JPH02142681A - Resistance welding equipment - Google Patents

Abstract

PURPOSE:To perform welding steel plate layers and other materials to be welded with high quality by conducting electricity between the material to be welded by the high pressurizing force at the time of initial preliminary electric conduction of a welding process, melting a resin layer between steel plates by the pressurizing force and heat of electric conduction and carrying out main electric conduction by the low pressurizing force after the steel plate layers being brought into contact with each other. CONSTITUTION:Second material 2 to be welded such as a nut or a bolt is jointed to the long surface of first material 1 to be welded laminated with the plural steel plates via the resin layer. A second electrode 8 which faces a first electrode 7 to come into contact with one side of the two materials to be welded and moves while approaching the first electrode and separating from it and comes into contact with the second material to be welded is set up. The high pressurizing force is applied to the material to be welded at the time of preliminary electric conduction of the welding initial stage by a pressurizing cylinder 11 of the second electrode and electric conduction is carried out thereto. The resin layer in the steel plate layers is molten and destroyed by the pressurizing force and generated heat and the steel plate layers are brought into contact with each other. The pressurizing force is reduced after preliminary electric conduction is finished and simultaneously, main electric conduction is carried out by the first and second electrodes to press the materials to be welded mutually and the steel plate layers and other materials to be welded are welded together. By this method, a welding nugget is uniformized and a welded product with high quality without generating sparks is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to resistance welding in which nuts and bolts are welded to the surface of a laminated plate in which a plurality of steel plates are laminated with an insulating layer interposed therebetween, such as a vibration-damping steel plate. Regarding the device, it is particularly suitable for projection welding.

(Prior Art) For example, vibration-damping steel plates are often used as sheet metal parts of automobiles, such as oil pans, in order to absorb vibration energy and prevent vibration noise from propagating to the outside. This damping steel plate is a laminated steel plate with an insulating resin layer of a viscoelastic polymer material interposed between two steel plates, and is also called a composite steel plate.

When welding bolts, nuts, etc. to the surface of such damping steel plates, resistance welding using Joule heat is used, and conventionally, a welding device as shown in FIG. 6 has been used.

FIG. 6 is a diagram showing a case where a nut 2 is welded to a damping steel plate 1 consisting of upper and lower steel plate layers 1a, an IC, and a resin layer 1b interposed between these. Welding is performed such that the center of the nut 2 is located at the center of the hole 3 formed in the steel plate 1. A protrusion 4 is formed in an annular shape on the lower surface of the nut 2, and the objects to be welded are joined together by passing an electric current through this part and generating resistance heat in a relatively small part, which is generally called projection welding. ing.

As shown in the figure, a lower electrode 7 having a locate pin 6 on its upper surface is attached via an insulator on the support base 5, and an upper electrode 8 is vertically movable toward the lower electrode 7. In order to move the upper electrode 8 up and down, a cylindrical sub-platen 10 is attached to the holding stand 9 so as to be able to move up and down.The upper electrode 8 is fixed to this sub-platen 10 via an insulator, and the holding stand The lower end of the piston rod 12 of the platen driving cylinder 11 attached to the
A spring member 13 for cushioning is located within the sub-platen 10 and between this and the bottom surface of the sub-platen 10.

A current is supplied to each of the picture electrodes 7.8 from a transformer 14, and a control signal from a control section 15 is applied to a cyrisk composed of a plurality of cyrisks.
The signal is sent via the stack 16 to the transformer 14 by a signal line 17. Further, fluid pressure such as air pressure is supplied from the control section 15 to the sub-platen 10 through a hose 18.

(Problem to be Solved by the Invention) In such a conventional resistance welding device, the lower electrode 7
After placing the damping steel plate 1 on top of the bolt and positioning the nut 2 on the locate pin 12, welding is started. Then,
First, the upper electrode 8 moves toward the lower electrode 7, and the two-part electrode 8 presses the nut 2 from its upper surface. A thyristor stack 16 serving as a switching means is activated by a control signal from the control section 15, and a predetermined current flows between the nut 2 and the damping steel plate 1. At this time,
If the thickness of the intermediate resin layer 1b located between the steel plate layer 1a and the IC is thin, the steel plates will come into contact with each other due to the pressurizing force, so that electricity will be supplied. However, if the thickness of the resin layer 1b is relatively thick, It has also been attempted to short-circuit two steel plate layers using another conduction means.

However, in such conventional welding equipment,
Under pressurized conditions, the resin layer 1b is not necessarily destroyed uniformly, and the current is biased in the initially destroyed portion.

Furthermore, when the current begins to flow, the projection 4 portion, that is, the projection portion, begins to soften, and the projection effect itself disappears. For this reason, not only does the molten nugget become non-uniform, but if an excessive current flows without sufficient initial destruction of the intermediate resin layer 1b, sparks are generated, making it impossible to obtain a high-quality product. .

The present invention has been made in view of the above-mentioned prior art, and includes a laminate of vibration-damping steel plates or the like in which a resin layer is laminated between the steel plates;
The purpose is to enable high-quality welding of parts such as nuts and bolts.

(Means for Solving the Problems) To achieve the above object, the present invention includes a first object to be welded, which is formed by laminating a plurality of steel plates with a resin layer interposed therebetween, and a first object, such as a nut or bolt, on the surface of the object. In a resistance welding device for joining two objects to be welded, a first electrode that is in contact with one of the two objects to be welded is opposed to the first electrode, the electrode moves toward and away from the first electrode, and the second electrode is moved toward and away from the first electrode and connected to the other object to be welded. A second electrode is installed in contact with the second electrode, and a pressurizing means for pressurizing the second electrode toward the first electrode is connected to the second electrode, and a high pressurizing force is set during pre-energization and from this during main energization. The pressurizing means is provided with a pressurizing force adjusting means for setting a low pressurizing pressure, and the pre-energizing means contacts the first workpiece during the pre-energizing and electrically connects to the first electrode through this. This is a resistance welding device having an electrode.

(Function) At the time of pre-energization at the initial stage of the welding process, current is applied between one of the welded objects and the electrode in contact with the welded objects, with the objects being welded under strong mutual pressure. As a result, the resin layer in the pressurized portion between the steel plate layers is melted and destroyed by the pressurizing force and the heat generated by energization, and the steel plate layers located on both sides of this portion come into contact with each other. When the pre-energization process is completed in this way, main energization is carried out by the @1 and second electrodes that pressurize the workpieces together while lowering the pressing force, and the steel plate layers are joined to each other. Other objects to be welded are welded.

(Example) Hereinafter, the present invention will be described in detail based on the illustrated example of the present invention. FIG. 1 is a diagram showing a resistance welding device according to an embodiment of the present invention, and members common to those in the conventional projector welding device shown in FIG. 6 are given the same reference numerals. It is.

A lower electrode 7 is attached to the support base 5 via an insulator.
is a first electrode that contacts the damping steel plate 1 as the first object to be welded. Further, the upper electrode 8 attached to the lower surface of the sub-platen 10 serves as a second electrode that contacts the weld nut 2 as the second object to be welded.

A lower electrode 21 for pre-energization is attached to a plurality of insulating receivers fixed to the support stand 5 by means of a stand 20, and the upper surface of the lower electrode 21 is approximately at the same level as the upper surface of the lower electrode 7. It becomes. The lower current-carrying electrode 21 may be formed in an annular shape, and the number of receivers may be rod-shaped corresponding to the number of stands 20. A plurality of cylinders 22 for sub-energization are attached to the lower surface of the holding table 9 through insulators, and upper electrodes 23 for pre-energization are attached to the tips of the piston rods of these cylinders 22. There is. This electrode 23 has a through hole 24 having an inner diameter larger than the diameter of this electrode 8 in order for the electrode 8 to partially penetrate through the center thereof, and the lower surface is in contact with the steel plate layer 1a of the vibration damping steel plate 1. An annular convex portion 25 is formed.

The upper and lower electrodes 21.23 for pre-energization are connected to one terminal 27a of the transformer 14a for sub-energization by a secondary cable 26a and a secondary cable 26b branched from the secondary cable 26a. The terminal 27b and one terminal 28b of the transformer 14b for main energization are connected to the lower electrode 7 by two secondary cables. On the other hand, the other terminal 28a of this transformer 14b is connected to the secondary cable 3.
0 to the upper electrode 8. The operation of these transformers 14a and 14b is controlled by a signal line 17 from the control section 15.
Cyrisk stack 16a, 16b by a, 17b
It is controlled by signals sent to.

In the welding apparatus of the present invention, at the beginning of the welding process, the vibration damping steel plate 1 is connected to the vibration damping steel plate 1 with the respective pre-energizing electrodes 21 and 23 in contact with the steel plate layers 1a and lc of the vibration damping steel plate 1. After applying electricity between the lower electrode 7 and the electrode 21.23 through the vibration damping steel plate 1 and the nut 2, electricity is applied from the upper and lower picture electrodes 8.7.

During pre-energization at the initial stage of welding, an insulator 31 that contacts the lower electrode 21 via the damping steel plate 1 is fixed to the lower surface of the upper electrode 23 .

During the pre-energization, a high pressure is applied to the upper electrode 8,
During the main energization, a lower pressing force than this is applied to the upper electrode 8. This low force value is
The pressure force applied during the entire welding process in the welding apparatus shown in FIG. 6 is approximately the same. In order to change the pressing force between pre-energization and main energization as described above without significantly changing the structure of the sub-platen 10 shown in FIG. An adjusting screw 32 is screwed to the side of the housing 10 .

The lower end surface of this adjustment screw 32 is adapted to abut against the negative wall of the sub-platen 10.

An inlet port 35 formed in the cylinder 11
A high pressure source 37a and a low pressure source 37b are connected to the and outlet port 36 by hoses, respectively, and in order to establish communication between one pressure source and the inside of the cylinder 11, switching valves 38a and 38b are connected. is provided. The operation of these switching valves 38a and 38b is controlled by signals sent from the control section 15 through signal lines 39a and 39b.

When pressurized air from the high pressure source 37a is supplied into the cylinder 11, the lower surface of the adjusting screw 32 comes into direct contact with the sub-platen 10 due to the high pressure applied to the piston rod 12, and the pressure is applied to the piston rod 12. A pressing force is applied to the upper electrode 8 by the force. On the other hand, when pressurized air from the low pressure source 37b is supplied into the cylinder 11, the lower surface of the adjusting screw 32 does not come into contact with the sub-platen 10, and the spring force determined by the spring force of the spring member 13 causes the upper electrode 8 Pressure force will be applied to the The respective pressure sources 37a and 37b can be formed, for example, by providing a pressure regulating valve in a pneumatic path branched from the same pneumatic pump. Furthermore, air pressure is supplied to and discharged from the cylinder 22 for moving the pre-energizing upper electrode 23 downward by a switching valve 40.
An actuation signal from the control section 15 is sent to the switching valve 40 via a signal line 41.

Switching from the pre-energization state to the main energization state is automatically performed depending on the state of destruction of the resin layer 1b of the object to be welded 1. An example of means for controlling the switching is shown in FIG. 2.

A current detector 45 is connected to the secondary cable 26a that connects the upper electrode 23 for pre-energization and the terminal 27a of the transformer 14a to detect the value of the current flowing therein. An interelectrode voltage detector 46 is connected between the secondary cable 26a and the secondary cable 29 in order to detect the potential difference between the electrode 7 and the secondary cable 26a. These detectors 45, 46 are connected to a comparison calculation circuit 47,
Each detection signal is sent to a comparison calculation circuit 47. The comparison calculation circuit 42 sends the calculation result to the control section 15.

When the energization process is completed, a portion of the resin layer 1b in the damping steel plate 1 corresponding to the protrusion 4 of the nut 2 is destroyed in an annular shape. Then, secondary cable 2
Since current begins to flow through 6a, this is detected by the current detector 45, and a change in the current value is determined by the arithmetic circuit 47.
This is sent to the control section 15 as a control signal. Further, the voltage between the lower electrode 7 and the upper electrode 23 for pre-energization is reduced due to a voltage drop in the transformer 14a due to current flowing between them, that is, a self-voltage drop, so that the pre-energization is terminated. This voltage drop can also be detected by the electrode-to-electrode voltage detector 46. in this way,
The pre-energization upper electrode 23 constitutes a part of a device that controls automatic switching from partial energization to main energization.

In the control means shown in FIG. 2, a control signal is sent to the control unit 15 by detecting both of these signals, but control may be performed using either one of the signals.

Furthermore, if conditions such as the thickness of the damping steel plate 1 are determined, the time required for the resin layer 1b to be destroyed by pre-energization is approximately constant, so switching between pre-energization and main energization may be controlled by a timer. You can also do it.

Next, referring to FIGS. 3 and 4, a procedure for welding the damping steel plate 1 and the nut 2 using the resistance welding apparatus of the present invention will be described.

A damping steel plate 1 is placed on the lower electrode 7 and the lower electrode 21 for pre-energization, with the locate pin 6 positioned in the hole formed therein, and the nut 2 is inserted into the locate pin 6.
is positioned and placed on the damping steel plate 1. In this state, pressure from the high pressure source 37a is supplied into the cylinder 11 by operating the switching valve 38a. As a result,
The piston rod 12 presses against the sub-platen 10 via the adjustment screw 32, and the upper electrode 8 is pressurized toward the lower electrode 7 via the nut 2 and the damping steel plate 1.

At the same time, with high pressure being applied to the damping steel plate 1, electricity is applied from the transformer 14a to the lower electrode 7 and the upper and lower electrodes 21 and 23 for pre-energization.

As a result, a current initially flows between the lower electrode 7 and the pre-energization lower electrode 21 via the steel plate layer 1c. By applying pressure to the damping steel plate by the upper electrode 8 along with this energization,
The portion of the steel plate layer IC directly below the protrusion 4 generates heat, and the corresponding portion of the resin layer 1b softens.

Since a high enough pressure is applied to the upper electrode 8 to break the insulation of the softened portion of the resin layer 1b, the lower electrode 7 and the upper electrode for child current 23 are connected to the upper and lower steel plate layers 1a and 1c. The parts are electrically connected, and current flows between them. As a result, the insulation of the resin layer 1b is increasingly destroyed.

The above-mentioned pre-energization state is shown in FIGS. 3(A) and 3(B).

When the pre-energization state described above progresses to a certain extent, the current detector 4
5 indicates that a predetermined current has flowed through the secondary cable 26a, and the interelectrode voltage detector 46 indicates that the pre-energization upper electrode 2
It is detected that the voltage between electrodes 3 and lower electrode 7 has become less than a predetermined value, and a pre-energization end signal is sent from arithmetic circuit 47 to control section 15 . As a result, the two switching valves 38
a and 38b are switched to opposite states, and air at a pressure lower than that at the time of pre-energization is supplied from the low pressure source 37b into the cylinder 11, and at the same time, the switching valve 40
The cylinder 22 is operated, and the upper electrode 23 for pre-energization is activated.
rises. Furthermore, at the same time, transformer 1 for child energization
4a is turned off, the transformer 14b for main energization is turned on, and current is supplied between the upper and lower electrodes 7.8. The state of main energization switched in this way is shown in Figure 4 (A
) (B).

In this state, the lower surface of the adjustment screw 32 is attached to the sub-platen 10.
The spring force of the spring member 13 located between the piston rod 12 and the bottom wall of the sub-platen 10 is applied to the upper electrode 8 . In this state, a current from the transformer 14b flows between the picture electrodes 7.8 through the nut 2, the steel plate layer 1a, and the steel plate layer 1c.
A stable molten zone can be obtained at the portion c.

FIG. 5 is a diagram showing a welding apparatus according to another embodiment of the present invention, and this embodiment is used to weld a bolt to a damping steel plate 1 in place of the nut 2 in the embodiment described above. It embodies. In this case, as shown in FIG. 5, a hole 8a into which the threaded portion 51 of the bolt 50 enters is formed at the lower end of the upper electrode 8.
The head is pointed at the center of the tip. Bolt 5 like this
0 and the damping steel plate 1 are welded in the same manner as in the case of the nut 2 described above.

(Effects of the Invention) As described above, according to the present invention, a first object to be welded having a steel plate layer on both sides of a resin layer and a second object to be welded such as a nut or bolt to be joined thereto are processed. Before energizing the first and second electrodes, the first object to be welded was energized to melt and destroy its resin layer while applying a strong pressure. When the resin layer corresponding to the joint part of the welded object is reliably destroyed and removed, the original current is applied, the molten nugget becomes uniform, there is no generation of sparks, and a high-quality welded product can be obtained. Became.

[Brief explanation of the drawing]

1 is a sectional view including a circuit section showing a resistance welding device according to an embodiment of the present invention; FIG. 2 is a circuit diagram showing a pre-energization end detection means incorporated in the device shown in FIG. 1; Figure 3 (A)
is a cross-sectional view showing the energized state during pre-energization, and FIG. 3 (B
) is an enlarged cross-sectional view of the main part of Fig. 3 (A), Fig. 4 (A) is a cross-sectional view showing the energized state during main energization, and Fig. 4 (B) is an enlarged view of the main part of Fig. 4 (A). 5 is an enlarged sectional view of a main part showing a welding device according to another embodiment of the present invention, and FIG. 6 is a sectional view including a circuit section showing a conventional welding device. 1... Vibration damping steel plate (first object to be welded), 1a, 1c...
Steel plate layer, 2... Nut (second object to be welded), 4... Protrusion, 7... Lower electrode, 8...l partial electrode, 10...
Sub-platen, 11... cylinder (pressurizing means), 21
...lower electrode for pre-energization, 23...upper electrode for pre-energization, 38a, 38b... switching valve (pressure force adjustment means).

Claims (1)

[Claims] In a resistance welding device for joining a first workpiece made of a plurality of steel plates laminated with a resin layer interposed therebetween and a second workpiece such as a nut or bolt on the surface of the first workpiece, the two workpieces are A second electrode that moves toward and away from the first electrode and contacts the other object to be welded is installed opposite to the first electrode that contacts the first electrode, and the second electrode is directed toward the first electrode. A pressurizing means for applying pressure is connected to the second electrode, and the pressurizing means is provided with a pressurizing force adjusting means for setting a high pressurizing force during pre-energization and setting a lower pressurizing force lower than this during main energizing,
A resistance welding device comprising a pre-energization electrode that contacts the first workpiece during the pre-energization and electrically connects to the first electrode through the electrode.