Electric heating – Metal heating – By arc
Reexamination Certificate
1999-10-08
2001-08-21
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C219S125100, C901S042000
Reexamination Certificate
active
06278082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a welding apparatus, such as an arc welding apparatus for a welding robot system formed of a combination of a teaching playback type robot and a welding power source.
2. Prior Art
A prior art embodiment has a configuration shown in
FIG. 4
, as disclosed in Japanese Laid-open Patent Application No. Hei 9-85443.
First, the robot controller and the welding power source of the prior art embodiment are each provided with an analog command voltage value uniquely determined for a welding current command value, an analog command voltage value uniquely determined for a welding voltage command value and output characteristic curves for uniquely determining the respective values. Referring to
FIG. 4
, a welding current command signal i and a welding voltage command signal v are issued from a robot controller
101
to a welding power source
103
as analog voltage signals on the basis of their output characteristic curves via D/A converters respectively corresponding thereto. The analog command voltages are converted into digital data by the A/D converters of the welding power source
103
, and a welding current command value and a welding voltage command value are obtained on the basis of the output characteristic curves, and taken in the welding condition control portion of the welding power source
103
.
Next, the welding condition control portion carries out control to output an actual welding current and an actual welding voltage corresponding to the welding current command value and the welding voltage command value, respectively. At this time, for the robot, a movement target position is designated by teaching, and whether the target position having been designated by teaching is a welding position or not is determined by teaching. In addition, when the target position is a welding position, welding condition command values are also designated by teaching and stored as data in the memory inside the robot controller
101
.
During robot operation, the welding torch of the robot
5
moves in accordance with the data designated by teaching and stored in the memory. When the welding torch of the robot
5
reaches the predetermined arc welding position, a welding current command voltage and a welding voltage command voltage, which are analog command voltages to be output to the welding power source
103
, are obtained on the basis of the output characteristic curves of the welding current command and the welding voltage command in accordance with the data designated by teaching and stored in the memory. Binary data is then set and written to the buses of the D/A converters so that their desired command voltages are generated.
By this operation, the desired actual welding current and voltage are output to the welding power source
103
.
Furthermore, as disclosed in Japanese Laid-open Patent Application No. Sho 63-119979, another prior art embodiment has a configuration wherein its robot controller must be provided with a hardware device for each condition to be commanded to the welding power source.
However, both the control portion of the robot controller
101
and the control portion of the welding power source
103
are digital circuits mainly composed of microcomputers. At the interface to the above-mentioned welding power source, the welding current and voltage command values, which are digital data, are D/A converted into analog commands, respectively, on the basis of their output characteristic curves, and transmitted from the robot to the welding power source. At the welding power source, the respective analog voltages are A/D converted into digital data on the basis of their output characteristic curves, and welding control is carried out.
Although the two control portions are digital circuits, analog circuits are present as described above, thereby causing conversion errors. This causes a problem wherein the welding current command value and the welding voltage command value transmitted from the robot are different from the welding current command value and the welding voltage command value received by the welding power source.
Furthermore, the prior art embodiment also causes a problem wherein the analog circuits are affected by drift because of changes in environment (temperature in particular) and changes with time.
In addition, in the case when the welding power source
103
or the robot controller
101
becomes faulty and at least one of them is replaced, welding confirmation adjustment comprising welding and condition calling must be carried out, even when the teaching data on the robot side is identical, because the individual analog circuits are slightly different from each other although there is no difference in model. This causes a problem of being unable to resume the operation of the robot welding system promptly.
Accordingly, the present invention is intended to provide a welding apparatus for an automatic welding line using a robot and a welding power source, comprising a digital communication control portion provided for each of the robot controller and the welding power source thereof, wherein welding current and voltage command values, which are digital data, are transmitted from the robot to the welding power source by digital communication, thereby excluding conversion errors because of the existence of the analog circuits of the prior art embodiment.
SUMMARY OF THE INVENTION
The welding apparatus of the present invention is a welding apparatus wherein the robot controller of its teaching playback type robot is combined with the control portion of its welding power source. Each of the control portions of the robot controller and the welding power source is a digital-control type and provided with a digital communication control portion. Welding condition commands including at least a welding current command value are transmitted by using digital (discrete) data through the communication control portions from the robot controller to the control portion of the welding power source.
In accordance with the welding apparatus of the present invention, welding condition commands are transmitted as digital data from the robot controller to the welding power source via the communication control portions. As a result, it is not necessary to use means for converting digital data into analog data, and it is thus possible to attain signal transmission without conversion errors. Therefore, the apparatus is not affected by drift because of the existence of analog circuits, and not affected by individual differences in analog circuits at the time of device replacement. Furthermore, since digital communication is used instead of analog transmission, transmission time can be shortened significantly, and information can be transmitted quickly, whereby prompt welding control can be carried out.
In the above-mentioned apparatus, information on welding speed is transmitted as digital data from the robot controller to the control portion of the welding power source at the start of welding.
In accordance with this configuration, welding control corresponding to three kinds of welding condition commands can be carried out. Therefore, it is not necessary to prepare individual hardware devices, and only the communication control portion is provided for each of the robot controller and the welding power source, whereby the apparatus is excellent in expandability. It is thus possible to provide inexpensive products to users.
REFERENCES:
patent: 4590577 (1986-05-01), Nio et al.
patent: 4616326 (1986-10-01), Meier et al.
patent: 4959523 (1990-09-01), Fihey et al.
patent: 5148000 (1992-09-01), Tews
patent: 5305183 (1994-04-01), Teynor
patent: 5932123 (1999-08-01), Marhofer et al.
patent: 63-119979 (1988-05-01), None
patent: 9-85443 (1997-03-01), None
European Search Report, EP 99 12 0457, dated Feb. 7, 2000.
Matsushita Electric - Industrial Co., Ltd.
Shaw Clifford C.
Stevens Davis Miller & Mosher LLP
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