JP2691827B2 - Pressure control device for spot welding gun driven by electric motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling a pressing force during welding of a spot welding gun driven by an electric motor.

[0002]

Conventionally, as a welding gun that is driven by an electric motor is shown in FIGS. 3. That is, in FIG. 3 , 31 is an electric motor installed at the rear end of a cylinder 32, a small gear 34 is attached to a rotating shaft 33 of the electric motor, and a large gear 35 meshing with the small gear 34 is attached to the lead screw 3.
6 is fixed. The movable arm 39, to which the electrode 37 is attached at the tip and the nut 38 which is screwed with the screw of the lead screw 36 is fixed at the rear end, is provided in the cylinder 3
2 is arranged so that it cannot rotate and can move forward and backward. A fixed arm 40 has an electrode 41 attached to one end and the other end fixed to the cylinder 32 .

In the above structure, the rotation of the electric motor 31 is reduced by the small gear 34 and the large gear 35 to rotate the lead screw 36, and the movable arm 39 is moved by the nut 38 screwed with the lead screw 36. Move forward and backward. Then, the pressing operation starts from the state where each of the electrodes 41 and 37 is in contact with the work 42, and the welding current is supplied to perform the welding after the work 42 is brought into the pressurizing state.

By the way, the work 42 is connected to the electrodes 41 and 3.
Two methods are conceivable for controlling the pressing force when pressurizing at 7. That is, the first is simply open loop control for keeping the torque of the drive motor 31 at the set value, and the second is the electrodes 41, 3
This is a closed loop control in which the pressure applied to 7 is measured by a pressure sensor and the value is fed back to control the electric motor 31.

[0005]

However, although the open loop control has a simple mechanism and a low cost, it is difficult to keep the applied pressure at the set value accurately. On the contrary, closed-loop control has high control accuracy, but it is not practical because there is no stable and inexpensive pressure sensor and the cost is high.

The present invention has been made in view of the above problems of the prior art, and its object is to accurately obtain a welding pressure suitable for welding at low cost by closed loop control. It is an object of the present invention to provide a pressurizing force control device for a spot welding gun driven by an electric motor.

[0007]

In order to achieve the above object, a pressure control device for a spot welding gun driven by an electric motor according to the present invention comprises a spring at a front portion of a lead screw that reciprocates in association with rotation of the electric motor. A spring is stretched between the holding member and the sliding body at the rear end of the movable arm, and a switch operated by the movement of the spring holding member in the sliding body is connected to the electric motor via a motor driver to connect the electric motor. In the one to be controlled , the electric motor
A pulse oscillator is installed in the
And the output of the gate circuit is connected to the gate circuit.
Motor through the motor driver after connecting to the motor
It is characterized by being connected to .

Further, a nut is screwed on the front portion of the lead screw which rotates in association with the rotation of the electric motor, and the nut is non-rotatably slidably arranged on the sliding body at the rear end of the movable arm. A spring is stretched between the sliding member and the sliding body, and a switch operated by the movement of the nut in the sliding member is connected to the electric motor through a motor driver to control the electric motor.
A pulse oscillator is installed in the
And the output of the gate circuit is connected to the gate circuit.
Motor through the motor driver after connecting to the motor
It is characterized by being connected to .

[0011]

In the welding pressure control device for the spot welding gun configured as described above, the lead screw advances due to the rotation of the electric motor, and the movable arm also advances due to this advance so that both electrodes contact the work. Further, as the lead screw advances, the spring is compressed and the reaction force is transmitted to the movable arm, and the work is pressed by both electrodes. The compression of the spring shortens the positional relationship between the sliding body and the spring holding member.

Further, the lead screw is rotated by the rotation of the electric motor, and this rotation causes the movable arm to move forward through the nut so that both electrodes come into contact with the work. Further, as the lead screw rotates, only the nut advances and the spring is compressed, and the reaction force is transmitted to the movable arm, and the work is pressed by both electrodes. The compression of the spring shortens the positional relationship between the sliding body and the nut.

[0015] Then, landing body and the distance of the spring holding member or nut approaches the desired value (closer to the pressure desired value) and the switch is closing operation, the closing signal enters the gate circuit, the pulse generator The pulses from will be output to the counter. Therefore, when the desired number of pulses is counted (the pressing force reaches a desired value), the signal is transmitted to the electric motor via the motor driver to stop the driving of the electric motor.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral 1 denotes an electric motor installed at the rear end of a cylinder 2, a small gear 4 is attached to a rotary shaft 3 of the electric motor 1, and a central portion hole of a large gear 5 whose outer periphery meshes with the small gear 4. A screw 6 is formed, the screw 6 meshes with a lead screw 7, and the large gear 5 is restricted by the cylinder 2 so that it can rotate but cannot move forward and backward. 7 is designed to move forward and backward. A spring holding member 8 is fixed to the front end of the lead screw 7. A sliding body 11 slides in the cylinder 2 at the rear end of the movable arm 10 having the electrode 9 attached to the tip thereof, but is fixed so as not to rotate. A spring 12 is arranged inside the sliding body 11, one end of the spring 12 is fixed to the spring holding member 8 and the other end is fixed to the sliding body 11. Incidentally, 13 is a fixed arm having an electrode 14 attached to the tip thereof, and 15 is a work.

In the spot welding gun as described above, the rotation of the electric motor 1 is decelerated via the small gear 4 and the large gear 5 to move the lead screw 7 forward and backward. As the lead screw 7 advances, the movable arm 10 also advances and both electrodes 9, 1
4 contacts the work 15. Further lead screw 7
Is moved forward, the spring 12 is compressed and its reaction force is transmitted to the movable arm 10, and the work 15 is pressed by both electrodes 9, 14. And this spring 12
The positional relationship between the sliding body 11 and the spring holding member 8 is shortened by the compression of. When the pressure applied by the electrodes 9 and 14 reaches a desired value, the rotation of the electric motor 1 is stopped and welding work is performed.

By the way, contacts 18 and 19 are provided at the tips of the lead wire 16 from the spring holding member 8 and the lead wire 17 from the sliding member 11 to form a switch 20. The switch 20 is a gate circuit 2
7 is connected, and 26 is an electric power according to the rotation of the electric motor 1.
28 is a pulse transmitter that emits a Qi pulse.
Is a counter that counts the pulses from the circuit 27
Output when the set value from the count setter 29 is reached.
It has become. 21 is a motor driver
The motor driver 21 is connected to the electric motor 1 so as to drive and stop the electric motor 1. And the electric motor 1
The pulse from the pulse generator 26 is constantly
It is sent to the auto circuit 27.

Therefore, the work 15 enters a pressurized state by both electrodes 9 and 14, and the sliding body 11 and the spring holding member 8
When the contact point 18 comes into contact with the contact point 19, it means that the work 15 is applied with some pressure.
When the contact 18 comes into contact with the contact 19 and the switch 20 is closed, the signal is sent to the gate circuit 27. The result
As a result, whether the pulse from the pulse oscillator 26 is the gate circuit 27
Will be output to the counter 28, which is the count.
Is counted by the counter 28, and the value is counted by the counter setter 29.
When the counter 28 reaches the set value,
To the electric motor 1 via the motor driver 21
Then, the drive of the electric motor 1 is stopped. Of this example
In some cases, adjust the pressure by adjusting the count.
You can adjust it or keep the count constant.
Adjusting the position of the contact 19
It can be adjusted. Then, the welding work is performed in this state.

When the welding is completed, the electric motor 1 is driven to rotate the rotating shaft 3 in the reverse direction, whereby the lead screw 7 is retracted. By this retreat, the pressure applied to the work 15 is first released, then the movable arm retreats, and the electrode 9
You will be away from

FIG. 2 shows the second embodiment, which is different from the first embodiment in that the lead screw 22 is fixed to the large gear 5 so that the lead screw 22 does not reciprocate due to the rotational movement. A nut 23 is screwed into the nut 22, and the nut 23 is formed into the square hole 2 formed in the sliding member 11.
Since it is arranged in the No. 4, when the electric motor 1 is driven and the lead screw 22 is rotated, both electrodes 9, 1 are attached to the work 15.
4, the sliding body 11 advances together with the nut 23, and when both electrodes 9 and 14 come into contact with the work 15, the nut 23 slides forward in the sliding body 11 to move the sliding body 11 thereafter.
The positional relationship between the nut and the nut 23 is shortened. Since the remaining structure is substantially the same as that of the first embodiment, only the main part thereof will be described.

In the spot welding gun as described above, the work 15 is put into a pressurized state by both electrodes 9 and 14, and the sliding body 1
When the contact point 18 comes into contact with the contact point 19 when the distance between the nut 1 and the nut 23 is close to each other, the work 15 is slightly applied with pressure. When the contact 18 comes into contact with the contact 19 and the switch 20 is closed, the subsequent operation is the same as in the first embodiment.

As the switch 20 in the first and second embodiments, any switch such as a normal limit switch, a proximity switch, a photoelectric switch, and other on-off switches can be used.

[0026]

According to the first and second aspects of the present invention, since the pressure force of the spot welding gun is generated by utilizing the reaction force of the spring, the mechanical response of the electrode portion is remarkably improved. and very inexpensive switch together is
A pulse generator enables easier and more accurate control of pressure.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram including a partial cross-sectional view of a pressure control device for a spot welding gun driven by an electric motor according to the present invention.

FIG. 2 is a partial sectional view of a pressure control device for a spot welding gun driven by an electric motor according to another embodiment of the present invention.

FIG. 3 is a sectional view of a conventional spot welding gun driven by an electric motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric motor 7,22 Lead screw 8 Spring holding member 10 Movable arm 11 Sliding body 12 Spring 20 Switch 21 Motor driver 23 Nut 26 Pulse transmitter 27 Gate circuit 28 Counter

Claims (2)

(57) [Claims] 1. A welding gun that is driven by an electric motor
There are, in conjunction with the rotation of the motor is stretched the spring between the sliding body of the rear end of the front portion of the spring holding member and the movable arm of the lead screw for reciprocating in sliding body of the spring retaining member A switch operated by movement is connected to the electric motor through a motor driver to control the electric motor.
A pulse oscillator, and the pulse oscillator and the switch
Connect to the gate circuit and output the output of the gate circuit to the counter
After connecting, connect to the motor via a motor driver
A force control device for a spot welding gun driven by an electric motor. 2. A welding gun that is driven by an electric motor
The nut is screwed onto the front part of the lead screw that rotates in conjunction with the rotation of the electric motor, and the nut is slidably and non-rotatably arranged on the sliding body at the rear end of the movable arm. In the one in which a spring is stretched between the body and a switch that is operated by the movement of the nut in the sliding body and is connected to the electric motor through a motor driver to control the electric motor, a pulse is applied to the electric motor. Outgoing
And a gate between the pulse generator and the switch.
Circuit, and connect the output of the gate circuit to a counter
After that, the device is connected to the electric motor via a motor driver, and a pressing force control device for a spot welding gun driven by the electric motor.