JPH0432182A - Infrared heater - Google Patents

Abstract

PURPOSE:To keep good electrical connection between a power supply terminal and a conductive film, maintain reasonable fastening force and prevent imperfect contacts and damages to the conductive film and a base substance by forming a heating element with the conductive film on the surface of the insulating base substance, connecting the conductive film to the power supply terminal attached to the base substance and inserting a soft conductive metal between the conductive film and the power supply terminal. CONSTITUTION:A cylindrical base substance 1 is formed of insulating ceramics such as boron nitride and manufactured by a gas phase growth technique. A heat element with a conductive film 12 formed on the surface of the base substance 11 is made of carbon group material such as graphite and formed on the surface of the base substance 11 by a gas phase growth technique. A power supply terminal 13 is fastened to the end of the cylindrical base substance 11 because the inner dia. is reduced by threadingly fastening a screw 14 between the ends opposite to each other. In this case, a soft conductive metal 15 is inserted between the inner face of the power supply terminal 13 and the outer face of the cylindrical base substance 11.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to an infrared heater in which a heating element made of a conductive film is provided on the surface of an insulating substrate.

(Prior Art) For example, infrared heaters are used to dry food and various industrial parts.

As infrared heaters used in such fields, heaters having structures shown in FIGS. 5 and 6 are conventionally known. This device includes a cylindrical base 1 made of an insulating ceramic such as alumina, a heating element 2 made of a carbon-based conductive film such as graphite formed on the surface of the base 1, and the above-mentioned It consists of a power supply terminal 3.3 made of a heat-resistant conductive metal, such as stainless steel, wound around the end of the cylindrical base 1.

The heating element 2 made of the conductive film is attached to the outer surface of the cylindrical base 1 by sputtering or coating, and is formed, for example, in a meandering wiring pattern extending in the axial direction. The power supply terminal 3.3 has a band shape and is wound around the end of the cylindrical base 1, and is fastened to the outer surface of the base 1 by tightening the screw 4 (see FIG. 2). It is adapted to be in close contact with the end portion of the conductive film 2.

Note that cords 6.6 for power supply connection are connected to the power supply terminals 3.3, respectively.

Therefore, when the power supply terminal 3.3 is connected to a power source, a current flows through the heating element 2, which generates heat and emits infrared rays.

(Problem to be Solved by the Invention) However, in the above conventional case, the band-shaped power supply terminal 3.3 is directly wrapped around the cylindrical base 1, and this power supply terminal 3 is formed on the surface of the base 1. Since it had a structure in which it was in direct contact with the conductive film 2, there was a problem that the contact between the power supply terminal 3.3 and the conductive film 2 was not good.

That is, the heating element made of the conductive film 2 is placed on the surface of the base 1,
Since it is simply attached by sputtering or coating, it rubs against the power supply terminal 3.3 when it is covered with the power supply terminal 3.3.

It peels off easily.

If the power supply terminal 3.3 is tightly tightened, there is a risk that the base body 1 made of insulating ceramics will be destroyed due to compressive stress.Therefore, if the tightening force is weakened, a gap will occur because the conductive film is thin. , poor contact between the power supply terminal 3.3 and the conductive film 2 occurs.

Furthermore, when the temperature rises due to the heating effect, the power supply terminal 3.
Due to the difference in thermal expansion between the power supply terminal 3.3 and the ceramic substrate 1, the contact area between the power supply terminal 3.3 and the conductive film 2 becomes loose, resulting in a decrease in contact pressure, resulting in significant fluctuations in contact resistance and abnormal discharge at these contact areas. There are concerns that this may cause the conductive film 2 to evaporate and scatter, destroy the substrate, and even change the heat generation characteristics of the conductive film.

The present invention was developed based on the above circumstances, and its purpose is to maintain a good electrical connection between the power supply terminal and the conductive film, maintain an appropriate tightening force, and prevent poor contact. The present invention aims to provide an infrared heater that can prevent damage to a conductive film and a base.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an infrared ray generator in which a heating element made of a conductive film is formed on the surface of an insulating base, and this conductive film is connected to a power supply terminal attached to the base. The heater is characterized in that a soft conductive metal is inserted between the conductive film and the power supply terminal.

(Function) According to the present invention, the soft conductive metal inserted between the power supply terminal and the conductive film is appropriately elastically deformed by the tightening of the power supply terminal, and the tightening absorbs force, thermal expansion difference, etc. and maintain good contact between the power supply terminal and the conductive film.

(Example) The first invention of the present invention will be described below based on the first example shown in FIGS. 1 and 2.

The infrared heater shown in the figure has the same basic configuration as the conventional one; 11 is an insulating cylindrical base; 12 is a heating element made of a conductive film formed on the surface of this base 11; 13.
13 is a power supply terminal attached to the end of the cylindrical base 11.

The cylindrical substrate 11 of this embodiment is made of an insulating ceramic such as boron nitride, and is manufactured by a vapor phase growth method.

The base body 11 formed by the vapor phase growth method of boron nitride has, for example, an inner diameter of 10+i+a, an outer diameter of 12 m5,
It has a perfect circular cylindrical shape with a length of 250 cm.

A heating element made of a conductive film 12 formed on the surface of this base 11 is made of a carbon-based material such as graphite, and is formed on the surface of this base 11 by a vapor phase growth method.

In the case of this embodiment, the heating element made of the conductive film 12 is formed on the outer surface of the cylindrical base 11 in the form of a meandering band long in the axial direction. In this case, the film thickness is 0.11 mm, the band width is 5 mm, and the distance between adjacent bands is 1 mm. C1+m+ is formed.

The ends of such a serpentine conductive film 12 are connected to power supply terminals 13.13 attached to the ends of the base body 11.

The power supply terminal 13 is formed by molding a stainless steel belt with a width of 5 cm and a thickness of 1 cm into a ring shape with an inner diameter of 12.3 ms, with both ends facing each other, so that the end of the cylindrical base 11 It is wrapped around the and,
This power supply terminal 13 has a screw 14 between its opposed ends.
By screwing them together and tightening them, the inner diameter is reduced, so that they can be fastened to the end of the cylindrical base 11.

In this case, a soft conductive metal 15 is inserted between the inner surface of the power supply terminal 13 and the outer surface of the cylindrical base 11.

The soft conductive metal 15 is made of, for example, copper foil, and a foil strip having a width of 6 cm and a thickness of 0.05 sv is placed on the end of the conductive film 12 and wrapped around the outer surface of the cylindrical base 11 about 4 to 5 times. It is.

Therefore, the power supply terminal 13 is wound around the outer periphery of the soft conductive metal 15 and tightens the soft conductive metal 15.

Therefore, the conductive film 12 and the power supply terminal 13 are connected via the soft conductive metal 15.

Note that 16 is a cord for connecting to a power source.

The operation of the infrared heater having such a configuration will be explained.

Power supply terminal 1 through cord 16.16 for power connection
When a power supply voltage is applied to 3.13, a current flows from the power supply terminal 13 and the soft conductive metal 15 to the heating element made of the conductive film 12, and this heating element generates heat. In this case, the heating element made of the conductive film 12 is formed on the outer surface of the cylindrical base 11 in the shape of a meandering band that is long in the axial direction, and has a predetermined length in the axial direction and is arranged at regular intervals in the circumferential direction. Therefore, infrared rays can be emitted uniformly over a predetermined length in the circumferential direction.

In the embodiment described above, since the soft conductive metal 15 is interposed between the power supply terminal 13 and the cylindrical base 11, it is possible to maintain a good contact state between the power supply terminal 13 and the conductive film 12.

That is, since the end of the heating element made of the conductive film 12 is covered with the soft conductive metal 15, the power supply terminal 13.13 does not directly rub against the conductive film 12 when covering the power supply terminal 13.13, and the power Peeling of the conductive film 12 when attaching the supply terminals 13.13 is prevented.

Furthermore, when the screw 14 is tightened, the diameter of the power supply terminal 13 is reduced and the soft conductive metal 15 is tightened. Therefore, the soft conductive metal 15 is deformed.

Therefore, application of excessive clamping force to the cylindrical base 11 is reduced, and destruction of the base 1 made of insulating ceramics due to compressive stress is prevented.

Therefore, even if the screw 14 is tightened somewhat strongly, the tightening force of the power supply terminal 13.13 can be maintained at an appropriate level, and the contact between the power supply terminal 13.13 and the soft conductive metal 15 is ensured. The soft conductive metal 15 can be deformed and brought into close contact with the conductive film 12, and poor contact can be prevented.

Then, when the temperature rises due to the heating effect, the power supply terminal 13
．． 13 and the Lamic base 11, the soft conductive metal 15 inserted between them absorbs the difference in thermal expansion and maintains the contact pressure between the power supply terminal 13.13 and the conductive film 12 at a predetermined level. can be kept at a value.

Therefore, it is possible to prevent the contact resistance between the power supply terminals 13, 13 and the conductive film 12 from fluctuating significantly, or to prevent abnormal discharge or abnormal heat generation from occurring at these contact parts. Evaporation and scattering of the conductive film 12, destruction of the base 11, and fluctuation of the heat generation characteristics of the conductive film 12 can be prevented.

Note that since the conductive film 12 of this example was formed on the surface of the cylindrical substrate 11 made of boron nitride by chemical reaction, that is, vapor phase growth, the binding force of the conductive film 12 to the substrate 11 is extremely strong.

Therefore, even if a mechanical shock or a thermal shock such as a sudden temperature change is applied, the conductive film 12 is prevented from peeling off.

Therefore, local heat generation due to peeling is prevented, temperature unevenness and deterioration of heat generation characteristics are reduced, and wire breakage is also prevented.

The rated input is 2KW with the dimensions and size described in the above example.
We manufactured 10 infrared heaters, and the results of experiments on them will be explained.

In these heaters, in the work of attaching the power supply terminal 13 to the base body 11 and tightening it with the screws 14, there was no damage to the conductive film 12, and the base body 11 was not damaged.

Then, input 2KW to these heaters and turn them on for 5 hours.
A usage test was conducted in which electricity was repeatedly turned on with 30 minutes of interruption, and changes in resistance and temperature near the power supply terminal 13 and 13 were examined at check times of 100 hours, 300 hours, 500 hours, and 1000 hours. .

The change in resistance value is in the range of 2 to 3% compared to the case of 0 hours at any check time, and the change in temperature is also
All check times were within the range of 1 to 2% compared to the case of 0 hours, and these changes were recognized to be within the range of measurement error, and no defects were identified.

In the above embodiment, the cylindrical substrate 11 is formed of boron nitride by vapor phase growth, which makes it possible to reduce the thickness and weight. However, the cylindrical substrate 11 is formed of boron nitride by vapor phase growth. Not only that, but
As in the past, alumina or the like may be press-molded and fired.

Next, a second embodiment of the present invention will be described based on FIGS. 3 and 4.

The difference in this embodiment from the first embodiment is that the conductive film 12
The outer surface of the heating element is covered with an insulating layer 20 formed by vapor phase growth.

The insulating layer 20 is formed of an insulating ceramic such as boron nitride, coated by a vapor phase growth method, and has a film thickness of about 0.085 m.
It is formed over a length of 230 cm along the axial direction of the cylindrical base 11.

In the case of the second embodiment, since the conductive film 12 is covered with the insulating layer 20, the conductive film 12 is not exposed directly.
This prevents dust and dirt from adhering and accumulating on the surface of 2.

Therefore, problems such as obstruction of infrared radiation caused by dust and dirt are prevented, and the conductive film 12 reacts with oxygen, resulting in an increase in resistance value, a decrease in temperature, and damage to the conductive film 12. The problem will be resolved.

Furthermore, since the conductive film 12 is protected by the insulating layer 20, problems such as damage to the conductive film 12 or staining of the surface during handling are prevented.

In each of the above embodiments, the soft conductive metal 15 is made of copper foil, but it may be made of metal such as platinum, gold, nickel, or Graphoil (trade name).

[Effects of the Invention] As explained above, according to the present invention, since the soft conductive metal is inserted between the power supply terminal and the conductive film, the soft conductive metal absorbs tightening force and thermal expansion difference. However, it is possible to maintain good electrical connection between the power supply terminal and the conductive film, and prevent poor contact and damage to the conductive film and the base.

5 and 6 show the conventional structure, FIG. 5 is a side view of the heater, and FIG.
It is a sectional view taken along the line V[-Vl in the figure.

11... Cylindrical substrate, 12... Conductive heating coating, 1
3... Power supply terminal, 14... Screw, 15... Soft conductive metal, 20... Insulating layer.

Fig. 1 is a side view of the heater, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, Figs. 3 and 4 show the second embodiment, and Fig. 3 shows the heater.
The figure is a side view of the heater, and Figure 4 is Takehiko Suzue, patent attorney representing the third applicant.

Claims (2)

[Claims] (1) In an infrared heater in which a heating element made of a conductive film is formed on the surface of an insulating substrate, and this conductive film is connected to a power supply terminal attached to the base, a soft conductive material is connected between the conductive film and the power supply terminal. An infrared heater characterized by interposing metal. (2) The infrared heater according to claim 1, wherein the heating element made of the conductive film is formed on the surface of the insulating substrate by vapor phase growth.