Ceramic heater

Abstract

To improve thermal shock resistance. [Solution] The ceramic heater 11 is a ceramic heater 11 for heating liquids and comprises a ceramic body 22 having a ceramic base 21 extending in the longitudinal direction and a heating resistor 23 formed on the surface of the base 21, and a resin layer 29 configured to cover at least a region R1 on the outer surface 22A of the ceramic body 22 that has the heating resistor 23 in the longitudinal direction, wherein the resin layer 29 has heat resistance to a temperature higher than the heating temperature of the ceramic body 22.

Description

Technical Field

[0001] The present disclosure relates to a ceramic heater.

Background Art

[0002] Conventionally, an electric heating hot water heating device described in Japanese Patent Laid-Open No. 2013-126844 (Patent Document 1 below) is known. The electric heating hot water heating device of Patent Document 1 includes a case having an inlet, a flow path, and an outlet for a heat medium, and a ceramic heater disposed in the flow path. This ceramic heater includes, for example, a support made of ceramics such as alumina, silicon nitride, aluminum nitride, or silicon carbide, and a heating element embedded in a side surface of the support.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] For example, when boiling occurs on the surface of a ceramic heater, an air layer is formed. In this air layer, the ceramic heater is rapidly heated to form a high-temperature portion, and when the liquid heating medium comes into contact with the high-temperature portion, the ceramic heater is prone to cracking. Since ceramic heaters are thus vulnerable to thermal shock and prone to cracking, it is necessary to improve thermal shock resistance for use as a heat exchanger.

[0005] The present disclosure has been completed based on the above circumstances, and an object thereof is to improve thermal shock resistance.

Means for Solving the Problem

[0006] The ceramic heater of this disclosure is a ceramic heater for heating liquids, comprising: a ceramic body having a ceramic substrate extending in the longitudinal direction and a heating resistor formed on the surface of the substrate; and a resin layer configured to cover at least a region of the outer surface of the ceramic body having the heating resistor in the longitudinal direction, wherein the resin layer has heat resistance to a temperature higher than the heating temperature of the ceramic body. [Effects of the Invention]

[0007] According to this disclosure, thermal shock resistance can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing the overall configuration of a ceramic heater according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view showing the internal structure of a ceramic heater. [Figure 3] Figure 3 is an explanatory diagram illustrating the manufacturing process of insulators. [Figure 4] Figure 4 is a cross-sectional view showing an enlarged view of the dashed-dotted line in Figure 2. [Figure 5] Figure 5 is a perspective view showing a ceramic heater according to Embodiment 2. [Figure 6] Figure 6 is a perspective view showing a ceramic heater according to Embodiment 3. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure will be listed and described. (1) The ceramic heater of the present disclosure is a ceramic heater for heating liquid, comprising: a ceramic body having a ceramic substrate extending in the longitudinal direction and a heating resistor formed on the surface of the substrate; and a resin layer configured to cover at least a region of the outer surface of the ceramic body with respect to the longitudinal direction, wherein the resin layer has heat resistance to a temperature higher than the heating temperature of the ceramic body.

[0010] With this configuration, the surface of the ceramic body is covered with a resin layer, which reduces the thermal conductivity between the liquid heating medium and the ceramic body. Therefore, even when there is a large temperature difference between the liquid heating medium and the ceramic body, it is possible to avoid the ceramic body cracking due to rapid cooling by the liquid heating medium, thereby improving thermal shock resistance.

[0011] (2) The ceramic heater of the present disclosure is a ceramic heater for heating liquid, comprising a ceramic body having a rod-shaped ceramic base extending in the longitudinal direction and a heating resistor embedded in the base, and a resin layer configured to cover at least a region of the outer surface of the ceramic body with respect to the longitudinal direction where the heating resistor is located, wherein the resin layer has heat resistance to a temperature higher than the heating temperature of the ceramic body.

[0012] (3) In the ceramic heater described in (1), it is preferable that the average thickness of the resin layer is thinner than the distance from the heating resistor to the outer surface.

[0013] If the average thickness of the resin layer is greater than the distance from the heat-generating resistor to the outer surface, there is a concern that heat will not be easily transferred to the liquid heating medium. On the other hand, in the above configuration, the average thickness of the resin layer is less than the distance from the heat-generating resistor to the outer surface, so it is possible to improve thermal shock resistance while maintaining the ability to transfer heat to the liquid heating medium.

[0014] The ceramic heater according to any one of (4) (1) to (3), wherein the resin layer includes an inner resin layer that directly covers a surface of the ceramic body, and an outer resin layer that covers the surface of the ceramic body via the inner resin layer, and it is preferable that main components of the inner resin layer and the outer resin layer are different from each other.

[0015] The inner resin layer can be a resin layer having heat resistance, and the outer resin layer can be a resin layer having high mechanical strength and high thermal conductivity, whereby the resin layer can have a plurality of functions.

[0016] The ceramic heater according to any one of (5) (1) to (4), wherein a heat resistant temperature of the resin layer is preferably 150°C or higher.

[0017] Water, coolant, and the like are widely used as heating media. Since the boiling point of water is 100°C and the boiling point of coolant is approximately 120°C, if an air layer is formed due to boiling, it is expected that the temperature of the resin layer will reach 100°C or higher. In such a case, the resin layer can withstand heat up to 150°C.

[0018] As a resin having a heat resistant temperature of 150°C or higher, super engineering plastics such as PPA (aromatic polyamide), PPS (polyphenylene sulfide), LCP (liquid crystal polymer), PSU (polysulfone), PES (polyethersulfone), PEI (polyetherimide), PAI (polyamideimide), PEEK (polyetheretherketone), and PTFE (polytetrafluoroethylene) can be used.

[0019] The ceramic heater according to any one of (6) (1) to (5), wherein the resin layer preferably contains glass fibers.

[0020] By including glass fibers in the resin layer, it is possible to improve heat resistance and increase strength.

[0021] [Details of Embodiments of the Present Disclosure] Embodiments of this disclosure will be described with reference to Figures 1 to 4. This disclosure is not limited to these examples, but is intended to include all modifications within the meaning and scope of the claims, as indicated by the claims. In the following description, for multiple identical components, only some components may be reference-labeled, while the reference numerals for others may be omitted.

[0022] <Embodiment 1> <Heat exchanger> The heat exchanger 10 according to this embodiment is a device for heating a liquid such as water or coolant as a heating medium. The heat exchanger 10 is installed in a vehicle such as an electric vehicle (EV) and is used for heating the passenger compartment or keeping the battery warm. As shown in Figures 1 and 2, the heat exchanger 10 comprises a ceramic heater 11 and a housing 60 that houses the ceramic heater 11.

[0023] <Ceramic heater> The ceramic heater 11 comprises an insulator tube 20, a first flange 30, a second flange 40, and a terminal portion 25. The insulator tube 20 is cylindrical with an axis AX as its center. The insulator tube 20 extends in the longitudinal direction (the direction in which the axis AX extends). The insulator tube 20 comprises a cylindrical ceramic tube 20A, a cylindrical ceramic body 22 arranged on the outer circumference of the ceramic tube 20A, and a resin layer 29 covering the outer surface 22A of the ceramic body 22. The ceramic body 22 has a ceramic base 21 extending in the longitudinal direction, a heating resistor 23 and a pair of internal terminals 24 formed on the surface of the base 21. The base 21 is made of a ceramic material such as alumina.

[0024] As shown in Figure 3, a heating resistor 23 and a pair of internal terminals 24 are formed on the inner circumferential surface (the surface facing the ceramic tube 20A) or inside the ceramic body 22. The heating resistor 23 is in the shape of a meandering thin wire. The internal terminals 24 are rectangular in shape and are wider than the heating resistor 23. These internal terminals 24 are electrically connected to a terminal portion 25 via via conductors or the like (not shown). The terminal portion 25 is formed on the outer circumferential surface of the ceramic body 22.

[0025] The insulator tube 20 can be manufactured, for example, by wrapping a ceramic sheet 26 around a pre-fired base body 21 and then firing it. A conductive layer 27, such as tungsten, is formed on the surface or inside the ceramic sheet 26. After firing, the ceramic sheet 26 becomes the base body 21 that constitutes the ceramic body 22. After firing, the conductive layer 27 becomes the heat-generating resistor 23, internal terminals 24, and terminal portion 25.

[0026] The resin layer 29 is configured to cover at least a region R1 on the outer surface 22A of the ceramic body 22 that has a heat-generating resistor 23 in the longitudinal direction. The resin layer 29 has heat resistance to a temperature higher than the heating temperature of the ceramic body 22. The heating temperature refers to the temperature when heated by the heat-generating resistor 23. The average thickness T1 of the resin layer 29 is thinner than the distance D1 from the heat-generating resistor 23 to the outer surface 22A, as shown in Figure 4.

[0027] The resin layer 29 may have an internal resin layer 29A that directly covers the outer surface 22A of the ceramic body 22, and an external resin layer 29B that covers the outer surface 22A of the ceramic body 22 via the internal resin layer 29A. In that case, it is preferable that the main components of the internal resin layer 29A and the external resin layer 29B are different.

[0028] The heat resistance temperature of the resin layer 29 is 150°C or higher. Super engineering plastics such as PPA (aromatic polyamide), PPS (polyphenylene sulfide), LCP (liquid crystal polymer), PSU (polysulfone), PES (poethersulfone), PEI (polyetherimide), PAI (polyamideimide), PEEK (polyetheretherketone), and PTFE (polytetrafluoroethylene) can be used as resins with a heat resistance temperature of 150°C or higher. The resin layer 29 preferably contains glass fibers.

[0029] <Enclosure> As shown in Figures 1 and 2, the housing 60 houses the ceramic heater 11. The housing 60 constitutes part of the flow path FC through which the liquid flows. The housing 60 watertightly secures the ceramic heater 11 via the first flange 30. The housing 60 also secures the ceramic heater 11 via the second flange 40. In detail, the housing 60 may also watertightly secure the ceramic heater 11 via the second flange 40. Here, watertight securing means that multiple members are fixed by fixing parts, and that liquid leakage through these fixing parts is prevented.

[0030] The housing 60 comprises a third housing 70, a second housing 80, and a first housing 90, which are formed separately. The third housing 70 is assembled to the second housing 80. The first housing 90 is assembled to the third housing 70. The third housing 70 is watertight fitted to the first flange 30. The second housing 80 is watertight fitted to the second flange 40. Here, watertight fitting means that multiple members are fitted together at the fitting portion, and that leakage of liquid through this fitting portion is prevented.

[0031] <Effects of Embodiment 1> As described above, the ceramic heater 11 of Embodiment 1 is a ceramic heater 11 for heating liquids, comprising a ceramic body 22 having a ceramic base 21 extending in the longitudinal direction and a heating resistor 23 formed on the surface of the base 21, and a resin layer 29 configured to cover at least the region of the outer surface 22A of the ceramic body 22 that has the heating resistor 23 in the longitudinal direction, wherein the resin layer 29 has heat resistance to a temperature higher than the heating temperature of the ceramic body 22.

[0032] With this configuration, since the outer surface 22A of the ceramic body 22 is covered with a resin layer 29, the thermal conductivity between the liquid heating medium and the ceramic body 22 is reduced by the resin layer 29. Therefore, even when there is a large temperature difference between the liquid heating medium and the ceramic body 22, it is possible to avoid the ceramic body 22 from rapidly cooling and cracking due to the liquid heating medium, thereby improving thermal shock resistance.

[0033] The average thickness T1 of the resin layer 29 is preferably thinner than the distance D1 from the heat-generating resistor 23 to the outer surface 22A.

[0034] If the average thickness T1 of the resin layer 29 is greater than the distance D1 from the heat-generating resistor 23 to the outer surface 22A, there is a concern that heat will not be easily transferred to the liquid heating medium. On the other hand, in the above configuration, the average thickness T1 of the resin layer 29 is thinner than the distance D1 from the heat-generating resistor 23 to the outer surface 22A, so that thermal shock resistance can be improved while maintaining the ability to transfer heat to the liquid heating medium.

[0035] The resin layer 29 has an internal resin layer 29A that directly covers the surface of the ceramic body 22 and an external resin layer 29B that covers the surface of the ceramic body 22 via the internal resin layer 29A, and it is preferable that the internal resin layer 29A and the external resin layer 29B have different main components.

[0036] The internal resin layer 29A can be a heat-resistant resin layer, and the external resin layer 29B can be a resin layer with high mechanical strength and thermal conductivity, so that the resin layers have multiple functions.

[0037] The heat resistance temperature of the resin layer 29 is preferably 150°C or higher. Water and coolant are widely used as heating media. Since the boiling point of water is 100°C and the boiling point of coolant is approximately 120°C, it is expected that the resin layer 29 will reach temperatures above 100°C when an air layer is formed due to boiling. In that case, the resin layer 29 can withstand temperatures up to 150°C.

[0038] The resin layer 29 preferably contains glass fibers. By incorporating glass fibers into the resin layer 29, heat resistance can be increased and strength can be enhanced.

[0039] <Embodiment 2> Embodiment 2 will be described with reference to Figure 5. The ceramic heater 12 of Embodiment 2 has a ceramic body 122 and a resin layer 129, and unlike the ceramic heater 11 of Embodiment 1, it is rod-shaped. The ceramic body 122 has a ceramic base 121 extending in the longitudinal direction and a heating resistor 23. The heating resistor 23 is embedded in the base 121, which is rod-shaped and extends in the longitudinal direction. The resin layer 129 is configured to cover at least the region R2 on the outer surface of the ceramic body 122 that has the heating resistor 23 in the longitudinal direction. The same components as in Embodiment 1 will not be described, and the same reference numerals as in Embodiment 1 will be used.

[0040] <Embodiment 3> Embodiment 3 will be described with reference to Figure 6. The ceramic heater 13 of Embodiment 3 has a ceramic body 222 and a resin layer 229, and unlike the ceramic heater 11 of Embodiment 1, it is plate-shaped. The ceramic body 222 has a ceramic base 221 extending in the longitudinal direction and a heating resistor 23. The heating resistor 23 is formed on the surface of the base 221, which is plate-shaped and extends in the longitudinal direction. The resin layer 229 is configured to cover at least a region R3 on the outer surface of the ceramic body 222 that has the heating resistor 23 in the longitudinal direction. The same components as in Embodiment 1 will not be described, and the same reference numerals as in Embodiment 1 will be used.

[0041] <Other Embodiments> (1) In embodiments 1 to 3, the average thickness T1 of the resin layer 29 was exemplified as being thinner than the distance D1 from the heat-generating resistor 23 to the outer surface 22A, but the average thickness of the resin layer 29 may be the same as or thicker than the distance D1.

[0042] (2) In embodiments 1 to 3, a resin layer 29 consisting of an internal resin layer 29A and an external resin layer 29B was illustrated, but the resin layer may be a single layer or composed of three or more layers. [Explanation of symbols]

[0043] 10...Heat exchanger 11, 12, 13… Ceramic heater 20…Insulator tube 20A…Ceramic tube 21,121,221…Base 22,122,222…Ceramic body 22A…Outer surface 23…Heating resistor 24…Internal terminal 25…Terminal section 26…Ceramic sheet 27…Conductor layer 28…Heating section 29,129,229…Resin layer 29A…Internal resin layer 29B…External resin layer 30...First flange 40...Second flange 60…Cabinet 70... Third cabinet 80...Second cabinet 90...First cabinet AX: Axis T1: Average thickness D1: Distance FC…flow path R1, R2, R3…domain

Claims

1. A ceramic heater for heating liquids, A ceramic body having a ceramic substrate extending in the longitudinal direction and a heat-generating resistor formed on the surface of the substrate, The ceramic body comprises a resin layer configured to cover at least a region of the outer surface of the ceramic body having the heat-generating resistor in the longitudinal direction, The resin layer has heat resistance to a temperature higher than the heating temperature of the ceramic body, thus forming a ceramic heater.

2. A ceramic heater for heating liquids, A ceramic body having a rod-shaped ceramic base extending in the longitudinal direction and a heat-generating resistor embedded in the base, The ceramic body comprises a resin layer configured to cover at least a region of the outer surface of the ceramic body having the heat-generating resistor in the longitudinal direction, The resin layer has heat resistance to a temperature higher than the heating temperature of the ceramic body, thus forming a ceramic heater.

3. The ceramic heater according to claim 1, wherein the average thickness of the resin layer is thinner than the distance from the heating resistor to the outer surface.

4. The ceramic heater according to claim 1, wherein the resin layer comprises an internal resin layer that directly covers the surface of the ceramic body and an external resin layer that covers the surface of the ceramic body via the internal resin layer, and the internal resin layer and the external resin layer have different main components.

5. The ceramic heater according to claim 1 or claim 2, wherein the heat resistance temperature of the resin layer is 150°C or higher.

6. The ceramic heater according to claim 1 or claim 2, wherein the resin layer contains glass fibers.

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