JPS6331311B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a thermal overload relay, in particular, a heating wire made of nichrome wire, which has a higher melting point than a bimetal, and a bimetal are welded together, and the shape change due to the thermal expansion of the bimetal is prevented. This invention relates to a thermal overload relay that operates the opening/closing mechanism using the

[Conventional technology]

3 to 6 show conventional devices, FIG. 3 is a sectional view of a main part showing an example of a thermal overload relay, and FIG. 4 is a sectional view taken along line AA in FIG. 3.

3 and 4, a fixed end 31 of a bimetal 3 is fixed to a case 2 of a thermal overload relay 1 with a screw 4, and a heater wire 6 is connected to a heat element 5 provided around the bimetal 3. is wound, and one end 61 of the heater wire 6 parallel to the plate surface of the bimetal 3 is connected to the free end 3 of the bimetal 3.
2, and the fixed end 31 of the bimetal 3 and the other end 62 of the heater wire 6 are connected to the main circuit of the thermal overload relay 1. Further, an operating portion 7 is provided which operates in the direction of the arrow in conjunction with the free end portion 32 of the bimetal 3 to open and close the opening/closing operation mechanism. Such a thermal type overload relay is well known from Japanese Patent Application Laid-Open No. 54-91780 (invention title: ``Thermal Type Overload Relay'').

In the thermal overload relay configured as described above, one side of the heater wire 6 is wound spirally around the outer periphery of the heat element 5 provided around the bimetal 3 as shown in FIGS. The end 61 of the bimetal 3 is spot welded along the plate surface of the free end 32 of the bimetal 3. The bimetal 3 is usually made by joining two (or three) types of alloys, and the properties of the bimetal change depending on the heating temperature. Generally, the hardness of bimetal 3 changes significantly at temperatures above 500 degrees Celsius, and when it reaches temperatures above 700 degrees Celsius, it becomes significantly softer and loses its springiness. For this reason, it is required that the bimetal 3 and the heater wire 6 be welded together in a short time and with as little temperature as possible.Therefore, spot welding is suitable for welding the bimetal 3 and the heater wire 6 because it can be welded in a short time.

[Problem that the invention seeks to solve]

However, if the material of the heater wire 6, which has a higher melting point than the bimetal 3, changes and its melting point or hardness changes, the heat generation situation during spot welding changes, and the line BB in Figure 5a in Figure 6 changes. As shown in the cross section, the heater wire 6 pressed by the welding electrode may sink into the bimetal 3 during spot welding. Furthermore, if the welding electrode pressure is too large, not only will the heater wire 6 sink into the bimetal 3 as shown in FIG. 6, but the heater wire 6 will be crushed more than necessary, reducing the contact area between the heater wire 6 and the bimetal 3. Since welding is not carried out on a very small contact surface, which is the main purpose of spot welding, there is insufficient penetration between the bimetal 3 and the heater wire 6, resulting in separation or breakage.

The present invention eliminates the above-mentioned drawbacks of the conventional device and provides a thermal overload relay in which a bimetal and a heater wire having a melting point higher than that of the bimetal are sufficiently melted by spot welding to obtain a welded part with stable strength. The purpose is to

[Means for solving problems]

To achieve this object, the present invention provides a bimetal whose one end is fixed to a case, a heater wire wound around the bimetal and whose one end is welded to the free end of the bimetal, and a heating wire that operates based on the curvature of the bimetal. In a thermal overload relay equipped with an opening/closing operation mechanism, a large number of linear small protrusions with a triangular cross section are continuously arranged in parallel at the welding location of the bimetal to be welded to the heater wire having a melting point higher than that of the bimetal. The heater wire is placed on the small protrusion of the bimetal in a direction perpendicular to the small protrusion, and the bimetal and the heater wire are welded by spot welding.

[Effect]

The heater wire, which has a higher melting point than the bimetal, is welded by spot welding by placing the heater wire in a direction perpendicular to a small straight protrusion with a triangular cross section formed at the welding point of the bimetal. The welding current and processing force of the welding electrode are concentrated at the contact point between the small protrusion with a small contact area and the heater wire, so even if the melting point and hardness of the heater wire changes, spot welding of the bimetal and the heater wire is always uniform and stable. will be carried out.

〔Example〕

Next, one embodiment of the present invention will be described in detail based on the drawings. FIGS. 1 and 2 each show an embodiment of the present invention. In the figures, only the points different from the conventional example shown in FIG. 3 are shown, and the explanation of the same parts as the conventional example is omitted.

In FIGS. 1a and 1b, a large number of small projections 33 are formed in the longitudinal direction of the plate surface of the free end portion 32 of the bimetal 3. A heater wire 6 made of, for example, nichrome wire having a higher melting point than the bimetal 3 is wound around the outer periphery of the heat element 5 around the bimetal 3, and an end 61 of the heater wire 6 parallel to the plate surface of the bimetal 3 and The tips of the small protrusions 33 are spot welded. As shown in FIGS. 2a and 2b, which are enlarged views of this welded part, a large number of small protrusions 33 formed continuously in the longitudinal direction of the plate surface of the free end 32 of the bimetal 3 have a triangular cross section and a straight line. It is formed in the shape of The small protrusions 33 can be formed by, for example, embossing the plate surface of the bimetal 3. When the heater wire 6 is placed on the small protrusion 33 of the bimetal 3 in a direction perpendicular to the small protrusion 33, the heater wire 6 and the small protrusion 3
The contact area at the point of contact with the small protrusion 33 is extremely small because the tip of the small protrusion 33 is thin and sharp.

When the heater wire 6 is placed on the small protrusion 33 of the bimetal 3 and spot welded, the contact area between the small protrusion 33 and the heater wire 6 is small, so the contact resistance is high, and the welding occurs at the tip of the small protrusion 33. Since the current and the pressure of the welding electrode are concentrated, sufficient heat is generated for welding, and the locally melted heater wire 6 is pressed against the small protrusion 33, causing the heater wire 6 and the bimetal 3 to melt at each point perpendicular to each other. The plate surface is melted, and the part crushed by the welding electrode due to the small protrusion can easily escape depending on the direction of pressure, and after melting, the flow can be improved, so that the bimetal 3 and the heater wire 6 are fully connected. It can be a large fused spot weld.

〔Effect of the invention〕

According to the present invention described above, when welding a bimetal of a thermal overload relay and a heater wire whose melting point is higher than that of the bimetal, a small straight protrusion with a triangular cross section is continuously formed at the welding point of the bimetal. A large number of heater wires are formed in parallel in parallel, and the heater wires are placed on the small protrusions of the bimetal in a direction perpendicular to the small protrusions and spot welded.
Even if the direction in which the heater wire is placed is slightly off, contact between the heater wire and the small protrusion is ensured in a small area, and the welding current and welding electrode pressure are concentrated at each contact point, so the material of the heater wire To provide a thermal overload relay in which a bimetal and a heater wire are welded by spot welding, and even if the melting point and hardness of the two metals are changed, uniform and stable spot welding can be performed at all times.

[Brief explanation of the drawing]

1 and 2 each show an embodiment of the present invention, FIGS. 1a and 1b are a front view and a side view of main parts, respectively, and FIGS. 2a and 2b
are a main part front view and a side sectional view, respectively.
Figures 3 to 6 show conventional devices, Figure 3 is a sectional view of the main parts of a thermal overload relay, Figure 4 is a sectional view taken along line A--A in Figure 3, and Figure 5 shows a bimetallic part. 5a and 5b are a front view and a side view, and FIG. 6 is a sectional view taken along the line BB in FIG. 5a. 3: Bimetal, 5: Heat element, 6:
Heater wire, 32: Bimetal free end, 33: Bimetal small protrusion.

Claims (1)

[Claims] 1 A heating device comprising a bimetal with one end fixed to a case, a heater wire wound around the bimetal and one end welded to the free end of the bimetal, and an opening/closing operation mechanism operated based on the curvature of the bimetal. In the type overload relay, a large number of linear small protrusions with a triangular cross section are continuously arranged in parallel at the welding point of the bimetal to be welded with the heater wire having a melting point higher than that of the bimetal, and the heater wire is welded to the heater wire with a higher melting point than the bimetal. A thermal overload relay characterized in that the bimetal is placed on a small protrusion in a direction perpendicular to the small protrusion, and the bimetal and the heater wire are welded by spot welding.