JP2000176647A - Projection welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the setting state of a nut with an extremely simple structure and to prevent welding defects. SOLUTION: The upper electrode 15 is provided with a lower face 15d which has the outer diameter D1 slightly larger than that of the upper face 2d of a nut 2, and the lower face 15d is brought into contact with the entire upper face 2d of the directly facing nut 2. An electrically conductive collar 17 is mounted around the lower outer circumference of the upper electrode 15. The conductive collar 17 is provided with a lower face 17a which is almost flush with the lower face 15d of the upper electrode 15, and which is abutted on the plural parts 2b to be welded of the inverted nut 2. Insulating materials 16, 18 insulates electrically between the upper electrode 15 and the conductive collar 17. An abnormality detection controller energizes the conductive collar 17 and discriminates the set state of the nut 2 based on the presence/absence of the energization from the conductive collar 17 to the nut 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection welding machine for welding a nut to a work, which detects an abnormal setting such as a reverse setting of the nut and prevents erroneous welding.

[0002]

2. Description of the Related Art Generally, a projection welding machine for welding a nut to a work includes a lower electrode having a guide pin and an upper electrode which can be moved up and down. In this projection welding machine, when welding a nut to a work, first the work is positioned by fitting the work's insertion hole into a guide pin, and then the nut is supplied onto the work by a manual operation or a nut feeder, and the nut is supplied to the work. The nut is set on the work by fitting the hole into the guide pin, and then the upper electrode is lowered, and the welded portion of the nut is pressed against the upper surface of the work by the pressing force of the upper electrode, for a predetermined time between the upper electrode and the lower electrode. A series of steps of energizing are performed, and the welded portion of the nut is melted by energizing and then solidified, thereby welding the nut to the work.

In this type of projection welding machine, the nut is set in the correct position on the work with the nut facing forward, that is, the welded part is located on the work side and the nut hole is fitted on the guide pin. If the nut is set, normal welding is performed. However, for some reason, if the nut is set to the correct position on the work in the opposite direction, or if the nut is set to the wrong position on the work while the nut is in the correct direction, poor welding strength such as insufficient welding strength is caused. Will be.

Therefore, various measures have been taken to prevent such poor welding, and related prior arts are disclosed in Japanese Utility Model Publication No. Sho 56-14945, Japanese Utility Model Publication No. Sho 59-175490, and Fairness 3-24299
Gazette, Japanese Utility Model Publication No. 60-39172, Japanese Utility Model Publication 7-4
No. 1582, Japanese Unexamined Patent Publication No. 7-299571 and the like are known.

[0005] These prior arts are roughly classified into two types. One type is such that an insulating cover is provided around the outer periphery of an upper electrode and a nut or the like abuts on a protruding lower end surface of the insulating cover. It is configured to detect the forward or reverse direction of the nut depending on the presence or absence of the nut.Other types use the difference in height between the normal posture and abnormal posture of the nut as the difference in the stroke of the upper electrode. It is configured to detect the set state of the nut by replacing.

[0006]

However, in either type of prior art, this type of welding employs a structure in which the lower end surface of the insulating cover protrudes below the lower end surface of the upper electrode. The electrode surface cannot be polished while the insulating cover is attached to the upper electrode during the work of repairing the electrode surface that is required regularly or irregularly. A complicated operation is required after polishing the surface and then attaching the insulating cover to the upper electrode again.

Further, the insulating cover itself is worn when the nut in the abnormal posture is pressed, so that the insulating cover needs to be replaced.

Further, in the method of detecting the setting state of the nut based on the difference in the stroke of the upper electrode, the mechanism for ensuring the detection accuracy becomes more complicated as the stroke difference becomes smaller. Since the detection reference position sometimes changes, it is necessary to reset the detection reference position.

Further, in a projection welding machine, cooling water is usually circulated in the electrode in order to suppress an increase in the temperature of the electrode due to Joule heat, and cooling in the upper electrode is performed as shown in FIG. A water injection pipe 80 is inserted into the cooling hole 15f at the upper center of the upper electrode 15, and cooling water is injected from the water injection pipe 80 into the cooling hole 15f.
This is performed by discharging the cooling water through 5f.
During the circulation of the cooling water, if there is a slight distortion or a difference in shape at the fitting portion between the upper electrode holder 14 and the upper electrode 15,
The cooling water flows to the outer peripheral surface of the upper electrode 15 through the minute gap, and this water leak propagates along the outer peripheral surface of the upper electrode 15, and the lower surface 15 d of the upper electrode 15, the insulating member 16 and the lower surface 17 a of the conductive collar 17 are provided. A water drop 40 as shown by a two-dot chain line in FIG. When such water droplets 40 are formed, the conductive state is established between the upper electrode 15 and the conductive collar 17 irrespective of the presence of the insulating member 16, and the welded portion 2 b of the reverse nut 2 is connected to the conductive collar 17. 17 is welded.

[0010] Such a problem is caused by the fact that light oil for processing or the like, which often adheres to the surface of a work or a nut, adheres to and accumulates on the lower end surface of the upper electrode due to repeated projection welding. It also becomes a deposit 41 as shown by a two-dot chain line, and also occurs when the upper electrode 15 and the conductive collar 17 are brought into conduction.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and is mainly a projection welding machine capable of accurately detecting the setting state of a nut by a simple structure and preventing poor welding. The purpose is to provide.

[0012]

In order to achieve the above object, a projection welding machine according to the present invention comprises a plurality of workpieces extending obliquely outward from the vicinity of the outer periphery of the lower end of a nut body on the upper surface of a work. What is claimed is: 1. A projection welding machine for welding a nut to a workpiece by welding a welding portion, comprising: a lower surface having an outer diameter slightly larger than an outer diameter of an upper surface of the nut; An upper electrode that is abutted, and a conductive collar that is wrapped around a lower periphery of the upper electrode, the lower surface being substantially flush with the lower surface of the upper electrode, and the plurality of inverted nuts on the lower surface. A conductive collar with which the welded part is in contact, an insulating material for electrically insulating the upper electrode and the conductive collar, and applying a minute voltage to the conductive collar, and applying a small voltage from the conductive collar to the nut. Whether there is continuity Zui and characterized in that it comprises a abnormality detecting controller for determining the set state of the nut.

Here, a conductive ring is detachably mounted around the outer periphery of the conductive collar, and a lead wire of the abnormality detection controller is connected to the conductive ring.

Preferably, when the abnormality detection controller detects an abnormality, the upper electrode is held under pressure.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall configuration diagram of a projection welding machine according to one embodiment. In this projection welding machine 1, a nut 2 shown in FIG.
Etc.). The nut 2 includes a nut body 2a and a plurality of welded parts 2b extending obliquely outward from near the outer periphery of the lower end of the nut body 2a. The nut body 2a has a nut hole 2c. .

In FIG. 1, the main body 10 of the welding machine has a substantially C-shaped side surface as shown by a two-dot chain line. The upper electrode pressurizing solenoid valve 11 is disposed on the upper surface of the welding machine main body 10 and is a component of the pneumatic system. The upper electrode pressurizing cylinder 12 is provided on the upper protruding portion 10 a of the welding machine main body 10, and is controlled by the upper electrode pressurizing solenoid valve 11. The upper electrode unit 13 is supported by the upper electrode pressurizing cylinder 12 so as to be able to move up and down.

The upper electrode section 13 holds an upper electrode holder 14. The upper electrode 15 is, as shown in FIG.
It is detachably taperedly fitted to the lower part of the upper electrode holder 14.

As shown in FIG. 2, the upper electrode 15 has a large-diameter portion 15a at an upper portion and a small-diameter portion 15b at a lower portion. Outer diameter D ₁ of the small diameter portion 15b is set slightly larger than the outer diameter D ₃ of the upper surface 2d of the nut 2 shown in FIG. The small diameter portion 15b has a guide pin escape hole 1
5c. The outer peripheral surface of the small diameter portion 15b is covered with a heat-resistant insulating thin film 16.

The conductive collar 17 is pressed into the outer periphery of the heat-resistant insulating thin film 16. The conductive collar 17 includes the upper electrode 15
It is formed of a metal material having a higher hardness than that of the metal material. The conductive collar 17 may have any shape of a tubular body or a slotted tubular body. The conductive collar 17 has a lower surface 17a substantially flush with the lower surface 15d of the small diameter portion 15b.
The thickness of the conductive collar 17 t is set from the outer diameter D ₂ of the weld portion 2b of the nut 2 to the larger dimensions than half the numerical value obtained by subtracting the outer diameter D ₃ of the nut top surface 2d.

The insulating ring 18 is inserted between the upper surface 17a of the conductive collar 17 and the lower surface 15e of the large diameter portion 15a. The insulating ring 18 may be made of a single material or a heat-resistant insulating thin film coated on the upper end surface of the conductive collar 17.

As described above, the conductive collar 17 is electrically insulated from the upper electrode 15 by the insulating material including the heat-resistant insulating thin film 16 and the insulating ring 18, and is installed around the lower periphery of the upper electrode 15.

The conductive ring 19 is fitted around the outer periphery of the conductive collar 17. The outer periphery of the conductive collar 17 is tightened by spring elasticity so that the conductive ring 19 does not fall off the conductive collar 17 due to vibration or the like when the upper electrode 15 moves up and down.

The lower electrode portion 20 is disposed on the lower protruding portion 10b of the welding machine body 10. The lower electrode 21 is held by the lower electrode unit 20. As shown in FIG. 2 and the like, the lower electrode 21 includes a guide pin 22 as a positioning pin for the work 3 and the nut 2. The guide pin 22 can be moved up and down by a spring (not shown) provided inside the lower electrode 21 or air pressure.

The electric system of the projection welding machine 1 having the above configuration is configured as shown in FIGS.

1 and 10, one end of the lead wire 23 is joined to the conductive ring 19 on the upper electrode 15 side as shown in FIG. One end of the other lead wire 24 is joined to the lower electrode 21 as shown in FIG.
The other ends of these lead wires 23 and 24 are connected to an abnormality detection controller 25. The foot switch 26
It is electrically connected to the abnormality detection controller 25 via the signal line 27. The abnormality detection controller 25 is connected to the power supply 2
8 is connected. The welding machine timer 29 is connected to the power supply 28 and to the abnormality detection controller 25 via signal lines 30a and 30b. The upper electrode pressurizing solenoid valve 11 is connected to an abnormality detection controller 25 via a signal line 31. The abnormality detection controller 25 includes a reset button 32, an abnormality lamp 33, an abnormality buzzer 34, an upper electrode pressure holding switch 35, and an upper electrode lowering switch 3.
6 is provided.

When the nut 2 is supplied onto the work 3 by manual operation, the electric system is configured as described above. On the other hand, when the nut 2 is automatically supplied onto the work 3 by a nut feeder (not shown), the electric system is controlled by the nut feeder as shown by a two-dot chain line in FIG. The power supply 28 is connected to the panel 37 and the signal line 3
The control panel 37 is electrically connected to the abnormality detection controller 25 via the control line 8 and the control panel 3 is connected via the signal line 39.
7 is electrically connected to a welding machine timer 29.

Hereinafter, the nut 2 set on the work 3
With reference to FIGS. 2 to 8, the operation of the projection welding machine 1 will be described.

The set state is roughly divided into a set normal state and a set abnormal state.

Normal state of setting The normal state of setting is, as shown in FIG. 2 and FIG. 3, a state in which the nut 2 is oriented in the normal direction and the correct position on the work 3 (the nut position when the nut hole 2c is fitted on the guide pin 22). ). FIG. 2 corresponds to a state where the upper electrode 15 is at the upper end position, and FIG.
Is lowered from the state shown in FIG.
Corresponds to a state where the pressure reaches the position where the pressure is applied to the work upper surface 3a.

Set Abnormal State There are various set abnormal states as shown in FIGS. 4 to 8 in the set abnormal state.

The abnormal setting state shown in FIG. 4 is a posture state of the nut 2 in which the nut 2 is fitted in the guide pin 22 in the reverse direction. Hereinafter, this abnormal setting state is referred to as the nut reverse normal position state.

The abnormal setting state shown in FIG. 5 is a posture state of the nut 2 which is in the normal direction but is not fitted on the guide pin 22 and comes into contact with the upper electrode 15 when the upper electrode 15 is lowered. Hereinafter, it is referred to as a nut incorrectly positioned incorrectly position.

The abnormal setting state shown in FIG. 6 indicates that the nut 2 has not been supplied onto the work 3 or that the nut 2 has not been supplied.
Is set at a position relatively far away from the guide pin 22, so that the upper electrode 15 and the work 3 come into contact with each other when the upper electrode 15 descends. Hereinafter, the nut is absent.

The abnormal setting state shown in FIG. 7 is a state in which the nut 2 comes into contact with the upper electrode 15 in a state where the nut 2 is in the opposite direction and is not fitted to the guide pin 22. It is called an incorrect position state.

The set abnormal state shown in FIG. 8 is not strictly an abnormal set of the nut 2, but the upper electrode 1
This is a state in which the upper electrode 15 and the nut 2 come into contact with each other in a state where the water droplets 40 or the deposits 41 adhere to the lower surface 15d of the lower electrode 5, and will be hereinafter referred to as an electrode abnormal state.

Next, the operation of the projection welding machine 1 will be described in order based on the flowchart shown in FIG. In FIG. 12, steps S1 to S5 represent the contents of the operation when the nut 2 is manually supplied to supply the nut 2 to the work 3, and steps S6 to S10 are the steps in which the nut 2 is supplied to the work 3 by the nut feeder. The operation contents at the time of automatic supply of the nut to be supplied above are shown.
Steps S11 to S25 represent common operation contents during nut manual supply and automatic nut supply.

(1) Before Starting Operation Before starting the operation shown in FIG. 12, the upper electrode 15 is waiting at the upper end position, and the guide pin 22 of the lower electrode 21 is moved upward by a spring or air pressure. It is in a protruding state.

(2) a Operation at the time of manually supplying the nut In the above state, first, the work 3 is set on the guide pin 22 of the lower electrode 21 (S1).

Next, a nut is manually set to fit the nut 2 in a forward direction on the guide pin 22 on which the work 3 is set (S2). By the nut manual supply, the setting state of the nut 2 becomes one of the normal setting state and the abnormal setting state. When the nut 2 is set in the setting normal state by the manual supply of the nut, the nut welded portion 2b slightly floats from the work upper surface 3a (see FIG. 2).

Thereafter, the foot switch 26 (start switch) is turned on (S3).

The ON signal of the foot switch 26 is transmitted to the signal line 27, the abnormality detection controller 25, and the signal line 30a.
Is transmitted to the welding machine timer 29, and the welding machine timer 29 is turned on (S4). This welding machine timer 29
Signal line 30b, abnormality detection controller 25, and signal line 3
An upper electrode pressurizing signal is transmitted to the upper electrode pressurizing solenoid valve 11 via the first electrode switch 1, and the position of the upper electrode pressurizing solenoid valve 11 is switched by the upper electrode pressurizing signal. 13 is lowered, and the upper electrode 15 starts lowering (S5). Note that the upper electrode 15 that has started to descend can be raised when the foot switch 26 is turned off during the initial pressurization period T ₁ (see FIG. 13).
Initial pressurization period T ₁ after the foot switch 26 OF
It is controlled not to rise immediately even if F.

(2) b Operation during Automatic Nut Supply On the other hand, during automatic nut supply, the foot switch 26 is turned ON after the work set (S6) (S7).

The ON signal of the foot switch 26 is transmitted to the control panel 37 of the nut feeder via the signal line 27, the abnormality detection controller 25, and the signal line 38, and the control panel 37 transmits a nut supply start signal to the nut feeder. Then, the nut feeder feeds one nut 2 toward the work upper surface 3a so as to be fitted to the guide pin 22 in the state of one nut (S8). By the automatic nut supply, the setting state of the nut 2 becomes either the normal setting state or the abnormal setting state, as in the manual supply of the nut.

Thereafter, when a nut supply completion signal is transmitted from the control panel 37 to the welding machine timer 29 via the signal line 39, the welding machine timer 29 is turned on (S9). The welding machine timer 29 transmits an upper electrode pressurizing signal to the upper electrode pressurizing solenoid valve 11 in the same manner as when the nut is manually supplied, and the upper electrode 1
5 is started to descend (S10).

(3) Conduction detection (detection of abnormality) during initial pressurization period T ₁ After the start of lowering of the upper electrode 15 as described above, the abnormality detection controller 25 continuously applies a voltage between the lead wires 23 and 24. And a continuity detection circuit 25a provided at the input of the abnormality detection controller 25 as shown in FIG.
To detect the presence or absence of conduction between the lead wires 23 and 24, and the conduction detection circuit 25a detects
When continuity between the four is detected, a continuity detection signal is output from the continuity detection circuit 25a (S11). In other words, after the lowering of the upper electrode 15 starts, the conduction detecting circuit 25a
Determines whether the setting state of the nut 2 is the normal setting state or the abnormal setting state. In addition, based on the determination result, as described later, the upper electrode 15 and the lower electrode 2
Subsequent operations, such as passing a welding current between the two or sounding the abnormal buzzer 34 without passing the welding current, are determined.

When the setting state of the nut 2 is the normal setting state (FIG. 2), the conduction detecting circuit 25a causes the upper electrode 15 to come into contact with the conductive collar 17 as shown in FIG. Without contact, the nut comes into contact with only the upper surface 2d, and the gap between the lead wires 23 and 24 is kept in a cutoff state. Therefore, the conduction detection circuit 25a keeps the open state and does not output an abnormality detection signal. Thus, when the setting state of the nut 2 is the normal setting state, the conduction detection circuit 25a determines that the normal setting state is set.

When the nut 2 is set in the nut reverse normal position (FIG. 4), the upper electrode 15 descends so that the conductive collar 17 comes into contact with the nut welded portion 2b. From the lead wire 23 to the lower electrode 2 through the conductive ring 19, the conductive collar 17, the nut welded portion 2b, the nut upper surface 2d, the work 3, and the lower electrode 21.
A closed circuit reaching the lead wire 24 on the first side is generated, the conduction detection circuit 25a is closed, and the conduction detection circuit 25a outputs an abnormality detection signal. Thus, nut 2
When the set state is the nut reverse normal position state, the conduction detection circuit 25a determines that the set is abnormal.

When the nut 2 is set in the incorrect nut orientation position (FIG. 5), the lowering of the upper electrode 15 causes the conductive collar 17 to come into contact with the upper surface 2d of the nut. From the wire 23, through the conductive ring 19, the conductive collar 17, the nut upper surface 2d, the nut welded portion 2b, the work 3, and the lower electrode 21, the lower electrode 21
A closed circuit leading to the side lead 24 is generated. Therefore, as in the above, the conduction detection circuit 25a outputs an abnormality detection signal, and determines that the set is abnormal.

When the setting state of the nut 2 is the state where the nut is not present (FIG. 6), the upper electrode 15 comes into contact with the upper surface 3a of the work due to the lowering of the upper electrode 15.
A closed circuit is generated from the lead wire 23 on the upper electrode 15 side to the lead wire 24 on the lower electrode 21 side through the conductive ring 19, the conductive collar 17, the work 3, and the lower electrode 21. Therefore, as in the above, the conduction detection circuit 25a outputs an abnormality detection signal, and determines that the set is abnormal.

Also, when the nut 2 is set in the nut reverse incorrect position (FIG. 7), the upper electrode 15 descends so that the upper electrode 15 does not come into contact with the conductive collar 17 and only the nut welded portion 2b. As a result, the conduction detection circuit 25a keeps the open state and does not output the abnormality detection signal. Therefore, such an incorrect nut reverse orientation state is normally a set abnormal state, but the conduction detection circuit 25a
Is erroneously determined to be in the set normal state. In addition, in order to prevent the outflow of defective products after welding due to the erroneous determination, as described later, the operator is notified of the setting abnormality by the sounding of the abnormal buzzer 34 or the like after welding.

In a strict sense, it cannot be said that the nut 2 is in the set state, but when the electrode is in an abnormal state (FIG. 8), the upper electrode 15 is lowered to lower the upper surface 2d of the nut.
Lead wires 23 on the upper electrode 15 side
Then, a closed circuit is generated which reaches the lead wire 24 on the lower electrode 21 side through the conductive ring 19, the conductive collar 17, the water droplet 40 or the attached matter 41, the nut 2, the work 3, and the lower electrode 21. Therefore, as in the above, the conduction detection circuit 25a outputs an abnormality detection signal, and determines that the set is abnormal. However, when the water droplets 40 or the deposits 41 are small enough not to affect the welding quality (hereinafter referred to as a pseudo abnormal state), the set abnormal state is not determined as described above, and the set normal state is not performed. It is more preferable to make the following judgment and perform the subsequent welding. Therefore, as indicated by a two-dot chain line in FIG. 11, the resistance Rf is connected in parallel to the conduction detection circuit 25a.
And the conduction detection circuit 25a in the pseudo abnormal state.
Is configured to be smaller than a threshold value serving as a reference of the output of the abnormality detection signal. With such a configuration, the continuity detecting circuit 25 can be operated in a pseudo abnormal state.
a does not output an abnormality detection signal, and can determine that the set is normal.

[0053] As described above, conduction detection circuit 25a, in the initial pressurization period T _1, to detect the presence or absence of conduction between the leads 23 and 24, the set state of the nut 2 is set normal state (abnormality detection signal It is determined whether the state is not output (corresponding to a case where an abnormality detection signal is output) or a set abnormal state. Hereinafter, the subsequent operation will be roughly described when it is determined that the set is normal and when it is determined that the set is abnormal.

(4) a Operation when an abnormality detection signal is not output within the initial pressurizing period T ₁ and it is determined that the set is in the normal state. The abnormality detection controller 25 applies a welding current between the upper electrode 15 and the lower electrode 21. Then, the nut 2 is welded for a predetermined welding time (S12).

Then, until the welding machine timer 29 is up, the presence or absence of conduction between the lead wires 23 and 24 is detected (S14).

When the abnormality detection signal is not output from the conduction detection circuit 25a due to the normal setting state as shown in FIGS. 2 and 3, the welding machine timer 29 sets the predetermined upper electrode pressurizing time T ₂ (see FIG. 13). Has passed, that is,
When the welding machine timer 29 is up, the transmission of the upper electrode pressurizing signal to the upper electrode pressurizing solenoid valve 11 is stopped, whereby the upper electrode 15 starts to rise (S1).
5). Although FIG. 12 shows that the conduction detection (S14) is performed after the welding machine timer is up (S13), this is for the sake of convenience to avoid complication of the flowchart. Then, the foot switch 26
Is turned off, and the work 3 to which the nut 2 is welded is unloaded (S25).

On the other hand, in the conduction detection (S14), FIG.
In the case where the nut is in the wrong reverse orientation as shown in FIG. 5, the welding current melts the nut welded portion 2b, so that the conductive ring 19, the conductive collar 17, the nut 2, and the work are connected from the lead wire 23 on the upper electrode 15 side. 3. A closed circuit is generated through the lower electrode 21 to the lead wire 24 on the lower electrode 21 side, and an abnormality detection signal is output from the conduction detection circuit 25a. In such a case, the operation described below (S16)
Then, the abnormal buzzer 34 sounds and the setting abnormal state is notified to the operator.

[0058] (4) When the abnormality detection signal from the operation conduction detection circuit 25a when the abnormality detection signal to the b initial pressurization period T ₁ is determined to set the abnormal state is output is output,
Check if upper electrode pressure holding switch 35 is ON
The following different operations are performed depending on whether or not the operation has been performed (S14).

The upper electrode pressure holding switch 35 is turned off.
If so, the welding machine timer 29 is turned off and the abnormal lamp 33 and the abnormal buzzer 34 are turned on in response to the abnormality detection signal from the conduction detection circuit 25a (S17). This welding machine timer 29
Is switched to OFF, the welding machine timer 29
Stops transmitting the upper electrode pressurizing signal, and the upper electrode 15 starts to rise (S18). And this abnormal lamp 33
Is turned on and the abnormal buzzer 34 sounds, the operator can know the setting abnormality.

Thereafter, the operator turns the foot switch 26 to the O position.
FF is performed, and the reset button 32 is turned ON. By turning on the reset button 32, the abnormal lamp 33 and the abnormal buzzer 34 are turned off (S19). Then, the operator unloads the nut 2 having the abnormal setting (S2).
5).

When the upper electrode pressing and holding switch 35 is ON, the abnormality detection controller 25 turns on the upper electrode pressing and holding signal and sends the upper electrode pressing and holding signal to the upper electrode pressing solenoid valve 1.
1 (S20). Further, the welding machine timer 29 is turned off, and the abnormal lamp 33 and the abnormal buzzer 3 are turned off.
4 is turned on (S21). Therefore, the switching of the welding machine timer 29 to OFF stops the transmission of the upper electrode pressurization signal, but instead transmits the upper electrode pressurization holding signal. Will continue. Thereafter, the operator turns off the foot switch 26 and turns the reset button 32
N. When the reset button 32 is turned on, the abnormal buzzer 34 is turned off (S22). Then, the operator turns on the reset button 32 again. When the reset button 32 is turned on, the abnormal lamp 33 is turned off and the transmission of the upper electrode pressure holding signal is stopped (S2).
3). By stopping the transmission of the upper electrode pressure holding signal, the upper electrode 15 starts to rise (S24). Then, the operator unloads the nut 2 having the abnormal setting (S2).
5). 13 to 17 show timing charts for more specifically explaining the operation of the projection welding machine 1 as described above.

FIG. 13 shows a timing chart when the setting state of the nut 2 is the normal setting state (FIGS. 2 and 3). In the case of this set normal state, the initial pressurizing period T
_{When 1} has elapsed, a welding current flows, and the nut 2 is welded to the work 3. Then, the upper electrode 15 when the upper electrode pressurization period T ₂ has elapsed starts rising. Note that FIG.
The timing chart shown in FIG. 7 corresponds to the case where the upper electrode pressure holding switch 35 is OFF, but the same content applies when the upper electrode pressure holding switch 35 is ON.

FIG. 14 shows an abnormal setting state of the nut 2 as shown in FIGS. 4, 5 and 6.
Also, a timing chart when the upper electrode pressure holding switch 35 is in the OFF state is shown. In this case, the conduction between the leads 23 and 24 to the initial pressurization period T ₁ are detected, the upper electrode 15 starts rising and, abnormality lamp 33 and abnormality buzzer 34 the operator is turned ON Set abnormalities can be known.

FIG. 15 shows an abnormal setting state of the nut 2 as shown in FIGS. 4, 5 and 6.
Further, a timing chart when the upper electrode pressure holding switch 35 is in an ON state is shown. In this case, the conduction between the leads 23 and 24 to the initial pressurization period T ₁ is detected, set the abnormality lamp 33 and abnormality buzzer 34 abnormality is informed to the operator. Further, when the conduction between the lead wires 23 and 24 is detected, the upper electrode 15 is held under pressure without starting to rise, and starts to rise by the second abnormal reset, so that the operator sets the abnormal state of the set. You can actually see it. Therefore, holding the upper electrode 15 under pressure as described above is an effective means for quality control.

FIG. 16 shows the setting state of the nut 2 in FIG.
4 shows a timing chart when the set is in an abnormal state as shown in FIG. 5 and the upper electrode pressure holding switch 35 is in the OFF state. In this case, during welding, the lead wire 23,
Be sensed conduction between 24, the upper electrode 15 is not increased dwell, retention pressurization period T ₂ begins to rise from the time that has elapsed. Then, the operator can know the setting abnormality by the abnormal lamp 33 and the abnormal buzzer 34, and can prevent the outflow of defective welding products.

FIG. 17 shows the setting state of the nut 2 in FIG.
4 is a timing chart when the set is in an abnormal state as shown in FIG. 1 and the upper electrode pressure holding switch 35 is in the ON state. In this case, the upper electrode 15 is pressed and held by the upper electrode pressure holding signal even after the initial pressurizing period T ₁ has elapsed, and starts rising by the second abnormal reset. Therefore, as in the case of the setting abnormality shown in FIG. 15 described above, the operator can actually visually check the setting abnormality state.

FIGS. 13 to 17 described above show the operation in the case of supplying nuts manually by manually supplying the nuts 2. In the case of automatic supply of nuts, the start switch 26 is turned on. Then, the nut feeder is activated, and the welding machine timer 29 is turned on when the nut feeder has finished supplying one nut. The subsequent operation is the same as in the case of manually supplying the nut.

When the electrode surface is worn out and flatness is lost due to repeated welding, it is necessary to modify the electrode surface.

The operation for modifying the electrode surface will be described below.

First, the spring-like conductive ring 19 fitted on the outer periphery of the conductive collar 17 is removed, and the upper electrode 15 is removed from the upper electrode holder 14. Then, the upper electrode 15 is fastened to a chuck such as a lathe, and the lower surface 15d of the upper electrode 15 and the lower surface 17a of the conductive collar 17 are simultaneously cut to recover the flatness.

The grinding of the electrode surface can be repeatedly performed up to the vicinity of the set position of the conductive ring 19.

Then, after such electrode surface modification, the upper electrode 15 is attached to the upper electrode holder 14, and furthermore, the conductive ring 19 is attached to the conduction collar 17, and the operation is completed.

Thereafter, the operation of the abnormality detection controller 25 is confirmed. This operation check method is performed as follows.

First, after setting the work 3, the nut 2
Is set on the guide pin 22 in the forward direction. Then, the upper electrode lowering switch 36 is manually turned on. When the upper electrode lowering switch 36 is turned on, the abnormality detection controller 25 transmits an upper electrode lowering signal to the upper electrode pressurizing solenoid valve 11, and the upper electrode 15 starts lowering. Then, the operator confirms that the abnormality lamp 33 does not turn on due to the lowering of the upper electrode 15, thereby confirming that the abnormality detection controller 25 has correctly determined the normal setting state. During the checking operation, the welding machine timer 29 is disconnected and the welding current is not supplied. FIG. 18 shows the contents of the checking operation when the nut 2 is set in the normal setting state.

Next, the nut 2 is set on the guide pin 22 in the opposite direction. Then, as in the case of confirming the determination of the set normal state described above, the upper electrode lowering switch 36
Is turned on manually, and the upper electrode 15 is lowered. And
The operator confirms that the abnormal lamp 33 has been turned on by the lowering of the upper electrode 15, thereby confirming that the abnormality detection controller 25 has correctly determined the set abnormal state. FIG. 19 shows the contents of the checking operation when the nut 2 is set in an abnormal setting state.

[0076]

According to the projection welding machine of the present invention, an upper electrode having a lower surface having an outer diameter slightly larger than the outer diameter of the upper surface of the nut, and the entire upper surface of the nut facing the lower surface, A conductive collar that is mounted around the lower periphery of the upper electrode, has a lower surface substantially flush with the lower surface of the upper electrode, and has a lower surface to which a plurality of nut-welded portions of an inverted nut are abutted. An insulating material that electrically insulates between the upper electrode and the conductive collar, and an abnormality detection controller that supplies current to the conductive collar and determines a setting state of the nut based on whether or not power is supplied to the nut from the conductive collar. It is characterized by having.

According to the present invention, when the nut is set in the normal setting state, since the conductive collar does not come into contact with the nut, it is confirmed that there is no electricity from the conductive collar to the nut. The normal setting state of the nut can be correctly determined. On the other hand, if the nut is set in an abnormal setting state, the conductive collar comes into contact with the nut, so that it is confirmed that the conductive collar is energized to the nut, thereby correctly determining the abnormal setting state of the nut. Will be able to do it. Therefore,
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to detect the setting state of a nut accurately by a very simple structure, and to prevent poor welding.

Further, a conductive ring is removably mounted around the outer periphery of the conductive collar, and the lead of the abnormality detection controller is connected to the conductive ring. This allows
When repairing the worn electrode surface, by removing the conductive ring, only the upper electrode and the conductive collar can be set on a lathe, etc., so that the lower surface of the upper electrode and the lower surface of the conductive collar can be ground simultaneously. become.

When the abnormality detection controller detects an abnormality, the upper electrode is configured to be held under pressure. This allows the operator to visually confirm the abnormal set condition, which is an effective means for performing quality control.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a projection welding machine according to an embodiment of the present invention.

FIG. 2 shows a projection welding machine shown in FIG.
FIG. 5 is a partial cross-sectional view of a main part when an upper electrode is at an upper end position when a nut is set in a normal position on a work in a normal direction (when setting is normal).

FIG. 3 is a partial cross-sectional view of a main part when the upper electrode is lowered from the state shown in FIG. 2 and reaches a position where the welded portion of the nut is pressed against the upper surface of the work.

[Fig. 4] When the nut is set in the normal position on the work in the opposite direction (when setting is abnormal or the nut is set in the reverse normal position).
FIG. 7 is a partial cross-sectional view of the main part when the upper electrode is lowered to reach a position where the upper electrode comes into contact with the welded portion of the nut.

FIG. 5: When the nut is set to an incorrect position on the work with the nut facing forward (when setting is abnormal or when the nut is misoriented), the upper electrode descends and reaches a position where it contacts the upper surface of the nut. It is a fragmentary sectional view of the principal part of.

FIG. 6 is a partial cross-sectional view of a main part when an upper electrode is lowered to reach a position where the upper electrode is brought into contact with a workpiece when a nut is not present on the workpiece (when setting is abnormal or when the nut is absent).

FIG. 7: When the nut is set in an incorrect position on the workpiece in the opposite direction (when the setting is abnormal or the nut is set in the incorrect reverse position), the upper electrode is lowered to reach a position where the upper electrode comes into contact with the welded portion of the nut. FIG. 4 is a partial cross-sectional view of a main part when the operation is performed.

FIG. 8 is a partial cross-sectional view of a main part when the upper electrode is at the upper end position when water droplets or deposits are attached to the lower end surface of the upper electrode (when an electrode is abnormal).

FIG. 9 is a plan view, a longitudinal section and a bottom view of the nut.

FIG. 10 is an electrical diagram of the projection welding machine shown in FIG.

11 is a configuration diagram of an input unit of the abnormality detection controller shown in FIG.

FIG. 12 is a flowchart showing a series of operations by the projection welding machine shown in FIG.

FIG. 13 is a timing chart when the setting state of the nut is the normal setting state (FIGS. 2 and 3).

FIG. 14 is a perspective view of the nut set state shown in FIGS. 4, 5 and 6;
5 is a timing chart when the set is in an abnormal state as shown in FIG.

FIG. 15 shows a state in which the nut is set in FIGS. 4, 5, and 6;
5 is a timing chart when the set is in an abnormal state as shown in FIG.

FIG. 16 is a timing chart when the setting state of the nut is an abnormal setting state as shown in FIG. 7 and the upper electrode pressure holding switch is in an OFF state.

FIG. 17 is a timing chart when the setting state of the nut is an abnormal setting state as shown in FIG. 7 and the upper electrode pressure holding switch is in an ON state.

FIG. 18 is a timing chart showing the operation contents for confirming the operation of the abnormality detection controller when the nut is set in the normal setting state after the electrode surface modification.

FIG. 19 is a timing chart showing the operation contents for confirming the operation of the abnormality detection controller when the nut is set in an abnormal state after the electrode surface is modified.

FIG. 20 is a cross-sectional view for explaining a problem of a conventional projection welding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection welding machine 2 Nut 2a Nut main part 2b Welded part 2d Upper surface 3 Work 3a Upper surface 15 Upper electrode 15d Lower surface 16, 18 Insulation material 17 Conductive collar 19 Conductive ring 23 Lead wire 25 Abnormality detection controller 17 Conductive color

Claims (3)

[Claims] 1. A projection welding machine for welding a nut to a workpiece by welding a plurality of welded portions extending obliquely outward from near the outer periphery of a lower end of a nut body to an upper surface of the workpiece, wherein the nut is welded to the workpiece. An upper electrode having a lower surface having an outer diameter slightly larger than the outer diameter of the upper surface of the upper electrode, the upper surface of which is entirely in contact with the upper surface of the nut, and a conductive collar mounted around the lower outer periphery of the upper electrode. A conductive collar having a lower surface substantially flush with the lower surface of the upper electrode, and the lower surface being in contact with the plurality of welded portions of the nut in the opposite direction; and a conductive collar between the upper electrode and the conductive collar. An insulating material that electrically insulates, and an abnormality detection controller that applies a minute voltage to the conductive collar and determines a setting state of the nut based on whether there is conduction from the conductive collar to the nut. Special Projection welding machine according to. 2. The projection welding machine according to claim 1, wherein a conductive ring is detachably mounted on an outer periphery of the conductive collar, and a lead wire of the abnormality detection controller is connected to the conductive ring. 3. The projection welding machine according to claim 1, wherein the upper electrode is held under pressure when the abnormality detection controller detects an abnormality.