JPS61186177A - Actuator of resistance welding gun - Google Patents

Abstract

PURPOSE:To provide the titled actuator for resistance welding gun without using the operation medium of oil, air, etc. by constituting to drive with propelling mechanically a gun holder via screw from electric torque motor and to press a work with pinching by the gun held to the holder. CONSTITUTION:Actuator 1 is composed of electric torque motor 50, the screw means 12 to convert the rotary movement of the motor 50 to propelling movement and the gun holder 21 propelled via follow up cushion 22 by the means 12. In case of pressing by pinching a work by the welding gun held by the holder 21 the holder 21 is directly driven with propelling mechanically via the screw means 12 from torque motor 50. The actuator for resistance welding gun without using the operation medium of oil, air, etc. is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an actuator for a welding gun used for resistance welding such as spot welding and projection welding.

(Prior Art) As is known, the actuator of a resistance welding gun is constructed by bringing a pair of electrodes in an X-type welding gun or the like connected to the actuator close to each other, or by using a direct-acting type actuator connected to the actuator. After the movable electrode in the welding gun is brought close to the other fixed electrode, the object to be welded (work) is clamped between these electrodes, and welding current is passed through this clamping part. As the actuator, in addition to hydraulic cylinders, pneumatic cylinders have been favored because of their quick operation and easy hollow-up function.

The hollow-up function described above is a function that can instantly expand the gap between the electrodes by following the sudden expansion of the clamping part due to welding heat, and this function suppresses fluctuations in the welding current density. sell.

(Problems) However, such actuators have problems in terms of cost, layout, and energy usage efficiency because they require extensive equipment.

In other words, for example, even in a small-scale welding section, a hydraulic pump unit or air compressor and troublesome piping must be attached, and the efficiency of the pump for producing high-pressure hydraulic oil or high-pressure working air is low. In addition, large-scale welding sections involve a large energy loss, especially in the case of pneumatic cylinders, in which high-pressure used air is exhausted.

Therefore, an object of the present invention is to construct an actuator without using a medium such as hydraulic oil or working air.

(Means of the present invention) The means of the present invention that solves the above problems includes an electric torque motor, a screw means for converting the rotational motion of the electric torque motor into a propulsion motion, and a motor propelled by the screw means via a hollow-up cushion. It is constructed using a gun holder.

(Function) According to the above means, the gun holder is mechanically driven directly from the electric torque Tanabata through the screw means,
The welding gun held by this gun holder can clamp the workpiece.

(Example) FIG. 1 shows an example of the direct-acting welding gun in which the present invention is implemented, and the actuator 1 includes a cylinder device 10 and a thrust unit.

30 and an electric torque motor 50 are connected in series.

The outer shell of the cylinder device 10 is formed of a thick-walled cylindrical cylinder 11, and a screw means 12 using a known ball screw mechanism is configured inside this cylinder.

Referring to FIG. 2, in this screw means 12, 1
3 is the screw rond and the bearing ball rail 13a
is ground into a spiral shape, and has a head 15 with a rectangular socket hole 14 formed at its rear end (left end in the drawing). 16
is a ball nut that has a thick-walled cylindrical shape as a whole and can slide inside the cylinder 11. A female rail corresponding to the rail 13a is formed on a required portion of the inner surface of this ball nut, and is screwed into the screw rod 13 via the row of bearing balls. 16a.

16a is a circulation tube forming a circulation path for the bearing balls, and 16b is a holder for the tube. 17 is a spline groove, which is formed in several grooves on both sides of the ball nut 16, and 18 (FIG. 1) is a spline key curved on the inner surface of the cylinder 11 in correspondence with these spline grooves. 19 is a hollow extension extending forward from the ball nut 16, and 19a is the front bottom thereof.

20 is a bolt loosely inserted into the front bottom 19a of the extension 19 from inside, 20a is the bolt head, and 21 is the bolt 2.
21a is a flat surface formed on the side surface of the gun holder, and 22 is a hollow amplifier cushion interposed between the gun holder 21 and the front bottom 19a.

The hollow amplifier cushion 22 exhibits the hollow amplifier function, and is made of an elastic body such as a disk spring or a rubber ring, and the one shown is an annular air spring. This hollow-up cushion is made by connecting the threaded length of the gun holder 21 to 11M1, so that the front bottom 1 of the extension
9a with appropriate clamping force. Reference numerals 23 and 24 are key grooves and pins for preventing rotation of the bolt 20 during the above-mentioned screwing.

Therefore, when the above components 12 to 24 are inserted into the cylinder 21, the spline groove 1T of the ball nand 16 engages with the spline key 18, so that the ball nut 16 is fitted in a non-rotatable but slidable manner, and the gun holder 21 is fitted in a hollow state. The up cushion 220 can be moved back against the extension 19 against the elastic force.

25 is a punch fitted to the front end of the cylinder 11 and supports the circumferential surface of the gun holder 21 and the flat part 21a;
As a result, the gun holder 21 is prevented from rotating, and the above-mentioned threaded length is maintained as it was during adjustment.

In the thrust unit 30 and the electric torque motor 50, 31 is an outer shell cylinder of the thrust unit 30, and a threaded portion 32
It is connected to the front end of a motor case 51 of an electric torque motor 50, and an output shaft 52 of the torque motor 50 projects therein. 33 is a bearing housing formed at the rear of the outer shell cylinder 31, 34 and 34 are a pair of radial thrust bearings fitted into this housing,
The rear ends of the outer race and the inner race of the bearing are brought into contact with the stepped portion 33a of the bearing housing and the stepped portion 52a of the output shaft 52, respectively, and in this state, the retainer nuts 35 and 36 are used for positioning. 52b is a square shaft portion of the output shaft 52, 52c is a keyway formed across this square shaft portion, and 52d is a stepped portion behind this square shaft portion.

After inserting the square shaft part 52b into the socket hole 14 and fixing the thrust unit to the cylinder 11 by the threaded part 37, the gun holder 21 is pushed backward and the head 15 of the screw rond is inserted into the stepped part of the output shaft. 52d, and the knock screw 26 screwed onto this head is advanced to engage the keyway 52c.

Therefore, the forward and backward movement of the screw rond 13 is restricted.

'The electric torque motor 50 is, for example, a DC type high torque motor capable of forward and reverse rotation, and has a built-in torque trandue.

53 is a mounting stand installed on the motor head.

Incidentally, when the output shaft 52 of the torque motor is supported by a thrust bearing having sufficient pressure resistance, the thrust unit 30 can be omitted.

In FIG. 3, reference numeral 2 denotes a platen of a spot welding machine, and the actuator 1 is mounted on this platen with the stand 53 and the NAND 3 facing downward. 4 is the fc welding gun held by the gun boulder 21; 5 is the electrode tip (the moving electrode); 6 is the welding cable; 17 is the fixed electrode;
Further, W is a workpiece, and during welding, after lowering the platen 2 to a predetermined value R, the electric torque motor 50 is started to rotate the screw rond 13 in the normal direction. 21, the workpiece W is propelled forward (downward in the WJa diagram), and the electrode chimp 5 holds the workpiece W between it and the fixed electrode 1. Then, the electric torque motor 50
By energizing, this clamping portion is pressurized.

In the case of spot welding, this pressure is 150 to 300k.
IP level, radial thrust bearing 34
．． 34 opposes the reaction force. In this state, the welding cable 6 is passed through a predetermined number of cycles (1tt) to weld the part, and then the torque motor 50 is reversed to propel the ball nut 16 upward, and the electrode chimp 5
is separated from the workpiece W.

The block diagram shown in FIG. 3 shows one example of the pressurizing force control method.

In this method, the pressing force is controlled based on the voltage V of the electrodes 1t41 between the electrodes 5 and 7 that are energized, and the voltage V changes in inverse proportion to the pressing force.

In this block diagram, 61 is a voltage detector that detects the interelectrode voltage V, 62 is an amplifier that amplifies the detected value with a constant gain, and 63 is a reference voltage Vof during the welding period.
The reference voltage Vo is the optimum value of the inter-electrode voltage to be applied at each point λ during the progress of welding, and is usually determined experimentally. 64 is a proportional controller using, for example, a PID controller, which compares the output voltage of the amplifier 62 and the reference voltage Vo, and when there is a difference between them, outputs an amount of electricity proportional to the difference. Further, 65 is a power source for the electric torque motor 50, and 66 is a torque setting device installed in the power supply circuit. controller 64
Adjust this set voltage according to the output value of. 6γ is an amplifier which amplifies the output of the torque trandue length and inputs it to the comparator 6B, and also returns to the torque setting device 66.

In the above configuration, when the electrode tip 5 starts to clamp and pressurize the workpiece W as described above, the electric torque motor 5
By restricting the rotational motion of 0, the output torque increases rapidly, and the output reaches the torque tranquility. When this output reaches a predetermined value, that is, when a predetermined pressing force is applied to the workpiece W, the comparator 68 issues a signal St- to command the welding current to be applied. At this point, resistance welding is started and an interelectrode voltage V is generated. If this voltage V is less than or exceeds the reference voltage Vo, the torque setting device 6
6 increases or decreases the power supply voltage to increase or decrease the output torque, and the result is returned from the torque transducer to the torque setting device 66 to make the deviation close to zero. Ru.

Therefore, during the period of this control, the thrust force by the screw mid 13 varies to slightly displace the ball nand 16, thereby adjusting the pressurizing force in cooperation with the hollow up cushion 22. In this case, in this embodiment, since a ball screw mechanism is adopted as the screw means, the torque-propulsive force conversion efficiency is extremely high, which makes the above-mentioned displacement of the ball nut 16 nimble, and further reduces the electric power required for applying pressure. can.

(Effects) As explained above, the present invention eliminates the need for working media such as hydraulic oil and working air, so welding equipment can be simplified and the required power can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing one embodiment of the present invention, FIG. 2 is a perspective view of a main part of FIG. It is a diagram. 1... Actuator 12... Screw means 1
3...Screw mid 16...Ball nut 21...Gun holder 22
...Hollow up cushion 50...Electric torque motor Fig. 2 @ Fig. 3

Claims (1)

[Claims] An actuator for a resistance welding gun, comprising an electric torque motor, a screw means for converting rotational motion of the electric torque motor into a propelling motion, and a gun holder propelled from the screw means via a hollow up-action.