Ceramic heater and liquid heating device

Abstract

To provide a ceramic heater and a liquid heating device capable of improving heating efficiency without obstructing a flow of liquid to be heated.SOLUTION: A ceramic heater 100 for heating liquid includes a columnar ceramic body 10 having a heating resistor 13 and extending in a direction of an axis line O, and a radiation fin 20 protruding from a surface of the ceramic body, extending in the direction of the axis line, and having thermal conductivity higher than that of the ceramic body, where a plurality of radiation fins is provided apart from each other in a circumferential direction of the ceramic body and extend in the direction of the axis line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ceramic heater for heating a liquid and a liquid heating device used, for example, for air conditioning of an electric vehicle or for heating and keeping a battery 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).The ceramic heater generates heat by passing electricity through the heater pattern. Also, a technique is known in which heat dissipation fins are attached to the outer surface of a ceramic heater to improve the hot air generation characteristics of the air heater (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-133762 [Patent Document 2] Japanese Patent Application Publication No. 2-94384 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the heater described in Patent Document 2 is an air heater and does not take into consideration the flow of liquid around the heater. Therefore, when this air heater is used to heat liquid, the heating efficiency of the liquid can be improved, but depending on the relationship between the direction of the flow of the liquid around the heater and the direction in which the heat dissipation fins extend, the flow of the liquid around the heater may be obstructed. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a ceramic heater and a liquid heating device that can improve heating efficiency without impeding the flow of the liquid to be heated. [Means for solving the problem]

[0006] In order to solve the above problems, the ceramic heater of the present invention is a ceramic heater for heating liquid, and comprises a columnar ceramic body having a heating resistor and extending in the axial direction, and heat dissipation fins that protrude from the surface of the ceramic body, extend in the axial direction, and have a thermal conductivity greater than that of the ceramic body, and are characterized in that the heat dissipation fins extend in the axial direction.

[0007] In this ceramic heater, the heat dissipation fins extend in the axial direction. Therefore, if the ceramic heater is installed in the internal space of a liquid container so that the flow of the liquid is oriented along the axial direction at an angle of less than 45 degrees, the flow of the liquid around the ceramic heater will be along the direction in which the heat dissipation fins extend (i.e., the axial direction), and the liquid will flow smoothly along the heat dissipation fins without resistance, improving the heating efficiency of the liquid to be heated without impeding the flow.

[0008] In the ceramic heater of the present invention, the heat dissipation fins may be provided in plurality at intervals in the circumferential direction of the ceramic body. According to this ceramic heater, since a plurality of heat dissipation fins are provided, the heating efficiency of the liquid to be heated can be further improved.

[0009] The liquid heating device of the present invention is a liquid heating device comprising a container having an internal space, an inlet and an outlet communicating with the internal space, and the ceramic heater of claim 1, which extends in an axial direction and has a heating resistor located within the internal space, wherein the liquid is introduced from the inlet, passes through the internal space, and flows to the outlet in a flow path in which the liquid is heated by the ceramic heater, and heat dissipation fins face at least a part of the flow path, and when the part of the flow path facing the heat dissipation fins is defined as the target flow path, the flow direction in the target flow path is along the axial direction at an angle of less than 45 degrees.

[0010] With this liquid heating device, the flow direction of the liquid in the target flow path within the container is along the direction in which the heat dissipation fins extend (=axial direction), so the liquid flows smoothly along the heat dissipation fins without resistance, and the heating efficiency of the heated liquid can be improved without obstructing the flow.

[0011] In the liquid heating device of the present invention, the ceramic body has a through hole along the axial direction, one end of the through hole communicating with the inlet and the other end of the through hole facing the internal space, the flow path is defined so that it flows from the inlet through the through hole, exits to the outer surface of the ceramic body at the tip side of the ceramic body, then turns back at the wall of the internal space toward the rear end side, and flows along the outer surface of the ceramic body to the outlet, and the target flow path may be defined at least in the portion from the tip of the ceramic body to the outlet. According to this liquid heating device, the present invention can be applied to an embodiment in which a liquid is passed through the through holes of the ceramic body.

[0012] In the liquid heating device of the present invention, the axis of the opening end where the outlet faces the internal space may intersect with the axial direction, and a notch portion connected circumferentially may be formed in the heat dissipation fin at the portion that overlaps with the opening end in the axial direction. When the axis of the outlet intersects with the axial direction, the liquid flowing in the axial direction along the heat dissipation fins must change direction and flow in a direction that intersects with the axial direction. Therefore, by providing a cutout portion, the liquid flowing along the heat dissipation fin can more easily change direction in a direction that intersects with the axial direction, thereby further improving the heating efficiency without impeding the flow of the liquid to be heated.

[0013] In the liquid heating device of the present invention, the heat dissipation fins may be attached so as to cover the inner surfaces of the through holes of the ceramic body in addition to the outer surface of the ceramic body. By passing the liquid through the through-holes in the ceramic body, overheating of the heater can be prevented from occurring from the inside of the through-holes in the ceramic body as well. Furthermore, the liquid can be heated from the inside of the through-holes by the heat dissipation fins, further improving the heating efficiency of the liquid to be heated.

[0014] According to the present invention, a ceramic heater and a liquid heating device can be obtained that can improve heating efficiency without impeding the flow of the liquid to be heated. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view taken along the axial direction of a liquid heating device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view showing the configuration of the liquid heating device. [Figure 3] FIG. 2 is a perspective view showing a ceramic heater. [Figure 4] FIG. 2 is a front view of the ceramic heater as seen from the tip. [Figure 5] FIG. 4 is a cross-sectional view taken along line A-A in FIG. 3. [Figure 6] FIG. 2 is a perspective view showing the configuration of a ceramic body. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view along the axis O of a liquid heating device 200 according to an embodiment of the present invention, FIG. 2 is an exploded perspective view showing the configuration of the liquid heating device 200, FIG. 3 is a perspective view showing the ceramic heater 100, FIG. 4 is a front view of the ceramic heater 100 as seen from the tip, FIG. 5 is a cross-sectional view along line A-A in FIG. 3, and FIG. 6 is a perspective view showing the configuration of the ceramic body 10.

[0017] In this embodiment, the liquid heating device 200 has a built-in ceramic heater 100 and can be used, for example, for air conditioning of an electric vehicle or for heating and keeping a battery warm. The ceramic heater 100 is for heating a liquid, and heats a liquid such as a coolant liquid, thereby heating an object to be heated via the liquid.

[0018] As shown in FIGS. 1 and 2, the liquid heating device 200 has a generally cylindrical shape extending in the axial direction L as a whole, and includes a container 150 and one ceramic heater 100. The container 150 has a cylindrical body 151 having an internal space 150i for containing liquid W (water), a front end cap 153 and a rear end cap 155 that close both axial end openings of the body 151, and an inlet 157 and an outlet 159 for the liquid W. In this example, the direction toward the rear end cap 155 in the axial direction L is defined as the "rear end side."

[0019] Both ends of the body 151 in the axial direction L protrude radially like flanges, and both ends of the body 151, the front end cap 153 and the rear end cap 155 are airtightly sealed by O-rings 161, 163 (FIG. 2), respectively.

[0020] The rear end lid 155 is formed in a substantially block shape and has a through hole 155h that penetrates in the axial direction L. A cylindrical introduction port 157 is attached to the rear end side of the rear end lid 155 via an O-ring (not shown) so as to communicate with the through hole 155h. The extension direction of the introduction port 157 is along the axial direction L. The upper surface of the rear end of the body 151 protrudes in the shape of a rectangular box to form a protrusion 151p. The protrusion 151p has a through-hole 151h that penetrates in a direction perpendicular to the axial direction L and communicates with the internal space 150i. A cylindrical discharge port 159 is attached to the upper surface of the protrusion 151p via an O-ring (not shown) so as to communicate with the through-hole 151h. The direction in which the discharge port 159 extends is perpendicular to the axial direction L.

[0021] The ceramic heater 100 has a columnar (cylindrical) shape extending in the direction of the axis O, and is attached to the container 150 in a cantilevered manner by sandwiching a flange portion 15 (see FIG. 3) provided on the rear end side of the ceramic heater 100 between a body portion 151 and a rear end lid 155. The heating resistor 13 (see FIG. 5) on the front end side of the ceramic heater 100 is located within the internal space 150i. A recess 155r that accommodates the rear end of the ceramic heater 100 and communicates with the through-hole 155h is formed on the front end side of the rear end cover 155. Lead wires 15 and 16 (described later) for supplying power from the outside are connected to the external terminals 17 (see FIG. 3) of the ceramic heater 100, and the lead wires 15 and 16 are drawn out to the outside from lead holes 155h2 that communicate with the recess 155r and penetrate upward.

[0022] The inlet 157 and the outlet 159 are connected to the internal space 150i and are arranged at a distance in the axial direction L (also in the direction of the axis O), and liquid W introduced from the outside through the inlet 157 passes through the internal space 150i along the flow direction F and is discharged from the outlet 159. In addition, a gap is formed between the inner wall of the container 150 and the ceramic heater 100, and the liquid W introduced into the internal space 150i through the inlet 157 is heated while coming into contact with the outer surface of the ceramic heater 100 along the flow direction F, and then flows through a flow path leading to the outlet 159.

[0023] In this example, the ceramic heater 100 has a through hole 10h along the axis O direction, and the flow path is defined so that the air flows from the inlet 157 through the through hole 10h, exits the ceramic heater 100 from the tip of the through hole 10h, turns back at the wall of the internal space 150i, heads toward the rear end, and flows along the outer surface of the ceramic heater 100 to the outlet 159.

[0024] Here, in order to introduce liquid W into the through-hole 10h, the rear-facing surface of the ceramic heater 100 abuts against the through-hole 155h of the rear-end cover 155 via an O-ring 165, sealing the space between the through-hole 10h and the through-hole 155h liquid-tightly, while one end side (rear end side) of the through-hole 10h is connected to the inlet 157. Furthermore, the other end (tip side) of the through-hole 10h faces the internal space 150i, so that the liquid W that passes through the through-hole 10h flows into the internal space 150i.

[0025] In this example, the ceramic heater 100 is accommodated in the internal space 150i so that the axial direction L of the liquid heating device 200 (body portion 151) is parallel to the axial line O of the ceramic heater 100. However, the axial direction L may form an angle with the axial line O as long as the flow direction F in a target flow path described later is along the axial line O at an angle of less than 45 degrees.

[0026] Next, the configuration of the ceramic heater 100 will be described with reference to FIGS.

[0027] 3, the ceramic heater 100 includes a cylindrical ceramic body 10 extending in the direction of the axis O, and heat dissipation fins 20 attached to the ceramic body 10 so as to protrude from the surface of the ceramic body 10 and extend in the direction of the axis O. In this example, the heat dissipation fins 20 cover the surface of the ceramic body 10. In this example, a plurality of heat dissipation fins 20 are provided spaced apart in the circumferential direction 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. 5). Cylinders also include cylinders.

[0028] A pair of external terminals 17 (only one is shown in FIG. 3) 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 (in this example, a container 150) 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 .

[0029] 4 and 5, 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.

[0030] Here, a plurality of heat dissipating fins 20 (first heat dissipating fins 21 and second heat dissipating fins 22) are provided at intervals in the circumferential direction of the ceramic body 10 and extend in the direction of the axis O. Furthermore, cutout portions 21n that are continuous in the circumferential direction are formed in the first heat dissipation fins 21 at portions on the flange portion 15 side along the axis O. The cutout portions 21n only need to have a smaller diameter than the other portions of the first heat dissipation fins 21, and although the fins themselves extending in the axis O direction are formed on the outer surfaces of the cutout portions 21n in this example, the fins do not necessarily have to be formed on the outer surfaces of the cutout portions 21n. The function of the notch 21n will be described later.

[0031] 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.

[0032] The heat dissipating fins 20 (first heat dissipating fin 21 and second heat dissipating fin 22) may not have a base portion, and each heat dissipating fin may be directly attached to the surface of the ceramic body .

[0033] 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.

[0034] 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.

[0035] As described above, in the ceramic heater 100 according to the embodiment of the present invention, the surface of the ceramic body 10 is covered with the heat dissipation fins 20. Therefore, even if the heater is in an empty-heating state (air heating state) and the surface of the ceramic heater 100 becomes hot, droplets of liquid do not directly hit this hot part but instead hit the heat dissipation fins 20 and are cooled, so that it is possible to prevent cracks and the like from occurring in the heater due to thermal shock and damage to the heater. Moreover, by cooling the ceramic heater 100 itself with the heat dissipation fins 20, overheating of the heater can also be prevented.

[0036] 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.

[0037] Furthermore, in the ceramic heater 100 according to the embodiment of the present invention, a plurality of heat dissipating fins 20 (first heat dissipating fins 21 and second heat dissipating fins 22) are provided spaced apart in the circumferential direction of the ceramic body 10 and extend in the axis O direction. As shown in FIG. 1, the ceramic heater 100 is installed in the internal space 150i of the container 150 so that the flow direction DI in the target flow path Fs is aligned with the axis O at an angle of less than 45 degrees. As a result, the flow direction DI of the liquid W around the ceramic heater 100 is along the extension direction (=axis O direction) of the heat dissipation fins 20 (21, 22), so that the liquid W flows smoothly along the heat dissipation fins 20 without resistance, and the heating efficiency of the liquid to be heated can be improved without impeding the flow of the liquid W around the ceramic heater 100.

[0038] As shown in FIG. 1, the path along which the liquid W is introduced from the inlet 157 of the container 150, passes through the internal space 150i, and flows to the outlet 159 is referred to as a "flow path F." The flow path F is the shortest path that passes through the axis n1 of the opening end of the inlet 157 facing the internal space 150i and the center of gravity of the through hole 10h of the ceramic heater 100 located in the internal space 150i, and the shortest path that passes through the axis n2 of the opening end 159e of the outlet 159 facing the internal space 150i from the tip of the through hole 10h through the internal space 150i (the gap between the outer surface of the ceramic heater 100 and the wall surface of the container 150). The open ends of the inlet 157 and the outlet 159 are boundaries between the container 150 and the inlet 157 and the outlet 159, and are the portions where the inlet 157 and the outlet 159 face the internal space 150i.

[0039] The target flow path Fs is a portion of the flow path F that faces the heat dissipation fins 20 (the first heat dissipation fins 21 and the second heat dissipation fins 22). The flow direction DI is the path of the flow path F, which is the target flow path Fs.

[0040] When the flow direction DI in the target flow path Fs of the container 150 is at an angle of 45 degrees or more with respect to the axial direction O of the ceramic heater 100, the flow direction DI is no longer aligned with the extension direction (=axial direction O) of the heat dissipation fins 20 (21, 22), and therefore the liquid W does not flow smoothly along the heat dissipation fins 20, and the flow is obstructed. The angle between the flow direction DI and the direction of the axis O is preferably 30 degrees or less.

[0041] In addition, in the liquid heating device 200 of this example, the axis n2 of the outlet 159 intersects with the axis O direction, and a cutout portion 21n is formed in the heat dissipation fin 20 (first heat dissipation fin 21) at a portion that overlaps with the opening end 159e in the axis O direction. When the axis n2 of the outlet 159 intersects with the axis O, the liquid W flowing in the axis O along the first heat dissipation fin 21 must change direction and flow so as to intersect with the axis O. Therefore, by providing the cutout portion 21n, the liquid W flowing along the first heat dissipation fin 21 can be more easily redirected in a direction intersecting the axis O, thereby further improving the heating efficiency of the liquid to be heated.

[0042] In the liquid heating device 200 of this example, the heat dissipation fins 21 and 22 are attached so as to cover the inner surfaces of the through holes 10h of the ceramic body 10 in addition to the outer surface of the ceramic body 10. As a result, by passing the liquid W also through the through holes 10h of the ceramic body 10, it is possible to prevent the heater from overheating from the inner surfaces of the through holes 10h of the ceramic body 10. Furthermore, the liquid W can be heated from the inner surfaces of the through holes 10h by the heat dissipation fins 22, thereby further improving the heating efficiency of the liquid to be heated.

[0043] 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. For example, the shapes of the liquid heating device, ceramic heater, heat dissipation fin, etc. are not limited. 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]

[0044] 10 Ceramic body 10h through hole 13 Heating resistor 20, 21, 22 Heat dissipation fins 21n Notch 100 Ceramic heater 150 containers 150i interior space 157 entrance 159 Outlet 159e Open end of discharge port 200 Liquid heating equipment O axis W liquid F flow path Fs Target flow path Flow direction in the DI target flow path n2 Axis center of the open end of the discharge port

Claims

1. A ceramic heater for heating liquid, a columnar ceramic body having a heating resistor and extending in an axial direction; a heat dissipation fin protruding from a surface of the ceramic body, extending in the axial direction, and having a thermal conductivity higher than that of the ceramic body; Equipped with The ceramic heater is characterized in that the heat dissipation fins extend in the axial direction.

2. 2. The ceramic heater according to claim 1, wherein a plurality of said heat dissipation fins are provided at intervals in the circumferential direction of said ceramic body.

3. a container having an internal space and an inlet and an outlet communicating with the internal space; a ceramic heater according to claim 1 or 2, which extends in the axial direction and in which the heating resistor is located within the internal space; A liquid heating device comprising: The liquid is introduced from the inlet, passes through the internal space, and flows to the outlet in a flow path, where the liquid is heated by the ceramic heater; the heat dissipation fin faces at least a part of the flow path; A liquid heating device characterized in that, when the portion of the flow path facing the heat dissipation fin is defined as the target flow path, the flow direction in the target flow path is along the axial direction at an angle of less than 45 degrees.

4. the ceramic body has a through hole extending along the axial direction, One end of the through hole communicates with the inlet, and the other end of the through hole faces the internal space, the flow path is defined so that the fluid flows from the inlet through the through hole, exits to the outer surface of the ceramic body at the front end side of the ceramic body, turns back at a wall surface of the internal space, and flows toward the rear end side, along the outer surface of the ceramic body to the outlet, 4. The liquid heating device according to claim 3, wherein the target flow path is defined by at least a portion of the flow path extending from the tip of the ceramic body to the outlet.

5. an axis of an open end of the outlet facing the internal space intersects with the axial direction; 5. The liquid heating device according to claim 3, wherein a notch extending in a circumferential direction is formed in the heat dissipation fin at a portion of the fin that overlaps with the open end in the axial direction.

6. 5. The liquid heating device according to claim 4, wherein the heat dissipation fins are attached so as to cover not only the outer surface of the ceramic body but also the inner surface of the through-hole of the ceramic body.

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