JPS596633Y2 - Heating element device using positive temperature coefficient thermistor - Google Patents

Description

[Detailed Description of the Invention] Generally, in a heating element using a positive temperature coefficient thermistor, it is desirable to effectively dissipate the generated heat to the outside.

In other words, this problem can be improved by suppressing the thermal resistance between the PTC thermistor and the outside as much as possible.

This thermal resistance θ is the reciprocal of the heat dissipation coefficient and is expressed by the following equation.

? Here, α is a constant, k is thermal conductivity, A is effective heat radiation area, and t
is the thickness or distance from the equivalent center of generated heat to the heat radiation surface.

Equation (2) is applied when θ is calculated from the thermal conductivity and size of a substance, and Equation (2) is applied when θ is calculated from the stable state when electric power is actually applied.

Now, as shown in Fig. 1, a heat dissipation plate 5 is attached to one surface of a positive temperature coefficient thermistor 1, which has electrodes 2 and 3 on both planes, with a heat transfer plate 4 having good heat conduction interposed therebetween, to dissipate heat. In a device that uses PTC thermistor 1, the thermal resistance θ between the equivalent center point 0 of the heat generated by PTC thermistor 1 and the point The thermal conductivity of the heat plate 4, A, is the area in contact with the heat sink 5, t
can be calculated as the distance from point 0 to point X, that is, t+t2.

Furthermore, if the zero point temperature when a voltage is actually applied to the device shown in Figure 1 and stabilized is T1, the X point temperature is T2, and the power consumption at this time is P, then from the formula ■, P and △T = T1 - As T2, the thermal resistance θ between 0 and X can also be determined.

(In this case, it is assumed that the heat sink 5 is sufficiently large and there is no heat generation from the ground of the PTC thermistor 1.) And the thermal resistance θ
The sum of can be calculated in the same way as electrical resistance, and when n positive temperature coefficient thermistors with a thermal resistance of θ1 and heat exchanger plates with a thermal resistance of θ2 are attached to the same heat sink, it can be said that they are connected in parallel. Therefore, the total sum of thermal resistance θ becomes small.Also, when n pieces of similar 01 and 02 are stacked, they are connected in series, and the sum of thermal resistance θ becomes large (θ=n(θ1+
02)).

Therefore, in order to reduce the thermal resistance θ, various thermal resistance elements are
It is clear that it is sufficient to substantially connect them in parallel.

In other words, this can be achieved by converging the heat generated on both planes of the PTC thermistor onto the same heat sink.

In addition, this heat convergence is determined by the heat radiation effective area A in the above equation.
It is the same as increasing the thermal resistance θ
It turns out that you can make it smaller.

From this point of view, conventional thermistors with multiple positive temperature coefficients were attached to a heat sink, but because a large number of them were used, they had drawbacks such as high price and poor workability. However, it could not be said to be desirable in terms of practicality.

Furthermore, conventionally, when obtaining a positive temperature coefficient thermistor for high power use, it has been common practice to increase the size of the element, but this has had the disadvantage of increasing manufacturing costs.

In other words, the reality is that conventionally no consideration has been given to reducing the thermal resistance θ.

Therefore, due to the large thermal resistance θ, it was not preferable in terms of rapid response to ambient temperature, rapid heating performance, and other aspects.

The present invention was made in consideration of these points, and
It is an object of the present invention to provide a heating element device having a structure in which the thermal resistance between a positive temperature coefficient thermistor and the outside is reduced.

Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 2 to 4, reference numeral 11 denotes an annular insulating spacer made of porcelain or the like with good heat conduction, which has a through hole 12 in its center, and has a plurality of small holes 13 in its circumferential plane. Similarly, grooves 14,14' are provided in one part of the circumferential plane and in part of the other side thereof, which extend to the outer surface.

Note that this insulating spacer 11 is designed so that its radial thickness, that is, the dimension indicated by symbol A in FIG. It was shaped by

Reference numeral 15 denotes a disk-shaped positive temperature coefficient thermistor which is loaded into the through hole 12 of the insulating spacer 11, and electrodes 16 and 16' are provided on both surfaces thereof.

17, 1e (is a porcelain disk having approximately the same size as the outer diameter of the insulating spacer 11 and also having good thermal conductivity, and a film-like external connection electrode 17a, IBa is screen-printed and vapor-deposited in the center of one plane. The external connection electrodes 17b and 18b connected to the external connection electrodes 17a and 18a, respectively, are connected to the ceramic disc 17.1.
It is provided almost to the end of 8.

Numerals 19 and 20 are small holes provided at a plurality of locations near the circumferential ends of these ceramic discs 17 and 18, and these small holes 19 and 20 are aligned with the small holes 13 of the insulating spacer 11, respectively. It is something that

The porcelain disks 17 and 18 are connected to the insulating spacer 11.
Both electrodes 16 and 16 of the positive temperature coefficient thermistor 15 are brought into contact with each other so as to sandwich it, and the respective external connection electrodes 17 a and 18 a are loaded into the through hole 12 of the insulating spacer 11 . ' and are abutted respectively.

In this case, these porcelain disks 17,18 have their small holes 19
．． 20 must be aligned with the small hole 13 of the insulating spacer 11, and the electrodes 17b and 18b for external extraction must be positioned on the grooves 14 and 14' of the insulating spacer 11.

Bolts 21 are inserted through the small holes 19, 20 and 13 of the porcelain disk 17, 18 and the insulating spacer 11, and together with a nut 22, they are fixed together.

Note that this fixing means is not limited to bolts and nuts, but may also be any other fixing pins such as grommets and rivets.Furthermore, it is not beyond a mere design change to use a thermally conductive adhesive for fixing. do not have.

23.23' is fitted into the cut groove 14.14' provided in the insulating spacer 11, and is inserted into the porcelain disc 17.1.
These are lead wires that are electrically connected to the external extraction electrodes 17b and 18b of No.8, respectively.

Although the heating element device using the positive temperature coefficient thermistor of the present invention is essentially constructed as described above, the following points are not limited to those shown in the drawings.

(1) External connection electrodes 17 provided on the porcelain discs 17 and 18
a, 18a and the shapes of the external extraction electrodes 17b, 18b.

In short, these include both electrodes 16 of the positive temperature coefficient thermistor 15.
16' and is connected to the lead wires 23 and 23'.

(2) Increase the thickness of one side of the porcelain discs 17 and 18.

This is because the thicker the wall, the higher its thermal conductivity, allowing the heat of the positive temperature coefficient thermistor 15 to pass through its interior and be supplied to the other ceramic disk.

(3) The shapes of the ceramic disks 17 and 18, the insulating spacer 11, and the positive temperature coefficient thermistor 15 are circular.

It may be rectangular.

(4) The electrodes 16 and 16' of the positive temperature coefficient thermistor 15 are provided entirely on both planes.

Any electrode shape, such as a low heat resistance type, may be used as long as the electrode shape can extract heat from both sides.

Next, the case where the device of the present invention is actually applied as a heating element will be described in detail.

In this case, a heat sink (not shown) is brought into contact with the ceramic disk 18 side.

Connect a power source to the lead wires 23 and 23', and connect the external extraction electrodes 17b and 18b and the external connection electrodes 17a and 1.
A voltage is applied to the positive temperature coefficient thermistor 15 through 8a.

The positive temperature coefficient thermistor 15 then begins to generate heat, and this heat is transferred to the porcelain discs 17, 18.

The heat transferred to the porcelain disk 18 is directly transferred to the heat sink and radiated, and the heat transferred to the porcelain disk 17 is transferred to the annular plate whose radial thickness is greater than the thickness of the porcelain disk 17. Alternatively, the heat is transmitted to the porcelain disk 18 through the rectangular annular insulating spacer 11, and is also radiated from the heat sink.

In this case, since both the ceramic disk and the insulating spacer are made of materials with good thermal conductivity, heat transfer to the heat sink is very good.

That is, the heating element device of the present invention extracts the heat generated by the PTC thermistor 15 from both its planes, and uses the same heat sink (
This method satisfies the above-mentioned conditions for increasing the thermal resistance θ by increasing the effective heat dissipating area A and connecting various thermal resistors in parallel. Since the external connection electrode is a film-shaped electrode provided on the porcelain plate, its heat capacity is extremely small and the thermal coupling with the porcelain plate is good, so that the overall thermal resistance can be reduced.

Further, if a so-called low thermal resistance type thermistor 15 is used as the positive temperature coefficient thermistor 15, the overall thermal resistance can be further reduced.

Therefore, for example, when used as a heating element for a heat insulator,
Not only does it have good heat-fast properties, but it also responds sensitively to changes in ambient temperature and can provide good heat retention performance.

In other words, when the ambient temperature changes, the operating point of a positive temperature coefficient thermistor immediately changes at the steep part of its resistance-temperature characteristic.
Along with this, the power is quickly changed to keep the internal temperature constant.

In addition, by reducing the thermal resistance as described above, the heat dissipation coefficient can be substantially increased, and the amount of heat generated can be increased. At the same time, the dimensions of the positive temperature coefficient thermistor itself can be reduced, and the It can be made into something.

Furthermore, although no further description will be given in the present invention, it goes without saying that various well-known effects based on the reduction in thermal resistance are exhibited.

Note that these are all effects seen from the perspective of reducing thermal resistance, but the present invention also has the following structural effects.

In other words, since the entire product is made of insulating material, its uses are not only greatly expanded, but the user does not need any new insulation treatment, which reduces overall costs. By not applying this new insulation treatment, there is no change in thermal resistance, and the product can be used in good condition at all times.

Furthermore, if the entire device is made of porcelain material, it can be used at high temperatures, which further expands its uses.

Furthermore, since the entire structure is completely fixed, it is resistant to shocks such as vibration and has a long life, and has many construction benefits, such as having a small number of parts and being easy to manufacture.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the present invention, Fig. 2 is a side cross-sectional view showing one embodiment of the heating element device of the present invention, Fig. 3 is an example of the shape of an insulating spacer used in the present invention, Fig. 4 1 is also a diagram showing an example of the shape of a porcelain plate. 11 - insulating spacer, 13 - small hole, 15 - positive temperature coefficient thermistor, 16.16' - one electrode, 17.18 - porcelain disk, 1
7 a, 18 1-External connection electrode, 17b, 18b
1 electrode for external extraction, 19.20 1 small hole, 21 bolt, 22 nut, 23.24 lead wire.

Claims (1)

[Scope of utility model registration request] An annular or rectangular insulating spacer loaded with a positive temperature coefficient thermistor and having good thermal conductivity and having a thickness almost equal to the thickness of the positive coefficient thermistor, and a plurality of small holes provided at the periphery of the insulating spacer. and grooves for inserting lead wires provided radially on both sides of the insulating spacer, and a plurality of small holes that abut on both sides of the insulating spacer and match the small holes near the periphery. two porcelain plates; a film-like external connection electrode provided on the abutment surface of the positive temperature coefficient thermistor on both porcelain plates; an external extraction electrode provided on the external extraction electrode, a lead wire attached to the external extraction electrode and fitted into a lead wire insertion groove of the insulating spacer, the insulating spacer and two porcelain plates. and a fixing pin that is inserted into a small hole to fix them together, and the radial thickness of the insulating spacer is larger than the thickness of the two porcelain plates. A heating element device using