JPS6244478Y2 - - Google Patents

Description

[Detailed description of the invention] This invention uses two planar heating elements with a positive temperature coefficient of resistance to quickly raise the surface temperature of the heating device and to optimize the stable temperature. It is related to.

To explain a conventional heating device, for example, a foot warmer, as shown in FIG. mounted in close proximity to each other. The heater 1 is constructed by wrapping a metal heating wire such as a nichrome wire around an insulating material such as mica, and the heating temperature of the heater 1 can reach a considerably high temperature (about 150° C.). The heat from the heater 1 is transmitted through the air in the internal space and reaches the upper case 3 (the side on which the feet are placed), thereby performing the foot warming function. Since air transfer is used as the heat transfer method, the foot warmer has the disadvantage that the surface temperature of the foot warmer rises very slowly. One way to prevent this is to increase the power consumption of the heater 1, but as described above, the heater 1 becomes too hot and becomes dangerous. Therefore, a thermostat 2, etc., is provided in a position very close to the heater 1 to maintain safety performance. Note that the rise performance of the surface temperature is shown by B in FIG. With such conventional heating devices, 1. The speed at which the surface temperature rises is slow.

2 The heater becomes very hot and can be dangerous.

3 In addition to the heater, safety functional parts such as thermostats are required.

It had the following defects.

The present invention solves the above-mentioned conventional drawbacks, and an embodiment thereof will be described in detail below. As is clear from the structural external view of FIG. 3 and the cross-sectional view of FIG. 7
is supported in the interior space surrounded by the upper case 6 and lower case 8 by closing the mounting base 9. The two first and second planar heating elements 5 and 7 are electrically connected in series. The planar heating elements 5 and 7 used here are heating elements having a positive temperature coefficient of resistance as shown in FIG.

If electricity is now applied to these planar heating elements 5 and 7, the planar heating elements 5 and 7 start generating heat. Here, even if the planar heating elements 5 and 7 are designed to have the same resistance value, the heat dissipation conditions are different, so the temperature increase speed and the stable saturation temperature are different between the two. In other words, as shown in FIG.
The planar heating element 5 has a characteristic H ₁ and has better heat dissipation than the characteristic H ₂ of the second planar heating element 7 supported in the hollow, and is stabilized at a low temperature. Note that the temperature curve in FIG. 6A shows the time course of the surface temperature of the heating device.

As you will see, it is a sheet heating element and
If a heating element with PTC (positive temperature coefficient of resistance) characteristics is attached to the case, the surface temperature will rise much faster than before (characteristic A in Figure 2). This can be explained by the difference in heat transfer methods between direct heat transfer through a metal body and indirect heat transfer through an air layer. In the present invention, two sheet heating elements 5 and 7 are connected in series, and when calculating the power consumption value of each sheet heating element 5 and 7, W ₁ =V〓/R ₁ =V ² ×R ₁ /(R ₁ +R ₂ ) ² ...
…1 W ₂ =V〓/R ₂ =V ² ×R ₂ /(R ₁ +R ₂ ) ² …
...2 W ₁ ; Power consumed by the first sheet heating element 5 W ₂ ; Power consumed by the second sheet heating element 7 R ₁ ; Resistance value of the first sheet heating element 5 R ₂ ; Resistance value of the planar heating element 7 in No. 2 V; becomes the power supply voltage. On the other hand, since the resistance values of R ₁ and R ₂ change moment by moment as the temperature of the planar heating element increases, the power consumption values themselves and the relative ratios of W ₁ and W ₂ also differ. In other words, the power consumption of the first sheet heating element 5, which is attached to the upper case and has a large effect on the surface temperature of the upper case, is due to the fact that it itself has PTC characteristics and the power consumption of other heating elements. 2 sheet heating element 7 (also
It is automatically controlled by the combination of two factors: 1) having PTC characteristics) and 2) being connected in series.

Now suppose that at the initial stage R ₁ = R ₂ = ro When t ₁ has elapsed after the power is turned on, R ₁ = a ₁ ro, R ₂ = a ₂ ro, R ₂ / R ₁ = a ₂ / a ₁
= α At t=0 (initial) W ₁ = W ₂ = V ² /4ro ...3 When t=t ₁ , W ₁ = V ² /(1+α) ² a ₁ ro ...4 W ₂ = V ² ×α/(1+α) ² a ₁ ro...5 W ₂ /W ₁ =α...6 a ₁ , a ₂ , α>1.

In the temperature rise curve in Figure 6, at t = 0, the power consumption is equal as shown in equation 3, but as t ₁ and t ₂ pass, a ₁ and a ₂ also increase, and α, which means the ratio, also increases. Therefore, more power is consumed towards _W2 .
This means that after the switch is turned on, the power necessary for initial startup performance is consumed (however, if this power value is maintained, the surface temperature will become too high).
When it warms up to a certain extent, the power consumption value decreases,
Rather, the input to the heat heater (second planar heating element 7) is increased, and the surface temperature of the heating device is maintained at an optimum value.

FIG. 7 shows the power consumption value over time.

W, the total value of the first and second planar heating elements 5 and 7,
W ₁ ; value of the first planar heating element 5; W ₂ ; value of the second planar heating element 7.

From the above, the present invention has the effect of increasing the temperature very quickly and automatically controlling the surface temperature to the optimum value by simply using two planar heating elements with a positive temperature coefficient of resistance. .

[Brief explanation of drawings]

Figure 1 is a perspective view of a conventional foot warmer, Figure 2 is a diagram of surface temperature changes over time of a conventional foot warmer and a foot warmer according to an embodiment of the present invention, and Figure 3 is an example of an embodiment of the present invention. Figure 4 is a cross-sectional view of the foot warmer, Figure 5 is a PTC characteristic diagram of the sheet heating element, and Figure 6 is the sheet heating element and surface temperature of one embodiment of the present invention over time. Change chart, 7th
The figure is a graph of power consumption over time of a foot warmer according to an embodiment of the present invention. 5...First planar heating element, 6...Upper case, 7
...Second planar heating element, 8...Lower case, 9...
Mounting base.

Claims (1)

[Scope of utility model registration request] At least two sheet heating elements having a positive temperature coefficient of resistance are used, the first sheet heating element is attached to the inner wall surface of a metal plate that constitutes the outer shell of the appliance, and the second sheet heating element is attached to the inside wall of the metal plate that forms the outer shell of the appliance. 1. A heating appliance characterized in that it is mounted in a hollow position without contacting the metal plate forming the outer shell of the heating appliance, and that the first and second planar heating elements are electrically connected in series.