Method of controlling pulse output and consumable electrode type pulse arc welding device

When a welding voltage is lowered, a pulse period is shortened or a peak current is reduced so that an average of a pulse frequency is not changed. Therefore, short circuit is regularly generated and a quantity of generated spatter is reduced. When the welding voltage is changed immediately before a melting drop separates from a tip of a wire, separation of the melting drop is predicted and the pulse period is ended. Due to the foregoing, a melting drop is regularly shifted at each pulse, and a quantity of generated spatter is reduced.

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 10c.
 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; 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 peak current; a pulse period setting section for setting a pulse period;
 a peak current calculating section for setting a peak current while at
 least one of an output of the welding voltage detecting section, an output
 of the rectifying element and an output of the welding voltage setting
 section, an output of the pulse period setting section and an output of
 the pulse frequency setting section are used as an input; a base current
 setting section for setting a base current; and a switching circuit
 section for selecting either an output of the peak current calculating
 section or an output of the base current setting section by an output of
 the pulse output setting section.
 According to yet still another aspect of the invention, there is provided a
 method of controlling a pulse output, comprising the steps of: detecting a
 melting drop separation predicting signal for predicting separation of a
 melting drop from a tip of a wire by the welding output voltage; and
 setting a pulse period by using this melting drop separation predicting
 signal as a signal to determine a time at which the pulse period is ended.
 According to yet still 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 comparing
 section for outputting a melting drop separation predicting signal when an
 output of the welding voltage detecting section and an output of the
 voltage setting section are compared and calculated and the output of the
 welding voltage detecting section exceeds the output of the voltage
 setting section; 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 calculating section for setting a pulse
 frequency when an output of the error amplifying section is used as an
 input; a pulse output setting section for outputting a pulse output signal
 corresponding to a welding output by using an output of the comparing
 section and an output of the pulse frequency calculating section as an
 input, also by using an output of the pulse frequency calculating section
 as a peak period starting signal and also by using an output of the
 comparing section as a peak period ending signal; 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 period setting
 section.
 The above peak current setting section for setting a peak current of the
 consumable electrode type pulse arc welding device is set according to at
 least one of the settings of a quantity of a wire to be fed, a material of
 the wire and a diameter of the wire.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 According to the present invention, in a method of controlling a pulse
 output and the consumable electrode type pulse arc welding device, a pulse
 period 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.
 When the pulse period is set, at least one of a welding output voltage, a
 signal corresponding to the welding output voltage and a setting welding
 voltage is used, and a setting pulse frequency is also used. Concerning
 the pulse period, an upper limit and a lower limit are set according to
 one of the quantity of a wire to be fed, the diameter of the wire and the
 material of the wire. That is, according to the method of controlling a
 pulse output and the consumable electrode type pulse arc welding device,
 when the welding voltage is lowered, the pulse period is set so that an
 average of the pulse frequency is not changed. Due to the foregoing, short
 circuit, which is caused each time the welding voltage is lowered, is
 regularly generated at each pulse, so that a quantity of generated spatter
 can be reduced. In the pulse output setting section, there is provided a
 limiter setting section by which an upper limit and a lower limit of the
 pulse period are set according to at least one of the quantity of a wire
 to be fed, the diameter of the wire and the material of the wire. When
 this limiter setting section is provided in the pulse output setting
 section, welding is stabilized. The pulse frequency setting section to set
 a pulse frequency used for calculating a pulse period can be set according
 to at least one of the quantity of a wire to be fed, the diameter of the
 wire and the material of the wire. Therefore, it is possible to extend a
 range of setting.
 Also, according to the invention, in the method of controlling a pulse
 output and the consumable electrode type pulse arc welding device, a peak
 current is set by using at least one of the welding output voltage, the
 signal corresponding to the welding output voltage and the setting welding
 voltage and also by using the setting pulse frequency. When the welding
 voltage is lowered, the peak current is lowered so that an average of the
 pulse frequency is not changed. Due to the foregoing, short circuit is
 regularly generated at each pulse, so that a quantity of generated spatter
 can be reduced. The pulse period setting section for setting a pulse
 period can be set according to at least one of the quantity of a wire to
 be fed, the diameter of the wire and the material of the wire. The pulse
 frequency setting section to set a pulse frequency of the consumable
 electrode type pulse arc welding device of the second invention can be set
 according to at least one of the quantity of a wire to be fed, the
 diameter of the wire and the material of the wire. Therefore, it is
 possible to extend a range of setting.
 According to the invention, in a method of controlling a pulse output and
 the consumable electrode type pulse arc welding device, in a melting drop
 separation predicting signal for predicting a separation of a drop from a
 tip of a wire is detected by the welding output voltage, and a pulse
 period is set by using this drop separation predicting signal as a signal
 to determine a time at which the pulse period is ended. That is, when
 separation of the melting drop from the tip of the wire is predicted and
 the pulse period is ended, the melting drop can be regularly shifted from
 the tip of the wire to the base metal at each pulse, so that a quantity of
 generated spatter can be reduced.
 The base current setting section of the consumable electrode type pulse arc
 welding device of the first, the second and the third invention is set
 according to one of the quantity of the wire to be fed, the material of
 the wire and the diameter of the wire. Therefore, setting can be conducted
 for each of the quantity of the wire to be fed, the material of the wire
 and the diameter of the wire. Therefore, it is possible to extend a range
 of setting.
 The peak current setting section of the consumable electrode type pulse arc
 welding device of the first and the third invention is set according to
 one of the quantity of the wire to be fed, the material of the wire and
 the diameter of the wire. Therefore, setting can be conducted for each of
 the quantity of the wire to be fed, the material of the wire and the
 diameter of the wire. Therefore, it is possible to extend a range of
 application.
 Now, a description will be given in more detail of preferred embodiments of
 the invention with reference to the accompanying drawings.
 (FIRST EMBODIMENT)
 Referring to FIGS. 1 and 7, the consumable electrode type pulse arc welding
 device, to which the method of controlling a pulse output of the first
 invention is applied, will be explained below. In this connection, like
 reference characters are used to indicate like parts in the conventional
 structure and the structure of this embodiment, and the explanation is
 omitted here.
 The consumable electrode type pulse arc welding device of the first
 embodiment includes: a main transformer 4 for supplying electric power to
 a welding load, having an auxiliary coil on the secondary side; a welding
 voltage detecting section 7 for detecting a welding voltage; a rectifying
 element 30 for rectifying an output of the main transformer; a welding
 voltage setting section 9 for setting a welding voltage; and an error
 amplifying section 8 for amplifying a difference between two inputs, one
 input being an output of the welding voltage detecting section 7 or an
 output of the rectifying element 30, the other input being an output of
 the welding voltage setting section 9, wherein an average welding voltage
 VOUT obtained by using at least one of the output of the welding voltage
 detecting section 7, the output of the rectifying element 30 and the
 output of the welding voltage setting section 9, a welding voltage VP in
 the peak period from the output of the welding voltage detecting section 7
 or the output of the rectifying element 30, and a welding voltage VB in
 the base period, are detected by the voltage detecting section in the
 pulse output setting section 10a not shown in the drawing, and from an
 output PF of the pulse frequency setting section 11 for setting a pulse
 frequency and also from VOUT, VP and VB, the pulse period is calculated by
 the pulse period calculating section in the pulse output setting section
 10a not shown so that an average of the pulse frequency can not be
 changed. In this connection, VP and VB may be given as data, however, the
 pulse period may be calculated without using VP and VB. The pulse period
 may be set as a data table without conducting calculation. The pulse
 output setting section 10a outputs a pulse output signal corresponding to
 a welding output while a pulse frequency, which is set by the output of
 the error amplifying section 8, and the pulse period are combined with
 each other. Then, either the output of the peak current setting section
 for setting a peak current or the output of the base current setting
 section for setting a base current is switched in the switching circuit by
 the output of the pulse output setting section.
 FIG. 7 is a diagram showing a waveform of the welding voltage in the case
 where welding is conducted by the consumable electrode type pulse arc
 welding device of the first embodiment. The waveform of the welding
 voltage shown in FIG. 7 shows a welding voltage waveform in the case where
 the setting welding voltage is lowered from a welding condition of one
 pulse and one drop shown in FIG. 11, that is, a welding condition in which
 no short circuit occurs. These views are made on the assumption that the
 welding loads are the same. When it is assumed that the welding loads are
 changed, FIGS. 7 and 11 show a condition in which the pulse frequency of
 the welding voltage waveform is decreased.
 In the case where the setting welding voltage is lowered from the condition
 shown in FIG. 11, it can be understood that the pulse frequency is the
 same as that before setting welding voltage is changed when the pulse
 period is reduced. In this case, the pulse period is reduced to be shorter
 than the most appropriate value for one pulse and one drop. Therefore, it
 is impossible to provide a welding condition of one pulse and one drop.
 However, since a melting drop, the quantity of which is constant, is
 formed at a tip of a wire at each pulse, short circuit is caused each time
 the pulse period is ended. Therefore, a constant quantity of a melting
 drop is shifted from the tip of the wire to the base metal. That is, in
 the case where the welding voltage is lowered, a melting drop at the tip
 of the wire is not separated, however, a size of the melting drop which
 has been left at the tip of the wire becomes uniform. Therefore, the A
 melting drop is regularly shifted from the tip of the wire to the base
 metal according to the short circuit which occurs after the end of the
 pulse period. Even when the welding voltage is lowered, an average of the
 pulse frequency is not changed. Therefore, a quantity of a melting drop
 which shifted from the tip of the wire to the base metal at each pulse is
 the same as that of the welding condition of one drop and one pulse, that
 is, the welding condition in which the welding voltage is high. Due to the
 foregoing, the generation of spatter is suppressed and welding can be
 stabilized. As shown in FIG. 4, in the pulse output setting section 10a,
 there is provided a limiter setting section by which an upper limit and a
 lower limit of the pulse period are set according to at least one of the
 quantity of a wire to be fed, the diameter of the wire and the material of
 the wire. When this limiter setting section is provided in the pulse
 output setting section, it is possible to prevent a pulse period, which is
 not appropriate for welding, from being set. Therefore, welding can be
 stabilized.
 (SECOND EMBODIMENT)
 Referring to FIGS. 2 and 8, the consumable electrode type pulse arc welding
 device to which the method of controlling a pulse output of the second
 invention is applied will be explained below. In this connection, like
 reference characters are used to indicate like parts in the conventional
 structure, the structure of Embodiment 1 and the structure of this
 embodiment, and the explanation is omitted here.
 The consumable electrode type pulse arc welding device of the second
 embodiment includes: a main transformer 4 for supplying electric power to
 a welding load, having an auxiliary coil on the secondary side; a welding
 voltage detecting section 7 for detecting a welding voltage; a rectifying
 element 30 for rectifying an output of the main transformer; a welding
 voltage setting section 9 for setting a welding voltage; and an error
 amplifying section 8 for amplifying a difference between two inputs, one
 input being an output of the welding voltage detecting section 7 or an
 output of the rectifying element 30, the other input being an output of
 the welding voltage setting section 9, wherein an average welding voltage
 VOUT obtained by using the pulse period setting section 13 for setting a
 pulse period, also by using the pulse frequency setting section 11 for
 setting a pulse frequency used for the calculation of a peak current, and
 also by using at least one of the output of the welding voltage detecting
 section 7, the output of the rectifying element 30 and the output of the
 welding voltage setting section 9, a welding voltage VP in the peak period
 from the output of the welding voltage detecting section 7, and a welding
 voltage VB in the base period are detected by the voltage detecting
 section in the peak current calculating section 11 not shown in the
 drawing, and from an output PF of the pulse frequency setting section 11
 for setting a pulse frequency and also from VOUT, VP and VB, the peak
 current is calculated by the calculating section in the peak current
 calculating section 22 not shown so that an average of the pulse frequency
 can not be changed. In this connection, VP and VB may not be given as
 detected values but they may be given as data. Concerning the calculation
 of the peak current, VP and VB may not be used. The peak current may not
 be set by calculation, but it may be set as a data table. A pulse output
 signal corresponding to a welding output is outputted from the pulse
 output setting section 10b into which an output of the error amplifying
 section 8 and an output of the pulse period setting section 13 are
 inputted. Either an output of the peak current calculating section 22 for
 setting a peak current or an output of the base current setting section 15
 for setting a base current is switched by the switching circuit 12
 according to an output of the pulse output setting section 10b.
 FIG. 8 is a diagram showing a waveform of the welding voltage in the case
 where welding is conducted by the consumable electrode type pulse arc
 welding device of the second embodiment. The waveform of the welding
 voltage shown in FIG. 8 shows a welding voltage waveform in the case where
 the setting welding voltage is lowered from a welding condition of one
 pulse and one drop shown in FIG. 11, that is, a welding condition in which
 no short circuit occurs. These views are made on the assumption that the
 welding loads are the same. When it is assumed that the welding loads are
 changed, FIGS. 8 and 11 show a condition in which the pulse frequency of
 the welding voltage waveform is decreased.
 In the case where the setting welding voltage is lowered from the condition
 shown in FIG. 11, it can be understood that the pulse frequency is the
 same as that before setting welding voltage is changed when the pulse
 period is reduced. In this case, the peak current is reduced to be shorter
 than the most appropriate value for one pulse and one drop. Therefore, it
 is impossible to provide a welding condition of one pulse and one drop.
 However, since a melting drop, the quantity of which is constant, is
 formed at a tip of a wire at each pulse, short circuit is caused each time
 the pulse period is ended. Therefore, a constant quantity of a melting
 drop is shifted from the tip of the wire to the base metal. That is, in
 the case where the welding voltage is lowered, a melting drop at the tip
 of the wire is not separated, however, a size of the melting drop which
 has been left at the tip of the wire becomes uniform. Therefore, the
 melting drop is regularly shifted from the tip of the wire to the base
 metal according to the short circuit which occurs after the end of the
 pulse period. Even when the welding voltage is lowered, an average of the
 pulse frequency is not changed. Therefore, a quantity of a melting drop
 which shifted from the tip of the wire to the base metal at each pulse is
 the same as that of the welding condition of one drop and one pulse, that
 is, the welding condition in which the welding voltage is high. Due to the
 foregoing, generation of spatter is suppressed and welding can be
 stabilized. As shown in FIG. 5, the pulse period setting section for
 setting a pulse period can be set according to at least one of the
 quantity of a wire to be fed, the diameter of the wire and the material of
 the wire. Therefore, it is possible to extend a range of setting. As shown
 in FIG. 5, the pulse frequency setting section for setting a pulse
 frequency of the consumable electrode type pulse arc welding device of the
 first and the second invention can be set according to at least one of the
 quantity of a wire to be fed, the diameter of the wire and the material of
 the wire. Therefore, it is possible to extend a range of setting.
 (THIRD EMBODIMENT)
 Referring to FIGS. 3 and 9, the consumable electrode type pulse arc welding
 device to which the method of controlling a pulse output of the third
 invention is applied will be explained below. In this connection, like
 reference characters are used to indicate like parts in the conventional
 structure, the structure of Embodiment 1, the structure of Embodiment 2
 and the structure of this embodiment, and the explanation is omitted here.
 The consumable electrode type pulse arc welding device of the third
 invention includes: a main transformer 4 for supplying electric power to a
 welding load, having an auxiliary coil on the secondary side; a welding
 voltage detecting section 7 for detecting a welding voltage; a rectifying
 element 30 for rectifying an output of the main transformer; a comparing
 section 16 for comparing an output of the welding voltage detecting
 section 7 with an output of the voltage setting section 17, the comparing
 section 16 outputting a melting drop separation predicting signal when the
 output of the welding voltage detecting section 7 exceeds the output of
 the voltage setting section 17; a welding voltage setting section 9 for
 setting a welding voltage; an error amplifying section 8 into which an
 output of the welding voltage detecting section 7 or an output of the
 rectifying element 30 and an output of the welding voltage setting section
 9 are inputted, the error amplifying section 8 amplifying a difference
 between the above two inputs; a pulse frequency calculating section 18 for
 setting a pulse frequency, the pulse frequency calculating section 18
 being inputted with an output of the error amplifying section 8; a pulse
 output setting section 10c into which an output of the comparing section
 16 and an output of the pulse frequency calculating section 18 are
 inputted, the pulse output setting section 10c setting a pulse period when
 an output of the pulse frequency calculating section 18 is used as a pulse
 period starting signal and an output of the comparing section 16 is used
 as a pulse period ending signal; a peak current setting section 14 for
 setting a peak current; a base current setting section 15 for setting a
 base current; and a switching circuit section 12 for selecting either an
 output of the peak current setting section 14 or an output of the base
 current setting section 15 by an output of the pulse output setting
 section 10c.
 FIG. 9 is a view showing a shift of a melting drop and also showing a
 waveform of a welding voltage in the case where welding is conducted by
 the consumable electrode type pulse arc welding device of the third
 invention. In the case shown in FIG. 9, the welding voltage is lowered
 compared with the case shown in FIG. 11. When it is shifted from the base
 period to the pulse period, a melting drop formed at a tip of a wire grows
 from (a) to (b) as shown in FIG. 9. Next, a constricted part is formed in
 the melting drop by an electromagnetic pinching force generated by the
 peak current so that the melting drop can be separated from the tip of the
 wire. Since constant current control is conducted in the pulse period,
 resistance is increased when the constricted part is formed in the melting
 drop. Therefore, the welding voltage is raised. When the rise of the
 welding voltage is compared with a predetermined voltage, it is possible
 to detect a time immediately before the separation of the melting drop
 from the tip of the wire. After that, the pulse period is ended. That is,
 when a constant quantity of melting drop is formed at the tip of the wire,
 the pulse period is ended. Therefore, after the end of the pulse period,
 short circuit is regularly generated, so that the melting drop is shifted
 as shown by (d) in FIG. 9. Due to the foregoing, the melting drop can be
 regularly shifted at each pulse, and a quantity of generated spatter can
 be reduced.
 As shown in FIG. 6, in the consumable electrode type pulse arc welding
 device of the first, the second and the third invention, the base current
 setting section can be set according to at least one of the quantity of
 the wire to be fed, the material of the wire and the diameter of the wire.
 Therefore, the most appropriate value can be set at each of the quantity
 of the wire to be fed, the material of the wire and the diameter of the
 wire. Therefore, a range of setting can be extended.
 As shown in FIG. 6, in the consumable electrode type pulse arc welding
 device of the first, the second and the third invention, the peak current
 setting section can be set according to at least one of the quantity of
 the wire to be fed, the material of the wire and the diameter of the wire.
 Therefore, the most appropriate value can be set at each of the quantity
 of the wire to be fed, the material of the wire and the diameter of the
 wire. Therefore, a range of setting can be extended.
 The method of controlling a pulse output and the consumable electrode type
 pulse arc welding device of the present invention provide the following
 advantages. When the welding voltage is lowered, a size of each melting
 drop can be made uniform and short circuit can be regularly generated by
 shortening a pulse period or reducing a peak current. Due to the
 foregoing, it is possible to suppress the occurrence of spatter. When the
 peak period is ended by predicting the separation of a melting drop from a
 tip of a wire, in the same manner, a size of each melting drop can be made
 uniform and short circuit can be regularly generated.