater 240 is the same as the ceramic heater 40 except for the substrate 210 and the heat generating portion 221. In the ceramic heater 240 shown in FIG. 5, the resistor 220 differs from the resistor 120 of the first aspect only in the heat generating portion 221. The substrate 210 has the same configuration as the substrate 110 of the ceramic heater 40 (FIG. 2) of the first aspect, except that the position where the resistor is embedded is changed. In FIGS. 5 and 6, the same parts as those of the ceramic heater 40 and the glow plug 1 of the first aspect shown in FIG. 2 and the like are designated by the same reference numerals as the respective parts, and detailed description thereof will be omitted. ..

The ceramic heater 240 and glow plug 201 of the second aspect shown in FIG. 5 also include the basic features of the ceramic heater 40 and glow plug 1 of the first aspect. The ceramic heater 240 includes a substrate 210 and a resistor 220 extending along the axial direction from the rear end side to the front end side. The resistor 220 has a pair of conductive portions (first conductive portion 122 and second conductive portion 123) and a heat generating portion 221 similar to those in the first aspect. The first conductive portion 122 and the second conductive portion 123 are arranged on the rear end side of the substrate 210 and extend along the axial direction. The heat generating portion 221 is connected to the first conductive portion 122 and the second conductive portion 123, and is configured to generate heat by energization from the conductive portion. The heat generating portion 221 is made of the same material as the first conductive portion 122 and the second conductive portion 123, and has a smaller cross-sectional area than the first conductive portion 122 and the second conductive portion 123.

As shown in FIG. 5, the heat generating portion 221 includes a first resistance portion 221A, a second resistance portion 221B, and a connecting portion 221C. As shown in FIGS. 5 and 6, the rear end side of the first resistance portion 221A is connected to the tip end side of the first conductive portion 122 and extends from the first conductive portion 122 to the tip end side of the substrate 210. The rear end side of the second resistance portion 221B is connected to the tip end side of the second conductive portion 123, and extends from the second conductive portion 123 to the tip end side of the substrate 210. The connecting portion 221C connects the tip end side of the first resistance portion 121A and the second resistance portion 121B.

Bending portions 232 and 233 are formed in the first resistance portion 221A and the second resistance portion 221B, respectively. The first resistance portion 221A includes a proximal side resistance portion 234A extending in a predetermined direction and a distal end side resistance portion 234B extending in a direction different from the proximal end side resistance portion 234A on the distal end side of the proximal end side resistance portion 234A. Have. Then, the bent portion 232 is formed in a form of connecting the proximal end side resistance portion 234A and the distal end side resistance portion 234B. In the example of FIG. 5, the proximal end side resistance portion 234A is formed in a shaft shape and extends linearly in parallel with the central shaft CL of the glow plug 201. The tip-side resistance portion 234B is configured to have a shaft shape, and is configured to be inclined to one side in a predetermined "opposite direction" with respect to the tip-side resistance portion 234B. The "opposing direction" is a direction in which the first resistance portion 221A and the second resistance portion 221B face each other, and is a direction along the third direction D3, among the directions orthogonal to the axial direction. The tip end side resistance portion 234B extends linearly in a form inclined by a predetermined angle θ4 with respect to the axis C4 of the base end side resistance portion 234A (in this second aspect, the axis parallel to the central axis CL of the glow plug 201). ing. The angle θ4 is a direction parallel to the central axis C3, which is a virtual line passing through the center of the tip end side resistance portion 234B, and the axis C4 of the proximal end side resistance portion 234A (in this second aspect, the central axis CL of the glow plug 201). Axis direction))). The bent portion 232 is configured as a corner portion connecting the base end side resistance portion 234A and the tip end side resistance portion 234B, and has a shape in which the current density is locally increased when the heat generating portion 221 is energized. ..

The second resistance portion 221B includes a proximal side resistance portion 235A extending in a predetermined direction and a distal end side resistance portion 235B extending in a direction different from the proximal end side resistance portion 235A on the distal end side of the proximal end side resistance portion 235A. Have. Then, the bent portion 233 is formed in a form of connecting the proximal end side resistance portion 235A and the distal end side resistance portion 235B. In the example of FIG. 5, the proximal end side resistance portion 235A is formed in an axial shape and extends linearly in parallel with the central axis CL. The tip-side resistance portion 235B is configured to have a shaft shape, and is configured to be inclined to one side in the "opposite direction" with respect to the tip-side resistance portion 235B. That is, in the "opposing direction", the side on which the tip side resistance portion 234B is inclined and the side on which the tip side resistance portion 235B is inclined are the same side. The tip end side resistance portion 235B extends linearly in a form inclined by a predetermined angle θ3 with respect to the axis C6 of the base end side resistance portion 235A (in this second aspect, the axis parallel to the central axis CL of the glow plug 201). ing. The angle θ3 is a direction parallel to the central axis C5, which is a virtual line passing through the center of the tip end side resistance portion 235B, and the axis C6 of the proximal end side resistance portion 235A (in this second aspect, the central axis CL of the glow plug 201). Axis direction))). In the example of FIG. 5, the inclination angle θ4 of the tip side resistance portion 234B with respect to the axial direction and the inclination angle θ3 of the tip side resistance portion 235B with respect to the axial direction are the same, but may be different. The bent portion 232 is configured as a corner portion connecting the base end side resistance portion 234A and the tip end side resistance portion 234B, and has a shape in which the current density is locally increased when the heat generating portion 221 is energized. ..

Both the bent portions 232 and 233 formed in the first resistance portion 221A and the second resistance portion 221B are located in the same cross section Cs orthogonal to the axial direction. The cross section Cs is a cross section that passes through the above-mentioned "high temperature region" and is orthogonal to the axial direction. In FIG. 5, a region in which the surface temperature of the ceramic heater 240 is 96% or more of the maximum heat generation temperature of the surface when the heat generating portion 221 is energized is conceptually indicated by reference numeral AR. When the heat generating portion 221 is energized, the surface temperature is 96% or more of the maximum heating temperature in the range of the symbol AR in the axial direction, and the vicinity of the surface portion in this range corresponds to the "high temperature region" in the ceramic heater 240. .. The cross section Cs is a cross section that passes through such a "high temperature region".

As shown in FIG. 5, in the ceramic heater 240, the shortest distance t between the surface of the substrate 210 and the heat generating portion 221 is 0.2 mm or more. In this configuration, as shown in FIG. 5, the shortest distance t is between the predetermined position of the heat generating portion 221 (specifically, the predetermined position P3 of the connecting portion 221C) and the predetermined position P4 near the tip of the substrate 210. By setting this shortest distance t to 0.2 mm or more, the corrosion resistance is improved. The shortest distance t can be, for example, 1.5 mm or less.

A4. Effect As shown in FIGS. 3 and 4, in the ceramic heater 40 of the first aspect, since the bending portions 132 and 133 are formed in the first resistance portion 121A and the second resistance portion 121B, the vicinity of the bending portions 132 and 133 is formed. The current density can be increased locally. Moreover, the bent portions 132 and 133 pass through the "high temperature region" having a surface having a temperature of 96% or more with respect to the maximum heat generation temperature of the surface in the ceramic heater 40, and are within a predetermined cross section Cs orthogonal to the axial direction. Is located in. That is, the current density can be increased in the vicinity of the "high temperature region" of the ceramic heater 40, and the heat generation can be further increased in the "high temperature region". Therefore, the temperature tends to rise more rapidly on the surface of the "high temperature region", and the power consumption required to bring the surface temperature of the ceramic heater 40 to the target temperature is suppressed. Moreover, since the above-mentioned effect can be produced without significantly reducing the cross-sectional area of the heat generating portion 121, it is unlikely that the durability will be lowered. The same effect is produced by the ceramic heater 240 (FIG. 5) of the second aspect.

In particular, since the bent portions 132 and 133 are formed in the first resistance portion 121A and the second resistance portion 121B which are relatively thin, the current density is likely to increase and the surface of the ceramic heater 40 is locally raised. The effect of warming is more likely to occur.

In the ceramic heater 40 of the first aspect, bending portions 132 and 133 are formed in both the first resistance portion 121A and the second resistance portion 121B, respectively. Then, both of the bent portions 132 and 133 formed in the first resistance portion 121A and the second resistance portion 121B are located within a predetermined cross section that passes through the above-mentioned "high temperature region" and is orthogonal to the above-mentioned axial direction. doing. Since the ceramic heater 40 can increase the current density in each of the first resistance portion 121A and the second resistance portion 121B, the power consumption required to bring the surface temperature of the ceramic heater 40 to the target temperature is further increased. It can be suppressed. Moreover, since the above-mentioned effect can be produced without significantly reducing the cross-sectional areas of the first resistance portion 121A and the second resistance portion 121B, the durability is less likely to be lowered. Moreover, since the ceramic heater 40 can increase the current density in each of the first resistance portion 121A and the second resistance portion 121B, in the opposite direction in which the first resistance portion 121A and the second resistance portion 121B face each other. The heat is equalized. The same effect is produced by the ceramic heater 240 (FIG. 5) of the second aspect.

In the ceramic heater 40 of the first aspect, both the bending portions 132 and 133 formed in the first resistance portion 121A and the second resistance portion 121B are located in the same cross section Cs, and the cross section Cs is the above-mentioned "high temperature". It is a cross section that passes through the "region" and is orthogonal to the above-mentioned axial direction. Since both the bent portions 132 and 133 are located within the same cross-section Cs orthogonal to the axial direction in this way, the heat is equalized in the opposite directions in which the first resistance portion 121A and the second resistance portion 121B face each other. , The heat generation can be more concentrated in the vicinity of the predetermined position in the axial direction (near the Cs in the same cross section). The same effect is produced by the ceramic heater 240 (FIG. 5) of the second aspect.

In the ceramic heater 40 of the first aspect, the shortest distance t between the surface of the substrate 110 and the heat generating portion 121 is 0.2 mm or more. The ceramic heater 40 suppresses power consumption while suppressing a decrease in durability, and secures a distance between the surface of the substrate 110 and the heat generating portion 121, so that the heat generating portion 121 is less likely to be exposed to the outside air. , Corrosion resistance can be improved. The same effect is produced by the ceramic heater 240 (FIG. 5) of the second aspect.

In the ceramic heater 40 of the first aspect, both of the tip side resistance portions constituting the first resistance portion 121A and the second resistance portion 121B are connected to each of the proximal end side resistance portions as described above. It is configured to incline to one side of the "direction". The "vertical direction" is a direction orthogonal to the above-mentioned "opposing direction" and the above-mentioned "axis direction", and if the tip side resistance portion is inclined to one side of the "vertical direction" in this way, bending is performed. It becomes easy to increase the bending angle of the portions 132 and 133 (the inclination angle of the tip side resistance portion with respect to the proximal end side resistance portion).

In the ceramic heater 240 of the second aspect, both of the tip side resistance portions constituting the first resistance portion 221A and the second resistance portion 221B are connected to the proximal end side resistance portion in the above-mentioned "opposite direction". It has a structure that inclines to one side. In this way, if the tip side resistance portion is inclined to one side in the "opposing direction", the heat generating portion 221 does not become bulky in the "vertical direction" as shown in FIG. 6, and the tip side resistance portion is oriented in the orthogonal direction. It is advantageous in manufacturing the ceramic heater 40 because it is possible to reduce the labor or burden in manufacturing (for example, complicated mold design) caused by the bulkiness.

A5. Evaluation test Next, the results of a test conducted to verify the effect of the present invention will be described.
Seven types of ceramic heaters were prepared as Examples 1 to 7 used in the verification test. The seven types of ceramic heaters differ only in the shape of the heat generating portion and the internal shape of the substrate that matches the shape of the heat generating portion, and the other configurations are the same. Specifically, as Examples 1 to 5 and 7, the ceramic heater 40 of the first aspect shown in FIGS. 2 to 4 was prepared. Examples 1 to 5 and 7 differ in the position of the bent portion, the shortest distance t between the surface (outer surface) of the ceramic heater 40 and the heat generating portion 121, or the angles θ1 and 2 of the bent portions 132 and 133, respectively. Further, as Example 6, the ceramic heater 240 of the second aspect shown in FIGS. 5 and 6 was prepared.

The value of "position of bending portion" shown in Table 1 is how much the temperature of the surface of the ceramic heater 40 in the cross section orthogonal to the axial direction and passing through the bending portion is relative to the maximum heat generation temperature of the surface of the ceramic heater 40. It is a value indicating whether it is a ratio. For example, in the ceramic heater of the first embodiment, the position of the bent portions 132, 133 (FIGS. 3 and 4) is 96% of the maximum heat generation temperature of the surface (heater surface) of the ceramic heater 40. It is a position in the cross section that passes through and is orthogonal to the axial direction. Further, in the ceramic heater of the sixth embodiment, the position of the bent portion 232, 233 (FIGS. 5 and 6) is 96% of the maximum heat generation temperature of the surface (heater surface) of the ceramic heater 40. It is a position in the cross section that passes through and is orthogonal to the axial direction.

The “heat-generating portion diameter” shown in Table 1 is the diameter of the heat-generating portion. For example, in the ceramic heaters of Examples 1 to 5 and 7, the heat-generating portion 121 shown in FIGS. 3 and 4 passes through the high-temperature region AR. , The equivalent circle diameter of the cross section orthogonal to the axial direction. In the ceramic heater of the sixth embodiment, of the heat generating portions 221 shown in FIGS. 5 and 6, the diameter is equivalent to a circle in a cross section that passes through the high temperature region AR and is orthogonal to the axial direction. The “distance from the surface” shown in Table 1 is the shortest distance between the surface (outer surface) of the ceramic heater and the heat generating portion. For example, in the ceramic heaters of Examples 1 to 5 and 7, in FIGS. 3 and 4. It is the shortest distance t between the surface of the ceramic heater 40 and the heat generating portion 121 shown. In the ceramic heater of the sixth embodiment, the shortest distance t between the surface of the ceramic heater 240 shown in FIGS. 5 and 6 and the heat generating portion 221 is t. The "angle of the bent portion" shown in Table 1 is, for example, the angles θ1 and 2 shown in FIG. 4 in the ceramic heaters of Examples 1 to 5 and 7, and the angle shown in FIG. 5 in the ceramic heater of Example 6. It is θ3 and 4.

Further, as Comparative Examples 1 to 3, three types of ceramic heaters were prepared. In Comparative Examples 1 and 2, the ceramic heater 40 of the first aspect shown in FIGS. 2 to 4 is changed to a configuration in which a bent portion is not provided. That is, the angles θ1 and θ2 shown in FIG. 4 are set to 0 °. The conditions other than this point are as shown in Table 1. In Comparative Example 3, the ceramic heater 40 of the first aspect shown in FIGS. 2 to 4 is slightly changed, and the position of the bent portion is changed to a position corresponding to 94%. In Comparative Example 3, in the ceramic heaters 40 shown in FIGS. 3 and 4, the positions of the bent portions 132 and 133 are 94% of the maximum heat generation temperature of the surface (heater surface) of the ceramic heater 40. It is a position in the cross section that passes through and is orthogonal to the axial direction. The conditions other than this point are as shown in Table 1.

A test for measuring the power consumption was performed on each of the ceramic heaters of Examples 1 to 7 and Comparative Examples 1 to 3 prepared in this manner. The conditions of the test for measuring the power consumption are as follows.

A constant DC voltage was applied to the ceramic heater to be tested, and the input power (power consumption) when the surface temperature of the ceramic heater was saturated at 1200 ° C. was measured in the state where the constant DC voltage was applied. The judgment when the input power when the surface temperature reached 1200 ° C. was less than 40 W was set as “◯”, and the judgment when the input power was 40 W or more was set as “x”. When it is determined as "◯", it means that the surface of the ceramic heater can be heated to a higher temperature with less input power. Table 1 shows the measurement results and determination results of the power consumption of Examples 1 to 7 and Comparative Examples 1 to 3.

In addition, energization durability tests were performed on each of the ceramic heaters of Examples 1 to 7 and Comparative Examples 1 to 3. The conditions of the energization durability test are as follows.

A voltage is applied to the ceramic heater to be tested so that the temperature becomes 1350 ° C. 2 seconds after the start of energization, and then the energization is stopped, and the ceramic heater is forcibly cooled with compressed air during the energization stop. This cycle was repeated. Then, the case where the temperature can be raised to 1350 ° C. even if the temperature exceeds 50,000 cycles is marked with "◯", and the case where the wire is broken before 50,000 cycles and the power cannot be supplied is marked with "x". Table 1 shows the measurement results and the determination results of the energization durability test for each of Examples 1 to 7 and Comparative Examples 1 to 3.

Further, an oil corrosion test was performed on each of the ceramic heaters of Examples 1 to 7 and Comparative Examples 1 to 3. The conditions of the oil corrosion test are as follows.

The ceramic heater to be tested was immersed in diesel engine oil, and then the ceramic heater was removed from the diesel engine oil. Then, with the diesel engine oil adhering to the surface of the ceramic heater, the applied voltage is controlled so that the surface temperature of the ceramic heater reaches 1350 ° C., the glow plug is energized for 2 minutes, and then the energization is stopped to cool the glow plug. The operation was performed continuously for 10,000 cycles with one cycle as one cycle. The judgment when the resistor was not exposed at the time of 10000 cycles was set as "◯", and the judgment when the resistor was exposed in less than 10000 cycles was given as "x". Table 1 shows the measurement results and judgment results of the oil corrosion test for each of Examples 1 to 7 and Comparative Examples 1 to 3.

As shown in Table 1, in each of Examples 1 to 7, the input power (power consumption) when the surface temperature of the ceramic heater is saturated at 1200 ° C. is smaller than that of Comparative Example 1. It is considered that the reason is that the temperature rising performance in the high temperature region is further improved by providing the bent portion in the vicinity of the high temperature region, and the surface of the ceramic heater can be heated to a higher temperature with a smaller input power.

Further, all of Examples 1 to 7 have higher energization durability than Comparative Example 2. The reason is that the ceramic heater of Comparative Example 2 is inferior in strength because the diameter of the heat generating portion is small, and moreover, since the volume of the heat generating portion is relatively small, it is necessary to generate more heat in order to reach the target temperature. It is probable that the wire was not sufficiently strong against the stress and the wire was broken at an early stage.

Further, in each of Examples 1 to 7, the input power (power consumption) when the surface temperature of the ceramic heater is saturated at 1200 ° C. is smaller than that of Comparative Example 3. The reason is that in Comparative Example 3, the distance from the position of the maximum heat generation temperature on the heater surface to the bent portion is larger than that in Examples 1 to 7, and the degree to which the bent portion contributes to the temperature rise in the “high temperature region” is small. Therefore, it is considered that the electric power for raising the vicinity of the position of the maximum heat generation temperature to the target temperature increases accordingly.

From this, since the bent portion is formed in at least one of the first resistance portion and the second resistance portion, the current density in the vicinity of the bent portion can be locally increased in the heat generating portion. Moreover, the bent portion is located in a predetermined cross section of the ceramic heater, which passes through a high temperature region having a surface having a temperature of 96% or more with respect to the maximum heat generation temperature of the surface and is orthogonal to the axial direction. That is, the current density can be increased in the vicinity of the high temperature region of the ceramic heater, and the heat generation can be further increased in the high temperature region. Therefore, the temperature tends to rise more rapidly on the surface of the high temperature region, and the power consumption required to bring the surface temperature of the ceramic heater to the target temperature is suppressed. Moreover, since the above-mentioned effect can be produced without significantly reducing the cross-sectional area of the heat generating portion, it is unlikely that the durability will be lowered.

Moreover, in all of Examples 1 to 6, the oil corrosion test was better than that of Example 7. It is considered that the reason is that in Examples 1 to 6, the shortest distance from the surface of the ceramic heater to the resistor is sufficiently secured. On the other hand, in Example 7, it is considered that the resistor was too close to the surface of the ceramic heater, so that the surface temperature became high and corrosion was promoted.

<Other embodiments>
The present invention is not limited to each aspect of the embodiments described by the above description and drawings, and for example, the following examples are also included in the technical scope of the present invention.

In the description of each aspect of the first embodiment, a resistor (heat generating resistor) in which a heat generating portion and a pair of conductive portions functioning as lead portions are integrally made of the same one kind of material has been exemplified. However, the present invention is not limited to this example, and the heat generating portion and the pair of conductive portions may be formed of different conductive ceramic materials having different electrical resistivitys. In this way, when the heat generating portion and the pair of conductive portions are formed of different materials, the portion of the material on the tip end side of the resistor, that is, the portion of the material different from the base end side is referred to as the "heating portion" and the resistance. The portion of the material on the base end side of the body can be the "conductive portion".

In the description of each aspect of the first embodiment, the bent portion is formed in each of the first resistance portion and the second resistance portion, but the bent portion may be formed in only one of them.

In the description of each aspect of the first embodiment, one bending portion is formed in each of the first resistance portion and the second resistance portion, but the bending portion is bent in the first resistance portion or the second resistance portion. The portions may be formed at a plurality of positions.

In the description of each aspect of the first embodiment, both the bent portion of the first resistance portion and the bent portion of the second resistance portion are located in the same cross section orthogonal to the axial direction, but the bent portion of the first resistance portion and the bent portion are located. The bent portion of the second resistance portion may be displaced in the axial direction.

In the description of each aspect of the first embodiment, the distal end side resistance portion of the first resistance portion is inclined with respect to the proximal end side resistance portion, and the distal end side resistance portion of the second resistance portion is on the proximal end side resistance portion. On the other hand, the side that is inclined is the same side, but they may be inclined to different sides.

In the description of each embodiment of the first embodiment and the description of each embodiment of the second embodiment, the tip end side resistance portions of the first resistance portion and the second resistance portion are "vertical direction" with respect to the base end side resistance portion. , Or in the "opposing direction", but the tip-side resistance portion may be tilted in another direction with respect to the proximal end-side resistance portion.

In the description of each aspect of the first embodiment, the bent portion is configured as a corner portion, but the surface on the convex side may be configured as a curved portion formed as a curved surface. In the case of a bent portion having a curved surface, the bent portion may be configured such that the curved surface of the bent portion is located in a cross section that passes through the above-mentioned "high temperature region" and is orthogonal to the above-mentioned "axis direction". Even in this case, a linear base end side resistance part and a tip end side resistance part are arranged on the base end side and the tip end side of the bent part (curved part) so that the angle formed by these is within a predetermined angle range. The configuration may be bent to. In this case as well, the base end side resistance portion may be arranged along the axial direction, and the tip end side resistance portion may be inclined in an angle range of 5 ° or more and 25 ° or less with respect to the axial direction.

1,201 ... Glow plug 20 ... Main metal fittings (metal fittings)
110, 210 ... Base 120, 220 ... Heat-generating resistor (resistor)
121,221 ... Heat generating parts 121A, 221A ... First resistance parts 121B, 221B ... Second resistance parts 121C, 221C ... Connecting parts 122 ... First conductive parts (conductive parts)
123 ... Second conductive part (conductive part)
132, 133, 232, 233 ... Bending part 134A, 135A, 234A, 235A ... Base end side resistance part 134B, 135B, 234B, 235B ... Tip side resistance part 40, 240 ... Ceramic heater CL ... Axis

Claims (7)

A substrate made of insulating ceramic that extends along the axial direction from the rear end side to the front end side,
A resistor made of a conductive ceramic and embedded in the substrate. It is connected to a pair of conductive portions arranged on the rear end side of the substrate and extending along the axial direction, and connected to the pair of conductive portions. A resistor having a heat generating portion that generates heat when energized from the conductive portion is provided.
The heat generating portion has a first resistance portion whose rear end side is connected to the tip end side of one of the conductive portions and which extends from one of the conductive portions to the tip end side of the substrate, and the rear end side of itself is the other. A second resistance portion that is connected to the tip end side of the conductive portion and extends from the other conductive portion to the tip end side of the substrate, and a connecting portion that connects the first resistance portion and the tip end side of the second resistance portion. It is a ceramic heater equipped with
At least one of the first resistance portion and the second resistance portion has a proximal resistance portion extending in a predetermined direction and a direction different from the proximal resistance portion on the distal end side of the proximal resistance portion. A tip-side resistance portion extending to and a bending portion for connecting the base-end-side resistance portion and the tip-end-side resistance portion are formed.
The bent portion is located in a predetermined cross section of the ceramic heater, passing through a high temperature region having a surface having a temperature of 96% or more with respect to the maximum heat generation temperature of the surface, and orthogonal to the axial direction.
Ceramic heater. The bent portion is formed in the first resistance portion and the second resistance portion, respectively.
Each of the bent portions of the first resistance portion and the second resistance portion is located in a predetermined cross section that passes through the high temperature region and is orthogonal to the axial direction.
The ceramic heater according to claim 1. Both the bent portion of the first resistance portion and the second resistance portion are located in the same cross section that passes through the high temperature region and is orthogonal to the axial direction.
The ceramic heater according to claim 2. The shortest distance between the surface of the substrate and the heat generating portion is 0.2 mm or more.
The ceramic heater according to any one of claims 1 to 3. The tip end side resistance portion is configured to be inclined to one side of the base end side resistance portion in the opposite direction in which the first resistance portion and the second resistance portion face each other and in the vertical direction orthogonal to the axial direction. Make a
The ceramic heater according to any one of claims 1 to 4. The tip end side resistance portion is configured to be inclined to one side in the opposite direction in which the first resistance portion and the second resistance portion face each other with respect to the base end side resistance portion.
The ceramic heater according to any one of claims 1 to 4. A glow plug including a ceramic heater and a metal fitting for holding the ceramic heater.
The ceramic heater is a glow plug including the ceramic heater according to any one of claims 1 to 6.

Images