JPS58106786A - Method of producing sheathed heater - 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] The present invention relates to a method for manufacturing a sheathed heater, and in particular, it is possible to minimize changes in the resistance value of heating wires during the processing process, and therefore facilitate process control and design calculations. The purpose of this invention is to provide a method for manufacturing a sheathed heater that can perform the following steps.

In recent years, sheathed heaters have been widely used not only for industrial purposes but also for home appliances.

However, in the conventional manufacturing method of a sheathed heater, the heating wire 1 is coiled in a circular shape as shown in Fig. 1, and the resistance value of the heating wire 1 changes greatly during the manufacturing process. The reality is that the set resistance value is determined in advance by adding or subtracting an amount commensurate with the amount of change, or that several trial productions are performed to determine the set resistance value.

In addition, even during mass production, it is necessary to make prototypes for each loft with different conditions such as material properties, which not only complicates daily process control, but also makes it difficult to accurately grasp the amount of change during design. was the point.

The mechanism by which the resistance value of the electric heating a1 changes is inferred as follows based on experiments conducted by the inventors. That is, as shown in FIG. 2, the area around the heating wire 1 is filled with an insulating powder 2, and the external force P1 is applied toward the center when the metal pipe 3 is compressed to reduce its diameter. , heating wire 1
Due to the circular shape of the coiling, the external force P1 changes to a uniform component force P2 in the circumferential direction of the heating wire 1, and from a microscopic perspective, the electric heating #! 1 becomes compressed, the wire diameter of the heating wire 1 becomes thicker, and the overall resistance value decreases. According to experiments, the smaller the coiling pitch of the heating wire 1, the greater this effect. On the contrary, when the heating wire 1 is in a straight state without being coiled, the external force P1 acts in the direction of extension, the heating wire 1 becomes thinner, and the resistance value increases.

If we use this phenomenon in reverse, that is, the heating wire 1
Changes in resistance can be minimized by forming the tube in advance into a shape that is less likely to increase in diameter due to the influence of the gas, and then performing filling and diameter reduction processing.

The present invention solves the above-mentioned drawbacks of the conventional sheathed heater, and embodiments of the present invention will be described below with reference to FIGS. 3 to 6.

In FIGS. 3 to 6, 11 is a metal pipe with a circular cross section. A heating wire 13 with terminal rods 12 connected to both ends is inserted into the metal pipe 11, and a heat-resistant insulating powder 14 is filled around the wire 13. has been done.

The heating wire 23 is formed into an elliptical shape or a polygonal shape such as a substantially triangular or substantially quadrangular shape, as shown by the two-dot chain line in FIGS. After this, a process of reducing the diameter of the metal pipe is performed.

According to the above manufacturing method, the external force applied when reducing and compressing the metal pipe 11 is unevenly applied to the heating wire 12, and the heating wire 13
The heating wire 13 is deformed from an elliptical or polygonal shape to a shape close to a circle as shown by solid lines in FIGS. Therefore, changes in resistance value are less likely to occur.

In order to form the heating wire 13 into an elliptical or polygonal shape, the core wire mandrel during winding may be made into an elliptical shape, or the wire may be processed by pressing after being wound into a circular shape. good.

As is clear from the above explanation, according to the method of manufacturing a sheathed heater of the present invention, the heating wire is shaped in a shape other than circular, so that the heating wire deforms and absorbs the external force when the diameter is reduced, resulting in a change in resistance. can be kept to a minimum as much as possible, and its industrial value is great.

[Brief explanation of drawings]

FIG. 1 is a front sectional view of a conventional sheathed heater, FIG. 2 is a sectional view of the same side, FIG. 3 is a front sectional view of the sheathed heater according to the present invention-e-embodiment before diameter reduction, and FIG. 4 is the same side sectional view. 6 and 6 are side sectional views of a sheathed heater in other embodiments of the present invention, respectively. 11...Metal pipe, 13...Heat-resistant insulating powder 0 Name of agent: Patent attorney Toshi Nakao and 1 other person 1st
5! +1

Claims (1)

[Claims] A method for manufacturing a sheathed heater, which involves inserting a heating wire coiled into an elliptical or polygonal shape into a metal pipe, filling the metal pipe with heat-resistant insulating powder, and then reducing the diameter of the metal pipe.