JPH0443523A - Thermally moving element - Google Patents

Abstract

PURPOSE:To stabilize the weld strength when the welding is carried out continuously, and to make the replacement of the weld electrode unnecessary when the rating of a thermodynamic element is changed, by providing a plane part at the opposite side of the weld position at the periphery of the end of a heater wire. CONSTITUTION:In the end periphery of a heater wire 3, the surface 3c opposite to a plane 4a of the power source side of a power feeding terminal 4 is made in the original circular form, and the opposite side of the contact point 20, that is, the part opposite to the welded part of the end periphery of the heater wire 3, is formed in a plane. Since the side of the heater wire 3 opposite to the lower electrode 11 is made in a plane, there is no round groove of the lower electrode as in the conventional example. Therefore, between the lower electrode 11 and the heater wire 3 when the welding current flows, the electric resistance is reduced, because the surface of the plane 3d of the heater wire 3 is plain, and the welding space is wider, even though the lower electrode 11 is also in a plane form. Consequently, a heat concentration is generated only at the contact point 20, and a stable welding can be carried out.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention relates to a thermal element used in a thermal overcurrent relay used to protect a mold from burnout, and in particular to an improvement in a welded part of a heater wire. It is related to.

[Prior Art] FIG. 6 is a side view showing a conventional thermal element used in a thermal overcurrent relay, and FIG. 7 is a front view thereof. In the figure, (1) is a tanzaku-shaped bimetal coated with an insulator (2).

In this figure, the insulator (2) is sleeve-shaped and inserted through the bimetal (1), but it may also be covered by winding a tape-shaped insulator. (3) is a heater wire,
It is wound around a bimetal (1) with an insulator (2) interposed therebetween. (4) is the power supply side power supply terminal, one end (4a)
is formed into a flat plate shape, and a heater wire (
The power supply side terminal (3a) of 3) is welded and joined. In addition, the load side terminal (3b) of the heater wire (3) is a bimetallic (
It is welded to the lower end (1a) of 1). The upper end (1b) of the bimetal (1) is fixedly connected to the load side power supply terminal (5) by a method such as welding.

In the thermal element configured as above, current flows through the path of power supply side power supply terminal (4) -> heater wire (3) - bimetal (1) -> load side power supply terminal (5).
And bimetal (1) due to heat generation in bimetal (1)
is curved as shown by the broken line in Figure 6. This curve is used to detect overcurrent in the case of a thermal overcurrent relay. By the way, as the heater wire (3) shown in FIGS. 6 and 7, a wire made of a resistor material such as a nichrome wire or a copper-nickel alloy wire is used. Further, as for the shape of the wire, a wire with a circular cross section is often used because of the ease of manufacturing the wire and the simplicity of the winding work.

Therefore, in the conventional device, the welding between the heater wire (3) of the circular cross-section wire and the one end (4a) of the power supply side feed terminal or the lower end (1a) of the bimetal is performed by resistance welding as shown in Fig. 8. was.

That is, in FIG. 8, (10) is an upper electrode for resistance welding, and (11) is a lower electrode. (3) is the heater wire, (4) is the power supply side power supply terminal (power supply side power supply terminal (
The same effect can be obtained by replacing 4) with the lower end (1a) of the bimetal (1). A round groove (lla) matching the curvature of the circular cross section of the heater wire (3) is formed in the lower electrode.

In this figure, when the welding current flows from the upper electrode (lO) to the lower electrode (11), the contact point (20) between the heater wire (3) and the power supply side power supply terminal (4) (actually at one point) The largest current concentration occurs at the contact point (although it is a straight line), and the electric resistance at this point is large, so the heat generation at this point is large, and the heater wire (3) is connected from the contact point (20) to ) and the terminal (4) begin to melt, resulting in a welded joint. In other words, the lower electrode (11) and the heater wire (3)
By forming a round groove (lla) between the two and expanding the contact area, and by lowering the electrical resistance and concentrating heat only on the contact point (20), we succeeded in obtaining stable and strong welding. are doing.

However, if the heater wire (3) comes off the round groove (lla) of the lower electrode as shown in Fig. 9, the heating point (20)
and (21), the heat generation is dispersed, and even if bonded under the same conditions, the strength of the bond in FIG. 9 is inferior to that in FIG. 8.

[Problems to be Solved by the Invention] In the conventional thermal element as described above, there is a problem in that a welding failure occurs when the heater wire comes off from the round groove of the lower electrode when joining the heater wire. This means that when a large number of heater wires are joined, the round groove (IL) of the lower electrode
There is also a risk that similar welding defects will occur if the curvature of the round groove (lla) changes due to wear of a). Also, if the current carrying rating of the thermal element differs, the diameter of the heater wire (3) will change, so it is necessary to prepare multiple lower electrodes with round grooves that match the curvature of these and replace them while welding. The above-mentioned problems are particularly highlighted when trying to automate the joining of heater wires without any personnel, and the setup changes when automatically welding various ratings, i.e., the lower Exchange of electrodes, positioning of heater wires, that is, alignment of heater wires with round grooves, and monitoring of wear conditions of lower electrode round grooves during continuous welding have become factors that impede unmanned automation.

This invention was made to solve these problems, and it provides stability in welding strength during continuous welding, and a thermal element that does not require replacing the welding electrode when the rating of the thermal element changes. The purpose of this method is to achieve unmanned automation of welding and obtain an inexpensive thermal element.

[Means for Solving the Problems] A thermal element according to a first aspect of the present invention includes a heat generating portion made of a heater wire with a circular cross section, a bimetal that is deformed by being heated by at least the heat generating portion, and a bimetal bonded to the heater wire. The terminal and the heater wire are joined by resistance welding between the end of the heater wire and a flat plate provided on the terminal, and the welding position on the outer periphery of the end of the heater wire is The flat part is provided on the opposite side.

Further, a thermal element according to a second aspect of the present invention includes a heat generating part made of a heater wire with a circular cross section, a bimetal that is heated and deformed by at least the heat generating part, and a terminal joined to the heater wire. , the terminal and the heater wire are joined by resistance welding between the end of the heater wire and the flat plate part provided on the terminal, and the flat part is attached to the outer periphery of the heater wire on the opposite side from the welding position. A plurality of chevron-shaped irregularities are formed on the heater wire at the welding location between the heater wire and the terminal.

[Function] In the first aspect of the present invention, since the flat portion is provided on the outer periphery of the end of the heater wire on the side opposite to the welding position,
Since there is no need to form a round groove for the heater wire on the welding electrode, the welding strength is stable during continuous welding, and since there is no round groove, it is necessary to replace the electrode when the diameter of the heater wire is different. I don't.

Further, in the second aspect of the present invention, a flat portion is provided on the outer periphery of the end of the heater wire on the opposite side to the welding position,
In addition, since the welding point between the heater wire and the terminal is formed by forming multiple chevron-shaped irregularities on the heater wire, there is no need to form a round groove for the heater wire on the welding electrode, so when continuous welding is performed. The welding strength is stable, and since there is no round groove, there is no need to replace the electrode when the heater wire diameter is different.

Furthermore, the concentration of heat generation is further promoted in the plurality of mountain-shaped uneven portions.

[Example] Hereinafter, a first example of the present invention will be described with reference to the drawings. The overall shape and configuration of the thermal element is the same as that of the conventional example shown in FIGS. 6 and 7, and will therefore be omitted. The shape of the heater wire (3) at the joint portion will be explained with reference to FIG.

FIG. 1 is an explanatory view of the welded portion between the heater wire (3) and the power supply side power supply terminal (4), and shows the state before welding and joining. Second
The figure shows the principle diagram of welding, where (10) is the upper electrode, (11
) indicates the lower electrode.

In FIG. 1, the outer periphery of the end of the heater wire (3) is a surface (3c) facing the flat plate portion (4a) of the power supply side power supply terminal (4).
has the original circular shape, and the portion opposite to the contact point (20), that is, the portion opposite to the welding position on the outer periphery of the end of the heater wire (3), is formed into a planar shape as shown. The plane portion (3d) formed into this planar shape is formed by pressing or grinding in a process prior to welding. This heater wire (3
FIG. 3 shows a perspective view of a welded joint between the end portion (3a) of ) and the flat plate portion (4a) provided on the power supply side power supply terminal (4).

Figure 2 shows the principle of welding.As mentioned above, the side where the heater wire (3) faces the lower electrode (11) is flat, so the round groove in the lower electrode that was in the conventional example is eliminated. ing.

That is, between the lower electrode (11) and the heater wire (3) when welding current flows, since the surface of the flat part (3d) of the heater wire (3) is flat, the lower electrode (11) is also flat. Even if the welding surface is wider, the electrical resistance will be lower.
Heat generation is concentrated only at the contact point (20), resulting in stable welding. In other words, even if the heater wire is misaligned, welding can be completed under the same conditions.

Next, a second example will be described.

FIG. 4 is an explanatory diagram of the welding part between the heater wire and the power supply side power supply terminal in the second embodiment, and the heater wire (3) is connected to the terminal (
4) is also formed with chevron-shaped unevenness (3e) so as to further increase the contact resistance.

This mountain-shaped unevenness (3e) further promotes heat generation concentration,
The purpose is to obtain stable welding.

FIG. 5 is a perspective view of the joint portion of the heater wire shown in FIG. 4.

A plane part (3d
) and chevron-shaped unevenness (3e) if done manually (unless automated), one more step of forming work will be required, but when automation is performed, it is necessary to The loss of working time due to incorporating this work into the process is small, and the increase in work speed due to the automation achieved by doing this more than compensates for the above.

In addition, in the above embodiment, the heater wire (3) is attached to the bimetal (1).
), but the heater wire (3) only needs to have a function as a heat generating part, and the bimetal (1) is deformed by being heated by this heat generating part, for example, 1
It may be used as long as it detects current (the structure is not limited to that of the embodiment).

In addition, in the embodiment, the heater wire (3) and the bimetal (1) are connected in series, and the bimetal (1) itself generates heat, but the bimetal is heated only by the heater wire (3). It may be something that

Also, one end (3b) of the heater wire (3) is joined to the lower end (1b) of the tanzaku-shaped bimetal (1); in this case, the lower end (1b) of the bimetal (1) It plays the role of a terminal, and the lower end (1b) has a function equivalent to the flat plate part (4a) of the terminal (4),
Further, it can be seen that the terminal is constituted only by the lower end (1b), that is, the flat plate portion. Therefore, in this specification, the term "terminal" includes not only independent terminals but also parts that function as terminals, such as the lower end (lb) of bimetal (1).

[Effects of the Invention] As explained above, in the first aspect of the present invention, a flat part is provided on the outer periphery of the end of the heater wire on the side opposite to the welding position, so that the welding electrode has a circular shape for the heater wire. Since grooves are not required, welding defects due to misalignment of the heater wire and welding defects due to round groove wear are eliminated, resulting in stable welding, and there is no need to replace the electrode when the diameter of the heater wire changes. .

Therefore, automation and unmanned heater wire welding have been achieved,
This has the effect of being able to supply inexpensive equipment.

Further, as explained above, the second aspect of the present invention is to provide a flat portion on the side opposite to the welding position on the outer periphery of the end of the heater wire, and to provide a plurality of welding points between the heater wire and the terminal on the heater wire. Since welding is performed by forming the mountain-shaped unevenness, in addition to the effect of the first invention, the concentration of heat generation is further promoted in the plurality of mountain-shaped uneven parts, and there is an effect that a more stable welded joint can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the present invention, and is an explanatory diagram of the welding part between the heater wire and the power supply terminal, and FIG. 2 is an explanatory diagram illustrating the principle of welding the heater wire and the power supply terminal. , FIG. 3 is a perspective view of the welded part of the heater wire, FIG. 4 shows a second embodiment of the invention, and is an explanatory diagram of the welded part between the heater wire and the power supply side power supply terminal, and FIG. 5 shows the second embodiment. Fig. 6 is a side view of the thermal element, Fig. 7 is a front view of the thermal element, and Fig. 8 is a welding of the heater wire and terminal of a conventional thermal element. FIG. 9 is an explanatory diagram for explaining the principle, and FIG. 9 is an explanatory diagram for explaining a problem in conventional welding between a thermal element and a terminal. In the figure, (1) is a bimetal, (3) is a heater wire (
(20
) is the contact point. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure Agent Patent Attorney Muneharu Sasaki Figure 2 Figure e 1: Bimetal 3: Shi-y 繞G1 Cod #) Figure Figure

Claims (2)

[Claims] (1) A heat generating part made of a heater wire with a circular cross section, and at least a bimetal that is heated and deformed by the heat generating part;
and a terminal joined to the heater wire, wherein the terminal and the heater wire are joined by resistance welding between an end of the heater wire and a flat plate portion provided on the terminal. A thermal element characterized in that a flat portion is provided on the outer periphery of the end portion of the heater wire on the side opposite to the welding position. (2) a heat generating part made of a heater wire with a circular cross section, and a bimetal that is heated and deformed by at least the heat generating part;
and a terminal joined to the heater wire, wherein the terminal and the heater wire are joined by resistance welding between an end of the heater wire and a flat plate portion provided on the terminal. A flat part is provided on the opposite side of the outer periphery of the end of the heater wire from the welding position, and the welding location between the heater wire and the terminal is such that the heater wire has a plurality of chevron-shaped irregularities. A thermal element characterized in that it is formed and welded.