JPH0636949A - Welding transformer of resistance welding machine - Google Patents

Abstract

PURPOSE:To obtain a welding transformer of a resistance welding machine which transformer is capable of realizing small size, light weight and low cost. CONSTITUTION:A welding transformer 24 is provided with a primary coil 30, a secondary coil 32 wherein a center tab terminal plate 38 is fixed to a tap 36, and a core 34. Since the center tap terminal plate 38 is lead out so as to keep a distance longer than or equal to a specified value from the core 34, the magnetic flux PHI induced in the core 34 is not affected by the magnetic flux induced by a secondary current I2 flowing in the center tap terminal plate 38, and all of the flux PHI passes the core 34. Thereby the efficiency of the core 34 can be improved, so that the welding transformer 24 can be made 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 center tap terminal plate is arranged is reduced by the influence of the welding current flowing through this center tap terminal plate. It has been confirmed that it will be lower than. 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, and aims to optimize the positional relationship between the core and the center tap terminal plate, thereby reducing the size, weight and cost. It is an object of the present invention to provide a welding transformer of a resistance welding machine capable of realizing the above.

[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. It is characterized by comprising an annular core passing through the axis and a center tap terminal plate connected to the center tap of the secondary coil and pulled out at a predetermined distance or more from the annular core.

[0007]

In the welding transformer of the resistance welding machine according to the present invention,
An annular core is arranged on the central axes of the primary coil and the secondary coil, and the center tap terminal plate connected to the center tap of the secondary coil is pulled out from the annular core at a predetermined distance or more. The magnetic flux induced by the secondary current and passing through the core is not affected by the magnetic flux induced by the secondary current flowing through the center tap terminal plate.

Therefore, the efficiency of the core can be improved, and the core can be reduced in size, weight and cost.

[0009]

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 is provided with a welding transformer 24 and diodes 26 and 28. The welding transformer 24 is provided with a primary coil 30 and a central axis of the primary coil 30. It is composed of a secondary coil 32 and 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 center tap terminal plate 38 is arranged along the central axis direction of the secondary coil 32 and at a predetermined distance or more from the outer peripheral portion of the core 34.

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.

Here, in the core 34 with respect to the configuration of FIG.
Arrange the cores 35 (phantom two-dot chain line in FIG. 3) so as to be symmetrical.
Magnetic flux density B of each core 34, 35 when installed
_mThe measured value of is shown in FIG. This FIG. 4 shows an inverter circuit 1
Primary current I output from 6 ₁For the duty ratio of
When the core 34 and the core 35 having the same cross-sectional area are used,
Magnetic flux density B of each_mIs the measured value of.

Thus, the magnetic flux density B_mThe difference is that
An intermediate tap terminal plate 38 extends near the outer periphery of the core 35.
Therefore, the secondary power generated in the center tap terminal plate 38
Flow I ₂Because it is affected by the magnetic flux induced by
It

Therefore, when the center tap terminal plate 38 is arranged extremely close to the core 35 as shown in the figure, the magnetic flux induced in the core 35 is reduced by the magnetic flux induced by the secondary current I ₂ .

Therefore, the center tap terminal plate 38 and the core 3
If the positional relationship with 5 is closer, the core 3 will be finally
5 can be dispensed with. As a result, the transformer 24 can be configured using only the core 34, and the size and weight of the transformer 24 can be reduced.

[0022]

In the welding transformer of the resistance welding machine according to the present invention, the core is downsized, the weight is reduced, and the cost is reduced by optimizing the positional relationship between the core and the center tap terminal plate. Therefore, it is possible to obtain a welding transformer which is inexpensive and has a minimum weight and a 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 diagram illustrating a relationship between a duty ratio of a primary current and a magnetic flux density of each core in a welding transformer including a pair of annular cores having the same cross-sectional area.

[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

Claims (1)

[Claims] 1. A primary coil, a secondary coil which is disposed so as to substantially coincide with a central axis of the primary coil, an annular core passing through the central axis, and a center tap of the secondary coil. A welding transformer for a resistance welding machine, comprising: a center tap terminal plate that is pulled out at a predetermined distance or more from the annular core.