JPH0636948A - Welding transformer of resistance welding machine - Google Patents

Abstract

PURPOSE:To realize small size, light weight and low cost, by making the sectional areas of cores suitable in the manner in which magnetic flux density of each core becomes equal. CONSTITUTION:A welding transformer 24 is provided with a primary coil 30, a secondary coil 32 whose center tap terminal plate is fixed to a tap 36, and a core 34 constituted of a pair of ring cores 34 composed of a first core 40 and a second core 42. When the center tap terminal plate is arranged in the vicinity of the outer periphery of the first core 40, the magnetic flux induced in the first core 40 is little as compared with the magnetic flux induced to the second core 42, so that the sectional area of the core 34 is made suitable by making the sectional area of the first core 40 smaller than that of the second core 42. Thereby the welding transformer 24 can be small and light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding transformer for a resistance welding machine, and more particularly to a welding transformer for a resistance welding machine which can be made compact and lightweight.

[0002]

2. Description of the Related Art In the industrial field, a resistance welding machine is widely used for welding various works. In this kind of resistance welding machine, welding is performed for cost reduction and space saving of the equipment. There is a demand for smaller and lighter transformers.

The welding transformer of the resistance welding machine comprises a primary coil, a secondary coil, and a pair of cores for magnetically coupling these coils. Further, the center tap of the secondary coil is a center tap. It is known that a terminal plate is fixed and used as an output terminal.

[0004]

By the way, in the above-mentioned welding transformer in the prior art, due to design considerations,
When the center tap terminal plate is pulled out toward one of the cores, the magnetic flux density of the core on the side where the output terminal plate is arranged is smaller than that of the other core due to the influence of the welding current flowing through this center tap terminal plate. It has been confirmed that it will be lower. In this case, both cores are formed in the same shape, and it has been pointed out that the weight and volume of the cores hinder the reduction in size and weight of the transformer.

The present invention has been made in order to solve such a conventional problem. By making the cross-sectional area of the core correspond to each magnetic flux density, the cross-sectional area of the core is optimized and the size is reduced. It is an object of the present invention to provide a welding transformer of a resistance welding machine that can realize cost reduction, weight reduction, and cost reduction.

[0006]

In order to achieve the above-mentioned object, the present invention provides a primary coil, a secondary coil which is disposed so as to substantially coincide with a center axis of the primary coil, and the center. A welding transformer of a resistance welding machine, comprising: a pair of annular cores passing through an axis; and a center tap terminal plate connected to a center tap of the secondary coil and drawn toward one of the annular cores with respect to the central axis. Thus, the cross-sectional area of the one annular core provided with the center tap terminal plate in the vicinity thereof is set smaller than the cross-sectional area of the other annular core.

[0007]

In the welding transformer of the resistance welding machine according to the present invention,
A pair of annular cores are arranged on the central axes of the primary coil and the secondary coil, and a center tap terminal plate connected to the center tap of the secondary coil is provided near one of the annular cores with respect to the central axis. When pulled out, the magnetic flux density of the one annular core near the center tap terminal plate becomes smaller than the magnetic flux density of the other annular core. It can be set smaller than the cross-sectional area of the annular core.

[0008]

The welding transformer of the resistance welding machine according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a resistance welding machine 10 embodying the present invention.
3 is a block diagram showing the overall configuration of FIG.

The resistance welding machine 10 includes a converter circuit 14 for full-wave rectifying the alternating current output from the alternating current power source 12, and an inverter circuit 1 for converting the full-wave rectified direct current into a high frequency alternating current.
6, a welding transformer circuit 18 that transforms and rectifies the high-frequency alternating current, a welding gun portion 20 that holds the work W, and a switching circuit 22 that energizes a switching element (not shown) of the inverter circuit 16.

The welding transformer circuit 18 comprises a welding transformer 24 and diodes 26 and 28. The welding transformer 24 is arranged with the primary coil 30 and the central axis of the primary coil 30 substantially in line 2. The secondary coil 32 is composed of a core 34 that magnetically couples the primary coil 30 and the secondary coil 32.

FIG. 2 is a perspective view of the welding transformer 24, and FIG. 3 is a side view of the welding transformer 24.

The secondary coil 32 is a plate coil having two turns, and a center tap terminal plate 38 fixed to a tap 36 of this coil serves as one output terminal of the welding transformer 24.

The core 34 is an annular first core 40 and a second core.
It is composed of a core 42. In this case, the center tap terminal plate 38 extends in the vicinity of the outer peripheral portion of the first core 40 along the central axis direction of the secondary coil 32.

The operation of welding the work W in the resistance welding machine 10 configured as described above will be described with reference to FIGS.
Will be described with reference to.

The converter circuit 14 converts alternating current supplied from the alternating current power supply 12 into direct current and outputs it to the inverter circuit 16. The inverter circuit 16 switches the direct current output from the converter circuit 14 by the pulse-shaped switching signal output from the switching circuit 22, and supplies the pulse-shaped primary current I ₁ to the primary coil 30 of the welding transformer 24. To do.

A magnetic flux Φ is induced in the core 34 by the primary current I ₁ , and the secondary coil 3 is further generated by the magnetic flux Φ.
A secondary voltage V ₂ is induced at both ends of 2. The secondary voltage V
₂ , the welding current I ₂ rectified by the diode 26 or 28 is applied to the work W through the welding gun portion 20.

In this case, it is known that the magnetic flux Φ ₁ induced in the first core 40 and the magnetic flux Φ ₂ induced in the second core 42 are not equal, and the magnetic flux Φ ₁ <magnetic flux Φ ₂ . FIG. 4 shows measured values of the magnetic flux density B _m of the first core 40 and the second core 42. FIG. 4 shows the magnetic flux density B _m of each of the first core 40 and the second core 42 having the same sectional area with respect to the duty ratio of the primary current I ₁ output from the inverter circuit 16. It is a measured value.

The difference in the magnetic flux density B _m is due to the fact that the center tap terminal plate 38 extends in the vicinity of the outer peripheral portion of the first core 40, so that the center tap terminal plate 38 has two
This is due to the influence of the magnetic field Φ _O induced by the next current I ₂ .

Therefore, since the magnetic flux density B _m is inversely proportional to the cross-sectional areas of the first core 40 and the second core 42, the variable range of the duty ratio D _U of the primary current I ₁ is set to be variable as shown in FIG. When D _{U1 and} D _U2 are set, if the cross-sectional area of the first core 40 is approximately ½ of that of the second core 42, then the respective magnetic flux densities can be the same.

As described above, according to this embodiment,
A welding transformer 2 which is an outer iron type core and in which a center tap terminal plate 38 is led out from a tap 36 of a secondary coil 32.
4, the center tap terminal plate 38 is attached to the first core 4
When the magnetic flux Φ ₁ induced in the first core 40 is extended to the vicinity of the outer peripheral portion of 0, the magnetic flux Φ ₁ induced in the second core 42 is
_Since it is significantly smaller than ₂ , the same output can be obtained even if the cross-sectional area of the first core 40 is reduced. Therefore, it is possible to limit the design of the welding transformer 24 to a smaller size.

[0022]

In the welding transformer of the resistance welding machine according to the present invention, the cross-sectional area of the core can be optimized, and the core can be reduced in size, weight and cost. In addition, it is possible to obtain the welding transformer having the minimum weight and the minimum volume.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a resistance welding machine for carrying out the present invention.

FIG. 2 is a perspective view of the welding transformer shown in the embodiment of FIG.

FIG. 3 is a side view of the welding transformer shown in FIG.

FIG. 4 is a graph illustrating the relationship between the duty ratio of the primary current and the magnetic flux density of each core when the cross-sectional areas of the first core and the second core are the same.

[Explanation of symbols]

 10 ... Resistance welding machine 18 ... Welding transformer circuit 24 ... Welding transformer 30 ... Primary coil 32 ... Secondary coil 34 ... Core 38 ... Center tap terminal plate 40 ... First core 42 ... Second core

Claims (1)

[Claims] 1. A primary coil, a secondary coil arranged substantially in line with a central axis of the primary coil, a pair of annular cores passing through the central axis, and a center tap of the secondary coil. A welding transformer of a resistance welding machine, comprising: a center tap terminal plate that is connected to and is pulled out toward one of the annular cores with respect to the central axis, wherein the center tap terminal plate is disposed in the vicinity. A welding transformer for a resistance welding machine, characterized in that the sectional area of the annular core is set smaller than the sectional area of the other annular core.