Electric heating – Metal heating – By arc
Reexamination Certificate
1999-06-15
2001-05-01
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C219S130210, C219S130310
Reexamination Certificate
active
06225597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of controlling a welding output and also relates to a consumable electrode type pulse arc welding device in which a consumable electrode, which will be referred to as a wire hereinafter, is automatically fed, and a peak current and a base current are alternately and repeatedly supplied between the wire and a welding base metal which will be referred to as a base metal hereinafter.
2. Description of the Related Art
FIG. 10
is a view showing an example of the conventional method of controlling an output of a consumable electrode type pulse arc welder. According to the above conventional method, an output of the pulse arc welder is controlled by fixing a pulse period and changing a pulse frequency. This pulse period is set at the most appropriate value so that a melting drop can be formed at a tip of a wire each time a peak current is outputted and the thus formed melting drop can be separated from the tip of the wire by an electromagnetic pinching force caused by the peak current and shifted to a base metal. Therefore, as shown in
FIG. 11
, under the outputting condition of one pulse and one drop, the occurrence of short circuit is suppressed and spattering is seldom caused during a process of welding.
Next, referring to
FIG. 10
, a structure of the conventional consumable electrode type pulse arc welding device will be explained below. In
FIG. 10
, reference numeral
1
is a three-phase input power source, reference numeral
2
is a first rectifying section, reference numeral
3
is an inverter circuit, reference numeral
4
is a main transformer, reference numeral
5
is a second rectifying section, reference numeral
6
is a reactor, reference numeral
20
is a positive output terminal, reference numeral
21
is a negative output terminal, reference numeral
22
is a chip, reference numeral
23
is a wire, and reference numeral
24
is a base metal. An error caused between an output of the welding voltage detecting section
7
and an output of the welding voltage setting section
9
is amplified by the error amplifying section
8
. By an output of this error amplifying section
8
, a pulse frequency signal is outputted by the pulse frequency calculating section
18
. By this pulse frequency signal and an output of the pulse period setting section
13
for setting a pulse period, a frequency appropriate for a welding output and a signal corresponding to the pulse period are obtained in the pulse output setting section
10
c.
When the most appropriate period for one pulse and one drop is set as described above, it is possible to suppress the occurrence of spattering. However, in recent years, there is a growing tendency of increasing a welding speed so that the productivity of welding can be enhanced. In order to increase the welding speed, it is necessary to lower a welding voltage. When the welding voltage is lowered, a pulse period is not changed according to the conventional controlling method as shown in FIG.
12
. Therefore, an average of the pulse frequency is lowered. However, a quantity of a wire to be fed is constant. Accordingly, although the most appropriate period for one pulse and one drop has been set, short circuit occurs before a melting drop is separated from a wire tip because the pulse frequency lacks with respect to the quantity of wire to be fed. Further, a size of the melting drop which has been left at the tip of the wire is not uniform. Therefore, frequency of the occurrence of short circuit becomes irregular. For the above reasons, a quantity of generated spatter is increased, and the thus generated spatter adheres to the base metal and the nozzle, which impairs the enhancement of productivity.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above problems with the prior art, and therefore one object of the present invention is to provide a method of controlling a pulse output and a consumable electrode type pulse arc welding device in which short circuit is regularly caused at each pulse so that a quantity of generated spatter can be reduced.
Another object of the present invention is to provide a method of controlling a pulse output and a consumable electrode type pulse arc welding device in which short circuit is regularly caused at each pulse so that a quantity of generated spatter can be suppressed when the peak current is lowered so that an average of the pulse frequency can not be changed in the case of lowering the welding voltage.
Still another object of the present invention is provide a method of controlling a pulse output and a consumable electrode type pulse arc welding device in which a melting drop is be regularly shifted from the tip of the wire to the base metal at each pulse due to the foregoing so that a quantity of generated spatter can be reduced, since according to the invention, when a welding voltage, which changes immediately before the separation of a melting drop from the tip of the wire, is detected, separation of the melting drop is predicted, and the pulse period is ended.
In order to accomplish the above object, according to a first aspect of the invention, there is provided a method of controlling a pulse output, comprising the step of: setting a period of a pulse of a current by using at least one of a welding output voltage, a signal corresponding to the welding output voltage and a setting welding voltage. When a period of a pulse is set, the period of a pulse of a current is set by using at least one of a welding output voltage, a signal corresponding to the welding output voltage and a setting welding voltage and also by using a setting pulse frequency. Concerning this period of a pulse, an upper limit and a lower limit of the period of a pulse of a current are set according to at least one of a quantity of a wire to be fed, a diameter of the wire and a material of the wire. Next, a consumable electrode type pulse arc welding device to which the method of controlling a pulse output is applied will be explained below.
According to another aspect of the invention, there is provided a consumable electrode type pulse arc welding device comprising: a welding voltage detecting section for detecting a welding voltage; a welding voltage setting section for setting a welding voltage; a main transformer for supplying electric power to a welding load, having an auxiliary coil on the secondary side; a rectifying element for rectifying an output of the main transformer; an error amplifying section for amplifying a difference between two inputs, one input being an output of the welding voltage detecting section or an output of the rectifying element, the other input being an output of the welding voltage setting section; a pulse frequency setting section for setting a pulse frequency to calculate a period of a pulse; a pulse output setting section for outputting a pulse output signal corresponding to a welding output from an output of the welding voltage detecting section or an output of the rectifying element, an output of the welding voltage setting section, an output of the pulse frequency setting section, and an output of the error amplifying section; a peak current setting section for setting a peak current; a base current setting section for setting a base current; and a switching circuit section for selecting either an output of the peak current setting section or an output of the base current setting section by an output of the pulse output setting section.
According to still another object of the invention, there is provided a method of controlling a pulse output, comprising the step of: setting a peak current by using at least one of a welding output voltage, a signal corresponding to the welding output voltage and a setting welding voltage and also by using a setting pulse frequency.
According to yet still another object of the invention, there is provided a consumable electrode type pulse arc welding device comprising: a welding voltage detecting section for detecting a welding voltage
Hamamoto Koji
Kawamoto Atsuhiro
Nakagawa Akira
Tanaka Yoshiaki
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
Shaw Clifford C.
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