JP3722416B2 - Resistance spot welder and electrode drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode drive device for a resistance spot welder using a servo motor drive as a pressure drive source of an electrode tip in the technical field belonging to a resistance welder .
[0002]
[Prior art]
Portable spot welding guns are used when welding manually-manufactured parts of large workpieces such as railway vehicles and automobile bodies. In general, a large portable spot air gun in which a welding gun and a welding transformer are integrated is used. Because this large gun is heavy, the welding gun and welding transformer are separated, and only the gun body is hung with a hanging bracket to balance the gun weight so that the direction of the portable spot gun can be changed as desired. However, since this type of gun is connected with a heavy low-reactance cable (so-called kickless cable) from the welding transformer, the above-mentioned cable is also manually routed together with the gun, and the operability is poor and the work efficiency can be satisfied. There wasn't.
[0003]
There are known C-type and X-type air guns as portable spot welders. For example, Japanese Patent Laid-Open No. 7-290251 and Japanese Patent Laid-Open No. 7-290251 disclose portable servo spot C guns and X guns using servo motor drive. A spot welding gun and a pressure unit disclosed in Japanese Unexamined Patent Publication No. 2000-94143, Japanese Patent Laid-Open No. 2000-126867 are known.
[0004]
In this type of servo spot welding gun and pressure unit, a motor rotor is disposed on the shaft core of an electric motor, and a screw portion of the motor shaft is inserted in combination with a ball nut fixed to the rotor. One electrode tip is attached to the tip of the motor shaft that meshes with the ball nut, and the other electrode tip opposite to the electrode tip is fixed to the other end of the gun arm fixed to the motor side, The electrode chip is pressurized by the reciprocating motion of the ball screw (see JP-A-7-290251 and JP-A-2000-94143).
[0005]
The other pressurizing unit has a screw portion formed on the motor shaft extending in front of the motor, and a screw portion formed concentrically with the screw portion of the motor shaft and formed on the inner diameter of the pressurizing shaft. The shaft is driven to rotate, and the pressure shaft is linearly driven, whereby a pressing force necessary for welding is supplied between the movable electrode tip and the fixed electrode tip on the gun arm side (see JP-A-2000-126867). .
[0006]
According to this type of conventional device, it is understood that the overall length of the electric spot C gun and the spot X gun is shortened to be light and compact, and the operability is improved.
[0007]
[Problems to be solved by the invention]
However, both the conventional servo spot gun and the pressurizing unit of this type have a motor shaft corresponding to the pressurizing shaft disposed through the shaft center of the electric motor, and seal the rear side of the electric motor from the outside air. Therefore, power can be supplied only from the pressure shaft side (that is, the point holder) extended in front of the electric motor.
[0008]
Therefore, because the shunt is attached to the point holder attached to the tip of the pressure shaft, the space around the electrode, that is, the height of the electrode arm, is restricted, and the problem of workpiece interference during gun insertion cannot be avoided.
[0009]
Also, in the method of driving the nut sleeve type pressure shaft by rotating the motor shaft, the pressure shaft is concentrically overlapped with the screw portion of the motor shaft, so that the diameter of the pressure shaft is increased and the frame case of the electric motor is increased. New design is forced.
[0010]
In addition, according to the prior art, the rotation mechanism for the pressure shaft may be provided inside the pressure shaft and the frame case, or the guide rail of the linear motion bearing may be used for rotation prevention. , Conventional air gun standard parts cannot be shared .
[0011]
【the purpose】
Therefore, the present invention provides an electrode drive device for a resistance spot welder that can be easily transferred to a servo motor drive without changing the standard type of the conventional pneumatic portable spot welding gun as much as possible. provide.
[0012]
[Means for Solving the Problems]
The present invention has been developed to achieve the above object, and the gist of the present invention is that one electrode tip is supported by a pressure rod penetrating the side wall on the head side of the casing, A gun arm having the other corresponding electrode tip is supported on the casing side of the actuator, and the actuator has a ball screw rotated by an electric motor and a ball nut incorporated in the ball screw. the resistance spot welder of the electrode driving unit for generating a torque for pressurizing force required for spot welding between the converted and the electrode tip into a linear movement of the pressure rod through the ball nut and the ball screw a is, the ball screw is respectively supported on the head side and the side wall of the cap side of its ends said casing The pressure rod and the ball screw are arranged so that their axial center lines are eccentric and parallel to each other in the casing, and the pressure rod is integrated with the ball nut via a connector. Thus, when the pressure rod moves in parallel with the ball screw, the pressure rod is prevented from rotating by the connecting portion of the ball nut and the through portion of the side wall. An electrode driving device for a resistance spot welder for driving an electrode tip is provided.
[0013]
In another aspect of the invention, the rear portion of the pressure rod is extended in the longitudinal direction of the pressure rod so as to pass through and protrude from the side wall on the cap side of the casing. An electrode driving device including being connected is provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a conceptual diagram when the driving method of the present invention is applied to a portable pod welding gun.
[0015]
This embodiment shows a C type portable spot welding gun 1 as a representative. The pressure rod passes through the bearings 3 and 4 on the head side and the cap side of the casing 2 and moves forward and backward. One electrode tip 6 is supported at the tip of the pressure rod 5. An arm support bracket 7 is supported integrally or detachably on the casing side.
[0016]
The casing protects sliding parts such as ball bearings, ball screws, and ball nuts from foreign materials such as spatter and dust by closing the cylindrical body (cylinder type) and concave body opening with a cover. As such, it has a sealed structure with the outside air.
[0017]
One end of the C-shaped gun arm 8 is detachably attached to the bracket by a bolt 9 with an insulating plate interposed therebetween. The other electrode tip 10 corresponding to the electrode tip 6 is supported at the tip of the gun arm 8 via a tip holder.
[0018]
The bracket 7 may be integrated with the casing 2 or may be integrated with the gun arm 8. Further, the bracket 7 may be omitted, and the casing 2 and the gun arm 8 may be integrated or detachably assembled.
[0019]
The actuator 11 constitutes one drive unit including a servo motor M for driving the pressure rod 5. The drive unit includes a coupling S on the output shaft Q of the servo motor M. The ball screw 12 is directly connected through the connector. A ball nut 13 is engaged with the ball screw 12 and incorporated.
[0020]
A pulley can be attached to the output shaft Q of the servo motor M and the ball screw 12, and the pulleys can be connected via a power transmission mechanism (not shown) such as a gear, a timing belt, and a chain.
[0021]
In this case, the servo motor M of FIG. 1 is arranged on the side wall 15 on the cap side in a folded form rather than a direct connection type with the ball screw.
[0022]
The ball screw 12 and the pressure rod 5 are disposed in parallel in the casing 2 in a positional relationship in which the axial center lines are decentered , and are provided on the side wall 14 on the head side and the side wall 15 on the cap side. 3 and 4 and bearings 16 and 17, respectively . The pressure rod 5 and the ball nut 13 are integrally connected by a connector 18. When the pressure rod passes through the bearings 3 and 4 and rotates the ball screw 12 by the output of the servo motor M to move in parallel along the ball screw 12, the connecting portion of the ball nut 13 and the side wall are moved. Rotation stop for preventing the rotation applied to the pressure rod is made at the through portion of the ball, and the ball nut 13 moves linearly integrally.
[0023]
The ball screw 12 of the actuator 11 may be configured to change the mounting angle in the circumferential direction around the axial center line of the pressure rod 5.
[0024]
The gun body is suspended by suspension brackets (not shown), and the entire gun can be moved smoothly while balancing the weight of the gun body.
[0025]
A connection terminal 19 for connecting a secondary cable is attached to the rear part of the gun arm 8. One cable terminal of the secondary cable is connected to the gun arm side through this connection terminal. The other cable terminal is connected to the side of the gun arm on the side of the conductive member 20 having a flexibility connected to the rear portion of the pressure rod 5 via an insulating plate or the flat braided wire.
[0026]
If a secondary cable is connected to the secondary cable connecting portion via, for example, a swivel-type universal joint (not shown), the degree of freedom can be further doubled in the movement of the gun body.
[0027]
In this embodiment, a low reactance cable generally known as a water-cooled secondary cable is used as the secondary cable. The cooling water passes through the cooling water flow path flowing in the cable, branches from the connection terminal 19, one passes through the inside of the gun arm 8, and the other passes from the rear part of the pressure rod 5 through the inside of the pressure rod 6 to each electrode tip 6. The cooling water passage 22 is constructed so as to return and circulate at the tip of.
[0028]
That is, the cooling water circulates through the pressure rod 5 in the actuator, the gun arm 8, and the reciprocating water passage formed in each of the electrode chips 6 and 10.
[0029]
The operation of the portable servo spot welding gun of the present invention having such a configuration will be described.
The gun body is operated in a free state by a human and moves to the spot position of the workpiece to adjust the spot angle of the electrode tips 6 and 10. When the position of the welding gun is determined, lock the welding gun and fix it.
[0030]
After the welding gun is locked, when the gun start switch 21 is pressed, the servo motor M is activated, the ball screw 12 is rotated, the ball nut 13 is advanced, and thereby the pressure rod 5 is linearly driven and applied to the electrode tip. When a torque for pressure is applied and a work inserted into the electrode tip 10 is sandwiched and a sufficient pressure is applied, an energization start signal is generated and energization is performed.
[0031]
The welding current flows from the welding transformer through the water-cooled secondary cable to the terminal, the flexible conductive wire 20 (flat knitted conductive wire), the pressure rod 5 and the electrode tip 6, and then through the workpiece to the electrode tip 10 on the gun arm side.
[0032]
The electric current passes through the gun arm 8 and returns from the terminal to the welding transformer via the secondary cable. In this cycle, the welding position of the workpiece is joined by forming a nugget by melting the metal by the temperature of the welded portion sandwiched between the electrode tip 6 and the electrode tip 10 due to the resistance heat generation of the current.
[0033]
When welding at a predetermined position is completed and the welding gun is moved to the next welding position, the actuator 11 is operated so as to be in a free state before welding as described above, so that the orientation and orientation of the welding gun can be controlled at hand. It can be moved easily.
[0034]
In this embodiment, the C type portable spot welding gun has been described. However, the basic idea of the present invention is not limited to these models, and the C type mounted on the robot as well as the X type portable gun. The range of application can be easily expanded to type and X type robot guns.
[0035]
【The invention's effect】
As described above, according to the first or second aspect of the present invention , when a manual work portion of a large workpiece such as a railway vehicle or an automobile body is welded, a conventional electric portable spot gun is used. In contrast to this, power can be supplied from a pressure rod that extends to the rear (cap side) of the casing. The size of the arm is no longer restricted, which eliminates the problem of interference between the welding gun and the workpiece or jig, greatly improves operability, and improves workability and safety .
[0036]
Further, according to the spot welding gun of the first aspect of the present invention , the conventional air drive is possible as much as possible in comparison with the above-mentioned conventional one in which the diameter of the pressure shaft is increased because it overlaps with the screw portion of the motor shaft. without changing the standard form of the formula portable spot welding gun becomes easy transition from the air driven to the servo motor drive, the gun arm, bearings, etc. can be used conventional standard, less accuracy and number of components assembled in simple I'm sorry.
[0037]
In the invention according to claim 1, both ends of the ball screw are supported by side walls on the head side and the cap side of the casing, and the pressure rod is eccentric with respect to the ball screw and parallel to the ball screw. Since the driven through portion that penetrates the side wall on the head side of the casing also serves as a detent mechanism that prevents rotation applied to the pressure rod, the connecting portion formed by the ball nut connecting tool is used in a conventional motor-through type addition. It is possible to provide a detent mechanism between the pressure shaft and the frame case, or to omit the use of an expensive linear guide rail, and the manufacturing cost is also reduced.
[0038]
The invention according to claim 2 makes it possible to circulate the cooling water flowing in the water-cooled secondary cable through the water passage in the pressure rod 5 as in the conventional air gun as well as the gun arm and the electrode tip. The effect is enhanced and deformation of the electrode tip due to high temperature can be suppressed.
[0039]
Further , the invention according to claim 2 is sufficient to obtain the cooling effect of the power feeding shaft in comparison with the motor shaft driven servo spot welding gun which drives the pressure shaft by the rotational driving of the motor shaft as described above. Especially, the piping path such as water cooling hose can be connected from the rear part of the pressure rod extended to the cap side opposite to the head side of the casing (that is, the point holder side) compared with the conventional one, and the piping structure is simple. , Maintenance is also easy.
[0040]
Further , in the invention according to claim 1 or 2, the actuator can be supported on the arm side of the robot or another hanging bracket device, and the electric drive device of the present invention is also applicable to an X gun or other resistance welding machine . The range of use can be expanded.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an overall concept including a cross section of a portable electric pressurizing resistance spot welder in an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Portable servo spot welding gun 2 Casing 3 Bearing 4 Bearing 5 Pressure rod 6 Electrode tip 7 Arm support bracket 8 Gun arm 9 Bolt 10 Electrode tip 11 Actuator 12 Ball screw 13 Ball nut 14 Head side wall 15 Cap side wall 16 Bearing 17 Bearing 18 Connector 19 Connection terminal 20 Flexible conductive member 21 Start switch 22 Cooling water passage

Claims (2)

One electrode tip is supported by a pressure rod penetrating the side wall on the head side of the casing, the gun arm having the other electrode tip corresponding to the electrode tip is supported on the casing side of the actuator, and the actuator is an electric motor in the rotary motion of the rotary driven ball screw and has a ball nut incorporated in the ball screw the electric motor is converted into linear motion of the pressure rod through the ball nut and the ball screw wherein An electrode driving device for a resistance spot welding machine for generating a torque for pressurizing force required for spot welding between electrode tips, wherein both ends of the ball screw are respectively attached to side walls on the head side and cap side of the casing. The pressure rod and the ball screw are supported so that their axial centerlines are eccentric and the And the pressure rod is integrated with the ball nut via a connector so that the pressure rod moves in parallel with the ball screw. An electrode driving device for a resistance spot welder, wherein the pressure rod is prevented from rotating by a connecting portion of the ball nut and a penetrating portion of the side wall to drive the one electrode tip. The rear portion of the pressure rod is extended in the longitudinal direction of the pressure rod and penetrated and protruded from the side wall on the cap side of the casing. The electrode driving device according to claim 1.

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