JP2023137752A - electric heater - Google Patents

Abstract

To enable a case to withstand a reaction force even when a heater unit is urged by using a spring member and to prevent an amount of heat radiation of the heater unit from being diminished.SOLUTION: A heater unit includes: a heat generating element; a heat radiating fin; an electrode; and a spring member configured to urge in a first direction that is a layering direction. A case includes a pair of first frame portions covering the heater unit at both ends in the first direction and a pair of second frame portions covering the heater unit at both ends in a second direction; and the first frame portions and the second frame portions define an air passage. In the case, a first connection portion for connecting the first frame portions is formed so as to protrude from the first frame portions to a heat radiating fin side. Recesses corresponding to the first connection portions are formed in a pair of plate members and a fin member of the heat radiating fin. Therefore, the heat radiating fins and the first connection portions do not interfere with each other. Further, sufficient heat radiation areas can be secured for the heat radiating fins.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to an electric heater that heats air, and is suitable for use, for example, in warming the interior of a car.

In some electric heaters, the heater portion is held within a resin case. In Patent Document 1, a spring member is used to press the heater section arranged inside the case.

However, the spring member mounted between the resin case and the heater section applies a load to the heater section and at the same time applies a reaction force to the resin case. When a resin case is subjected to a reaction force, a creep phenomenon (deformation of the resin part) occurs over time, and the load on the heater part gradually decreases accordingly.

Japanese Patent Application Publication No. 2009-51494

In view of the above points, the present disclosure devises a case shape so that even if the heater section is biased using a spring member, it can withstand the reaction force. In addition, the objective is to prevent the amount of heat dissipated from the heater portion from being impaired even by devising the shape of the case.

A first aspect of the present disclosure includes a flat heating element that generates heat when energized, a radiation fin that radiates the heat of the heating element to an air passage, an electrode that is connected to a power source to supply power to the heating element, and a heating element that is connected to a power source to supply power to the heating element. The heating element includes a spring member that is biased in a first direction, which is the direction in which the heat dissipation fins and the electrodes are stacked, to bring the heating element, the heat dissipation fins, and the electrodes into contact with each other. The first aspect of the present disclosure also provides a pair of first frame portions that cover the heater portion at both ends in a first direction, and a pair of first frame portions that cover the heater portion at both ends in a second direction that is orthogonal to the first direction. The present invention also includes a case made of a resin material, which has two frame parts and has an air passage inside the first frame part and the second frame part.

The first case of the present disclosure further includes a first connecting portion that connects the first frame portions, and the first connecting portion is formed to protrude from the first frame portion toward the radiation fin side. Further, the radiation fin includes a pair of plate members and a fin member disposed between the pair of plate members, and a recess corresponding to the first connecting portion is formed in the pair of plate members and the fin member.

In the first aspect of the present disclosure, since the case is provided with the first connecting portion that connects the first frame portions, the strength of the case in the first direction can be increased. In particular, since the first connecting portion is formed to protrude from the first frame portion toward the radiation fin side, the spring load resistance of the first connecting portion is high. Therefore, even if the case receives the urging force of the spring member for a long period of time, deformation of the case can be effectively suppressed.

Further, in the first aspect of the present disclosure, since the recess corresponding to the first connecting portion is formed in the pair of plate members and the fin member of the radiation fin, the first connecting portion is closer to the radiation fin than the first frame portion. Even if they are formed to protrude, the radiation fins and the first connecting portion do not interfere with each other. Therefore, even if the first connecting portion is formed to protrude from the radiation fin side, a sufficient heat radiation area can be ensured in the radiation fin.

In the second aspect of the present disclosure, the first connecting portion is disposed in both the third direction, which is the upstream side of the air passage, and the fourth direction, which is the downstream side, of the air passage with respect to the radiation fin. The radiation fins form recesses in both the third direction and the fourth direction. In the second aspect of the present disclosure, since the first connecting portions are arranged on both the upstream side and the downstream side, the spring load resistance strength of the case can be further increased. Moreover, the strength of the case can be balanced between the upstream and downstream sides. Further, in the second aspect of the present disclosure, since the radiation fins also form recesses in both the third direction and the fourth direction, the heat transfer area of the radiation fins can be maintained on both the upstream side and the downstream side. .

In a third aspect of the present disclosure, the case is formed so as to be separable in both the third direction and the fourth direction. In the present disclosure, the first connecting portion is formed to protrude from the first frame portion toward the radiation fin side, and the radiation fin also has a recessed portion corresponding to the first connecting portion in the pair of plate members and the fin member. Therefore, the assembly of the heater part and the case is important. In the third aspect of the present disclosure, the electric heater can be assembled by sandwiching the heater part between separate cases.

In a fourth aspect of the present disclosure, the heating element is disposed within the case at a location where the first connecting portion is not present. In the present disclosure, the first connecting portion is formed to protrude from the first frame toward the radiation fin side, but since the heating element is disposed in a non-existing portion of the first connecting portion, the first connecting portion is not connected to the heating element. There is no interference.

In a fifth aspect of the present disclosure, a plurality of first connecting portions are formed so as to partition the air passages at approximately equal intervals. Thereby, the spring load resistance strength of the case can be kept substantially uniform over the entire length in the second direction.

In a sixth aspect of the present disclosure, the case is further provided with a second connecting portion that connects the second frame portions. And the electrode is arranged within the projected area of this second connection part within the air passage. In the sixth aspect of the present disclosure, the strength of the case is improved by further providing a second connecting portion. In addition, by arranging the electrode within the projected area of the second connecting portion, even if the second connecting portion is formed, the cross-sectional area of the air passage is not substantially reduced.

FIG. 1 is a configuration diagram of an automotive air conditioner. FIG. 2 is a front view of the electric heater of the present disclosure. 3 is a right side view of the electric heater of FIG. 2. FIG. FIG. 4 is an exploded front view of the heater section. FIG. 5 is a front view of the heater section. FIG. 6 is a perspective view showing a part of the radiation fin. FIG. 7 is a perspective view illustrating the assembled state of the case. FIG. 8 is a cross-sectional view illustrating the heat exchange area of the radiation fins. FIG. 9 is a diagram illustrating heat radiation area and heat exchange efficiency. FIG. 10 is a diagram illustrating deformation of the case. FIG. 11 is an exploded perspective view of the heater section. 12 is a left side view of the electric heater of FIG. 2. FIG.

Hereinafter, an example of the present disclosure will be described based on the drawings. The electric heater 100 is used together with an automotive air conditioner 200, as shown in FIG. The automobile air conditioner 200 selectively takes in air from an outside air intake 201 or an indoor air intake, and blows the air indoors using a blowing fan 202 . Air is cooled by the evaporator 203 of the refrigeration cycle and heated by the hot water heater 204. The hot water heater 204 uses engine cooling water as its heat source. However, immediately after the engine starts, the engine coolant is not warmed up and the heating heat source is insufficient. In particular, as hybridization of automobiles results in smaller engines and lower engine operating rates, the lack of heat in the engine cooling water becomes noticeable.

The electric heater 100 is used to compensate for such a lack of heat source. It is arranged downstream of the hot water heater 204 in the air flow and heats the air sent from the blower fan 202. The air warmed by the hot water heater 204 or the electric heater 100 and the air cooled by the evaporator 203 are mixed by an air mix door 205 and controlled to a predetermined temperature. Mainly warm air is blown towards the windshield from the defroster outlet 206, mainly cold air is blown towards the occupant's head and chest from the upper outlet 207, and mainly warm air is blown towards the occupant's lower body from the lower outlet 208. Air is blown towards.

As shown in FIG. 2, the heater section 150 of the electric heater 100 is housed in a case 180. This case 180 is arranged within an air conditioning case 210 of the air conditioner 200. Specifically, the air conditioning case 210 has an opening that corresponds to the case 180 of the electric heater 100, and the case 180 is inserted into the air conditioning case 210 through the installation opening. The assembly opening of the air conditioning case 210 is closed by the flange 190 of the case 180. Note that the details of the case 180 will be described later.

4 and 11, the elements constituting the heater section 150 are shown in an exploded manner. The heater section 150 includes a heating element 110 and an electrode 140 that supplies power to the heating element 110. The heater section 150 also includes radiation fins 130 that radiate heat from the heating element to the air passage. The radiation fins 130 are also conductors that provide electrical continuity between the electrodes 140. Additionally, the heater section 150 also includes a spring member 170. In the following explanation, the lamination direction of the heat radiation fins 130, electrodes 140, heating elements 110, and spring members 170 (vertical direction in FIG. 4) is referred to as a first direction, and a direction perpendicular to this first direction (horizontal direction in FIG. 4) is referred to as a first direction. This is the second direction.

The heating element 110 is made of a PTC element or the like, and generates heat when energized. A PTC (Positive Temperature Coefficient) element has the property that its electrical resistance increases rapidly above a certain temperature, so it generates heat when it is energized, but when the temperature at which it generates heat exceeds a certain temperature, its electrical resistance increases. Because of this, almost no current flows, and no heat is generated above a certain temperature. Therefore, by using this element, overheating of the heater can be prevented. This heating element 110 has a rectangular shape with a length in the second direction of 35 mm, a width of 7 mm, and a thickness of about 1 mm in the first direction.

The radiation fin 130 is formed by sandwiching the fin member 131 between a pair of plate members, a first plate member 132 and a second plate member 133, as shown in FIGS. 5 and 6. The fin member 131 is made of an aluminum alloy containing manganese, and is bent and formed many times. The first plate member 132 and the second plate member 133 are also made of aluminum alloy, and the ends in the second direction are bent at a substantially right angle to form an L-shape.

The fin member 131, the first plate member 132, and the second plate member 133 are fixed to each other by integral brazing. The heat radiation fin 130 has a height of about 10 mm in the first direction and a width of about 7 mm. The length of the radiation fin 130 in the second direction varies depending on the capacity required of the electric heater 100, but is approximately 180 to 280 mm.

A recess 134 is formed in the radiation fin 130 at a portion corresponding to a first connecting portion 184 of a case 180, which will be described later. The recess 134 is formed in substantially the same shape in all of the fin member 131, the first plate member 132, and the second plate member 133, and its width in the second direction is approximately 2 mm. Further, the depth of the recess 134 is approximately 1 mm or more.

The heating element 110 is sandwiched between the radiation fins 130 and the electrodes 140. The electrode 140 is made of brass and includes a positive electrode 141 and a negative electrode 142 that receive power from a battery (not shown). In the example shown in FIGS. 4 and 5, the heat dissipation fins 130 are arranged in five layers in the first direction. Four layers of heating elements 110 are arranged between the radiation fins 130 and the electrodes 140. Only one layer of electrodes 140 is disposed at the bottom in the first direction of FIGS. 4, 5, and 11. Therefore, five layers of electrodes 140 are arranged, and positive electrodes 141 and negative electrodes 142 are arranged alternately. In this way, the heater section 150 is configured by stacking the radiation fins 130, the heat generating elements 110, and the electrodes 140 in multiple stages in the first direction.

The spring member 170 is bent in a wave shape having peaks and valleys toward the first direction over the entire length in the second direction, and when assembled to the case 180, the peaks and valleys of the spring member 170 are bent. is deformed so as to be crushed in the first direction. This deformation of the spring member 170 applies an urging force in the first direction to the heating element 110, the electrode 140, and the radiation fin 130. In other words, the heating element 110, the electrode 140, and the radiation fin 130 are brought into close contact with each other by the biasing force of the spring member 170. The biasing force of this spring member 170 is about 50 to 190 newtons.

The case 180 is made of polybutylene terephthalate PBT and has a first frame part 181 that covers both ends of the heater section 150 in the first direction and a second frame part 182 that covers both ends of the heater part 150 in the second direction. That is, the first frame portion and the second frame portion form a rectangular air passage 183. The size of the case 180 is large enough to accommodate the heater section 150, and is approximately 200 to 300 mm in the first direction and approximately 70 to 100 mm in the second direction. Further, assuming that the upstream side of the air flow flowing into the air passage 183 is the third direction, and the downstream side is the fourth direction, the width of the case 180 in the third and fourth directions is about 8 to 12 mm.

A first connecting portion 184 that connects the first frame portions 181 in a first direction is integrally formed in the case 180. Three first connecting portions 184 are formed at approximately equal intervals in the second direction, and these first connecting portions 184 divide the air passage 183 into four in the second direction. The first connecting portion 184 is formed to protrude slightly toward the heater portion 150 by about 1 mm. Since the first connecting portion 184 is not just a flat plate but is formed in a protruding rib shape, the load bearing capacity of the case 180 in the first direction is improved. Here, when the first connecting part 184 protrudes toward the heater part 150 side, the space in which the heater part 150 is arranged becomes narrower. However, if the first connecting portion 184 is made to protrude outward in the third and fourth directions, the dimensions of the case 180 in the third and fourth directions will increase, and the mounting condition in the air conditioning case 210 will be reduced. Undesirable. Note that the above-described heating element 110 is not arranged in the region where the first connecting portion 184 is formed. It is arranged between the second frame part 182 and the first connecting part 184. Therefore, even if the first connecting portion 184 is formed to protrude inward in the third and fourth directions, it will not interfere with the heating element 110.

Further, a second connecting portion 185 that connects the second frame portions 182 in the second direction is also integrally formed in the case 180. Four second connecting parts 185 are formed in the first direction, and the positions where the second connecting parts 185 are formed are the positions where the heating element 110 and the electrode 140 are arranged. In other words, the radiation fins 130 are not located within the projected area of the second connecting portion 185, and the heat radiation performance of the heater portion 150 is not adversely affected.

The width of the first connecting portion 184 in the second direction is about 2 mm. Further, as described above, the first connecting portion 184 is formed to protrude inward from the first frame portion 181 in the third direction and the fourth direction (as shown in FIG. 8). Since the first connecting portions 184 connect the first frame portions 181 in this way, are formed in three pieces at approximately equal intervals, and are formed to protrude inward in the third direction and the fourth direction, Deformation of the case 180 in the first direction can be effectively suppressed. Note that the number of first connecting portions 184 is not limited to three. It may be set as appropriate depending on the biasing force of the spring member 170. Further, the intervals between the first connecting portions 184 are preferably equal intervals, but can be selected as appropriate from a design standpoint. That is, the biasing force of the spring member 170 is concentrated at the connection point between the first frame portion 181 and the first connecting portion 184. The intervals between the first connecting portions 184 do not necessarily need to be equal unless excessive stress concentration that causes creep deformation occurs at this connection point. In any case, in the present disclosure, since the first connecting portion 184 is formed in a protruding rib shape, the thickness of the first frame portion 181 is made thinner than in an example in which the first connecting portion 184 is formed in a flat plate shape. It is also possible. Furthermore, the case 180 can be made of a material with lower load-bearing strength than in the case where the first connecting portion 184 is formed on a flat plate.

FIG. 10 shows the difference in radial deformation of the case 180 depending on the presence or absence of the first connecting portion 184. A deformation of the rectangular case 180 without the first connecting part 184 and only the first frame part 181 and the second frame part 182 is shown by A. The measurement point is an intermediate position in the second direction of the first frame portion 181, and the direction of deformation is outside in the first direction. As shown in FIG. 10, the first frame portion 181 deforms outward in the first direction by about 3.5 mm immediately after the spring member 170 is assembled. Then, when the case 180 is placed in an environment of 100 degrees Celsius, it deforms further outward in the first direction by about 1 mm after 1500 hours. Due to this deformation of the case 180, the biasing force of the spring member 170 may become insufficient, which may impede the conduction of electricity between the heating element 110 and the electrodes.

On the other hand, a modification of the case 180 provided with the first connecting portion 184 is indicated by B. In this example, the first connecting portion 184 has a width of 1.5 mm in the second direction, and an inward protrusion amount of 1 mm in the third and fourth directions. Further, four first connecting portions 184 are formed in the air passage 183 of the case 180. As shown in FIG. 10, even after the spring member 170 is assembled, the case 180 is hardly deformed in the first direction. Moreover, even after 1500 hours have passed in an environment of 100 degrees Celsius, there is still almost no deformation in the first direction.

Forming the first connecting portion 184 in this manner is effective in increasing the spring load resistance strength of the case 180 in the first direction. On the other hand, since the first connecting part 184 is formed to protrude inward in the third and fourth directions, the heat radiation area of the heat radiation fin 130 is reduced, as shown by C in FIG. 8 . Generally, in the radiation fin 130, the fin member 131 is held between a rectangular first plate member 132 and a second plate member 133, so that the first plate member 132 and the second plate member 133 In order to avoid interference with the radiation fins 130, the widths of the radiation fins 130 in the third and fourth directions must be shortened.

In contrast, in the present disclosure, as described with reference to FIGS. 6 and 11, the recesses 134 are formed in the radiation fins 130. As shown by D in FIG. 8, the first connecting portion 184 is made to correspond to this recessed portion 134. Note that in the heat dissipation fin 130 of this example, recesses 134 are cut out in advance at predetermined locations on the first plate member 132 and the second plate member 133, and the first plate member 132 and the second plate member 132 with the recesses 134 formed therein are cut out. The fin member 131 is held between the plate member 133 and the plate member 133 . In the sandwiched state, the fin member 131 does not have the recess 134 formed therein, but the fin member 131 is moved in the third direction and in the third direction and the position where the recess 134 is formed between the first plate member 132 and the second plate member 133. The fin member 131 is also crushed inward in four directions so that a recess 134 is formed therein.

In this way, crushing and molding the fin member 131 causes air flow resistance, which is originally undesirable. However, since the region where the recessed portion 134 is formed is hidden by the first connecting portion 184, its influence on heat transfer performance is limited. More than that, it is effective because the widths of the radiation fins 130 in the third and fourth directions can be increased in areas other than the portions where the recesses 134 are formed. In other words, in the region where the first connecting portion 184 is not present, the widths of the radiation fins 130 in the third and fourth directions can be expanded to approximately the same width as the case 180, increasing the heat radiation area of the radiation fins 130. can do.

FIG. 9 shows the relationship between the heating element 110 and the heat radiation area of the heat radiation fin 130. The horizontal axis in FIG. 9 indicates the width of the radiation fin 130 in the third direction and the fourth direction. 0 mm on the horizontal axis indicates the amount of heat dissipated from the heat dissipation fin 130 whose width in the third and fourth directions is 7 mm. On the other hand, the vertical axis in FIG. 9 indicates an increase or decrease in the amount of heat radiation due to an increase or decrease in the width dimension of the radiation fin 130. On the vertical axis, the heat radiation amount of the radiation fin 130 having a width of 7 mm is taken as 100%. 1 mm on the horizontal axis is the radiation fin 130 whose width is increased by 1 mm to 8 mm. The amount of heat dissipated is shown on the vertical axis, and it shows that the heat dissipation efficiency is improved by 5% to 105%. Conversely, -1 mm on the horizontal axis indicates a heat dissipation fin 130 with a width of 6 mm. The heat radiation amount shown on the vertical axis is 95%, which means that the heat radiation efficiency has deteriorated by 5%.

In this example, since the thickness of the first connecting portion 184 is approximately 1 mm, by forming the recessed portion 134, it is possible to increase the width by 1 mm in each of the third direction and the fourth direction. In the state shown in FIG. 9, it is 2 mm, and the heat dissipation efficiency can be improved by 10% while keeping the widths of the case 180 in the third and fourth directions the same.

Next, a procedure for assembling the electric heater 100 having the above configuration will be explained. As described above, the fin member 131 is sandwiched between the first plate member 132 in which the recess 134 is formed and the second plate member, and the first plate member 132, the second plate member 133, and the fin member 131 are brazed. Next, the fin member 131 is crushed to form a recess 134 in the fin member 131 as well.

The radiation fins 130, electrodes 140, and heating element 110 thus formed are combined and held with a jig as a sub-assembly of the heater section 150 as shown in FIG. As shown in FIG. 7, this heater section 150 is held between a third direction panel 186 and a fourth direction panel 187 of the case 180. More specifically, one panel (for example, the third direction panel 186) and the heater section 150 are assembled so that the first connecting section 184 is located in the recess 134 of the radiation fin 130. Next, the other panel (for example, the fourth direction panel 187) is assembled so that the first connecting portion 184 is located in the recess 134 of the radiation fin 130.

Next, the flange 190 is assembled from the second direction so that the electrode 140 fits into the electrode hole 191. As shown in FIG. 3, the flange 190 is formed with a first connector part 192 and a second connector part 193, and three electrodes 140 are arranged in the first connector part 192 and two electrodes 140 are arranged in the second connector part 193. be done.

Finally, the spring member 170 is inserted between the bottom plate portion 194 integrally molded on the flange 190 and the lowermost electrode. The spring member 170 is inserted through an insertion hole 189 formed in the mating surface 188 of the third direction panel 186 and the fourth direction panel 187 (as shown in FIG. 12). By inserting the leaf spring 170, a biasing force in the first direction is applied to the heater section 150, thereby strengthening the connection between the heating element 110, the electrode 140, and the radiation fin 130.

Note that the amount of heat generated by the heating element 110 is controlled by changing the number of positive electrodes 141 that are energized. When obtaining the maximum amount of heat generation, all the positive electrodes 141 are energized. The central plus electrode 141 supplies power to the upper and lower heating elements 110, so it supplies, for example, 300 watts of power, and the upper and lower plus electrodes 141 supply, for example, 150 watts of power. In order to reduce the amount of heat generated by the heater section 150, the number of positive electrodes 141 to be energized may be reduced.

Although the above-described example is a preferred implementation of the present disclosure, the present disclosure can be modified in various ways. In the above example, the fin member 131 is crushed in advance to form the recess 134, but the recess 134 may be formed only in the first plate member 132 and the second plate member 133. That is, when the first connecting portion 184 of the case 180 fits into the recess 134 of the first plate member 132 and the second plate member 133, the first connecting portion 184 may crush the fin member 131. Since the fin member 131 has a thin wall of about 0.2 mm, it can also be crushed by the first connecting portion 184.

As a method for forming the recess 134 in the fin member 131, a method other than crushing may be employed. For example, it is also possible to form the recess 134 by cutting. In that case, not only the fin member 131 but also the first plate member 132 and the second plate member 133 may be cut to form the recess 134.

In the above example, the first connecting portions 184 are arranged in both the third and fourth directions of the case 180, and the recesses 134 are also formed in the third and fourth directions. The arrangement is well-balanced between upstream and downstream airflow. However, even if the first connecting portion 184 is arranged only in either the third direction or the fourth direction, the spring load resistance strength of the case 180 can be maintained. In that case, the recess 134 may be formed only in the direction in which the first connecting portion 184 is arranged.

Further, in the above example, the spring member 170 is arranged on the bottom plate part 194 side, but the spring member 170 may be located at the end of the heater part 150 in the first direction. It may be arranged below as in the above example, or it may be arranged above. Moreover, it is also possible to arrange the spring members 170 on both the upper and lower sides.

Further, in the above example, as shown in FIG. 5, the heater part 150 is assembled into the case 180 after being made into a sub-assembly, but it is also possible to incorporate the radiation fins 130, the electrodes 140, and the heating element 110 into the case separately. .

Furthermore, in the above example, the heat generating element 110 was directly sandwiched between the radiation fins 130 and the electrodes 140. This is useful because the number of parts can be reduced. However, the heating element 110 may be held by a resin holding plate. By using the holding plate, insulation of the heating element 110 can be ensured.

Further, the above-mentioned materials and sizes are merely examples, and can be changed depending on required performance and the like. The number and arrangement of heating elements 110 can also be changed in various ways. The heating element 110 may be arranged not only between the second frame portion 182 and the first connecting portion 184 but also between adjacent first connecting portions 184. Moreover, the number of heat radiation fins 130 can also be changed.

100 Electric heater 110 Heat generating element 130 Radiation fin 134 Recess 140 Electrode 170 Spring member 180 Case 181 First frame 182 Second frame 184 First connecting portion 185 Second connecting portion

Claims (6)

A flat heating element that generates heat when energized, a radiation fin that radiates heat from the heating element to an air passage, an electrode that is connected to a power source to supply power to the heating element, the heating element, the radiation fin, and a heater section having a spring member that is biased in a first direction, which is a direction in which the electrodes are stacked, and brings the heating element, the radiation fins, and the electrodes into contact with each other;
A pair of first frame portions that cover the heater portion at both ends in the first direction; and a pair of second frame portions that cover the heater portion at both ends in a second direction that is orthogonal to the first direction. and a case made of a resin material, the interior of which is defined by the first frame portion and the second frame portion as the air passage;
The case further includes a first connecting portion connecting the first frame portions, and the first connecting portion is formed to protrude from the first frame portion toward the radiation fin,
The radiation fin includes a pair of plate members and a fin member disposed between the pair of plate members, and a recess corresponding to the first connecting portion is formed in the pair of plate members and the fin member. An electric heater characterized by: The first connecting portion is disposed in both a third direction, which is an upstream side of the air passage, and a fourth direction, which is a downstream side, of the air passage with respect to the radiation fin,
The electric heater according to claim 1, wherein the radiation fins form the recesses in both the third direction and the fourth direction. The electric heater according to claim 2, wherein the case is formed so as to be separable in both the third direction and the fourth direction. The electric heater according to any one of claims 1 to 3, wherein the heating element is disposed within the case at a location where the first connecting portion is not present. The electric heater according to any one of claims 1 to 4, wherein a plurality of the first connecting portions are formed so as to partition the air passage at approximately equal intervals. The case further includes a second connecting part that connects the second frame parts, and
The electric heater according to any one of claims 1 to 5, wherein the electrode is arranged within the projected area of the second connecting portion within the air passage.

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