Heater and heater unit

Abstract

Provided are: a heater that is capable of, in manner conforming to various fluid forms, uniformly and efficiently heating a fluid to be heated throughout the entire flow channel thereof; and a heater unit equipped with the heater. The heater is for heating a fluid to be heated flowing through a flow channel formed in the upper surface of a base, and comprises: a substrate that is disposed so as to cover the upper surface of the base; a heating element that is disposed on one surface side of the substrate; and a power supply line that is disposed on the one surface side of the substrate so as to lie along the flow channel. The heating element has a plurality of heating cells, each of which receives power individually. The heating cells are connected in parallel to the power supply line, and are arranged side by side so as to lie along the flow channel toward an outflow port from an inlet port provided in the base.

Description

Heaters and heater units

[0001] The present invention relates to a heater and a heater unit, and more particularly to a heater and a heater unit including the heater.

[0002] Fluid heaters that heat fluids such as water through a planar, meandering flow path are known (see, for example, Patent Documents 1 and 2). Patent Document 1 describes a fluid heater that includes a planar, meandering flow path and a ceramic heater that is a flat plate that covers the flow path and has a resistance heating element on its surface. Patent Document 2 describes a fluid heater that includes a single meandering heating resistor that is in contact with a planar, spirally meandering flow path.

[0003] Japanese Patent Application Publication No. 11-135241 Special Table No. 2015-524906

[0004] However, the fluid heaters described in Patent Documents 1 and 2 heat the entire flow path using a heating resistor extending along the flow path. This means that the entire flow path is not heated evenly in response to various fluid conditions (e.g., fluid velocity, fluid temperature, etc.), and certain areas tend to become very hot. This can lead to problems such as heater damage in high-temperature areas, or when the fluid is liquid in the high-temperature area and the liquid boils, the heat transfer from the heater to the liquid rapidly decreases, resulting in poor heating efficiency for the entire liquid, or the fluid deteriorating due to localized high heat. In particular, when a resistance heating element with a high temperature coefficient of resistance is used as the heater, the temperature rises further due to its own heat generation, while the heat generation in other areas is relatively reduced. This necessitates power control tailored to the high-heat-generating area, resulting in problems with the heating performance of the entire fluid heater. Furthermore, in conventional technology, when the heater substrate is made of steel, a thin substrate can warp, causing the heater side to convex, making it difficult to adhere to the housing and potentially resulting in fluid leakage. Therefore, a substrate thickness of, for example, 3 mm or more is required, and the heat capacity is large, requiring a long time for heating.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a heater and a heater unit equipped with the same that can heat the heated fluid evenly and efficiently throughout the entire flow path in response to various fluid forms.

[0006] The present invention is as follows: 1. A heater for heating a fluid to be heated flowing through a flow path formed on the upper surface of a base, comprising: a substrate arranged to cover the upper surface of the base; a heating element arranged on one side of the substrate; and a power supply line arranged on one side of the substrate along the flow path, wherein the heating element has a plurality of heating cells each receiving power separately, the plurality of heating cells being connected in parallel to the power supply line, and the plurality of heating cells being arranged in a row along the flow path from an inlet to an outlet provided in the base. 2. The heater described in 1 above, in which the resistance heating wire constituting the heating element is made of a material having a high temperature coefficient of resistance and / or a PTC material. 3. The heater described in 1 or 2 above, in which a reinforcing layer is arranged along the flow path on the surface of the substrate facing the flow path. 4. The heater described in 3 above, in which the reinforcing layer has an exposed portion that connects the surface of the substrate facing the flow path with the flow path. 5. The heater according to 4. above, wherein a heat sink is disposed on the surface of the substrate facing the flow path, protruding into the flow path via the exposed portion. 6. The heater according to 4. above, wherein an embedding member formed of a material having a higher thermal conductivity than the material constituting the substrate is embedded in the exposed portion. 7. The heater according to 3. above, wherein the reinforcing layer is an insulating layer. 8. The heater according to 3. above, wherein the reinforcing layer is a heat-soaking layer formed of a material having a higher thermal conductivity than the material constituting the substrate. 9. The heater according to 1. or 2. above, wherein the substrate is formed of a clad material or a bimetal. 10. The heater according to 1. or 2. above, further comprising an insulating layer disposed on one side of the substrate and covering the heating element. 11. The heater according to 1. or 2. above, wherein the heating element is a resistance heating wire printed on the substrate. 12. 3. The heater according to claim 1 or 2, wherein the heat generating cells are configured in a zigzag curved shape consisting of parallel portions formed in a direction perpendicular to the flow direction of the flow channel and bent portions connecting adjacent parallel portions.13. The heater according to 1. or 2. above, wherein the heat generating cells are configured with a zigzag curved shape consisting of parallel portions formed in a direction parallel to the flow direction of the flow path and bent portions connecting adjacent parallel portions. 14. A heater unit comprising a base and a heater that heats a fluid to be heated flowing through a flow path formed on the upper surface of the base, wherein the heater is the heater according to any one of 1. to 13. above.

[0007] According to the present invention, it is possible to heat the fluid to be heated evenly and efficiently throughout the entire flow path in response to various fluid forms.

[0008] The present invention will be further described in the following detailed description by way of non-limiting examples of exemplary embodiments according to the present invention and with reference to the mentioned drawings, wherein like reference numerals denote like parts throughout the several views of the drawings.

[0023] Figure 1 is a schematic plan view showing a heater unit including a heater according to Example 1.

[0024] Figure 2 is a cross-sectional view taken along line AA' of Figure 1.

[0025] Figure 2 is an enlarged view of a main portion of Figure 2.

[0026] Figure 3 is a schematic exploded perspective view showing a heater unit according to Example 1.

[0027] Figure 4 is a schematic plan view showing a circuit pattern of a heating element according to Example 1, where (a) shows an overall plan view and (b) shows an enlarged view of a main portion of (a).

[0028] Figure 5 is a schematic exploded perspective view showing a heater unit including a heater according to Example 2.

[0029] Figure 6 is a schematic longitudinal cross-sectional view showing a heater unit according to Example 2.

[0030] Figure 7 is a schematic exploded perspective view showing a heater unit including a heater according to Example 3.

[0031] Figure 8 is a schematic plan view showing an insulating layer according to Example 3.

[0032] Figure 9 is a schematic longitudinal cross-sectional view showing a heater unit according to Example 3. 10A and 10B are schematic plan views showing insulating layers according to other embodiments, where (a) shows a form in which V-shaped exposed portions are formed in a plan view, and (b) shows a form in which dot-shaped exposed portions are formed in a plan view. FIG. 10B is a schematic exploded perspective view showing a heater unit including a heater according to Example 4. FIG. 10C is a schematic perspective view showing a heat sink according to Example 4. FIG. 10D is a schematic vertical sectional view showing a heater unit according to Example 4. FIG. 10C is a schematic perspective view showing a heat sink according to other embodiments, where (a) and (b) show a form in which a plurality of heat sinks are arranged along a flow path, and (c) shows a form in which a plurality of heat sinks are arranged along the width direction of the flow path. FIG. 10D is a schematic exploded perspective view showing a heater unit including a heater according to Example 5. FIG. 10E is a schematic vertical sectional view showing a heater unit according to Example 5. FIG. 10F is a schematic exploded perspective view showing a heater unit including a heater according to Example 6. FIG. 10F is a schematic vertical sectional view showing a heater unit according to Example 6. FIG. 10H is a schematic exploded perspective view showing a heater including a heater according to Example 7. FIG. 10H is a schematic vertical sectional view showing a heater unit according to Example 7. 1A and 1B are schematic plan views showing a circuit pattern of a heating element according to another embodiment, in which (a) is a plan view of the entire heating element and (b) is an enlarged view of a main part of (a). 1B are schematic plan views showing a circuit pattern of a heating element according to yet another embodiment, in which (a) is a plan view of the entire heating element and (b) is an enlarged view of a main part of (a).26 is a schematic plan view showing a circuit pattern of a heating element according to yet another embodiment, where (a) is an overall plan view and (b) is an enlarged view of a main part of (a). 27 is a schematic plan view showing a circuit pattern of a heating element according to yet another embodiment, where (a) is an overall plan view and (b) is an enlarged view of a main part of (a). 28 is a schematic plan view showing a circuit pattern of a heating element according to yet another embodiment. 29 is an enlarged view of a main part of FIG. 26. 29 is a schematic plan view showing a circuit pattern of a heating element (a part corresponding to a curved part of a flow path) according to yet another embodiment, where (a) shows a form in which the beginning of the heating cell is a bent part, and (b) shows a form in which the beginning of the heating cell is a parallel part perpendicular to the flow path. 30 is a schematic overall view showing an experimental system used in a flowing water heating experiment. 31 is a schematic perspective view showing a heater unit constituting the experimental system, where (a) shows the disassembled state and (b) shows the assembled state. 1A is a schematic plan view showing a heater used in a flowing water heating experiment, where (a) shows the heater of an experimental example and (b) shows the heater of a comparative example. 2B is a schematic vertical cross-sectional view showing a heater used in a flowing water heating experiment. 3A is a table showing the experimental results of the flowing water heating experiment.

[0009] The matters set forth herein are for illustrative purposes only and are intended to provide an illustrative description of the embodiments of the present invention, with the aim of providing what is believed to be the most effective and easily understandable explanation of the principles and conceptual features of the present invention. In this regard, it is not intended to show structural details of the present invention beyond the extent necessary for a fundamental understanding of the present invention, and the description, taken together with the drawings, will make clear to those skilled in the art how some forms of the present invention may be actually embodied.

[0010] 1 to 4, the heater according to this embodiment is a heater 3 for heating a fluid to be heated flowing through a flow path 25 formed on the upper surface (flow path forming surface) 24 of the base 21. The heater 3 includes a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one side of the substrate 31, and a power supply line 35 arranged on one side of the substrate 31 along the flow path 25. As shown in FIG. 5, for example, the heating element 32 has a plurality of heating cells 33 each receiving power, and the plurality of heating cells 33 are connected in parallel to the power supply line 35. The plurality of heating cells 33 are arranged in a row along the flow path 25 from an inlet 26a to an outlet 26b provided in the base 21. The heating element 32 may be arranged on the surface of the substrate 31 facing the flow path 25, or on the surface of the substrate 31 opposite the surface facing the flow path 25.

[0011] According to the above configuration, by adjusting the heat generation amount of each heat generation cell 33, it is possible to adjust the heat generation amount according to the position of the flow path 25. Furthermore, the self-temperature compensation function works for each heat generation cell 33, enabling efficient and balanced heating for various fluid velocities and fluid temperatures.

[0012] (Base) The base 21 typically has an inlet 26a and an outlet 26b for the fluid that are connected to the flow path 25. The material of the base 21 is not particularly limited, and for example, a base made of metal, synthetic resin, or ceramic can be used. The shape of the base 21 is not particularly limited, and for example, a flat rectangular, polygonal, circular, elliptical, or irregularly shaped base can be used.

[0013] The flow path 25 is usually open on the upper surface 24 of the base 21. The shape of the flow path 25 is not particularly limited, and one or a combination of two or more of a linear, curved, or bent shape can be used. From the viewpoint of heat exchange efficiency, the flow path 25 is preferably a serpentine flow path in which linear flow paths and curved flow paths in which the flow direction is reversed are alternately arranged. The type of fluid to be heated is not particularly limited, and examples thereof include liquids such as water and oil, gases, and gels.

[0014] (Reinforcing layer) From the viewpoint of thinning (i.e., reducing weight) the substrate 31 and suppressing warping, it is preferable that reinforcing layers 41, 44 are arranged along the flow path on the side of the substrate 31 facing the flow path 25 (see, for example, Figures 7, 10, 14, 17 and 19).

[0015] The insulating layer 41 can be used as the reinforcing layer. The material of the insulating layer 41 is not particularly limited, but for example, glass, ceramics, glass-ceramics, etc. are preferable. Among these, when a metal (stainless steel, etc.) is used as the material constituting the substrate 31, the material of the insulating layer 41 is preferably glass, more preferably crystallized glass or semi-crystallized glass, from the viewpoint of its thermal expansion balance. Specifically, SiO ２ -Al ２ O ３ MO-based glass is preferred, where MO is an oxide of an alkaline earth metal (MgO, CaO, BaO, SrO, etc.). The thickness of the insulating layer is not particularly limited (for example, about 30 to 200 μm).

[0016] The reinforcing layer can be a heat spreader layer 44. The heat spreader layer 44 serves to even out thermal fluctuations in the heating element 32. That is, if there is a drop in the heating temperature, the layer can raise the temperature to the same temperature as the surrounding area, and if there is a peak in the heating temperature, the layer can lower the temperature to the same temperature as the surrounding area, thereby evening out the thermal fluctuations. This is particularly useful when the heating element 32 is formed using resistive heating wiring with a predetermined pattern shape, as it can even out thermal fluctuations caused by this pattern shape. That is, the pattern shape creates areas where the resistive heating wiring is present and areas where it is not, resulting in thermal fluctuations in which the areas where the resistive heating wiring is present are higher in temperature than the areas where it is not present. Such thermal fluctuations can be evened out by passing the heat through the heat spreader layer 44, thereby reducing the temperature difference. From this perspective, providing the heat spreader layer 44 is effective in heaters that include multiple heating cells 33 electrically connected in parallel as the heating element 32.

[0017] The uniform heat transfer layer 44 is formed of a material with a higher thermal conductivity than the material constituting the substrate 31. For example, when the substrate 31 is made of stainless steel, which has a low thermal conductivity of 50 W / mK or less, the heat sink 43 is preferably formed of a material with a thermal conductivity of 100 W / mK or more. Specifically, the thermally conductive metal may be silver, copper, gold, aluminum, tungsten, nickel, or an alloy containing at least one of these metals. These thermally conductive metals may be used alone or in combination. Among these, silver, copper, aluminum, and alloys containing at least one of these metals are preferred. Furthermore, when the substrate 31 is made of a ceramic, such as alumina, which has a low thermal conductivity of 50 W / mK or less, the heat sink 43 is preferably formed of a material with a thermal conductivity of 100 W / mK or more. Specifically, thermally conductive ceramics such as aluminum nitride can be used, as well as the various thermally conductive metals mentioned above.

[0018] The uniform heat layer 44 may be formed in any manner. Specifically, the uniform heat layer may be provided as a plating layer (electroless plating layer, electrolytic plating layer, composite plating layer of these, etc.). Alternatively, the uniform heat layer may be formed by printing a paste containing a thermally conductive material and then baking the printed coating. For example, a printing paste containing metal particles (metal powder) as the thermally conductive material may be used. In this case, the printing paste may contain, in addition to the metal particles, a vehicle for forming the paste and a glass or ceramic component as a co-substrate.

[0019] From the viewpoint of heat exchange efficiency, it is preferable that the reinforcing layers 41, 44 have an exposed portion 42 formed thereon, which connects the surface of the substrate 31 facing the flow path 25 with the flow path 25 (see, for example, FIG. 10 ). The exposed portion 42 may have, for example, (1) a shape formed in an elongated shape along the flow path 25 (see, for example, FIG. 9 ), or (2) a shape formed in multiple shapes along the flow path 25 (see, for example, FIG. 11 ). One type of these exposed portions 42 may be used, or two or more types may be used in combination.

[0020] In the above-described embodiment (1), the exposed portions 42 may be formed in a serpentine shape corresponding to the serpentine flow path 25. In the above-described embodiment (2), the exposed portions 42 may be formed in a planar V-shape, U-shape, W-shape, L-shape, or the like, or in a planar dot shape (e.g., a planar circle, a polygon, or the like). One type of these exposed portions 42 may be used, or two or more types may be used in combination. Furthermore, the planar dot-shaped exposed portions 42 may be arranged in a plurality (e.g., a plurality arranged in a staggered pattern) along the axial direction and width direction of the flow path 25.

[0021] (Heat Sink) From the viewpoint of heat exchange efficiency, it is preferable that a heat sink 43 protruding into the flow path 25 via an exposed portion 42 be disposed on the surface of the substrate 31 facing the flow path 25 (see, for example, FIG. 14).

[0022] The heat sink 43 may have, for example, a joining plate 43a joined (for example, by adhesion, welding, fitting, etc.) to the surface of the substrate 31 facing the flow path 25, and a heat dissipation plate 43b protruding from one surface of the joining plate 43a into the flow path 25. The heat dissipation plate 43b may have, for example, (1) a shape formed in an elongated shape along the flow path 25 (see, for example, FIG. 13 ), or (2) a shape formed in multiple pieces at predetermined intervals along the flow path 25 (see, for example, FIGS. 15( a) and 15(b) ). These shapes (1) and (2) may be used alone or in combination of two or more.

[0023] In the above-mentioned embodiment (1), the heat sink 43 may include only one heat dissipation plate 43b (see, for example, FIG. 13), or may include multiple heat dissipation plates 43b arranged opposite each other (i.e., arranged side by side in the width direction of the flow path 25) (see, for example, FIG. 15(c)). In the above-mentioned embodiment (2), the heat sink 43 may include a heat dissipation plate 43b arranged with one side substantially aligned or parallel to the axial direction of the flow path 25 (see, for example, FIG. 15(a)), or may include a heat dissipation plate 43b arranged with one side inclined with respect to the axial direction of the flow path 25 (see, for example, FIG. 15(b)).

[0024] The material of the heat sink 43 is not particularly limited. However, from the viewpoint of heat exchange efficiency, it is preferable that the heat sink 43 be formed from a material with a thermal conductivity greater than that of the material constituting the substrate 31. For example, when the substrate 31 is made of stainless steel, which has a low thermal conductivity of 50 W / mK or less, it is preferable that the heat sink 43 be formed from a material with a thermal conductivity of 100 W / mK or more. Specifically, silver, copper, gold, aluminum, tungsten, nickel, etc., or alloys containing at least one of these metals can be used as the thermally conductive metal. These thermally conductive metals can be used alone or in combination. Among these, silver, copper, aluminum, and alloys containing at least one of these metals are preferred. Furthermore, when the substrate 31 is made of a ceramic, such as alumina, which has a low thermal conductivity of 50 W / mK or less, it is preferable that the heat sink 43 be formed from a material with a thermal conductivity of 100 W / mK or more. Specifically, thermally conductive ceramics such as aluminum nitride can be used, as well as the various thermally conductive metals mentioned above.

[0025] Even in the heater 3 not having the reinforcing layers 41, 44 (see, for example, FIG. 3), a heat sink 43 can be disposed on the surface of the substrate 31 facing the flow path 25 in order to improve heat exchange efficiency.

[0026] From the viewpoint of heat exchange efficiency, it is preferable that an embedding member 45 made of a material with a higher thermal conductivity than the material constituting the substrate 31 is embedded in the exposed portion 42 (see, for example, FIG. 19 ). The material of the embedding member 45 may be the same as that of the above-described heat equalizing layer 44, for example.

[0027] 20 and 21 , for example, a heater may be employed in which a heating element 32 is disposed on the surface of the substrate 31 facing the flow path 25, a power supply terminal 36 electrically connected to the heating element 32 is disposed on the surface of the substrate 31 facing the flow path 25, a sealing heat spreader layer 46 is disposed on the surface of the substrate 31 facing the flow path 25 so as to seal the flow path 25, and the sealing heat spreader layer 46 is formed from a material having a higher thermal conductivity than the material constituting the substrate 31. The material of the sealing heat spreader layer 46 is not particularly limited, and the same material as that of the heat sink 43 described above may be used.

[0028] In the above embodiment, from the viewpoint of heat exchange efficiency, it is preferable that a thermally conductive grease layer or a thermally conductive adhesive layer 47 be disposed between the substrate 31 (specifically, the insulating layer 37) and the sealing uniform heat layer 46. The type of thermally conductive grease or adhesive is not particularly limited, but a base material such as modified silicone mixed with metal or metal oxide particles (filler) can be used. Particles such as silver, copper, gold, aluminum, tungsten, nickel, etc., or alloys containing at least one of these metals can be used as thermally conductive metals. These thermally conductive metals can be used alone or in combination of two or more. Among these, silver, copper, aluminum, and alloys containing at least one of these are preferred. Furthermore, particles such as alumina, magnesium oxide, and aluminum nitride can also be used. These can be used alone or in combination of two or more.

[0029] (Substrate) The substrate (31) is a substrate having a plurality of heat generating cells 33 arranged on one side thereof. The surface shape of the substrate 31 can be, for example, rectangular to match the flow path forming surface 24, but is not limited thereto, and any shape can be selected, such as square, L-shaped, arc-shaped, or fan-shaped, to match the shape of the flow path forming surface 24 of the base 21. The thickness of the substrate 31 may be determined depending on the material, planar dimensions, required strength, etc.

[0030] The material constituting the substrate 31 is not limited, and examples thereof include metals, ceramics, and composite materials thereof. Examples of metals constituting the substrate 31 include steel, with stainless steel being particularly preferred. The type of stainless steel is not particularly limited, and ferritic stainless steel and / or austenitic stainless steel are preferred. Among these stainless steels, varieties with particularly excellent heat resistance and / or oxidation resistance are preferred. Examples include SUS430, SUS436, SUS444, and SUS316L. These may be used alone or in combination. Furthermore, aluminum, magnesium, copper, and alloys of these metals may be used as metals constituting the substrate. These may be used alone or in combination. Among these, aluminum, magnesium, and their alloys (e.g., aluminum alloys, magnesium alloys, and Al-Mg alloys) have low specific gravities, and thus their use can reduce the weight of the heater. Furthermore, copper and its alloys have excellent thermal conductivity, and thus their use can improve the uniform heating of the heater. Furthermore, from the viewpoint of heat exchange efficiency, the substrate 31 is preferably formed of a clad material or a bimetal. The type of clad material or bimetal is not particularly limited, but it may have, for example, a first metal plate made of steel and a second metal plate having a higher thermal conductivity than the first metal plate. Stainless steel is preferably used as the first metal plate. On the other hand, silver, copper, gold, aluminum, tungsten, nickel, etc., or an alloy containing at least one of these metals, can be used as the second metal plate. Furthermore, the clad material or bimetal may be, for example, a structure in which the first metal plate is bonded to only one surface of the second metal plate (e.g., SUS-Cu, etc.), a structure in which the first metal plate is bonded to both surfaces of the second metal plate (e.g., SUS-Cu-SUS, etc.), or a structure in which the second metal plate is bonded to both surfaces of the first metal plate (e.g., Cu-SUS-Cu, etc.). Furthermore, a structure having three or more types of metal plates can also be used.

[0031] Furthermore, when the substrate is made of ceramics, the substrate material may be any material that can achieve electrical insulation between the wiring (resistance heating wire, power supply wiring, power supply terminal, etc.) provided thereon. Preferred substrate materials include, for example, aluminum oxide, aluminum nitride, zirconia, silica, mullite, spinel, cordierite, silicon nitride, etc. These may be used alone or in combination of two or more. Of these, aluminum oxide and aluminum nitride are more preferred. Furthermore, a composite material of metal and ceramic may also be used as the substrate. Preferred composite materials include, for example, SiC / C, SiC / Al, etc. These may be used alone or in combination of two or more.

[0032] (Heater) The heater (32) is made of a resistance heating wire formed on one side of the substrate 31. The heater (32) is also made up of a power supply wire (35) arranged along the flow path and a plurality of heat generating cells (33) connected to the power supply wires (35). Here, when the heater 32 is made by printing a resistance heating wire on the substrate 31, a plurality of heat generating cells 33 can be formed at once without increasing the number of manufacturing steps. Also, heat generating cells with different shapes, characteristics, etc. can be formed without any positioning errors.

[0033] The heating cell (33) includes one or more heating elements (34) connected to a pair of power supply lines (35). The heating cells 33 may be configured such that a plurality of them are formed along the flow path. For example, as shown in FIG. 5, the heating cell 33 may be configured as a single rectangular heating element 34, with both ends of the heating element 34 connected to respective power supply lines 35. Another example is a heating cell 33 as shown in FIG. 22, in which a plurality of rectangular heating elements 34 are connected to a pair of power supply lines 35. These heating elements 34 can be arranged so that their length is perpendicular to the flow direction of the flow path, as shown in FIGS. 5 and 22. Note that FIG. 5 shows a heater 3 in which the heating cell 33 is composed of a single heating element. Also, FIG. 22 shows a heater 3 in which the heating cells 33 are connected in series.

[0034] Furthermore, as shown in Figures 23 to 27, the heating cell may include a heating element 34 having parallel portions 38 formed in a direction perpendicular to or parallel to the flow direction of the flow channel 25 and bent portions 39 connecting adjacent parallel portions 38. In this case, both ends of the heating element 34 are connected to the respective power supply lines 35. Here, if the heating cell 33 is configured in a zigzag curved shape, the fluid can repeatedly come into contact with the heating cell 33, allowing the entire heater unit to significantly contribute to heating the fluid. As shown in Figures 23 to 25, this zigzag curved shape can be exemplified by a configuration consisting of parallel portions 38 formed in a direction perpendicular to the flow direction of the flow channel and bent portions 39 formed in a line and / or curves connecting adjacent parallel portions 38. Furthermore, as shown in Figures 26 to 27, a configuration consisting of parallel portions 38 formed in a line or curve parallel to the flow direction of the flow channel and bent portions 39 formed in a line and / or curves connecting adjacent linear portions can be exemplified. Note that Figure 23 shows a heater 3 in which the heating cell 33 is zigzag. Fig. 24 shows a heater 3 in which the heat generating cells 33 are zigzag folded, and the wire thickness of a portion of the heat generating element is thickened, and in which a portion of the heat generating cells 33 is replaced with a conductive material such as silver to adjust the resistance value of each heat generating cell 33 for greater efficiency. Fig. 25 shows a heater 3 in which two zigzag folded parallel heat generating cells 33 are arranged in sequence along the flow path 25. Figs. 26 and 27 show a heater 3 in which three zigzag folded parallel heat generating cells 33 are arranged in sequence along the flow path 25, with parallel portions arranged in the flow path direction, and with the wire thickness of a portion of the heat generating element thickened.

[0035] In particular, when the heating elements 34 are formed by printing, the parallel portions 38 of the heating elements 34 can be arranged so that they are perpendicular to the flow direction of the flow channel. When the heating elements 34 are formed by printing, curved portions tend to be shallower than straight portions. Therefore, it is preferable to position the bent portions 39, which tend to be thinner in printing thickness, in a position that will not cause thermal shock due to temperature changes. Therefore, as shown in FIG. 28( b), if the parallel portions 381 at the ends of the flow channels of the heating cells 33 are oriented perpendicular to the flow direction of the flow channels, the bent portions 39 are positioned toward the end of the flow channels on the substrate 31, making them less likely to come into contact with the fluid. This reduces the thermal shock of the heating elements 34 compared to when the bent portions 39 are at the ends of the flow channels as shown in FIG. 28( a), thereby preventing damage to the heating elements 34 due to thermal shock.

[0036] The heating element 32 is not limited to a single row in which the heating cells 33 are sequentially arranged along the flow path as illustrated in Figures 5 and 22 to 24, but may have two or more rows of heating elements 32. For example, as illustrated in Figure 25, there can be mentioned a heater 3 having two rows of heating elements 32, one row in which the heating cells 331 are sequentially arranged and the other row in which the heating cells 332 are sequentially arranged. Furthermore, as illustrated in Figures 26 and 27, there can be mentioned a heater 3 having three rows of heating elements 32, one row in which the heating cells 331 are sequentially arranged, one row in which the heating cells 332 are sequentially arranged, and another row in which the heating cells 333 are sequentially arranged. As such, a heater 3 having heating elements 32 consisting of multiple rows of heating cells 331 to 333 can adjust heat generation to accommodate temperature differences due to differences in position between the center and periphery of the flow path.

[0037] The heat generation amount of each heat generating cell 33 is appropriately set depending on the target heater unit. For example, the heat generation amount per area of ​​the heat generating cells may be the same for all heat generating cells, or may vary for each heat generating cell. When varying the heat generation amount per area, the heat generation amount may be gradually increased or decreased from the inlet to the outlet of the flow path, or may be increased or decreased near the center of the flow path. The method for changing the heat generation amount of the heat generating cell can be appropriately selected, for example, by changing the number of heat generating elements 34 per area or by changing the wire length, wire width, and / or wire thickness of the heat generating elements 34. When the heat generating elements 34 of a heat generating cell are connected in parallel, it is preferable that the electrical characteristics, such as resistance value and resistance heating characteristics, of each heat generating cell connected in parallel are approximately the same. This is because uniformity prevents a low-resistance heat generating element 34 from passing a larger current than the other heat generating elements 34, which may cause damage.

[0038] When a high TCR material (a material with a high temperature coefficient of resistance) is selected as the wiring material for the resistance heating wire, the heating element 34 can be formed in a rectangular shape, as shown in FIGS. 5 and 22. Furthermore, because the resistivity obtained with a high TCR material alone is low, a meandering shape combining parallel wiring and folded wiring, as exemplified in FIGS. 23 to 27, can be used to narrow the wiring width and lengthen the wiring by a factor of the number of folds to increase the resistance value, thereby achieving the heat generation amount required for a practical heater. In a meandering resistance heating wire, it is preferable that the thickness and width of the wiring be approximately the same within one heating cell. It is also preferable that they be approximately the same between different heating cells. Naturally, the thickness and width of the wiring may be varied within each heating cell as needed to create a temperature gradient or increase strength. 24 and 27 , for example, the connection portion 341 of the heating element 34 with the power supply line 35, the connection portion 342 with the bent portion 39 of the parallel portion 38 on the inner periphery of the flow path 25, and the central portion 343 located at the center of the flow path 25 on the substrate 31 can be made thicker because the printing is thin and the temperature change is large. Furthermore, to suppress local temperature increases due to current concentration inside the corners and temperature unevenness due to variations in the resistance values ​​of the heating elements 34 of each cell 33, the connection portion 342 and the central portion 343 can be made of a conductive material, such as silver, with a smaller area specific resistance than that of the heating element 34, thereby adjusting the resistance value of each cell 33. By making the connection portions 341, 342, and the central portion 343 thicker or selecting a suitable conductive material, damage to the resistance heating wire can be prevented.

[0039] As the material for the resistance heating wire that constitutes the heating cell, a conductive material that can generate heat according to the resistance value when current is applied can be used. This conductive material is not limited, but examples that can be used include silver, copper, gold, platinum, palladium, rhodium, tungsten, molybdenum, rhenium (Re), and ruthenium (Ru). These materials can be used alone or in combination of two or more. When two or more materials are used in combination, an alloy can be formed. More specifically, silver-palladium alloy, silver-platinum alloy, platinum-rhodium alloy, silver-ruthenium, silver, copper, and gold can be used.

[0040] Each heating cell may have any resistance heating characteristics, but it is preferable that the heating cells exhibit a self-temperature balancing effect (self-temperature complementing effect) between them. From this perspective, the conductive material constituting the resistance heating wire preferably has a positive temperature coefficient of resistance. Specifically, the temperature coefficient of resistance in the temperature range of -200°C to 1000°C is preferably 100 ppm / °C to 4400 ppm / °C, more preferably 300 ppm / °C to 3700 ppm / °C, and particularly preferably 500 ppm / °C to 3000 ppm / °C. Examples of such materials include silver-based alloys such as silver-palladium alloys. When multiple resistance heating wires (i.e., heating cells) formed using a conductive material with a positive temperature coefficient of resistance (PTC material) are electrically connected in parallel, these multiple heating cells exhibit a self-temperature balancing effect. That is, for example, if there is a second heating cell sandwiched between a first heating cell and a third heating cell, when the temperature of the second heating cell drops, heat is replenished from the first heating cell and the third heating cell. This replenishment of heat results in an increase in current to the first heating cell and the third heating cell, whose temperatures have dropped, and an action works to autonomously recover the temperature drop caused by the lost heat. In other words, the heating cells surrounding the second heating cell act to compensate for the temperature drop of the second heating cell. In this way, a heater including multiple resistance heating wires made of a conductive material with a positive temperature coefficient of resistance is autonomously controlled to generate heat uniformly across the multiple heating cells.

[0041] Looking at typical metal materials used for heater resistance heating wires, for example, silver (at 20°C, resistivity ρ = 1.62 × 10 －８ Ωm, temperature coefficient α=4.1×10 －３ / °C), although the temperature coefficient α is large, it is difficult to achieve a high resistance value because the resistivity ρ is small. Therefore, palladium (ρ=10.8×10 －８ Ωm, α=3.7×10 －３ / °C), but although the resistivity ρ increases, the temperature coefficient α decreases. Thus, when a material with high TCR characteristics is selected, the resistivity tends to decrease. Therefore, in order to make the resistive heating wiring have a high TCR and a practical resistance value, the wiring length must be increased. By adopting a meandering shape, the wiring length can be increased and a high resistance value can be achieved.

[0042] (Power Supply Line) The power supply line (35) is a wiring for supplying power from the power supply terminal (36) to the heating cell (33), and typically uses a low-resistivity resistance heating wire. The power supply line 35 is directly connected to the power supply terminal 36, as shown in FIG. 5 and FIGS. 23 to 26. Alternatively, as shown in FIG. 23, the power supply line 35 may be connected via another heating cell 33, i.e., multiple heating cells 33 may be connected in series. Here, if each heating cell 33 is powered independently from the power supply line 35 arranged along the flow path 25, the power supplied to each heating cell 33 can be adjusted individually without being affected by the other heating cells 33, allowing the heater unit as a whole to make a significant contribution to heating the fluid.

[0043] (Power supply terminal) The power supply terminal (36) is made of a low-resistance resistance heating wire or the like formed on the substrate (31). The power supply terminal 36 is usually formed on one side of the substrate 31 where the heating element 32 is also formed. At least one pair of power supply terminals 36 is provided. Furthermore, when multiple heating elements 32 are provided and power is supplied to each heating element 32 individually, a power supply terminal 36 is provided for each heating element 32. In this case, some of the power supply terminals 36 may be shared by multiple heating elements 32.

[0044] (Insulating Layer) The insulating layer (37) is a layer that covers the heating element on the substrate 31, thereby insulating the heating element 32 from contact with the outside air, fluid, etc. This protects the heating element 32 and allows for more efficient heating of the fluid. The material of the insulating layer 37 is not particularly limited, but for example, glass, ceramics, glass-ceramics, etc. are preferred. Among these, when a metal (stainless steel, etc.) is used as the material constituting the substrate 31, the material of the insulating layer 37 is preferably glass, and more preferably crystallized glass or semi-crystallized glass, from the viewpoint of its thermal expansion balance. Specifically, SiO ２-Al ２ O ３ MO-based glass is preferred, where MO is an oxide of an alkaline earth metal (MgO, CaO, BaO, SrO, etc.). The thickness of the insulating layer 37 is not particularly limited (for example, about 30 to 200 μm).

[0045] (Others) A temperature sensor, a fluid detection sensor, a fuse, and the like may be provided on the substrate 31 .

[0046] (Heater Unit) The heater units 1A to 1G according to the present embodiment include a base 21 and the heater 3 described above, which heats a fluid to be heated that flows through a flow path 25 formed on the upper surface of the base 21. The heater units 1A to 1G are not particularly limited in their applications, but can be used, for example, as heater units for battery temperature management and heating of vehicles (e.g., automobiles, railroad cars, aircraft, ships, etc.). In particular, they can be suitably used as heater units for battery temperature management and heating of electric vehicles (BEVs: Battery Electric Vehicles), fuel cell vehicles (FCEVs: Fuel Cell Electric Vehicles), plug-in hybrid vehicles (PHEVs: Plug-in Hybrid Electric Vehicles), and hybrid electric vehicles (HEVs: Hybrid Electric Vehicles).

[0047] The present invention will be specifically described below with reference to the drawings in accordance with Examples 1 to 7. In Examples 1 to 7, a heater unit (also referred to as a "coolant heater") used for battery temperature management in electric vehicles (BEVs), fuel cell electric vehicles (FCEVs), and the like will be exemplified as the "heater unit" according to the present invention.

[0048] <Example 1> As shown in Figures 1 to 4, a heater unit 1A according to Example 1 includes a base 21 and a heater 3 that heats a fluid to be heated (i.e., coolant) flowing through a flow path 25 formed on an upper surface 24 of the base 21.

[0049] The flow path 25 is open at the upper surface 24 of the base 21. The flow path 25 is a serpentine flow path formed by alternating linear flow paths and curved flow paths that reverse the flow direction. The base 21 has a fluid inlet 26a and an outlet 26b that are connected to the flow path 25. The base 21 is made of metal such as aluminum die-cast, and is formed in a rectangular shape in a plan view. The base 21 is housed in a box-shaped lower cover 22 that is open at the top, and is covered by a box-shaped upper cover 23 that is open at the bottom.

[0050] The heater 3 has a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one surface of the substrate 31 (specifically, the surface of the substrate 31 opposite to the surface facing the flow path 25), and a power supply line 35 arranged on one surface of the substrate 31 along the flow path 25. The substrate 31 is provided with a pair of power supply lines 35 connected to the heating element 32. Furthermore, an insulating layer 37 is provided on one surface of the substrate 31 and covers the heating element 32. Note that while FIG. 4 shows a state in which the heating element 32 is separated from the insulating layer 37, the heating element 32 is usually arranged in the middle of the insulating layer 37 in the thickness direction (see FIG. 3).

[0051] The heating element 32 has a plurality of heating cells 33, each of which receives a separate power supply. The heating cells 33 are arranged in a line along the flow path 25 from the inlet 26a toward the outlet 26b. Each heating cell 33 is made of a conductive material having a positive temperature coefficient of resistance. Each heating cell 33 is electrically connected in parallel to a pair of power supply lines 35. Note that the heating element 32 may have any of the configurations shown in FIGS. 22 to 28 instead of the configuration shown in FIG. 5.

[0052] Next, the effects of the heater unit 1A configured as described above will be described. The fluid to be heated is circulated between the heater unit 1A and a battery unit (not shown). In the heater unit 1A, the fluid to be heated flows into the flow path 25 from the inlet 26a, is heated by the heater 3, and then is sent to the battery unit from the outlet 26b, thereby maintaining the battery at an optimum operating temperature.

[0053] As described above, the heater 3 of the first embodiment includes a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one side of the substrate 31, and a power supply line 35 arranged on one side of the substrate 31 along the flow path 25. The heating element 32 has a plurality of heating cells 33 each receiving a power supply. The heating cells 33 are connected in parallel to the power supply line 35, and the plurality of heating cells 33 are arranged along the flow path 25 from the inlet 26a to the outlet 26b provided in the base 21. As a result, the plurality of heating cells 33, each receiving a power supply by being connected in parallel to the power supply line 35, heat the fluid to be heated flowing through the flow path 25. This allows each heating cell 33 to generate heat without being affected by the amount of current flowing through the other heating cells, making it less likely that uneven heat generation will occur due to the other heating cells. This prevents or suppresses the uneven temperature rise that occurs in conventional fluid heaters when a heating resistor extending along the flow path heats the entire flow path. As a result, the fluid to be heated can be heated uniformly and efficiently throughout the entire flow path 25 in response to various fluid conditions (for example, fluid velocity, fluid temperature, etc.).

[0054] In particular, in this embodiment 1, a plurality of heating cells 33 formed using a conductive material with a positive temperature coefficient of resistance are electrically connected in parallel, which allows the heating cells 33 to effectively achieve self-temperature balancing, thereby enabling the heated fluid to be heated more evenly and efficiently throughout the entire flow path 25 in response to various fluid forms.

[0055] Second Embodiment Next, a heater unit 1B according to a second embodiment will be described with reference to FIGS. 6 and 7. Components that are substantially the same as those in the heater unit 1A according to the first embodiment are designated by the same reference numerals and will not be described in detail.

[0056] The heater unit 1A according to the second embodiment includes a base 21 and a heater 3 that heats a fluid to be heated (i.e., a coolant) that flows through a flow path 25 formed in an upper surface 24 of the base 21 .

[0057] The heater 3 has a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one surface of the substrate 31 (specifically, the surface of the substrate 31 opposite to the surface facing the flow path 25), and a power supply line 35 arranged on one surface of the substrate 31 so as to run along the flow path 25. Furthermore, an insulating layer 41 (exemplified as a "reinforcing layer") is arranged on the surface of the substrate 31 facing the flow path 25 so as to run along the flow path 25. The insulating layer 41 is made of glass.

[0058] As described above, the heater unit 1B of the second embodiment achieves substantially the same effects as the heater unit 1A of the first embodiment. Furthermore, the insulating layer 41 is disposed on the surface of the substrate 31 facing the flow path 25, along the flow path 25, thereby thinning the substrate 31 (i.e., reducing its weight) and suppressing warping of the substrate 31. More specifically, in existing steel substrates 31, the substrate 31 is as thick as 3 mm and has a large heat capacity, which means it takes time for the fluid to heat up. Therefore, by providing the insulating layer (glass) 41 on the opposite side of the heater 3, the substrate 31 does not warp even when the thickness of the metal substrate 31 is 0.6 mm to 0.2 mm, reducing its heat capacity and enabling the heater 3 to have a quick response to temperature changes (i.e., improving fluid heating efficiency). In the second embodiment, a uniform heat layer formed of a material (e.g., silver, copper, aluminum) with a higher thermal conductivity than the material (e.g., stainless steel) constituting the substrate 31 may be used as the reinforcing layer instead of the insulating layer 41.

[0059] Third Embodiment Next, a heater unit 1C according to a third embodiment will be described with reference to FIGS. 8 to 10. Components that are substantially the same as those in the heater unit 1B according to the second embodiment are designated by the same reference numerals and will not be described in detail.

[0060] The heater unit 1C according to the third embodiment includes a base 21 and a heater 3 that heats a fluid to be heated (i.e., a coolant) that flows through a flow path 25 formed in an upper surface 24 of the base 21 .

[0061] The heater 3 has a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one surface of the substrate 31 (specifically, the surface of the substrate 31 opposite to the surface facing the flow path 25), and a power supply line 35 arranged on one surface of the substrate 31 so as to run along the flow path 25. Furthermore, an insulating layer 41 (exemplified as a "reinforcing layer") is arranged on the surface of the substrate 31 facing the flow path 25 so as to run along the flow path 25.

[0062] The insulating layer 41 has an exposed portion 42 formed therein, which connects the surface of the substrate 31 facing the flow path 25 with the flow path 25. The exposed portion 42 is formed in an elongated shape along the flow path 25. Specifically, the exposed portion 42 is formed in a serpentine shape corresponding to the serpentine shape of the flow path 25.

[0063] As described above, the heater unit 1C of the third embodiment not only achieves substantially the same effects as the heater unit 1B of the second embodiment, but also further improves heat exchange efficiency by forming an exposed portion 42 in the insulating layer 41 that connects the surface of the substrate 31 facing the flow path 25 with the flow path 25. More specifically, the insulating layer (glass) 41 on the surface opposite the heater 3 comes into contact with water. Because glass has poor thermal conductivity, providing the exposed portion 42 improves heat conduction efficiency. That is, the rear glass 41 is provided to reduce heat capacity, but because the rear glass 41 has poorer thermal conductivity than metal, providing the exposed metal portion 42 facilitates heat transfer to the fluid.

[0064] Here, instead of the insulating layer 41 (see FIG. 9 ), an insulating layer 41 having a plurality of V-shaped or dot-shaped exposed portions 42 formed along the flow path 25 as shown in FIG. 11 can be used. In this case, the large number of exposed portions 42 generates turbulence in the heated fluid flowing through the flow path 25, thereby further improving the heat exchange efficiency. In addition, in this third embodiment, instead of the insulating layer 41, a heat equalizing layer formed of a material (silver, copper, aluminum, etc.) having a higher thermal conductivity than the material (stainless steel, etc.) constituting the substrate 31 may be used as the reinforcing layer.

[0065] Fourth Embodiment Next, a heater unit 1D according to a fourth embodiment will be described with reference to FIGS. 12 to 14. Components that are substantially the same as those in the heater unit 1C according to the third embodiment are designated by the same reference numerals and will not be described in detail.

[0066] The heater unit 1D according to the fourth embodiment includes a base 21 and a heater 3 that heats a fluid to be heated (i.e., a coolant) that flows through a flow path 25 formed in an upper surface 24 of the base 21.

[0067] The heater 3 has a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one surface of the substrate 31 (specifically, the surface of the substrate 31 opposite to the surface facing the flow path 25), and a power supply line 35 arranged on one surface of the substrate 31 so as to run along the flow path 25. Furthermore, an insulating layer 41 (exemplified as a "reinforcing layer") is arranged on the surface of the substrate 31 facing the flow path 25 so as to run along the flow path 25.

[0068] The insulating layer 41 has an exposed portion 42 that connects the surface of the substrate 31 facing the flow path 25 with the flow path 25. A heat sink 43 that protrudes into the flow path 25 via the exposed portion 42 is disposed on the surfaces of the substrate 31 and the insulating layer 41 facing the flow path 25. The heat sink 43 has a bonding plate 43a that is bonded to the surface of the substrate 31 facing the flow path 25, and a heat dissipation plate 43b that protrudes into the flow path 25 from one surface of the bonding plate 43a. The heat dissipation plate 43b is formed in an elongated shape along the flow path 25.

[0069] As described above, the heater unit 1D of this embodiment 4 not only achieves substantially the same effects as the heater unit 1C of embodiment 3, but also has a heat sink 43 that protrudes into the flow path 25 via the exposed portion 42 arranged on the side of the substrate 31 facing the flow path 25, thereby further improving the heat exchange efficiency and more effectively suppressing warping of the substrate 31.

[0070] Here, instead of the above-described heat sink 43 (see FIG. 13 ), it is possible to use a heat sink 43 (see FIGS. 15( a ) and 15 ( b )) having a plurality of heat dissipation plates 43 b formed at predetermined intervals along the flow path 25. In this case, the heated fluid flowing on both the left and right sides of the heat dissipation plate 43 b intersects through the gaps between adjacent heat dissipation plates 43 b, so that the heated fluid can be heated more uniformly throughout the entire flow path 25.

[0071] In particular, when using a heat sink 43 (see Figure 15 (b)) having multiple heat sinks 43b arranged with one side inclined relative to the axial direction of the flow path 25, by making adjacent heat sinks 43b have a fin structure with different angles, it becomes easier to generate turbulence in the heated fluid, and the heated fluid can be further heated uniformly throughout the entire flow path 25.

[0072] Furthermore, instead of the heat sink 43 (see FIG. 13 ), a heat sink 43 (see FIG. 15( c )) having a plurality of heat dissipation plates 43 b arranged opposite each other (i.e., arranged side by side in the width direction of the flow path 25) can be used. In this case, the contact area between the heat sink 43 and the heated fluid increases, thereby further improving the heat exchange efficiency. In addition, in this fourth embodiment, instead of the insulating layer 41, a heat equalization layer formed of a material (silver, copper, aluminum, etc.) having a higher thermal conductivity than the material (stainless steel, etc.) constituting the substrate 31 may be used as the reinforcing layer.

[0073] Fifth Embodiment Next, a heater unit 1E according to a fifth embodiment will be described with reference to FIGS. 16 and 17. Components that are substantially the same as those in the heater unit 1C according to the third embodiment are designated by the same reference numerals and will not be described in detail.

[0074] A heater unit 1E according to the fifth embodiment includes a base 21 and a heater 3 that heats a fluid to be heated (i.e., a coolant) that flows through a flow path 25 formed in an upper surface 24 of the base 21.

[0075] The heater 3 has a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one surface of the substrate 31 (specifically, the surface of the substrate 31 opposite to the surface facing the flow path 25), and a power supply line 35 arranged on one surface of the substrate 31 so as to run along the flow path 25. Furthermore, an insulating layer 41 (exemplified as a "reinforcing layer") is arranged on the surface of the substrate 31 facing the flow path 25 so as to run along the flow path 25.

[0076] The insulating layer 41 has an exposed portion 42 that connects the surface of the substrate 31 facing the flow path 25 to the flow path 25. A heat spreader layer 44 (exemplified as a "reinforcing layer") is disposed between the substrate 31 and the insulating layer 41 so as to be exposed to the flow path 25 via the exposed portion 42. Furthermore, the heat spreader layer 44 is made of a material (silver, copper, aluminum, etc.) that has a higher thermal conductivity than the material (stainless steel, etc.) that constitutes the substrate 31. Note that the exposed portion 42 may have a configuration shown in FIG. 11 .

[0077] As described above, according to the heater unit 1E of this embodiment 5, in addition to achieving substantially the same effects as the heater unit 1C of embodiment 3, a heat equalizing layer 44 is disposed between the substrate 31 and the insulating layer 41 and is exposed to the flow path 25 via the exposed portion 42, and the heat equalizing layer 44 is formed from a material having a higher thermal conductivity than the material constituting the substrate 31, so that the heat exchange efficiency can be further improved and warping of the substrate 31 can be more effectively suppressed.

[0078] Sixth Embodiment Next, a heater unit 1F according to a sixth embodiment will be described with reference to FIGS. 18 and 19. Components that are substantially the same as those in the heater unit 1C according to the third embodiment will be designated by the same reference numerals and will not be described in detail.

[0079] The heater unit 1F according to the sixth embodiment includes a base 21 and a heater 3 that heats a fluid to be heated (i.e., a coolant) that flows through a flow path 25 formed in an upper surface 24 of the base.

[0080] The heater 3 has a substrate 31 arranged to cover the upper surface 24 of the base 21, a heating element 32 arranged on one surface of the substrate 31 (specifically, the surface of the substrate 31 opposite to the surface facing the flow path 25), and a power supply line 35 arranged on one surface of the substrate 31 so as to run along the flow path 25. Furthermore, an insulating layer 41 (exemplified as a "reinforcing layer") is arranged on the surface of the substrate 31 facing the flow path 25 so as to run along the flow path 25.

[0081] The insulating layer 41 has exposed portions 42 that connect the surface of the substrate 31 facing the flow path 25 to the flow path 25. An embedding member 45 is embedded in the exposed portions 42. The embedding member 45 is made of a material (silver, copper, aluminum, etc.) that has a higher thermal conductivity than the material (stainless steel, etc.) that constitutes the substrate 31. The exposed portions 42 may have a shape as shown in FIG. 11. In this case, an embedding member 45 corresponding to the shape of each exposed portion 42 is embedded in each of the multiple exposed portions 42.

[0082] As described above, the heater unit 1F of this sixth embodiment not only achieves substantially the same effects as the heater unit 1C of the third embodiment, but also has the embedded members 45 formed of a material having a higher thermal conductivity than the material constituting the substrate 31 embedded in the exposed portions 42, thereby further improving the heat exchange efficiency and more effectively suppressing warping of the substrate 31. Note that in this sixth embodiment, instead of the insulating layer 41, a heat equalizing layer formed of a material having a higher thermal conductivity (silver, copper, aluminum, etc.) than the material constituting the substrate 31 (stainless steel, etc.) may be used as the reinforcing layer.

[0083] Seventh Embodiment Next, a heater unit 1G according to a seventh embodiment will be described with reference to FIGS. 20 and 21. Components that are substantially the same as those in the heater unit 1A according to the first embodiment will be designated by the same reference numerals and will not be described in detail.

[0084] The heater unit 1G according to the seventh embodiment includes a base 21 and a heater 3 that heats a fluid to be heated (i.e., a coolant) that flows through a flow path 25 formed in an upper surface 24 of the base 21.

[0085] The heater 3 includes a substrate 31 disposed to cover the upper surface 24 of the base 21, a heating element 32 disposed on the surface of the substrate 31 facing the flow path 25, and a power supply line 35 disposed on the surface of the substrate 31 facing the flow path 25 so as to extend along the flow path 25. A power supply terminal 36 electrically connected to the heating element 32 via the power supply line 35 is disposed on the surface of the substrate 31 facing the flow path 25. A heat-sealing layer 46 is disposed on the surface of the substrate 31 facing the flow path 25 to seal the flow path 25. The power supply terminal 36 does not overlap the heat-sealing layer 46 in the thickness direction of the substrate 31, but is open via a space. The power supply terminal 36 is connected to a lead wire 49 by soldering, an insulating mold 48, or the like.

[0086] The sealing heat spreader 46 is made of a material (silver, copper, aluminum, etc.) having a higher thermal conductivity than the material (stainless steel, etc.) that constitutes the substrate 31. In addition, a thermally conductive grease layer or a thermally conductive adhesive layer 47 is disposed between the substrate 31 and the sealing heat spreader 46.

[0087] As described above, the heater unit 1G of this embodiment 7 not only achieves substantially the same effects as the heater unit 1A of the embodiment 1, but also further improves the heat exchange efficiency because the heating element 32 is arranged on the surface of the substrate 31 facing the flow path 25.

[0088] Furthermore, in the seventh embodiment, a power supply terminal 36 electrically connected to the heating element 32 is disposed on the surface of the substrate 31 facing the flow path 25, and a sealing heat spreader layer 46 is disposed on the surface of the substrate 31 facing the flow path 25 so as to seal the flow path 25, and the sealing heat spreader layer 46 is formed of a material having a higher thermal conductivity than the material constituting the substrate 31. This can further improve the heat exchange efficiency and more effectively suppress warping of the substrate 31.

[0089] Furthermore, in the seventh embodiment, a thermally conductive grease layer or a thermally conductive adhesive layer 47 is disposed between the substrate 31 and the sealing uniform temperature layer 46. This can further improve the heat exchange efficiency.

[0090] <Running Water Heating Experiment> Next, the running water heating experiment will be described. As shown in Fig. 29, the experimental system used in this running water heating experiment includes a heater unit 51, a tank 52 for storing running water, and a pump 53 for circulating the running water. The heater unit 51, tank 52, and pump 53 are connected via a hose 54. Thermometers 55 are disposed at the inlet 26a and outlet 26b of the heater unit 51, respectively. A thermoviewer (camera) 56 is disposed above the heater unit 51.

[0091] As shown in Figure 30, the heater unit 51 has an aluminum square pipe 57 (20 mm x 20 mm x 500 mm, 2 mm thick). The square pipe 57 has an inlet 26a attached to one axial end and an outlet 26b attached to the other axial end. A hole (10 mm x 325 mm) is formed in the top surface of the square pipe 57. Furthermore, a heater 58A or heater 58B (described below) can be installed on the top surface of the square pipe 57 so as to cover the hole 57a.

[0092] As shown in Figure 31(a), the heater 58A of the experimental example used in this flowing water heating experiment has a long substrate 31 and a heating element 32 arranged on one side of the substrate 31. The heating element 32 has a plurality of heating cells 33 (five in the figure), each of which is supplied with electricity. The heating cells 33 are arranged side by side along the flow path 25 from the inlet 26a to the outlet 26b. In other words, the heating cells 33 form a parallel circuit.

[0093] On the other hand, as shown in Figure 31(b), the heater 58B of the comparative example used in the main flow water heating experiment has a long substrate 31 and a heating element 32 arranged on one side of the substrate 31. The heating element 32 has a plurality of heating cells 33 (two in the figure) each of which is supplied with power. Each heating cell 33 extends along the flow path 25 from the inlet 26a to the outlet 26b. In other words, each heating cell 33 forms a series circuit.

[0094] As shown in FIG. 32 , heaters 58A and 58B have an insulating glass layer 61, a protective glass layer 62, and an overcoat layer 63 laminated in this order on one side and the other side of a substrate 31. The total thickness of these three layers 61 to 63 is 200 μm. The substrate 31 of heater 58A has a width of 11.9 mm, a thickness of 0.6 mm, a length of 407 mm, and an effective heat generation length of 324 mm. On the other hand, the substrate 31 of heater 58B has a width of 12 mm, a thickness of 0.6 mm, a length of 376 mm, and an effective heat generation length of 322 mm. Note that heaters 58A and 58B are basically identical in design, and although the substrate lengths are different, the experiment was conducted assuming that the effect on heating efficiency was small.

[0095] In this flowing water heating experiment, heater 58A or heater 58B was installed on the top surface of square pipe 57. Water was flowed through square pipe 57 at a flow rate of 1 L / min. Heater 58A or heater 58B was controlled at 110°C and heated at predetermined voltages (675 W, 1012.5 W, 1350 W, and 1500 W). The difference in inlet temperature was measured between the start of heating and 10 minutes after heating. As a result, at 675 W, series-circuit heater 58B exhibited a higher temperature than parallel-circuit heater 58A. However, at 1000 W, the relationship reversed, with the temperature rise of series-circuit heater 58B being lower than that of parallel-circuit heater 58A. This is thought to be because, as the heater power increased, localized heat generation in series-circuit heater 58B accelerated, causing water to boil (transition from liquid to gas) on the backside of the heater, generating bubbles. This partially reduced the efficiency of heat exchange between the heater and water, resulting in a decrease in the overall rise in water temperature. On the other hand, it is believed that the parallel circuit heater 58A's self-temperature compensation mechanism works to prevent localized heating and water from boiling on the backside of the heater, thereby maintaining the water temperature rise.

[0096] From the above, it was confirmed that the heater 58A of the experimental example in which the heat generating cells 33 form a parallel circuit (i.e., the heater 58A with a self-temperature compensation function) has a higher heat exchange efficiency than the heater 58B of the comparative example in which the heat generating cells 33 form a series circuit (i.e., the heater 58B without a self-temperature compensation function).

[0097] The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application. For example, a heater unit may be constructed by combining two or more of Examples 1 to 7.

[0098] 1A to 1G: heater unit, 21; base, 22; lower cover, 23; upper cover, 24; flow path forming surface, 25; flow path, 26a; inlet, 26b; outlet, 3; heater, 31; substrate, 32; heating element, 33, 331, 332, 333; heating cell, 34; heating element, 341, 342; connection portion, 343; center portion, 35; power supply line, 36; power supply terminal, 37; insulating layer, 38, 381; parallel portion, 39, 391; bent portion, 41; insulating layer, 42; exposed portion, 43; heat sink, 44; heat-equalizing layer, 45; embedded member, 46; sealing heat-equalizing layer, 51: heater unit, 52: tank, 53: pump, 54: hose, 55: thermometer, 56: thermoviewer, 57: square pipe, 58A: heater of experimental example, 58B: heater of comparative example, 61: insulating glass layer, 62: protective glass layer, 63: overcoat layer.

Claims

1. A heater for heating a fluid to be heated flowing through a flow path formed on an upper surface of a base, comprising: a substrate arranged to cover the upper surface of the base; a heating element arranged on one side of the substrate; and a power supply line arranged on the one side of the substrate along the flow path, wherein the heating element has a plurality of heating cells each receiving a power supply, the plurality of heating cells are connected in parallel to the power supply line, and the plurality of heating cells are arranged in a row along the flow path from an inlet to an outlet provided in the base.

2. The heater according to claim 1, wherein the resistive heating wire constituting the heating element is made of a material having a high temperature coefficient of resistance and / or a PTC material.

3. A heater according to claim 1 or 2, wherein a reinforcing layer is disposed along the flow path on the surface of the substrate facing the flow path.

4. A heater according to claim 3, wherein the reinforcing layer is formed with an exposed portion that connects the surface of the substrate facing the flow path with the flow path.

5. The heater according to claim 4, wherein a heat sink is disposed on the surface of said substrate facing said flow path and protrudes into said flow path via said exposed portion.

6. A heater according to claim 4, wherein a filling member made of a material having a higher thermal conductivity than the material constituting said substrate is filled in said exposed portion.

7. The heater according to claim 3, wherein the reinforcing layer is an insulating layer.

8. The heater according to claim 3, wherein the reinforcing layer is a uniform heat layer made of a material having a higher thermal conductivity than the material constituting the substrate.

9. A heater according to claim 1 or 2, wherein the substrate is made of a clad material or a bimetal.

10. The heater according to claim 1 or 2, further comprising an insulating layer disposed on one surface side of said substrate and covering said heating element.

11. The heater according to claim 1 or 2, wherein the heating element is a resistive heating wire printed on the substrate.

12. A heater as described in claim 1 or 2, wherein the heat generating cells are configured in a zigzag curved shape consisting of parallel sections formed in a direction perpendicular to the flow direction of the flow path and bent sections connecting adjacent parallel sections.

13. A heater as described in claim 1 or 2, wherein the heat generating cell is configured with a zigzag curved shape consisting of parallel sections formed in a direction parallel to the flow direction of the flow path and bent sections connecting adjacent parallel sections.

14. A heater unit comprising a base and a heater for heating a fluid to be heated flowing through a flow path formed on an upper surface of the base, wherein the heater is a heater as defined in any one of claims 1 to 13.

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