Ceramic heater

Abstract

To provide a ceramic heater for liquid heating capable of suppressing breakage of a heater even in a dry-fired state.SOLUTION: A ceramic heater 100 for liquid heating includes: a cylindrical ceramic body 10 having a heating resistor 13 and extending in a direction of an axis O; and heat radiation fins 20, 21, and 22 protruding from the surface of the ceramic body and having a higher thermal conductivity than the ceramic body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ceramic heater for heating liquid, which is used, for example, for air conditioning in electric vehicles or for heating and keeping batteries warm. [Background technology]

[0002] Systems that use ceramic heaters to heat coolant or other fluids are being considered for air conditioning or battery heating and insulation in electric vehicles. Battery performance declines in cold regions, making battery heating and insulation particularly important.

[0003] This ceramic heater has a structure in which a ceramic layer is wound around the outer periphery of a cylindrical or columnar ceramic tube that serves as a core material, and a heater pattern is formed on the ceramic layer (see Patent Document 1). When the heater pattern is energized and heated, the ceramic heater generates heat. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-133762 Summary of the Invention [Problem to be solved by the invention]

[0005] When a ceramic heater is used to heat a medium (liquid) such as a coolant, if the flow rate of the liquid flowing around the ceramic heater decreases or if the liquid decreases from inside the container due to a leak or the like, excessive boiling occurs and the heater enters an empty-fire state (air heating state). This causes the surface of the ceramic heater to become very hot, and if liquid droplets fall on this hot surface, the heater may crack due to thermal shock, resulting in damage to the heater.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a ceramic heater for heating liquid that can prevent damage to the heater even when the heater is in an empty-heat state. [Means for solving the problem]

[0007] In order to solve the above problems, the ceramic heater of the present invention is a ceramic heater for heating liquid, characterized in that it comprises a cylindrical ceramic body having a heating resistor and extending in the axial direction, and heat dissipation fins protruding from the surface of the ceramic body and having a thermal conductivity higher than that of the ceramic body.

[0008] This ceramic heater has heat dissipation fins protruding from the surface of the ceramic body, so even if the heater is in an empty-fired state (heated in air) and the ceramic body forming the surface of the ceramic heater becomes hot, liquid droplets do not directly hit this hot part but instead hit the heat dissipation fins and are cooled, preventing cracks and other damage to the heater due to thermal shock. Moreover, overheating of the heater can also be prevented by cooling the ceramic heater (ceramic body) itself with heat dissipation fins.

[0009] In the ceramic heater of the present invention, the heat dissipation fin has a fin portion and a base portion to which the fin portion is fixed, the entire surface of the ceramic body is covered with the fin portion and the base, and the ceramic heater may further include a sealing member that can maintain a liquid-tight seal between the surface of the ceramic body and the heat dissipation fin. This ceramic heater prevents liquid from entering the gap between the ceramic body and the heat dissipation fins, and prevents the liquid in the gap from boiling and overheating the heater.

[0010] In the ceramic heater of the present invention, the heat dissipating fins may be made of aluminum or an aluminum alloy, and the surfaces may be anodized. This ceramic heater has a high thermal conductivity of the heat dissipation fins, resulting in a large heat dissipation effect, and the alumite treatment can prevent corrosion of the heat dissipation fins due to liquids such as coolant.

[0011] In the ceramic heater of the present invention, the entire surface of the ceramic body may be covered with the base, and the fin portion may be a separate member from the base and protrude from the base. According to this ceramic heater, the fin portion, which is a separate member from the base portion, can be fixed to the base portion, and for example, damaged fin portions can be replaced. [Effects of the Invention]

[0012] According to the present invention, a ceramic heater for heating liquid can be obtained that can suppress damage to the heater even when the heater is in an empty-heat state. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing a ceramic heater according to an embodiment of the present invention. [Figure 2] FIG. 2 is a front view of the ceramic heater as seen from the tip. [Figure 3] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 2 is a perspective view showing the configuration of a ceramic body. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a ceramic heater 100 according to an embodiment of the present invention, FIG. 2 is a front view of the ceramic heater 100 as seen from the tip, FIG. 3 is a cross-sectional view taken along line A-A in FIG. 1, and FIG. 4 is a perspective view showing the configuration of a ceramic body 10. The ceramic heater 100 according to the embodiment of the present invention can be used, for example, for air conditioning of electric vehicles or for heating and keeping batteries warm, etc. The ceramic heater 100 is for heating liquid, and heats a liquid such as a coolant liquid, thereby heating an object to be heated via the liquid.

[0015] 1, the ceramic heater 100 includes a cylindrical ceramic body 10 extending in the direction of an axis O, and heat dissipation fins 20 attached to protrude from the surface of the ceramic body 10. In this example, the heat dissipation fins 20 cover the surface of the ceramic body 10. The heat dissipation fins 20 are made of a material having a higher thermal conductivity than the ceramic body, and for example, a metal such as aluminum can be used. A heating resistor 13 is embedded inside the ceramic body 10 (FIG. 3). Cylinders also include cylinders.

[0016] A pair of external terminals 17 (only one is shown in FIG. 1) for applying current to heat the heating resistor 13 are exposed on the outer surface of one end (rear end) of the ceramic body 10. Furthermore, a donut-shaped ceramic flange portion 15 for attaching the ceramic heater 100 to an object to be attached (such as an electric vehicle) is fitted onto the ceramic body 10 slightly distal to the external terminal 17 and fixed in place with glass or the like. The heat dissipation fins 20 cover the surface of the ceramic body 10 on the tip side of the flange portion 15 .

[0017] 2 and 3, in this example, the ceramic body 10 is cylindrical and has a through-hole 10h at its center. The liquid flowing inside the through-hole 10h is heated by the ceramic heater 100, and the liquid on the outer periphery of the ceramic heater 100 is also heated by the ceramic heater 100. The heat dissipating fins 20 include a first heat dissipating fin 21 that covers the outer surface of the ceramic body 10, and a second heat dissipating fin 22 that covers the inner surface of the ceramic body 10 (the surface of the through-hole 10h). Furthermore, the end face (the face facing the tip) of the ceramic body 10 is covered with a waterproof cap 30 made of a material having a higher thermal conductivity than the ceramic body 10, such as an aluminum alloy or a copper alloy.

[0018] Here, the first heat dissipation fin 21 integrally includes a cylindrical base 21b that fits along the outer surface of the ceramic body 10, and a plurality of fins 21a that protrude outward from the outer surface of the base 21b. The fins 21a are spaced apart in the circumferential direction of the base 21b. Similarly, the second heat dissipation fin 22 integrally includes a cylindrical base 22b that fits along the inner surface of the ceramic body 10, and a plurality of fins 22a that protrude from the inner surface of the base 22b toward the center. The fins 22a are spaced apart from one another in the circumferential direction of the base 22b, and the tips of the fins 22a that face each other toward the center have gaps between them, leaving the centers open.

[0019] In addition, the gap between the first heat dissipation fin 21 and the outer surface of the ceramic body 10, the gap between the second heat dissipation fin 22 and the inner surface of the ceramic body 10, and the gap between the first heat dissipation fin 21, the second heat dissipation fin 22 and the waterproof cap 30 are each sealed and fixed with a liquid-tight sealing member 40 (e.g., epoxy resin), thereby keeping these gaps liquid-tight. The sealing member 40 may be made of a material other than resin, such as thermally conductive grease, as long as it is liquid-tight.

[0020] Next, the configuration of the ceramic body 10 will be described with reference to FIG. The ceramic body 10 includes a ceramic tube 11 and a ceramic layer (ceramic sheet) 12 that covers almost the entire outer periphery of the ceramic tube 11. A heating resistor 13 having a serpentine pattern and a pair of internal terminals 26 are formed on the inner peripheral surface (the surface on the ceramic tube 11 side) or inside the ceramic layer 12. These internal terminals 26 are electrically connected to external terminals 17 at the end of the outer peripheral surface of the ceramic layer 12 through via conductors or the like (not shown). The heating resistor 13 is disposed near the front end of the ceramic body 10 , and the external terminal 17 is disposed near the rear end of the ceramic body 10 . The ceramic tube 11 and ceramic layer 12 may be made of alumina, for example.

[0021] As described above, in the ceramic heater 100 according to the embodiment of the present invention, the heat dissipation fins 20 protrude from the surface of the ceramic body 10. Therefore, even if the heater is in an empty-fired state (heated in air) and the surface of the ceramic heater 100 (ceramic body 10) becomes hot, droplets of liquid do not directly hit this hot part but instead hit the heat dissipation fins 20 and are cooled, thereby preventing cracks and other damage to the heater due to thermal shock. Moreover, by cooling the ceramic heater 100 (ceramic body 10) itself with the heat dissipation fins 20, overheating of the heater can also be prevented.

[0022] In addition, in this example, the entire surface (front and back) of the ceramic body 10 is covered with heat dissipation fins 20 (fin portions 21a, 22a and base portions 21b, 22b), and a sealing member 40 is further provided that can maintain a liquid-tight seal between the surface (front and back) of the ceramic body 10 and the heat dissipation fins 20. This prevents liquid from entering the gap between the ceramic body 10 and the heat dissipation fins 20, and prevents the liquid in the gap from boiling and overheating the heater.

[0023] It goes without saying that the present invention is not limited to the above-described embodiments, but covers various modifications and equivalents that fall within the spirit and scope of the present invention. The shape of the heat dissipation fins 20 is not limited as long as they protrude from the surface of the ceramic body. The heat dissipation fins 20 are made of aluminum or an aluminum alloy, and the surfaces may be anodized. This increases the thermal conductivity of the heat dissipation fins 20, resulting in a high heat dissipation effect, and the anodization also prevents the heat dissipation fins 20 from corroding due to liquids such as coolants. The heat dissipation fins 20 can be manufactured by, for example, drawing aluminum material or by pressing a metal plate to cut out the fin portions. [Explanation of symbols]

[0024] 10 Ceramic body 13 Heating resistor 20, 21, 22 Heat dissipation fins 21a, 22a Fin section 21b, 22b base 40 sealing material 100 Ceramic heater O axis

Claims

1. A ceramic heater for heating liquid, a cylindrical ceramic body having a heating resistor and extending in an axial direction; a heat dissipation fin protruding from the surface of the ceramic body and having a thermal conductivity higher than that of the ceramic body; A ceramic heater comprising:

2. The heat dissipation fin has a fin portion and a base portion to which the fin portion is fixed, the entire surface of the ceramic body is covered with the fin portion and the base, 2. The ceramic heater according to claim 1, further comprising a seal member capable of maintaining a liquid-tight seal between the surface of the ceramic body and the heat dissipation fins.

3. 3. The ceramic heater according to claim 1, wherein the heat dissipating fins are made of aluminum or an aluminum alloy, and the surfaces thereof are anodized.

4. 3. The ceramic heater according to claim 2, wherein the entire surface of the ceramic body is covered with the base, and the fin portion is a separate member from the base and protrudes from the base.

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