JP7678343B2 - Electric heater - Google Patents

Description

This disclosure relates to an electric heater that heats air and is suitable for use, for example, in warming the interior of an automobile.

In some electric heaters, the heater unit is held in a resin case. In Patent Document 1, a spring member is used to press the heater unit placed in the case.

However, the spring member mounted between the resin case and the heater section applies a load to the heater section and a reaction force to the resin case at the same time. The resin case to which the reaction force is applied will experience creep over time (deformation of the resin section), and the load on the heater section will gradually decrease accordingly.

JP 2009-51494 A

In view of the above, the present disclosure aims to design a case shape that can withstand the reaction force even when the heater section is biased using a spring member. Furthermore, it is an object of the present disclosure to ensure that the amount of heat dissipation from the heater section is not impaired even when the case shape is designed.

The first aspect of the present disclosure includes a heater section having a flat heating element that generates heat when energized, a heat dissipation fin that dissipates heat from the heating element into an air passage, an electrode that is connected to a power source and supplies power to the heating element, and a spring member that biases the heating element, the heat dissipation fin, and the electrode in a first direction in which the heating element, the heat dissipation fin, and the electrode are stacked to bring the heating element, the heat dissipation fin, and the electrode into contact with each other. The first aspect of the present disclosure also includes a case made of a resin material that has a pair of first frame sections that cover the heater section at both ends in the first direction, and a pair of second frame sections that cover the heater section at both ends in a second direction that is perpendicular to the first direction, and the inside of the case is partitioned by the first frame sections and the second frame sections and serves as an air passage.

The first case of the present disclosure further has a first connecting portion that connects the first frame portions, and this first connecting portion is formed to protrude from the first frame portions toward the heat dissipation fin side. Also, the heat dissipation fin includes a pair of plate members and a fin member disposed between the pair of plate members, and the pair of plate members and the fin member have recesses formed therein that correspond to the first connecting portion.

In the first aspect of the present disclosure, the case is provided with a first connecting portion that connects the first frame portions, thereby increasing the strength of the case in the first direction. In particular, the first connecting portion is formed to protrude toward the heat dissipation fin from the first frame portions, increasing the spring load resistance strength of the first connecting portion. Therefore, even if the case is subjected to the biasing force of the spring member for a long period of time, deformation of the case can be effectively suppressed.

In addition, in the first aspect of the present disclosure, a pair of plate members and fin members of the heat dissipation fin are formed with recesses corresponding to the first connecting portion, so that even if the first connecting portion is formed to protrude from the first frame portion toward the heat dissipation fin, there is no interference between the heat dissipation fin and the first connecting portion. Therefore, even if the first connecting portion is formed to protrude toward the heat dissipation fin, a sufficient heat dissipation area can be ensured for the heat dissipation fin.

In the second disclosure, the first connecting portion is arranged in both the third direction, which is the upstream side of the air passage, and the fourth direction, which is the downstream side, relative to the heat dissipation fin. The heat dissipation fin forms recesses in both the third and fourth directions. In the second disclosure, the first connecting portion is arranged on both the upstream and downstream sides, so the spring load resistance strength of the case can be further increased. In addition, the strength of the case can be balanced between the upstream and downstream sides. In addition, in the second disclosure, the heat dissipation fin also forms recesses in both the third and fourth directions, so the heat transfer area of the heat dissipation fin can be maintained on both the upstream and downstream sides.

In the third aspect of the present disclosure, the case is formed so as to be separable in both the third and fourth directions. In the present disclosure, the first connecting portion is formed to protrude from the first frame portion toward the heat dissipation fin side, and the heat dissipation fin also has a pair of plate members and fin members formed with recesses corresponding to the first connecting portion, so that assembly of the heater portion and the case is important. In the third aspect of the present disclosure, the electric heater can be assembled by sandwiching the heater portion between the separated cases.

In the fourth aspect of the present disclosure, the heat generating element is disposed in a portion of the case where the first connecting portion is not present. In the present disclosure, the first connecting portion is formed to protrude from the first frame portion toward the heat dissipation fin side, but since the heat generating element is disposed in a portion where the first connecting portion is not present, the first connecting portion does not interfere with the heat generating element.

The fifth aspect of the present disclosure is that the first connecting portion is formed in a plurality of parts so as to divide the air passage at approximately equal intervals. This allows the spring load resistance strength of the case to be kept approximately uniform over the entire length in the second direction.

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

FIG. 1 is a diagram showing the configuration of an automotive air conditioner. FIG. 2 is a front view of the electric heater of the present disclosure. FIG. 3 is a right side view of the electric heater of FIG. FIG. 4 is an exploded front view of the heater unit. FIG. 5 is a front view of the heater unit. FIG. 6 is a perspective view showing a part of the heat dissipation 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 heat dissipation fin. FIG. 9 is a diagram illustrating the heat dissipation area and the heat exchange efficiency. FIG. 10 is a diagram illustrating deformation of the case. FIG. 11 is an exploded perspective view of the heater unit. FIG. 12 is a left side view of the electric heater of FIG.

An example of the present disclosure will be described below with reference to the drawings. As shown in FIG. 1, the electric heater 100 is used together with an automotive air conditioner 200. The automotive air conditioner 200 selectively draws in air from an exterior air intake 201 or an interior air intake, and blows it into the interior of the vehicle with a blower fan 202. The air is cooled by an evaporator 203 in a refrigeration cycle, and is heated by a hot water heater 204. The hot water heater 204 uses engine coolant as its heat source. However, immediately after the engine is started, the engine coolant is not warmed and there is a shortage of heat source for heating. In particular, when engines become smaller due to hybridization of automobiles and the engine operating rate decreases, the shortage of heat from the engine coolant becomes noticeable.

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

As shown in FIG. 2, the heater section 150 of the electric heater 100 is housed in a case 180. This case 180 is disposed in an air conditioning case 210 of the air conditioning device 200. Specifically, the air conditioning case 210 has an assembly opening corresponding to the case 180 of the electric heater 100, and the case 180 is inserted into the air conditioning case 210 through the assembly opening. The assembly opening of the air conditioning case 210 is closed by a flange 190 of the case 180. Details of the case 180 will be described later.

In Fig. 4 and Fig. 11, the elements constituting the heater section 150 are shown in exploded form. The heater section 150 includes a heat generating element 110 and an electrode 140 that supplies power to the heat generating element 110. The heater section 150 also includes a heat dissipation fin 130 that dissipates heat from the heat generating element to an air passage. The heat dissipation fin 130 is also a conductor that provides electrical conductivity between the electrodes 140. The heater section 150 also includes a spring member 170. In the following description, the stacking direction of the heat dissipation fin 130, the electrode 140, the heat generating element 110, and the spring member 170 (the vertical direction in Fig. 4) is referred to as a first direction, and the direction perpendicular to the first direction (the horizontal direction in Fig. 4) is referred to as a second direction.

The heating element 110 is made of a PTC element or the like, and generates heat when electricity is passed through it. A PTC (Positive Temperature Coefficient) element is an element that has the property that its electrical resistance increases rapidly above a certain temperature, and therefore generates heat when electricity is passed through it. However, when the temperature at which heat is generated exceeds a certain temperature, the electrical resistance becomes too high and almost no current flows, so heat is not generated above a certain temperature. Therefore, by using this element, it is possible to prevent the heater from overheating. This heating element 110 is rectangular, with a length of 35 mm in the second direction, a width of 7 mm, and a thickness of about 1 mm in the first direction.

As shown in Figs. 5 and 6, the heat dissipation 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. The fin member 131 is made of an aluminum alloy containing manganese, and is formed by bending it multiple times. The first plate member 132 and the second plate member 133 are also made of an aluminum alloy, and the ends in the second direction are bent at approximately right angles 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 dissipation fin 130 has a height of about 10 mm and a width of about 7 mm in the first direction. The length of the heat dissipation fin 130 in the second direction varies depending on the capacity required for the electric heater 100, but is about 180 to 280 mm.

The heat dissipation fin 130 has a recess 134 formed in a portion corresponding to a first connecting portion 184 of the 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 has a width in the second direction of approximately 2 millimeters. The depth of the recess 134 is approximately 1 millimeter or more.

The heat generating element 110 is sandwiched between the heat dissipation fin 130 and the electrode 140. The electrode 140 is made of brass and has a positive electrode 141 that receives power from a battery (not shown) and a negative electrode 142. In the example of Figs. 4 and 5, the heat dissipation fin 130 is arranged in five layers in the first direction. Four layers of the heat generating element 110 are arranged between the heat dissipation fin 130 and the electrode 140. At the bottom in the first direction in Figs. 4, 5, and 11, only one layer of the electrode 140 is arranged. Therefore, the electrode 140 is arranged in five layers, with the positive electrodes 141 and the negative electrodes 142 arranged alternately. In this way, the heat dissipation fin 130, the heat generating element 110, and the electrode 140 are stacked in multiple stages in the first direction to form the heater section 150.

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

The case 180 is made of polybutylene terephthalate (PBT) and has a first frame 181 that covers both ends of the heater section 150 in the first direction and a second frame 182 that covers both ends in the second direction. That is, the first and second frames form a rectangular air passage 183. The size of the case 180 is large enough to house the heater section 150, and is approximately 200 to 300 millimeters in the first direction and approximately 70 to 100 millimeters in the second direction. In addition, if the upstream side of the air flow flowing into the air passage 183 is defined as the third direction and the downstream side as the fourth direction, the width of the case 180 in the third and fourth directions is approximately 8 to 12 millimeters.

The case 180 is integrally molded with a first connecting portion 184 that connects the first frame portions 181 in the first direction. Three first connecting portions 184 are formed at approximately equal intervals in the second direction, and the air passage 183 is divided into four in the second direction by these first connecting portions 184. The first connecting portion 184 is formed to protrude toward the weak heater portion 150 by about 1 millimeter. The first connecting portion 184 is not simply a flat plate, but is formed to protrude in a rib shape, thereby improving the load-bearing capacity of the case 180 in the first direction. Here, the protrusion of the first connecting portion 184 toward the heater portion 150 narrows the arrangement space of the heater portion 150. However, if the first connecting portion 184 is protruded outward in the third and fourth directions, the dimensions of the case 180 in the third and fourth directions will increase, which is not preferable for mounting on the air conditioning case 210. The heating element 110 is not located where the first connecting portion 184 is formed. It is located between the second frame portion 182 and the first connecting portion 184. Therefore, even if the first connecting portion 184 is formed to protrude inward in the third and fourth directions, it does not interfere with the heating element 110.

The case 180 also has integrally formed second connecting portions 185 that connect the second frame portions 182 in the second direction. Four second connecting portions 185 are formed in the first direction, and the positions at which the second connecting portions 185 are formed are positions at which the heating elements 110 and the electrodes 140 are disposed. In other words, the heat dissipation fins 130 are not located within the projected area of the second connecting portions 185, and therefore there is no adverse effect on the heat dissipation performance of the heater portion 150.

The width of the first connecting portion 184 in the second direction is about 2 millimeters. As described above, the first connecting portion 184 is formed to protrude inward in the third and fourth directions from the first frame portion 181 (see FIG. 8). The first connecting portion 184 connects the first frame portions 181 in this way, and is formed in three pieces at approximately equal intervals, and is formed to protrude inward in the third and fourth directions, thereby effectively suppressing deformation of the case 180 in the first direction. The number of first connecting portions 184 is not limited to three. It may be set appropriately according to the biasing force of the spring member 170. In addition, the intervals between the first connecting portions 184 are preferably equal, but can be selected appropriately in design. 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. As long as there is no excessive stress concentration at this connection point that causes creep deformation, the intervals between the first connecting portions 184 do not necessarily need to be equal. In any case, in the present disclosure, the first connecting portion 184 is formed as a protruding rib, so it is possible to make the plate thickness of the first frame portion 181 thinner than in an example in which the first connecting portion 184 is formed as a flat plate. Also, it is possible to use a material with a lower load-bearing strength for the case 180, compared to an example in which the first connecting portion 184 is formed on a flat plate.

Figure 10 shows the difference in radial deformation of the case 180 depending on whether or not the first connecting portion 184 is present. The deformation of the square-shaped case 180 without the first connecting portion 184 and consisting only of the first frame portion 181 and the second frame portion 182 is indicated by A. The measurement point is the middle position of the first frame portion 181 in the second direction, and the deformation direction is outward in the first direction. As shown in Figure 10, the first frame portion 181 deforms outward in the first direction by about 3.5 millimeters immediately after the spring member 170 is assembled. Then, when the case 180 is placed in an environment of 100 degrees Celsius, it deforms outward in the first direction by another 1 millimeter after 1500 hours. This deformation of the case 180 may cause the biasing force of the spring member 170 to be insufficient, which may cause a problem in the flow of electricity between the heating element 110 and the electrode.

On the other hand, the deformation of the case 180 provided with the first connecting portion 184 is shown by B. In this example, the width of the first connecting portion 184 in the second direction is 1.5 mm, and the amount of inward protrusion in the third and fourth directions is 1 mm. Furthermore, four first connecting portions 184 are formed in the air passage 183 of the case 180. As shown in FIG. 10, even when the spring member 170 is assembled, the case 180 hardly deforms in the first direction. Furthermore, even after 1,500 hours in an environment of 100 degrees Celsius, there is still almost no deformation in the first direction.

In this way, forming the first connecting portion 184 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 portion 184 is formed to protrude inward in the third and fourth directions, it reduces the heat dissipation area of the heat dissipation fin 130, as shown by C in FIG. 8. Generally, the heat dissipation fin 130 sandwiches the fin member 131 between the rectangular first plate member 132 and second plate member 133, so that the width of the heat dissipation fin 130 in the third and fourth directions must be shortened in order to prevent the first plate member 132 and second plate member 133 from interfering with the first connecting portion 184.

In contrast, in the present disclosure, as described in FIG. 6 and FIG. 11, the recess 134 is formed in the heat dissipation fin 130. As shown by D in FIG. 8, the first connecting portion 184 corresponds to this recess 134. In the present embodiment, the heat dissipation fin 130 is formed by cutting out the recess 134 at a predetermined position of the first plate member 132 and the second plate member 133, and the fin member 131 is sandwiched between the first plate member 132 and the second plate member 133 in which the recess 134 is formed. In the sandwiched state, the recess 134 is not formed in the fin member 131, but the fin member 131 is crushed inward in the third and fourth directions at the position where the recess 134 is formed between the first plate member 132 and the second plate member 133, so that the recess 134 is also formed in the fin member 131.

In this way, squeezing and molding the fin member 131 creates resistance to air flow, which is not desirable in the first sense. However, since the area where the recess 134 is formed is an area hidden by the first connecting portion 184, the effect on heat transfer performance is limited. Furthermore, it is effective in widening the width of the heat dissipation fin 130 in the third and fourth directions in areas other than where the recess 134 is formed. In other words, in areas where the first connecting portion 184 does not exist, the width of the heat dissipation fin 130 in the third and fourth directions can be widened to approximately the same as the width of the case 180, and the heat dissipation area of the heat dissipation fin 130 can be increased.

9 shows the relationship between the heat generating element 110 and the heat dissipation area of the heat dissipation fin 130. The horizontal axis of FIG. 9 shows the width of the heat dissipation fin 130 in the third and fourth directions. 0 mm on the horizontal axis shows the heat dissipation amount of the heat dissipation fin 130 with a width of 7 mm in the third and fourth directions. On the other hand, the vertical axis of FIG. 9 shows the increase or decrease in the heat dissipation amount with the increase or decrease in the width dimension of the heat dissipation fin 130. On the vertical axis, the heat dissipation amount of the heat dissipation fin 130 with a width dimension of 7 mm is set to 100%. 1 mm on the horizontal axis is a heat dissipation fin 130 with a width increased by 1 mm to 8 mm. The heat dissipation amount is shown on the vertical axis, and indicates that the heat dissipation efficiency has 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 dissipation amount shown on the vertical axis is 95%, indicating that the heat dissipation efficiency has deteriorated by 5%.

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

Next, the procedure for assembling the electric heater 100 configured as above will be described. As described above, the fin member 131 is sandwiched between the first plate member 132 and the second plate member in which the recess 134 is formed, 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 the recess 134 in the fin member 131 as well.

The thus formed heat dissipation fin 130, electrode 140, and heating element 110 are combined and held by a jig as a sub-assembly of the heater unit 150 as shown in FIG. 5. This heater unit 150 is sandwiched between the third direction panel 186 and the fourth direction panel 187 of the case 180 as shown in FIG. 7. More specifically, one panel (e.g., the third direction panel 186) and the heater unit 150 are assembled so that the first connecting portion 184 is positioned in the recess 134 of the heat dissipation fin 130. Next, the other panel (e.g., the fourth direction panel 187) is assembled so that the first connecting portion 184 is positioned in the recess 134 of the heat dissipation fin 130.

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

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

The amount of heat generated by the heating element 110 is controlled by changing the number of positive electrodes 141 that are energized. To obtain the maximum amount of heat, all of the positive electrodes 141 are energized. The central positive electrode 141 supplies power to the upper and lower heating elements 110, so for example, 300 watts of power is supplied, and the upper and lower positive electrodes 141 are supplied with, for example, 150 watts of power. To reduce the amount of heat generated by the heater section 150, the number of energized positive electrodes 141 can be reduced.

The above example is a desirable response of this disclosure, but 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 is thin, about 0.2 millimeters, it can also be crushed by the first connecting portion 184.

Methods other than crushing may be used to form the recesses 134 in the fin member 131. For example, it is also possible to form the recesses 134 by cutting. In that case, the recesses 134 can be formed by cutting not only the fin member 131 but also the first plate member 132 and the second plate member 133 together.

In the above example, the first connecting parts 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. This is a well-balanced arrangement upstream and downstream of the air flow. However, even if the first connecting parts 184 are arranged only in either the third or fourth direction, the spring load resistance strength of the case 180 can be maintained. In that case, the recesses 134 need only be formed in the direction in which the first connecting parts 184 are arranged.

In the above example, the spring member 170 is disposed on the bottom plate portion 194 side, but the position of the spring member 170 may be any position as long as it is at the end of the heater portion 150 in the first direction. It may be disposed downward as in the above example, or it may be disposed upward. It is also possible to dispose the spring member 170 both above and below.

In the above example, the heater section 150 is assembled as a sub-assembly into the case 180 as shown in FIG. 5, but it is also possible to assemble the heat dissipation fins 130, the electrodes 140, and the heating element 110 separately into the case.

In the above example, the heat generating element 110 is directly sandwiched between the heat dissipation fin 130 and the electrode 140. This is useful as it reduces the number of parts. However, the heat generating element 110 may also be held by a resin holding plate. By using a holding plate, insulation of the heat generating element 110 can be ensured.

The above-mentioned materials and sizes are merely examples and can be changed according to the required performance, etc. The number and arrangement of the heating elements 110 can also be changed in various ways. The heating elements 110 can be arranged not only between the second frame portion 182 and the first connecting portion 184, but also between adjacent first connecting portions 184. Furthermore, the number of heat dissipation fins 130 can also be changed.

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

Claims (6)

a heater section including a flat heating element that generates heat when current is applied, a heat dissipation fin that dissipates heat from the heating element into an air passage, an electrode that is connected to a power source and supplies power to the heating element, and a spring member that biases the heating element, the heat dissipation fin, and the electrode in a first direction in which the heating element, the heat dissipation fin, and the electrode are stacked, to bring the heating element, the heat dissipation fin, and the electrode into contact with each other;
a pair of first frame portions covering the heater portion at both ends in the first direction, and a pair of second frame portions covering the heater portion at both ends in a second direction perpendicular to the first direction, and a case made of a resin material, the case defining an interior portion defined by the first frame portions and the second frame portions as the air passage;
The case 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 portions toward the heat dissipation fins,
The electric heater is characterized in that the heat dissipation fin comprises a pair of plate members and a fin member arranged 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. the first connecting portion is disposed on both an upstream side of the air passage in a third direction and a downstream side of the air passage in a fourth direction with respect to the heat dissipation fin;
The electric heater according to claim 1 , wherein the heat dissipation fin has 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. 4. The electric heater according to claim 1, wherein the heating element is disposed in a portion of the case where the first connecting portion is not present. 5. The electric heater according to claim 1, wherein the first connecting portion is formed in plurality so as to divide the air passage at substantially equal intervals. The case further includes a second connecting portion that connects the second frame portions,
6. The electric heater according to claim 1, wherein the electrode is disposed within a projected area of the second connecting portion in the air passage.

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