JPS5963686A - Positive temperature coefficient thermistor heating element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positive temperature coefficient thermistor heating element for generating hot air using a positive temperature coefficient thermistor.

Conventional Structures and Their Problems Conventionally known heating elements include those using metal resistors such as nichrome wires and positive temperature coefficient thermistors made of barium titanate semiconductors. The resistance of a metal resistor is almost constant regardless of temperature, so when used as a heat source for a hot air heater, for example, when the fan stops or the hot air path is blocked and the air volume decreases, the metal The temperature of the resistor rose rapidly, causing it to become red hot, potentially causing wire breakage or a fire.

A positive temperature coefficient thermistor has the property that its resistance value increases rapidly at a certain temperature, so for example, when it is energized and used as a heating element in a hot air heater, its heat generation value decreases rapidly even when the air volume decreases. , will not overheat above a certain temperature. Furthermore, even if the ambient temperature or applied voltage changes, the amount of heat generated is self-controlled, and a nearly constant temperature can be obtained. When a positive temperature coefficient thermistor is used in this way, a safe and convenient heating element can be obtained.

When constructing a heating element using this positive temperature coefficient thermistor, in order to increase the input power, it is common to attach a metal heat sink to the positive temperature coefficient thermistor, and to provide electrodes 2 and 3 made of aluminum spraying on the main surface. Generally, metal heat radiators 4 and 5 made of extruded aluminum or the like were fixed to the surface with a silicone adhesive (not shown) while applying force in the direction of the arrow. In order to increase the input power in such a configuration, the surface area of the metal heat sink must be increased. However, with this configuration, in order to increase the surface area of the metal heat sink, it is necessary to reduce its thickness and increase the number of fins, or to increase its height h. However, if a metal heat radiator is made by extrusion molding, the thickness is limited to about 0.7 mm or more and the height h is limited to 10 mm or less, making it difficult to create a metal heat radiator with a large surface area. In addition, since it is thick, when used as a hot air heating element, the ventilation resistance becomes large.

In order to eliminate these drawbacks, as shown in Fig. 2, a metal heat sink 9 is made by sandwiching a bent plate 6, which is a thin aluminum plate bent into a corrugated shape, between two aluminum plates 7 and 8 and fixed with brazing. There was also a configuration in which the electrode 11t12 of the characteristic thermistor 1o was fixed with a silicone adhesive (not shown) while applying a force 13.14 to the surface. According to this configuration, the thickness of the metal heat sink depends on the thickness of the plate before bending, so 0.1
It becomes possible to easily produce a metal heat sink of 1 nWl or less, and a metal heat sink with a large surface area can be provided at low cost with less materials used.

Furthermore, ventilation resistance can also be reduced. However, in this configuration, since the heat sink is made thin, there is a limit to the fixing force. This is because if you try to increase the ridge fixing force, the heat sink will buckle and break if it is thin, so if you weaken the fixing force, the thermal coupling between the heat sink and the positive temperature coefficient thermistor will become smaller, and the surface area will increase. Despite using a large heat sink, the increase in input power was not that large.

Purpose of the Invention The purpose of the present invention is to solve such walking problems and to provide at low cost a positive temperature coefficient thermistor heating element that has large input power, is compact, has low ventilation resistance, uses less material, and is lightweight. That is.

Structure of the Invention The positive temperature coefficient thermistor heating element of the present invention includes a positive temperature coefficient thermistor having electrodes formed on both main surfaces, a heat sink formed by bending a thin metal plate into a corrugated shape, and a heat sink formed by bending a thin metal plate into a corrugated shape. and means for fixing to the electrode surface of the characteristic thermistor, the heat radiator also serves as a power supply path to the electrode, and the heat radiator is provided with cut-and-raised ribs in a direction perpendicular to the electrode surface. .

When a positive temperature coefficient thermistor heating element is constructed in this way, the compressive strength increases due to the cut and raised shape, and the thickness of the heat dissipation element is reduced without reducing the crimp force. DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the attached drawings and surfaces. In FIGS. A heat sink 18.19 is fixed to the positive temperature coefficient thermistor 15 having a diameter of 16.17 with silicone adhesive (not shown).The heat sink 18.19 is made by bending a thin aluminum plate into a corrugated shape. The radiation fins 20.21 are sandwiched between two aluminum plates 22.23 and 2.4.25 and fixed by brazing.The radiation fins 20.21 are provided with cut-out ribs 26 on each side. Three ribs 26 are formed at a time.FIG. 4 is a cross section taken along the line A-B in FIG.

To explain the operation in the above configuration, when a voltage is applied to the positive temperature coefficient thermistor 15 through the heat sinks 18 and 19,
The positive temperature coefficient thermistor 15 generates heat, enters a thermal equilibrium state, and its temperature becomes constant around the Curie temperature. The heat generated by the PTC thermistor 15 is conducted to the heat sinks 18 and 19 and radiated into the air. At this time, the positive characteristic thermistor 16
Since the input power of is equal to the energy dissipated into the air, in order to increase it, a heat sink of 18°1 is required.
9 and to increase the surface area of the heat sinks 18 and 19. Then, positive characteristic thermistor 1
5 is almost constant, in order to raise the temperature of the heat sinks 18 and 19, the thermal coupling between the heat sinks 18 and 19 and the positive temperature coefficient thermistor 15 must be increased, that is, if they are almost fixed together with a large force. good. According to the invention, the heat sink 18.1
Since 9 is made by bending a thin plate, heat sink 1B,
, 19 can be easily made thin, and the surface area can be made very large. In addition, the heat sink 18°1
Even though 9 has become thinner, the cut and raised ribs 26 are added to prevent a decrease in strength, so the adhesion force can be made sufficiently large, and the heat sink 1'8.19 and positive temperature coefficient thermistor 15 Large input power is now possible without deterioration of thermal coupling with Furthermore, because of the cut and raised ribs 26, the air flow becomes turbulent, and the amount of heat exchange between the heat sinks 18 and 19 and the air increases, resulting in an effect of further increasing the input power.

The above effects will be further explained using a specific example. cucumber one temperature 2
2.00G, size 157ff7AX 24mm x 3
A positive temperature coefficient thermistor is held between two heat sinks each having 10 fins formed by bending a thin aluminum plate with a thickness of 0.4 mm. When ventilation was applied and the power was measured, it was found that if a similar heating element was constructed from a thin aluminum plate, it would be impossible to fix it with a force greater than 6"yc4 because the heat sink would buckle, and the input power at that time would be 86W. Next, the heating element of the present invention was constructed by similarly bending a thin aluminum plate with a thickness of 0.2 mm and using a heat radiating element with six cut-and-raised ribs formed on each side. , it can be fixed with 10Rν oak as before, and the input power is now 102W.

FIG. 6 shows another example of cut and raised ribs according to the present invention, in which the cut and raised ribs are oriented both on the front and back sides. In this way, the generation of turbulence becomes even greater, and the increase in input power has a greater effect.

In addition, in the above embodiment, a method of bonding with silicone adhesive was used as a means of fixing the heat dissipation body, but this may also be a method of fixing with a spring or screw, etc. without using adhesive. The number of positive temperature coefficient thermistors is not limited to one, and a plurality of them may be used. Furthermore, it is also possible that the heat dissipation bodies may be stacked in multiple stages, so the present invention is not limited to this. In short, it is sufficient that the heat dissipation body is formed by bending a thin plate, has cut and raised ribs on it, and that the heat dissipation body is fixed to the PTC thermistor.

Effects of the Invention As is clear from the above embodiments, the positive temperature coefficient thermistor heating element of the present invention is characterized in that the heat dissipation element is particularly thin and the ribs are provided perpendicularly to the surface to which the positive temperature coefficient thermistor is fixed. As a result, the heat sink can be easily made thinner without reducing the adhesion strength, and the amount of heat exchanged by the heat sink is also increased, making it lightweight, compact, and with little ventilation resistance.
It is possible to provide a positive temperature coefficient thermistor heating element with large input power.

[Brief Description of the Drawings] - Figures 1 and 2 are perspective views showing a positive temperature coefficient thermistor heating element; Figure 3 is a perspective view showing an embodiment of the positive temperature coefficient thermistor heating element according to the present invention; FIG. 4 is an enlarged sectional view of the main part taken along the line B in FIG. 3, and FIG. 6 is an enlarged sectional view of the main part showing another embodiment of the present invention. 16...Positive characteristic thermistor, 16/17...
...Electrode, 18, 19... Heat sink, 26...
...cut ribs. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 5

Claims (1)

[Claims] A positive temperature coefficient thermistor having an electrode formed on an amphibile surface, a heat sink formed by bending a thin metal plate into a corrugated shape, and means for fixing the heat sink to the electrode surface of the positive temperature coefficient thermistor, A positive temperature coefficient thermistor heating element whose body also serves as a power supply path to the electrode, and whose heat sink is provided with cut-and-raised ribs in a direction perpendicular to the electrode surface.