JP3068662B2 - Manufacturing method of heater coil for radiant heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a heater coil for a radiant heater which can be used at a high voltage and a low current.

[0002]

2. Description of the Related Art In a radiant heater, a heater coil is inserted into a quartz glass tube, leads are drawn out from both ends, and the coil portion of the heater coil is heated by energization from the leads to enable radiation in a radiation direction. . This radiant heater is frequently used in home appliances such as stoves, kotatsu, refrigerators, dryers, toasters, and microwave ovens.

FIG. 2 shows an example of a radiant heater (1). The radiant heater (1) has a heater coil (3) closely wound in an elongated quartz glass tube (2).
The lead (4) of the heater coil (3) is caulked to a disk (5) made of a conductive material. Due to the contraction force of the heater coil (3), one end of the power cord (6) which is in close contact with the end face of the quartz glass tube (2) is similarly swaged to the disk (5). The power cord (6) is electrically connected to the lead (4) of the heater coil (3) via the disk (5). An insulating cap (7) made of vinyl chloride is fitted to the end of the quartz glass tube (2) to provide electrical insulation to the outside and prevent moisture from being sucked into the quartz glass tube (2). The configuration of the left end and the right end is the same.

As described above, a radiant heater having a power supply of 200 to 220 volts is used in some cases. In this case, a heater wire having a small diameter is used because the current value must be suppressed, and the heater wire is closely adhered to a large diameter coil. A radiant heater in which the whole resistance value is increased by winding is required.

[0005] Since the close contact winding of the heater wire makes an electrical connection between the wires, an electric insulating film is formed on the outer surface of the heater wire. This film is put into an electric furnace with the heater coil (3), and the both ends are pulled to break the adhesion.
It is generated by performing a heat treatment at the above temperature for about 60 minutes.

[0006]

As described above, since the heater coil for high voltage uses a thin wire and is fired at a high temperature, the strength is inevitably reduced.

A radiant tube as shown in FIG. 2 may be subjected to an unexpected impact during the distribution process or during use. In this case, the heater coil is subjected to vibration such that the coil part moves to one side, one of the lead parts at both ends is slackened and the other is pulled, and the reaction is reversed to the opposite state, and the lead part is often turned. Deform and break.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to develop a means that does not reduce the strength of the lead portion of the heater coil, and to solve the above-mentioned disadvantages of the prior art.

[0009]

According to the present invention, in order to solve the above-mentioned problems, basically, after a formed heater coil is subjected to a primary firing treatment, a wire material at an end portion of the coil is drawn out and wire processing is performed by this portion. To form a lead portion, and then hold the lead portion with a current-carrying jig and perform primary current heating treatment in a state where the wire material of the coil portion is separated to form an electrically insulating oxide film on the wire material surface, Thereafter, means for compressing and shrinking the coil portion to bring the coil portion into a tightly wound state and performing a second energization heating process is used.

[0010] As the heater wire, preferably, Fe-
A Cr-Al-based material having a diameter of 0.25 to 0.30 mmΦ is used, and this is wound tightly around 7 to 8 mmΦ to form a coil portion.

[0011] The heater coil is placed in an electric furnace, subjected to a high-temperature firing treatment, and an oxide film is formed on its surface. This film is a Cr-based oxide film, which imparts corrosion resistance to the wire rod and removes stress during forming, thereby facilitating handling of the coil in a later step.

A wire is stretched from the end of the heater coil which has been subjected to the primary firing, and the wire is subjected to double stranding to form plastic work hardened leads at both ends of the coil. The pitch of the stranded wire processing is set to 2 mm or less, and by this processing, the oxide film formed in the primary firing is peeled off, and the direct contact of the wire material is sufficiently obtained, and the current-carrying characteristics are obtained.

The heater coil provided with a lead portion at the end is slightly stretched, the coils are separated from each other, the contact state is released, and the lead portion is held by a current-carrying jig and heated. This is called primary energization heat treatment. By this primary energization heating treatment, an oxide film mainly composed of alumina having good insulation properties is formed on the surface of the heater coil. Since the lead portion is a stranded wire, the electric resistance is small and the calorific value is small, and the heat is good because the lead portion is held in contact with the conducting jig. Therefore, the plastic work hardening state imparted by the twisting is maintained, and a decrease in the strength of the lead portion can be avoided.

After the primary energization heating process, the coil portion is pressed and shrunk to bring the coil portion into a tightly wound state, and the energization heating process is performed again. This is called secondary energization heating treatment, and the coil is formed into a tightly wound state by this secondary energization heating treatment.

The heater coil subjected to the above-described processing is assembled as described with reference to FIG.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A 0.29 mmΦ FCHW-1 heater wire is turned into 560 turns to form an 8 mmΦ coil portion (10) (see FIG. 1). The length of the coil part (10) is 125 mm. This heater wire is put into an electric furnace,
It was baked under the conditions of 60 minutes. Cr with good corrosion resistance on the surface
Oxide was confirmed.

The end of the coil portion (10) is pulled out, and this portion is doubled and stranded to form a lead portion (11). The pitch of the stranded wire processing was 2 mm.

The heater coil is placed in the quartz glass tube (2) so that the length of the coil portion (10) is 140 mm, that is, the coils are separated from each other and the lead portion (1) is separated.
1) was held by a current-carrying jig, and subjected to primary current-heating treatment at 400 volts for 15 seconds to form an electrically insulating alumina oxide film on the surface of the wire rod of the coil portion (10). In this energization heating treatment, the temperature of the coil portion becomes 900 ° C. or higher, but the temperature rise of the lead portion is small, and therefore, the softening of the lead portion (11) is small.

Next, the coil portion (10) is pressed and shrunk in the axial direction to bring the coil portion into a tightly wound state, and the coil portion is again pressed 350
The bolt was subjected to an electric heating process (second electric heating process) for 3 seconds. By this processing, the coil portion (10) is habitually formed in a tightly wound state, and is made into a closely wound heater coil.

The heater coil subjected to the above-described processing was assembled in the same manner as in FIG. 2 and used as a radiant heater.

[0021]

According to the present invention, the formed coil is subjected to primary firing to form a slight oxide film on the surface and to remove processing distortion due to coil processing. And the distance between the coils can be made uniform. After the primary firing, the wire at the end of the coil is stretched, and the lead is formed by doubling this portion to form a lead, so that the lead is plastically hardened. Since the cured state is maintained after the subsequent secondary heating treatment, a radiant heater heater coil having a strong lead can be obtained. Accidental damage is prevented.

[Brief description of the drawings]

FIG. 1 is a front view of a heater coil made according to an example of the present invention.

FIG. 2 is a cross-sectional view of a radiant heater.

[Explanation of symbols]

 2 Quartz glass tube 10 Coil part 11 Lead part

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-73985 (JP, A) JP-A-53-117835 (JP, A) JP-A-59-167985 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H05B 3/56 H05B 3/44 H05B 3/02

Claims (4)

(57) [Claims] After the heater wire is formed into a coil shape,
A primary sintering of the coil to form an oxide film on the surface, a wire material at the end of the coil is stretched, and the stretched portion is multiplexed and subjected to wire processing to be reinforced and a plastic work hardened lead portion. Holding the lead portion with a current-carrying jig and applying an electric heating process in a state where the heater wire of the coil portion is separated from each other to form an oxide film on the surface of the heater wire, and then compress the coil portion. A method of manufacturing a heater coil for a radiant heater, wherein the heating is performed again through a current-carrying jig in a state of close contact winding. 2. The heater wire is an Fe—Cr—Al-based alloy, the oxide film formed by primary firing is an oxide of Cr,
2. The method for manufacturing a heater coil according to claim 1, wherein the oxide film formed by energization is alumina. 3. The method of manufacturing a heater coil according to claim 2, wherein the current-carrying cross-sectional area is made larger than that of the coil portion by stranded wire processing of the lead portion. 4. The method for manufacturing a heater coil according to claim 2, wherein the energization process is performed in a quartz glass tube.