WO2017168896A1

WO2017168896A1 - Ceramic heater

Info

Publication number: WO2017168896A1
Application number: PCT/JP2016/088805
Authority: WO
Inventors: 牧野　友亮; 直也中西; 敦俊杉山; 秀史鈴木
Original assignee: 日本特殊陶業株式会社
Priority date: 2016-03-30
Filing date: 2016-12-27
Publication date: 2017-10-05
Also published as: CN108886840B; JP2017183070A; CN108886840A; EP3439428A4; EP3439428A1; KR102136520B1; JP6604884B2; KR20180124029A

Abstract

The objective of the invention is to provide a ceramic heater allowing reliability to be increased by preventing the breakdown of insulation occurring in a heater wiring. This ceramic heater comprises a ceramic sheet 19 wrapped around the outer periphery of a support body 17 and has a built-in heater wiring 41. The heater wiring 41 comprises wiring portions 44 extending along the axial line direction of the support body 17, and connecting portions connecting adjacent wiring portions 44 to one another. When t is the thickness from a surface 46 of the heater wiring 41 to the outer periphery surface 47 of the ceramic sheet 19, V is the voltage applied to the heater wiring 41, w is the distance from an end of the heater wiring 41 to an edge surface 48 of the ceramic sheet 19, and L is the distance between a pair of wiring portions 44 which are disposed on opposite sides of a winding-alignment portion 20, the relationship t ≥ 0.2 mm is satisfied while at the same time at least one relationship among L/V ≥ 9/500 and w/V ≥ 3/500 is satisfied.

Description

Ceramic heater

The present invention relates to a ceramic heater used for, for example, a hot water washing toilet seat, a fan heater, an electric water heater, a 24-hour bath, a soldering iron, a hair iron, and the like, and more particularly, a ceramic in which a heater wiring is built in the outer periphery of a support. The present invention relates to a ceramic heater having a structure in which a sheet is wound.

Usually, a heat exchange unit having a resin container (heat exchanger) is used for a warm water washing toilet seat. A cylindrical ceramic heater is attached to the heat exchange unit in order to warm the washing water accommodated in the heat exchanger.

As this type of ceramic heater, a ceramic heater is known that is formed by winding a ceramic sheet on which a heater wiring is printed on a cylindrical ceramic support and firing it integrally (for example, see Patent Document 1).

Japanese Patent No. 3038039 (FIG. 1 etc.)

By the way, since the ceramic heater for the warm water washing toilet seat is always in water, it is hardly energized and heated in a dry state. On the other hand, when water is shut off or a pipe is broken, there is a possibility that electricity is applied and heated in a dry state. However, when heated in a dry state, a potential difference is generated between a pair of heater wires located on opposite sides of the winding portion of the ceramic sheet, and heat is generated. In the ceramic sheet near the heated heater wire, There exists a possibility that the glass component which exists may melt | dissolve. In this case, since electrons easily move, partial discharge occurs between a pair of heater wires located on opposite sides of the winding portion, leading to dielectric breakdown. In addition, the ceramic component present in the ceramic sheet is melted by the spark generated during the partial discharge, so that the ceramic heater is damaged.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a ceramic heater capable of improving reliability by preventing dielectric breakdown occurring in the heater wiring.

And as means (means 1) for solving the above-mentioned problems, in the ceramic heater comprising a ceramic support and a ceramic sheet wound around the outer periphery of the support and incorporating the heater wiring, the heater wiring Comprises a plurality of wiring portions extending along the axial direction of the support and a connecting portion for connecting the adjacent wiring portions to each other, from the surface of the heater wiring to the outer peripheral surface of the ceramic sheet in the ceramic sheet. And the voltage applied to the heater wiring is V (V), and the distance from the edge of the heater wiring to the end face of the ceramic sheet is w in the winding portion of the ceramic sheet. (Mm), and the distance between the pair of wiring parts arranged on opposite sides of the winding part is L (mm). Can, together satisfy the relationship of t ≧ 0.2 mm, there is a ceramic heater and satisfies at least one relationship between L / V ≧ 9/500 and w / V ≧ 3/500.

Therefore, according to the invention described in the means 1, the dielectric breakdown strength is satisfied by satisfying the relationship of t ≧ 0.2 mm and satisfying at least one of the relationships of L / V ≧ 9/500 and w / V ≧ 3/500. Can be increased. As a result, since melting of the glass component present in the ceramic sheet in the vicinity of the winding portion is prevented, it is possible to prevent dielectric breakdown between a pair of heater wires located on opposite sides across the winding portion, Damage to the ceramic heater can be prevented. Therefore, the reliability of the ceramic heater can be improved.

The ceramic heater preferably satisfies at least one of the relations t / V ≧ 1/500 and w / t ≧ 3. Furthermore, a slit that extends along the axial direction of the support and exposes the outer peripheral surface of the support is formed in the winding portion, and when the width of the slit is derived from the equation of L-2w, 0.2 It is preferable to satisfy the relationship of ≦ L−2w ≦ 1.5. If the setting is made as described above, the dielectric breakdown strength is more reliably increased, so that it is possible to reliably prevent dielectric breakdown between a pair of heater wires located on opposite sides of the winding portion, and to damage the ceramic heater. Can be reliably prevented. Therefore, the reliability of the ceramic heater is further improved.

The ceramic heater includes a ceramic support and a ceramic sheet wound around the outer periphery of the support. Preferred examples of the ceramic forming the support and the ceramic sheet include alumina, aluminum nitride, silicon nitride, boron nitride, zirconia, titania, mullite, and the like. In particular, the support and the ceramic sheet are preferably made of alumina. In this way, a ceramic heater excellent in heat resistance, chemical resistance and strength can be produced at low cost. Moreover, the ceramic sheet has a heating element (heater wiring) made of tungsten, molybdenum, tantalum, or the like, for example. The heater wiring preferably contains at least one of tungsten and molybdenum as a main component. In this way, since the heater wiring can be securely adhered to the ceramic sheet, the reliability of the ceramic heater is further improved.

The front view of the ceramic heater in this embodiment. The top view which shows a ceramic heater. FIG. 2 is a sectional view taken along line AA in FIG. 1. Explanatory drawing which expand | deploys and shows a ceramic sheet. (A)-(d) is explanatory drawing which shows the manufacturing method of a ceramic heater. Explanatory drawing which shows the manufacturing method of a ceramic heater in other embodiment.

Hereinafter, a ceramic heater and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings.

The ceramic heater 11 of the present embodiment is used for warming cleaning water in a heat exchanger of a heat exchange unit of a warm water cleaning toilet seat, for example.

As shown in FIGS. 1 and 2, the ceramic heater 11 includes a cylindrical ceramic heater main body 13 and a metal annular flange 15 that is externally fitted to the heater main body 13. . The flange 15 is an annular member formed by bending a metal plate such as stainless steel, and has a concave portion (cup shape) at the center.

In the present embodiment, as shown in FIG. 2, the space surrounded by the outer peripheral surface 14 of the heater main body 13 and the inner surface of the flange 15 in the concave portion of the flange 15 is the glass reservoir 35. The glass reservoir 35 is filled with glass 33, and the heater body 13 and the flange 15 are welded and fixed through the glass 33. In FIG. 2, the portion of the glass 33 is indicated by hatching.

As shown in FIGS. 1 to 3, the heater main body 13 includes a cylindrical ceramic support 17 and a ceramic sheet 19 wound around the outer periphery of the support 17. In the present embodiment, the support 17 and the ceramic sheet 19 are made of a ceramic such as alumina (Al ₂ O ₃ ). The thermal expansion coefficient of alumina is in the range of 50 × 10 ⁻⁷ / K to 90 × 10 ⁻⁷ / K, and in this embodiment, 70 × 10 ⁻⁷ / K (30 ° C. to 380 ° C.). ing. Moreover, in this embodiment, the outer diameter of the support body 17 is set to 12 mm, the inner diameter is set to 8 mm, the length is set to 65 mm, the thickness of the ceramic sheet 19 is set to 0.5 mm, and the length is set to 60 mm. The ceramic sheet 19 does not completely cover the outer periphery of the support 17. Therefore, a slit 21 that extends along the axial direction of the support 17 and exposes the outer peripheral surface 18 of the support 17 is formed in the winding portion 20 of the ceramic sheet 19.

3 and 4, the ceramic sheet 19 has a meandering pattern-shaped heater wiring 41 and a pair of internal terminals 42 incorporated therein. In the present embodiment, the heater wiring 41 and the internal terminal 42 contain tungsten (W) as a main component. Each internal terminal 42 is electrically connected to an external terminal 43 (see FIG. 1) formed on the outer peripheral surface of the ceramic sheet 19 via a via conductor (not shown).

Further, the heater wiring 41 includes a plurality of wiring portions 44 extending along the axial direction of the support body 17 and a connection portion 45 that connects the adjacent wiring portions 44 to each other. A pair of wiring portions 44 located at both ends when the ceramic sheet 19 is viewed from the thickness direction are disposed on opposite sides of the winding portion 20 of the ceramic sheet 19 (see FIG. 3). One end (upper end in FIG. 4) is connected to the internal terminal 42, and the second end (lower end in FIG. 4) is connected to the second end of the adjacent wiring portion 44 via the connection portion 45. Further, when the ceramic sheet 19 is viewed from the thickness direction, the wiring portion 44 located between the pair of wiring portions 44 described above has a first end connected to the first end of the wiring portion 44 adjacent to the first wiring portion 44 via the connection portion 45. In addition to being connected, the second end is connected to the second end of the adjacent wiring portion 44 via the connection portion 45.

As shown in FIGS. 3 and 4, the wiring portion 44 of the present embodiment has a line width W1 of 0.60 mm and a thickness of 15 μm. Similarly, the connecting portion 45 of the present embodiment is also set to have a line width W2 of 0.60 mm and a thickness of 15 μm. That is, the line width W1 of the wiring part 44 is the same as the line width W2 of the connection part 45. Further, since the thickness of the wiring part 44 is also the same as the thickness of the connection part 45, the cross-sectional area of the wiring part 44 is the same as the cross-sectional area of the connection part 45.

As shown in FIG. 3, in the ceramic sheet 19, the thickness t from the surface 46 of the wiring portion 44 (heater wiring 41) to the outer peripheral surface 47 of the ceramic sheet 19 is 0.2 mm. Moreover, in the winding part 20, the distance w from the edge of the wiring part 44 (heater wiring 41) to the end surface 48 of the ceramic sheet 19 is 0.7 mm. Here, “distance w” refers to the length along the circumferential direction of the cylindrical support 17. Furthermore, the distance L between the pair of wiring portions 44 arranged on the opposite sides of the winding portion 20 is 2.4 mm. Here, “distance L” refers to the length of a straight line connecting the edges of the pair of wiring portions 44. Note that the width of the slit 21 formed in the winding portion 20 is derived from the equation L-2w, and is 1 mm in this embodiment.

Next, a method for manufacturing the ceramic heater 11 of this embodiment will be described.

First, a clay-like slurry containing alumina as a main component is put into a conventionally known extruder (not shown) to form a cylindrical member. And after drying the shape | molded cylindrical member, the support body 17 (refer Fig.5 (a)) is obtained by performing temporary baking which heats to predetermined | prescribed temperature (for example, about 1000 degreeC).

Also, the first and second ceramic

green sheets

51 and 52 to be the ceramic sheet 19 are formed using a ceramic material mainly composed of alumina powder. In addition, as a formation method of a ceramic green sheet, well-known forming methods, such as a doctor blade method, can be used. Then, a conductive paste (in this embodiment, a tungsten paste) is printed on the surface of the first ceramic green sheet 51 using a conventionally known paste printing apparatus (not shown). As a result, the unfired electrode 53 to be the heater wiring 41 and the internal terminal 42 is formed on the surface of the first ceramic green sheet 51 (see FIG. 5B). Note that the position of the unfired electrode 53 is adjusted so that, for example, the size of the position of the heater wiring 41 plus the shrinkage during firing is added.

Then, after drying the conductive paste, the second ceramic green sheet 52 is laminated on the printed surface of the first ceramic green sheet 51 (formation surface of the unfired electrode 53), and a pressing force is applied in the sheet laminating direction. To do. As a result, the ceramic

green sheets

51 and 52 are integrated to form a green sheet laminate 54 (see FIG. 5C). The thickness of the second ceramic green sheet 52 is, for example, a size obtained by adding shrinkage during firing to the thickness t from the outer wiring portion 46 of the heater wiring 41 to the outer peripheral surface 47 of the ceramic sheet 19. It is adjusted to become. Further, a conductive paste is printed on the surface of the second ceramic green sheet 52 using a paste printing apparatus. As a result, an unfired electrode 55 that becomes the external terminal 43 is formed on the surface of the second ceramic green sheet 52.

Next, a ceramic paste (alumina paste) is applied to one side of the green sheet laminate 54, and the green sheet laminate 54 is wound around and bonded to the outer peripheral surface 18 of the support 17 (see FIG. 5 (d)). At this time, the size of the green sheet laminate 54 is adjusted so that the ends of the green sheet laminate 54 do not overlap each other. Next, after performing a drying process or a degreasing process according to a well-known method, a predetermined temperature at which the alumina and tungsten of the green sheet laminate 54 (the ceramic

green sheets

51 and 52 and the unfired electrodes 53 and 55) can be sintered. Simultaneous firing is performed by heating to (for example, about 1400 ° C. to 1600 ° C.). As a result, the alumina in the ceramic

green sheets

51 and 52 and the tungsten in the conductive paste are simultaneously sintered, the green sheet laminate 54 becomes the ceramic sheet 19, and the unfired electrode 53 becomes the heater wiring 41 and the internal terminal 42. Thus, the unfired electrode 55 becomes the external terminal 43. Thereafter, the external terminals 43 are plated with nickel to form the heater body 13.

Next, a plate material made of stainless steel is press-molded using a mold to form a cup-shaped flange 15. Then, the flange 15 is externally fitted to a predetermined mounting position of the heater body 13. Thereafter, the heater body 13 and the flange 15 are welded and fixed via the glass 33 to complete the ceramic heater 11.

<Experimental example>
Hereinafter, experimental examples performed for evaluating the performance of the ceramic heater 11 of the present embodiment will be described.

First, a measurement sample was prepared as follows. The thickness t (see FIG. 3) from the surface of the heater wiring (wiring portion) to the outer peripheral surface of the ceramic sheet is 0.18 mm, and the distance w from the edge of the heater wiring (wiring portion) to the end surface of the ceramic sheet (FIG. 3) Reference) is 0.6 mm, the distance L (see FIG. 3) between a pair of wiring parts arranged on opposite sides of the winding part is 1.4 mm, and the width L− of the slit formed in the winding part A ceramic heater having 2 w of 0.2 mm was prepared, and this was designated as sample A. Also, a ceramic heater having a thickness t of 0.18 mm, a distance w of 1 mm, a distance L of 3 mm, and a width L-2w of 1 mm was prepared, and this was designated as Sample B. A ceramic heater having a thickness t of 0.2 mm, a distance w of 0.5 mm, a distance L of 3 mm, and a width L-2w of 2 mm was prepared. A ceramic heater having a thickness t of 0.2 mm, a distance w of 0.7 mm, a distance L of 1.6 mm, and a width L-2w of 0.2 mm was prepared. A ceramic heater having a thickness t of 0.2 mm, a distance w of 0.7 mm, a distance L of 2.4 mm, and a width L-2w of 1 mm, ie, the same ceramic heater as the ceramic heater 11 of the present embodiment, is prepared. This was designated as Sample E. A ceramic heater having a thickness t of 0.2 mm, a distance w of 1 mm, a distance L of 3 mm, and a width L-2w of 1 mm was prepared. A ceramic heater having a thickness t of 0.3 mm, a distance w of 1 mm, a distance L of 2.4 mm, and a width L-2w of 0.4 mm was prepared. A ceramic heater having a thickness t of 0.3 mm, a distance w of 1 mm, a distance L of 3 mm, and a width L-2w of 1 mm was prepared. A ceramic heater having a thickness t of 0.4 mm, a distance w of 1.3 mm, a distance L of 3 mm, and a width L-2w of 0.4 mm was prepared. A ceramic heater having a thickness t of 0.4 mm, a distance w of 1.3 mm, a distance L of 3.8 mm, and a width L-2w of 1.2 mm was prepared. A ceramic heater having a thickness t of 0.4 mm, a distance w of 1.5 mm, a distance L of 4.5 mm, and a width L-2w of 1.5 mm was prepared. A ceramic heater having a thickness t of 0.5 mm, a distance w of 1.3 mm, a distance L of 3 mm, and a width L-2w of 0.4 mm was prepared. A ceramic heater having a thickness t of 0.5 mm, a distance w of 1.5 mm, a distance L of 3.8 mm, and a width L-2w of 0.8 mm was prepared. A ceramic heater having a thickness t of 0.5 mm, a distance w of 1.3 mm, a distance L of 3 mm, and a width L-2w of 0.4 mm was prepared. A ceramic heater having a thickness t of 0.5 mm, a distance w of 1.5 mm, a distance L of 4.3 mm, and a width L-2w of 1.3 mm was prepared. A ceramic heater having a thickness t of 0.5 mm, a distance w of 1.5 mm, a distance L of 4.3 mm, and a width L-2w of 1.3 mm was prepared. A ceramic heater having a thickness t of 0.5 mm, a distance w of 1.5 mm, a distance L of 4.5 mm, and a width L-2w of 1.5 mm was prepared. In addition, 10 samples A to Q were prepared.

Next, nichrome wire was soldered to a pair of internal terminals (heater wiring) provided in the ceramic sheets of each measurement sample (samples A to Q), and each measurement sample was dried and placed on the base. . Then, voltage V (any one of AC 100V, 140V, 200V, and 240V) was applied between the pair of internal terminals for 6 minutes, and the surface temperature of the ceramic sheet was measured with a thermo camera. More specifically, an AC voltage of 100V is applied to Samples A to E, an AC voltage of 140V is applied to Samples F to H, L, and M, and Samples I, J, and P are applied. In this case, an AC voltage of 200 V was applied, and an AC voltage of 240 V was applied to the samples K, N, O, and Q. In each of samples A to Q, values of t / V, w / t, L / V, and w / V were calculated. Further, whether or not dielectric breakdown occurred was observed between a pair of wiring parts located on opposite sides of the winding part, and when dielectric breakdown occurred, the occurrence time was measured and recorded. Then, in each sample A to Q, those having an insulation breakdown rate of 60% or more (that is, those causing breakdown in 6 or more samples out of 10) are judged as “x” and When the occurrence rate is 30% or more and 50% or less (that is, breakdown occurs in 3 to 5 samples out of 10), it is judged as “△”, and the breakdown occurrence rate is 10% or more. Those that are 20% or less (that is, those in which dielectric breakdown occurs in one or two samples out of 10) are judged as “◯”, and those in which the occurrence rate of dielectric breakdown becomes 0% (that is, 10 All samples were not evaluated for dielectric breakdown) as “◎”. The results are shown in Table 1.

As a result, in samples A and B having a thickness t of less than 0.2 mm, the occurrence rate of dielectric breakdown was 60% or more, so it was confirmed that the determination was “x”. In addition, although the thickness t is 0.2 mm or more, in the sample N in which L / V is less than 9/500 and w / V is less than 3/500, the occurrence rate of dielectric breakdown is 60% or more. It was confirmed. On the other hand, in the samples C to M and O to Q in which the thickness t is 0.2 mm or more and L / V is 9/500 or more or w / V is 3/500 or more, the occurrence rate of dielectric breakdown is 50. % Or less was confirmed. Further, among the samples C to M and O to Q, in the samples D, E, G to J, M, and O to Q in which t / V is 1/500 or more and w / t is 3 or more, insulation is performed. It was confirmed that the incidence of destruction was 20% or less. In particular, among samples D, E, G to J, M, and O to Q, samples E, H, J, M, and P in which L / V is 9/500 or more and w / V is 3/500 or more. , Q, it was confirmed that dielectric breakdown does not occur.

From the above, if t ≧ 0.2 mm, L / V ≧ 9/500, w / V ≧ 3/500, t / V ≧ 1/500 and w / t ≧ 3 are all set to satisfy the relationship. It was proved that the occurrence of dielectric breakdown was prevented.

Therefore, according to this embodiment, the following effects can be obtained.

(1) In the ceramic heater 11 of the present embodiment, since the thickness t is 0.2 mm, the distance w is 0.7 mm, the distance L is 2.4 mm, and the voltage V is 100 V AC, a relationship of t ≧ 0.2 mm. In addition, the relationship of L / V ≧ 9/500 and w / V ≧ 3/500 is satisfied, and the dielectric breakdown strength can be increased. As a result, melting of the glass component existing in the ceramic sheet 19 in the vicinity of the winding portion 20 is prevented, so that dielectric breakdown is caused between the pair of wiring portions 44 located on the opposite sides of the winding portion 20. While being able to prevent, damage to the ceramic heater 11 can be prevented. Therefore, the reliability of the ceramic heater 11 can be improved.

(2) In the present embodiment, the pair of internal terminals 42 formed on the ceramic sheet 19 are disposed on the inner side than the pair of wiring portions 44 positioned on opposite sides of the winding portion 20 of the ceramic sheet 19. (See FIG. 4). For this reason, when the ceramic sheet 19 is wound around the outer periphery of the support 17, both internal terminals 42 are positioned on opposite sides in the radial direction of the support 17. As a result, since the distance between the internal terminals 42 is increased, the occurrence of discharge between the internal terminals 42 can be prevented.

In addition, you may change this embodiment as follows.

In the above embodiment, the ceramic paste is applied to one side of the green sheet laminate 54, and the green sheet laminate 54 is wound around and adhered to the outer peripheral surface 18 of the support 17, but as shown in FIG. A part of the ceramic paste 61 may cover the end face of the green sheet laminate 62 serving as a ceramic sheet and the outer peripheral face 64 of the support 63. Also in this case, the distance w is the length from the edge of the heater wiring (unfired electrode 65) to the end surface of the ceramic sheet (green sheet laminate 62).

In the above embodiment, the support 17 of the ceramic heater 11 has a cylindrical shape, but the support may have a rod shape. That is, the ceramic heater may be used for a different one (for example, a fan heater) from the warm water cleaning toilet seat.

In the ceramic heater 11 of the above embodiment, an AC voltage is applied between the pair of internal terminals 42, but a DC voltage may be applied between the pair of internal terminals 42.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiment described above are listed below.

(1) In a ceramic heater comprising a ceramic support and a ceramic sheet wound around an outer periphery of the support and incorporating a heater wiring, the heater wiring is a plurality extending along the axial direction of the support. And a connecting portion for connecting the adjacent wiring portions to each other, wherein the thickness of the ceramic sheet from the surface of the heater wiring to the outer peripheral surface of the ceramic sheet is t (mm). V (V) is a voltage applied to the ceramic sheet, and w (mm) is the distance from the edge of the heater wire to the end surface of the ceramic sheet at the winding portion of the ceramic sheet. When the distance between the pair of wiring portions arranged on the opposite side is L (mm), the relationship t ≧ 0.2 mm is satisfied, and L / Meet at least one of the relations of ≧ 9/500 and w / V ≧ 3/500, and the ceramic heater and satisfies the relation of t / V ≧ 1/500 and w / t ≧ 3.

(2) The ceramic heater according to the above means 1, wherein the wiring portion has the same line width as the connection portion.

DESCRIPTION OF SYMBOLS 11 ...

Ceramic heater

17, 63 ...

Support body

18, 64 ... Outer peripheral surface 19 of support body ... Ceramic sheet 20 ... Winding part 21 ... Slit 41 ... Heater wiring 44 ... Wiring part 45 ... Connection part 46 ... Heater wiring surface 47 ... outer peripheral surface 48 of ceramic sheet ... end face L of ceramic sheet ... distance t between a pair of wiring parts arranged on the opposite side across the winding part ... thickness V from the surface of the heater wiring to the outer peripheral face of the ceramic sheet ... Voltage w ... Distance from the edge of the heater wiring to the end face of the ceramic sheet

Claims

In a ceramic heater comprising a ceramic support, and a ceramic sheet wound around the outer periphery of the support and incorporating heater wiring,
The heater wiring includes a plurality of wiring parts extending along the axial direction of the support and a connection part for connecting the wiring parts adjacent to each other.
In the ceramic sheet, the thickness from the surface of the heater wiring to the outer peripheral surface of the ceramic sheet is t (mm), and the voltage applied to the heater wiring is V (V). The distance from the edge of the heater wiring to the end surface of the ceramic sheet is w (mm), and the distance between the pair of wiring parts arranged on opposite sides of the winding part is L (mm). A ceramic heater characterized by satisfying the relationship of t ≧ 0.2 mm and satisfying at least one of the relationships of L / V ≧ 9/500 and w / V ≧ 3/500.
2. The ceramic heater according to claim 1, wherein at least one relationship of t / V ≧ 1/500 and w / t ≧ 3 is satisfied.
The winding portion is formed with a slit extending along the axial direction of the support and exposing the outer peripheral surface of the support,
3. The ceramic heater according to claim 1, wherein a relation of 0.2 ≦ L−2w ≦ 1.5 is satisfied when the width of the slit is derived from an equation of L−2w.
4. The ceramic heater according to claim 1, wherein the support and the ceramic sheet are made of alumina.
The ceramic heater according to any one of claims 1 to 4, wherein the heater wiring contains at least one of tungsten and molybdenum as a main component.