JP7529996B2 - 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.

A known structure for electric heaters is to place frames on both sides of the heater section in a first direction, which is the stacking direction of the heater section, and press the frames against the heater section to press the heating element, heat dissipation fins, and electrode plate in the heater section. It is also known to use a spring to press the frame against the heater section.

Patent document 1 proposes forming a bending point in the frame to increase the pressing force on the heater part side of the frame.

JP 2009-152172 A

It would seem that forming a bend point would result in a higher pressing force than with a flat frame. However, it was found that depending on the position of the bend point, there are also areas where the pressing force decreases as a result of the frame deforming around the bend point. In particular, sufficient pressing force is required between the heating element and the electrode plate, and at the connection points between the heating element and the heat dissipation fins, to ensure that electricity flows through the heating element and that heat is transferred appropriately from the heating element. If the pressing force decreases in such areas, it could lead to a decrease in the performance of the electric heater.

In view of the above, the objective of this disclosure is to minimize the number of areas where the pressing force from the frame is reduced.

The first aspect of the present disclosure has a flat heating element that generates heat when electricity is applied, a plate that holds multiple heating elements in the flat plate surface direction, heat dissipation fins that are arranged in the air passage and transfer heat from the heating element to the air passage, and an electrode plate that supplies power to the heating element, and the plate, heat dissipation fins, and electrode plate are each stacked in multiple layers to form a heater section.

In addition, the first aspect of the present disclosure provides a pair of frames with a U-shaped cross section, with the heater section side serving as the bottom and both sides of the bottom serving as wall sections, on both sides of a first direction, which is the stacking direction of the heater section, and provides springs that bias the frames toward the heater section on both sides of a second direction, which is a direction perpendicular to the stacking direction of the heater section.

In the first aspect of the present disclosure, the shape of the bottom of the frame when not biased by the spring is an arc shape that bulges continuously from the end in the second direction toward the center toward the heater unit in the first direction without multiple bending points. This narrows the area of insufficient pressing force that occurs toward the center in the second direction compared to a shape having multiple bending points. Here, the arc shape does not necessarily have to be a circle, and may include an ellipse or a parabola, as long as it is a shape that bulges continuously without bending points.

In this way, since the frame is formed into a circular arc shape that bulges continuously without multiple bending points, it is possible to prevent the frame from deforming with a specific bending point as a fulcrum even when the frame is biased by a spring. Therefore, according to the first aspect of the present disclosure, it is possible to connect between the heat generating element and the electrode plate, and between the heat generating element and the heat dissipation fins with sufficient pressing force.

In the first aspect of the present disclosure, the rigidity of the frame is made higher on the center side in the second direction than on the end sides in the second direction. Since the frame is pressed by the spring on both sides in the second direction, the pressing force is lower on the center side in the second direction than on the end sides, and there tends to be an area where the pressing force is insufficient . To compensate for this, in the first aspect of the present disclosure, the rigidity of the center side is increased.

In another aspect of the present disclosure, the frame is shaped to form a bulging portion that bulges outward on the center side of the wall portion in the second direction. By providing the bulging portion, the rigidity of the center side of the frame can be increased.

In another aspect of the present disclosure, the frame is shaped so that the height of the wall portion on the center side in the second direction is greater than the height of the end side in the second direction. By making the wall portion taller on the center side, the rigidity of the center side of the frame can be increased.

In another aspect of the present disclosure, the frame is shaped such that holes are formed in the wall portions at the ends in the second direction. By forming the holes, the rigidity of the end portions of the frame can be reduced and the rigidity of the center portion can be relatively increased.

In another aspect of the present disclosure, the frame is shaped so that a rib is formed on the center side of the bottom in the second direction. By forming the rib, the rigidity of the center side of the frame can be increased.

In the present disclosure, the shape of the bottom of the frame when not biased by the spring is expressed as follows : h = 0.1 + 2.4/1000 × (L - 180) + A, where L is the length of the frame in the second direction and h is the height of the frame from the end to the center in the first direction.
The relationship is expressed by the following formula. The unit in this formula is millimeters. A is the manufacturing tolerance, which is plus or minus 0.2 millimeters. However, when L is 230 millimeters or less, the tolerance A is plus 0.2 millimeters, but the lower limit of height h is secured to 0.02 millimeters. By defining the degree of bulge within an optimal range, it is possible to connect the heating element and the electrode plate, and the heating element and the heat dissipation fins with an appropriate pressing force.

In the present disclosure, one side of the spring is integrally formed with the frame. Since the one side is joined, the spring only needs to be fixed on the other side, which reduces the number of assembly steps.

In the present disclosure, the bottom of the frame is formed double, and the shape of the bottom on the heater side is an arc shape that bulges continuously in the first direction from the end in the second direction toward the center without multiple bending points when not biased by the spring. Because it is a double bottom, it is also possible to interpose an arc-shaped spacer that bulges continuously in the first direction without multiple bending points between the frame with a U-shaped cross section and the heater.

FIG. 1 is a front view of the electric heater of the present disclosure. FIG. 2 is an exploded front view of the electric heater of FIG. FIG. 3 is an enlarged front view of the heating element portion of the electric heater of FIG. FIG. 4 is a front view showing the shape of the bottom of the frame having two bending points when not biased by a spring. FIG. 5 is a front view illustrating a deformed state of a frame having three bending points. FIG. 6 is a front view showing the shape of the bottom of the frame having no bending points when not biased by a spring. FIG. 7 is a schematic diagram illustrating the deformation states of a frame having a bending point and a frame having no bending point. FIG. 8 is a front view showing the height in the first direction and the length in the second direction of the frame. FIG. 9 is a diagram showing the relationship between the height h of the frame and the proportion of the area A receiving the pressing force of the heating element. FIG. 10 is a diagram showing the relationship between the height in the first direction and the length in the second direction of the frame. FIG. 11 is a front view showing a modified example of the present disclosure. FIG. 12 is a front view of the frame shown in FIG. FIG. 13 is a front view showing another modified example of the present disclosure. FIG. 14 is a front view showing still another modified example of the present disclosure. FIG. 15 is a front view showing still another modified example of the present disclosure. FIG. 16 is a front view showing another example of the arrangement of the heating elements. FIG. 17 is a front view showing still another modified example of the present disclosure. FIG. 18 is a front view showing still another modified example of the present disclosure.

An example of the present disclosure will be described below with reference to the drawings. FIG. 1 is a front view showing an example of an electric heater 100. The electric heater 100 is used together with an automotive air conditioner. The automotive air conditioner uses engine coolant as its heat source for heating. 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 in the engine coolant becomes noticeable.

The electric heater 100 is used to compensate for this lack of heat source. It is placed downstream of the air flow of the heater core of the automotive air conditioner, and heats the air sent from the blower fan of the automotive air conditioner. Figure 2 is a front view showing the components of this electric heater 100 disassembled.

110 is a heating element such as a PCT element, which generates heat when electricity is applied. This heating element 110 is rectangular, approximately 35 mm long, 6.6 mm wide, and 1.2 mm thick, and is held in a holding portion 121 of a plate 120 made of a resin material such as nylon. The thickness of the plate 120 is approximately 1 mm, which is set to be almost the same as but slightly smaller than the thickness of the heating element 110. Therefore, when the heating element 110 is stored in the holding portion 121 of the plate 120, one side 111 and the other side 112 of the heating element 110 are completely exposed. This is to ensure that the electrical connection with the electrode plate 140, which will be described later, is made.

In Fig. 3, the other surface 112 of the heating element 110 is joined to a heat dissipation fin 130. The heat dissipation fin 130 is made of an aluminum alloy containing manganese, and is composed of a fin portion 131 formed by multiple folding and a frame portion 132 that houses the fin portion 131. The fin portion 131 and the frame portion 132 are integrally brazed. The heat dissipation fin 130 is 10 mm high and 7 mm wide, and the length varies depending on the capacity required for the electric heater 100. As will be described later, the length is about 180 to 280 mm.

The electrode plate 140 made of an aluminum alloy is in contact with one surface 111 of the heating element 110, and as described above, is electrically connected to the electrode plate 140. The electrode plate 140 is also in contact with the heat dissipation fins 130, and in Fig. 3, the electrode plate 140 on the heating element 110 side is a positive electrode 141. The electrode plate 140 on the heat dissipation fins 130 side is a negative electrode 142.

In the example of FIG. 1, the heat dissipation fins 130 are arranged in five layers, and four layers of plates 120 (heat generating elements 110) are arranged between the heat dissipation fins 130. The electrode plates 140 are arranged in five layers, with positive electrodes 141 and negative electrodes 142 arranged alternately. In this way, the heat dissipation fins 130, plates 120, and electrode plates 140 are stacked in multiple stages to form the heater section 150. Note that the stacking direction (the up-down direction in FIG. 1) is defined as the first direction, and the direction perpendicular to the stacking direction (the left-right direction in FIG. 1) is defined as the second direction.

In the example of FIG. 1, the first plate 123, which is the top of the plates 120, has four heating elements 110 arranged at equal intervals in the second direction. The four heating elements 110 are, from the right in the figure, the first element 114, the second element 115, the third element 116, and the fourth element 117. In the second plate 124, which is the second from the top, two heating elements 110 are arranged at positions corresponding to the first element 114 and the third element 116 of the first plate 123. In the third plate 125, which is the third, two heating elements 110 are arranged at positions corresponding to the second element 115 and the fourth element 117. And, in the fourth plate 126, four heating elements 110 are arranged at equal intervals, similar to the first plate 123. No heating elements 110 are arranged on the fifth plate 127, which is the lowest.

Therefore, in the heater section 150 as a whole, the first element 114, the second element 115, the third element 116, and the fourth element 117 are arranged in three in the first direction. The arrangement of the heating elements 110 is balanced in both the first and second directions of the heater section 150. As a result, the air passing through the electric heater 100 has a homogenous temperature, which contributes to the temperature control of the automotive air conditioner. The length of the heater section 150 in the first direction and the length of the heater section 150 in the second direction are set according to the duct of the automotive air conditioner. In this disclosure, the width in the second direction is about 200 to 300 millimeters, and the width in the first direction is about 50 to 100 millimeters. Here, it is desirable that both the first and second directions are constant without individual variation, but tolerances during manufacturing must be allowed. In particular, it is difficult to completely suppress variation in the first direction. In addition, the thickness of the heater section 150 is about 8 millimeters. For installation in automotive air conditioning systems, a thinner thickness is preferable, but a balance has been struck between the required heat generation and ease of installation, leaving the thickness at around 8 millimeters.

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 generated, all three positive electrodes 141 are energized. At this time, a positive voltage is applied to the heating element 110 arranged on the first plate 123 from the positive electrode 141 of the upper first positive electrode plate 145, and the heating element 110 is grounded to the electrode plate 140 of the negative electrode 142 via the lower heat dissipation fin 130. A positive voltage is applied to the heating element 110 arranged on the second plate 124 from the positive electrode 141 of the intermediate second positive electrode plate 146, and the heating element 110 is grounded to the negative electrode 142 shared with the first plate 123 via the upper heat dissipation fin 130.

A positive voltage is applied to the heating element 110 arranged on the third plate 125 from the positive electrode 141 of the intermediate second positive electrode plate 146, and the heating element 110 is grounded to the lower negative electrode 142 via the lower heat dissipation fin 130. A positive voltage is applied to the heating element 110 arranged on the fourth plate 126 from the positive electrode 141 of the lower third positive electrode plate 147, and the heating element 110 is grounded to the negative electrode 142 shared with the third plate 125 via the upper heat dissipation fin 130.

The amount of heat generated by the heater section 150 can be reduced by reducing the number of electrode plates 140 that are energized. To achieve the minimum amount of heat, only the second positive electrode plate 146 is energized. At this time, the heating elements 110 arranged on the second plate 124 and the third plate 125 generate heat. Even in this state of minimum heat generation, the heating elements 110 are arranged in the heater section 150 in a balanced manner in both the first and second directions. Therefore, when installed in an automotive air conditioning system, the air can be heated evenly.

A stainless steel frame 160 is disposed on both sides of the heater section 150 in the first direction to hold the heater section 150 in place. The length of the frame 160 in the second direction is equal to or slightly longer than that of the heat dissipation fins 130. The frame 160 has a U-shaped cross section with walls 162 extending from both sides of the bottom 161 (see Figures 11 to 15). The width of the bottom 161 is approximately 8 millimeters, the same as the thickness of the heater section 150, and the height of the walls 162 is approximately 10 millimeters. The thickness of the frame 160 is approximately 1 millimeter.

Springs 170 are arranged on both sides of the frame 160 in the second direction. The springs 170 are stainless steel rods with a diameter of about 4 mm. The springs 170 have a straight portion 171 along the second direction end of the heater unit 150, bent portions 172 formed at both ends of the straight portion in the first direction, and a pressing portion 173 that presses the frame 160 toward the heater unit 150. The springs 170 have spring properties due to the bent portions 172, and press the frame 160 toward the heater unit 150 (first direction) with a force of about 50 to 190 Newtons. The pressing force of the pair of springs 170 is set to be the same on the left and right, but manufacturing variations in the pressing force on the left and right must be allowed. Although not shown in FIG. 1, the springs 170 are housed in a case made of polybutylene terephthalate (PBT).

The connections between the electrode plate 140 of the heater section 150, the heat dissipation fins 130, and the plate 120, and between the heater section 150 and the frame 160, are maintained solely by the pressing force of this spring 170. In other words, the electrode plate 140, the heat dissipation fins 130, the plate 120, and the frame 160 are mechanically assembled, and are not secured by brazing, welding, or the like. However, in this disclosure, non-securing is not a requirement, and it is possible to glue the heat dissipation fins 130, the plate 120, etc.

Here, in order to apply sufficient pressing force to the heating elements 110 stacked in the first direction, it is possible to form two bending points 164 on the bottom 161 of the frame 160 and to separate the end 165 of the frame 160 in the second direction from the heater section 150, as described in Patent Document 1. This seems desirable in terms of increasing the pressing force of the spring 170. However, if the frame 160 is shaped to have two bending points 164 and pressed by the spring 170, the frame 160 will deform with the bending point 164 as a fulcrum, as shown in Figure 4. As a result, the center side of the frame 160 in the second direction will be raised, and the pressing force at the center will be insufficient.

In Patent Document 1, two bending points 164 are formed, but as shown in FIG. 5, it is also possible to have three bending points 164. However, if three or more bending points 164 are set, when the spring is assembled, the two lowest bending points 164 will come into contact with the frame 160, and the remaining bending points 164 will have a reduced pressing force due to height variations, or will not be able to transmit the pressing force. For this reason, it is not possible to set three or more bending points 164, and this is not compatible with heater units 150 that have multiple heating elements 110 arranged therein. In an example in which there is only one bending point 164, the pressing force will be concentrated only at the bending point 164, which is also undesirable.

In the present disclosure, as shown in Fig. 6, the shape of the bottom 161 of the frame 160 is an arc shape that bulges continuously from an end 165 in the second direction toward the center without multiple bend points 164 being present. Here, the arc shape does not strictly define a circle, but also includes an elliptical shape and a parabolic shape. The important point is that there are no multiple bend points 164, and the shape bulges continuously from the end 165 toward the heater unit 150 side. Therefore, the arc shape includes a bulging shape with a continuously changing curvature, a smooth bulging shape, a shape bulging in the first direction, a shape bulging toward the center in the second direction, and the like.

Fig. 7 shows a modification of the frame 160 having two bending points 164 shown in Fig. 4 and the continuously expanding frame 160 of the present disclosure shown in Fig. 6. Fig. 7(a) shows the shape of the bottom 161 of the frame 160 having two bending points 164, and Fig. 7(b) shows the shape of the bottom 161 of the frame 160 of the present disclosure not having multiple bending points 164. The solid line k shows the shape of the bottom 161 in a state where it is not subjected to the pressing force of the spring 170, and the dashed line l shows a modification in a state where the heater unit 150, which is made of four layers of plates 120 that hold the heating elements 110, is pressed with an appropriate load.

The region o where sufficient pressing force cannot be applied to the heater section 150 side due to deformation of the bottom section 161 differs depending on the presence or absence of the bending points 164. When there are no multiple bending points 164 as in the present disclosure ( FIG. 7B ), the region o where the pressing force is insufficient can be narrowed compared to a shape having multiple bending points 164 ( FIG. 7A ).

If the number of plates 120 is increased, the pressing force of the spring 170 must be increased. In that case, the deformation of the bottom 161 becomes larger, as shown by the dashed line m in FIG. 6. However, even in the example of the dashed line m, if there are no multiple bending points 164 as in the present disclosure (FIG. 7(b)), the region p where the pressing force is insufficient is narrower than the shape having multiple bending points 164 (FIG. 7( a )). Also, even if there is variation in the first direction length of the heater section 150 or there is a difference in the pressing force of the pair of left and right springs 170, the region p where the pressing force is insufficient is narrower in the shape not having multiple bending points 164 as in the present disclosure (FIG. 7(b)) than the shape having multiple bending points 164 (FIG. 7( a )). In this way, the shape not having multiple bending points 164 as in the present disclosure (FIG. 7(b)) makes it easier to provide the necessary pressing force to the heater section 150.

In this disclosure, the relationship between the length L of the frame 160 in the second direction and the height h in the first direction (shown in FIG. 8) at the top where the frame 160 is not subjected to the pressing force of the spring 170 is examined. Specifically, when the pressing force of the spring 170 is applied to the frame 160 and the heating element 110 is pressed by the heat dissipation fins 130 and the electrode plate 140, it is examined how much of the area of the heating element 110 is actually subjected to the pressing force from the heat dissipation fins 130 and the electrode plate 140. The height h in the first direction is the distance between the center of the frame 160 and the end 165.

In Figure 9, the horizontal axis shows the height h in the first direction, and the vertical axis shows the proportion of area A of the portion of heating element 110 that is receiving a pressing force. The portion that is receiving this pressing force refers to the portion that is receiving a pressing force of about 70 kilopascals or more, which is a pressing force at which factors such as contact resistance can be ignored. The solid line shows the proportion of area A of second element 115 and third element 116, which are located toward the center of heating element 110, and the dashed line shows the proportion of area A of first element 114 and fourth element 117, which are located at the ends in the second direction. The triangular solid line a and dashed line w show an example in which the length L of the frame 160 (heater unit 150) in the second direction is 188 mm, the circular solid line b and dashed line x show an example in which the length L of the frame 160 in the second direction is 229 mm, the square solid line c and dashed line y show an example in which the length L of the frame 160 in the second direction is 269 mm, and the diamond solid line d and dashed line x show an example in which the length L of the frame 160 in the second direction is 296 mm. The comparative example, the solid line e, shows the area ratio of the second element 115 and the third element 116 arranged at the center of the example in which the length L is 229 mm in the frame 160 having two bending points shown in FIG. 4, and the point v shows the area ratio of the first element 114 and the fourth element 117 arranged at the end side in the second direction.

As shown in the comparative example of FIG. 9, in the shape with two bending points of FIG. 4, the second element 115 and the third element 116 arranged in the center receive a pressing force only over a small area of about 3 to 5% (solid line e). Even in the first element 114 and the fourth element 117 arranged on the end side in the second direction, the proportion of the area receiving the pressing force is less than 8% (point v). In contrast, in the case of a continuously bulging arc shape without bending points as disclosed herein, the pressing force is applied to about 50% of the heating element 110 on average.

Also, from Figure 9, it can be seen that for the second element 115 and the third element 116, which are located towards the centre, there is a tendency for the proportion of the area receiving the pressing force to increase as the height h in the first direction is increased. However, for the first element 114 and the fourth element 117, which are located towards the ends in the second direction, there is a converse tendency for the proportion of the area receiving the pressing force to decrease as the height h in the first direction is increased. From this, it can be seen that there is a height h in the first direction that is most balanced when looking at the heater section 150 as a whole.

In the example where the length L of the frame 160 in the second direction is 188 mm, the intersection f of the solid line a and the dashed line w is set as the height at which balance can be achieved. Similarly, in the example where the length L of the frame 160 in the second direction is 229 mm, the intersection g of the solid line b and the dashed line x is set as the height at which balance can be achieved; in the example where the length L of the frame 160 in the second direction is 269 mm, the intersection i of the solid line c and the dashed line y is set as the height at which balance can be achieved; and in the example where the length L of the frame 160 in the second direction is 296 mm, the intersection j of the solid line d and the dashed line z is set as the height at which balance can be achieved.

In Figure 10, the horizontal axis represents the length L of frame 160 in the second direction, and the vertical axis represents the height h in the first direction, and intersection points f, g, i, and j, which are the heights at which balance can be achieved, are plotted. From Figure 10, it can be seen that there is a clear correlation between the length L of frame 160 in the second direction and the height h in the first direction with respect to the heights at which balance can be achieved. If the plotted points in Figure 10 are approximated by a straight line, the correlation becomes the following linear equation.

h=0.1+2.4/1000×(L-180)+A
In the above formula, the length L of the frame 160 in the second direction and the height h in the first direction on the vertical axis are in millimeters. Considering manufacturing tolerances, a tolerance A of about plus or minus 0.2 mm is allowed. However, when L is 230 mm or less, the tolerance A is plus or minus 0.2 mm, but when the height h The lower limit is ensured to be 0.02 millimeters.

In this example, since the second direction length of the heating element 110 is constant regardless of the second direction length L of the frame 160, it is considered that this linear equation holds. That is, when the second direction length L of the frame 160 is short, the distance between adjacent heating elements 110 is short, and therefore, even if the height h in the first direction is short, sufficient pressing force can be applied to the heating element 110. On the other hand, when the second direction length L of the frame 160 is long, the distance between adjacent heating elements 110 is correspondingly long, and the pressing force is easily lost between the adjacent heating elements 110. Therefore, in order to obtain a sufficient pressing force on the heating element 110, it is necessary to increase the height h in the first direction.
In this disclosure, based on the above linear equation, when the length of the frame 160 in the second direction is 180 mm, the amount of expansion in the first direction is set to 0.1 mm, when the length of the frame 160 in the second direction is 230 mm, the amount of expansion in the first direction is set to 0.2 mm, and when the length of the frame 160 in the second direction is 290 mm, the amount of expansion in the first direction is set to 0.35 mm.

As described above, the use of a continuously bulging shape without multiple bending points 164 as in the present disclosure is desirable in terms of increasing the proportion of the area A to which the pressing force is applied to the heat generating element 110. However, even if the shape is a continuously bulging arc, the spring 170 presses both ends 165 of the frame 160 in the second direction, and as a result, there is a concern that the pressing force may be insufficient on the center side in the second direction, as shown in FIG. 7. Therefore, in the present disclosure, the rigidity of the frame 160 on the center side in the second direction is increased. There are various means for increasing the rigidity.

In the example of Figures 11 and 12, a bulge 166 that bulges outward is formed on the center side of the frame 160. By forming the bulge 166 on the wall 162 of the frame 160, the rigidity of the wall 162 can be increased on the center side.

In the example of FIG. 13, the height of the wall portion 162 is changed. The height of the wall portion 162 on the center side is made higher than the height on the end portion 165 side to form a high wall portion 167. This high wall portion 167 increases the rigidity of the center side of the frame 160.

In the example of FIG. 14, a hole 168 is formed in the wall 162 on the end 165 side of the frame 160. The hole 168 reduces the rigidity of the end 165 side of the frame 160 and relatively increases the rigidity of the center side of the frame 160.

In the example of FIG. 15, a rib 169 is formed on the bottom 161 on the center side of the frame 160. The rib 169 is formed to bulge out from the bottom 161 in the opposite direction to the heater section 150. By providing the rib 169, the rigidity of the center side of the frame 160 can be increased.

In the present disclosure, the shape of the frame 160 is such that it bulges continuously without bending points 164, and is shaped to increase the rigidity of the center side, which combines to enable the pressing force from the frame 160 to the heater section 150 to be maintained at or above a predetermined pressure over the entire length in the second direction. In particular, the electric heater 100 of the present disclosure is structured to maintain the bond between the heating element 110 and the heat dissipation fins 130 and the electrode plate 140 only by the pressing force of the spring 170, so that the heater section 150 can maintain a pressing force of at least a predetermined pressure over the entire length in the second direction in order to demonstrate the performance of the heating element 110.

Note that the above example is a desirable response of this disclosure, but this disclosure can be modified in various ways. The above materials and sizes are examples and can be modified according to the required performance, etc.

The number and arrangement of the heating elements 110 can also be changed in various ways. In the example of FIG. 1 and FIG. 2, four heating elements 110, namely, the first element 114, the second element 115, the third element 116, and the fourth element 117, are arranged on the first plate 123 and the fourth plate 126. However, as shown in FIG. 16, two heating elements 110 may be arranged on each plate 120. In the example of FIG. 16, the first element 114 and the fourth element 117 are arranged on the first plate 123. Similarly, the first element 114 and the third element 116 are arranged on the second plate 124, the second element 115 and the fourth element 117 are arranged on the third plate 125, and the first element 114 and the fourth element 117 are arranged on the fourth plate 126. The fact that no heating elements 110 are arranged on the fifth plate 127 is the same as the example of FIG. 2.

In the example of FIG. 16, the position of the heating element 110 within the heater section 150 is balanced in both the first and second directions. Also in the example of FIG. 16, the amount of heat generated by the heater section 150 is controlled by controlling the current flow to the positive electrode 141. The most power-saving operation is when current is flowed only to the second positive electrode plate 146. Even during this minimum power operation, the first element 114 and the third element 116 are arranged on the second plate 124, and the second element 115 and the fourth element 117 are arranged on the third plate 125, so that the position of the heating element 110 is balanced in both the first and second directions.

In the above example, the left and right springs 170 have the same shape, but it is also possible for the spring 170 on one side to be integral with the frame 160. In the example of FIG. 17, the left spring 170 is an integral spring 175 formed integrally with the frame 160. Only the right spring 170 is attached to the frame 160. Even in this example, it is possible for the frame 160 to have a shape that bulges continuously without the bending point 164. It is also possible for the frame 160 to have a shape that increases the rigidity of the center side.

Furthermore, in the above example, the bottom 161 of the frame 160 is a single wall, but it may be a double wall. In the example of Fig. 18, a second bottom 1611 is interposed between the bottom 161 and the heater unit 150. The shape of this second bottom 1611 is a shape that bulges continuously without having multiple bending points 164. Even if the second bottom 1611 is provided, it is possible to shape the frame 160 to have a shape that increases the rigidity of the center side.

REFERENCE SIGNS LIST 100 Electric heater 110 Heating element 120 Plate 130 Heat dissipation fin 140 Electrode plate 150 Heater section 160 Frame 170 Spring

Claims (8)

A flat heating element that generates heat when electricity is applied;
A plate that holds a plurality of the heating elements in a planar direction;
a heat dissipation fin disposed in the air passage and configured to transfer heat from the heat generating element to the air passage;
an electrode plate for supplying power to the heating element;
The plate, the heat dissipation fins, and the electrode plate are each stacked in a plurality of stages to form a heater portion;
a pair of frames each having a U-shape in cross section are disposed on both sides of the heater section in a first direction, which is a stacking direction of the heater section, the heater section being a bottom portion and both sides of the bottom portion being wall portions;
a spring for biasing the frame toward the heater portion is disposed on both sides in a second direction perpendicular to the stacking direction of the heater portion;
the shape of the bottom of the frame when not biased by the spring is an arc shape that bulges continuously from an end in the second direction toward the center toward the heater section in the first direction without intervening multiple bending points , thereby narrowing an insufficient pressing force region occurring toward the center in the second direction compared to a shape having multiple bending points;
The frame has a higher rigidity in the pressing force insufficient region generated on the center side in the second direction than on the end side in the second direction.
1. An electric heater comprising: The electric heater according to claim 1 , wherein the frame has a bulging portion that bulges outward on a center side of the wall portion in the second direction. The electric heater according to claim 1 , wherein the frame is formed such that a height of the wall portion on a center side in the second direction is greater than a height of an end side in the second direction. The electric heater according to claim 1 , wherein the frame has a hole formed in an end side of the wall portion in the second direction. The electric heater according to claim 1 , wherein the frame has a rib formed on a center side of the bottom in the second direction. The shape of the bottom of the frame when not biased by the spring is expressed as follows: h = 0.1 + 2.4/1000 × (L - 180) + A, where L is the length of the frame in the second direction and h is the height of the frame between the end and the center in the first direction.
The electric heater according to any one of claims 1 to 5, characterized in that the relationship is expressed by the following formula, the units of length L, height h, and A are millimeters, A indicates a manufacturing tolerance of plus or minus 0.2 millimeters, and when L is 230 or less, A is plus 0.2 millimeters, but the lower limit of height h is 0.02 millimeters. 7. The electric heater according to claim 1, wherein one of the springs is formed integrally with the frame. 8. The electric heater according to claim 1, wherein the bottom of the frame is formed in a double layer, and the shape of the bottom on the heater section side is an arc shape that bulges continuously toward the heater section side in the first direction from the end in the second direction toward the center when not biased by the spring, without any intervening bending points.

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