JPH02139140A - Method and device for thread fastening - Google Patents

Abstract

PURPOSE:To improve the reliability in thread fastening work by descending a bit at a low speed rotation by synchronizing with the descent of a thread suction part, moving the bit to specified position with its high speed rotation by its holding a screw and performing thread fastening at a set torque value. CONSTITUTION:This device is composed of a 1st stage descending a bit 16 at a low speed rotation by synchronizing with the descent of a vacuum suction pipe 13 so as to suck a screw 15 by a screw part feeding unit 23, a 2nd stage holding the screw by the bit 16 and rotating the bit at high speed thereafter and a 3rd stage performing thread fastening at a preset torque value by moving the bit 16 to specified position. Consequently, the instability in separation and suction of the screw 15 is eliminated by taking out the screw 15 by its separation by the vacuum suction pipe 13 by reaching onto a taping screw feeding unit 23 by descending a motor with its actuation at a low speed rotation and transferring to a high speed rotation as well. Also, thread fastening is performed at a set torque value to realize the thread fastening of good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a screw tightening method in which a screw held in a threaded parts assembly formed into a taping structure is tightened against a workpiece by the downward movement of a bit and a vacuum suction pipe. and its apparatus.

Conventional technology In recent years, screw tightening work has become highly reliable in all aspects of equipment and operation due to the diversification of screws such as microscrews and the appearance of various workpieces, and screw tightening work with high quality in terms of torque accuracy and torque range. is required.

A screw tightening operation using a conventional screw tightening device will be described below with reference to the drawings. FIG. 6 shows an outline of a screw tightening device, and FIGS. 6 and 7 show an example of an electrically controlled electric screwdriver. In FIG. 6, 1 is a rectifier. 2 is a power transistor (hereinafter referred to as power Tr) which controls the electric power of the motor. 3 is a driver motor, 4 is a detection resistor for detecting the current flowing through the motor, 6 is a volume for adjusting a current judgment level, 6 is a comparison judgment device thereof, and 7 is a transistor for driving a power transistor. 7th
In the figure, 8 indicates an example of the current flowing through the motor, 9 is a determination level, and 1o is a level for completion of screw tightening.

The operation of the screw tightening device configured as described above will be explained below. First, electric power is supplied to the motor 3 by a start signal given to the power Tr 2.
starts rotating, the air cylinder 11 is activated and the electric screwdriver 12 is lowered. Vacuum suction pipe 13
is pressed against the catcher 14, and the screw 15 is sucked up and positioned at the tip of the bit 16. Furthermore, electric screwdriver 12
continues to descend, the current rises as it sits on the workpiece, and when it matches the value 9 set with the level adjustment volume 6, the comparator 6
operates, and the power Tr 2 is set to O by the drive transistor 7.
FF is completed and screw tightening is completed.

As another conventional example, FIGS. 8 and 9 show examples of conventional mechanically controlled electric screwdrivers, in which 3 is a motor, 17 is a driving cam, 18 is a driven cam, and 16
19 is a tightening bit, 19 is a torque spring, 20 is a limit switch, and 15 is a screw.

The operation of the mechanical electric screwdriver configured as described above will be described below. Electric power is supplied to the motor 3 shown in FIG. 8 in a form similar to the circuit shown in FIG.
Hold the screw 16 at the tip of the rotating bit 16, and then
Screw tightening is performed. When the screw 16 is seated on the workpiece and reaches the torque value set by the torque spring 19, the driving cam 17 and the driven cam 18 rest on the heads of each of the four cams as shown in FIG. Then, the limit switch 20 operates to turn off the power to the motor 3, completing the screw tightening.

Problems to be Solved by the Invention However, in the above two conventional configurations, it is extremely difficult to vacuum suction and reliably take out screws one by one from the screw supply unit during the downward movement of the electric screwdriver.
There were many problems, such as not being able to separate and supply screws one by one from the screw supply unit, and not being able to hold the screws at the tip of the vacuum suction pipe and causing them to drop. In addition, even with the electrical method, it is very difficult to determine the level in a short time when the motor rotates at high speed, and it is very difficult to stop the motor and gears without inertia, resulting in large variations in torque values.

In view of the above-mentioned problems, the present invention controls a motor rotating at high speed and includes a screw supply unit equipped with a conveying section capable of pitch-feeding an assembly of screw parts formed into a chipping structure, thereby facilitating screw tightening work. The present invention provides a screw tightening device with improved reliability.

Means for Solving the Problems and Technical Means of the present invention for solving the above-mentioned problems is to suck a threaded part from a threaded part supply part to a suction part, and screw the threaded part at a predetermined position with a rotatable bit. In the tightening method, the bit rotates at low speed in synchronization with the descent of the suction part to suck the threaded part from the threaded part supply part, and the bit holds the threaded part, and then the bit rotates at high speed. The second step is to move the bit to a predetermined position, and the third step is to tighten the screw at a preset torque value.

Further, means for generating a rotational speed detection signal of an electric driver motor that is attached to a plate that can be moved vertically and rotates at high speed, and a means for generating a vertical movement detection signal that is provided on a vacuum suction pipe that is slidable in the vertical direction on the plate. means for
A circuit that performs PWM control of the power supply and motor drive circuit while feeding back the current flowing to a predetermined motor based on a seed detection signal, an input circuit that externally selects a screw tightening pattern according to the screw and workpiece, and a screw tightening circuit that A circuit is provided to display and output torque data.

For production The effect of this technical means is as follows.

The motor is started at low speed by PWM current control, descends and reaches above the assembly of threaded parts made into a taping structure.
As the vacuum suction pipe separates and takes out the threaded parts, it also moves to high-speed rotation, which eliminates the separation of threaded parts and the instability of suction. In addition, the faster the motor rotates, the greater the change from rotation to stop. Therefore, seating can be detected in a very short time, and the reverse brake circuit, which also includes current limiting, prevents over-tightening due to inertia and instability. By controlling the power supply and the power Tr thereafter, no inertia is generated even when the screw tightening is completed after reaching the second final setting torque, and accurate screw tightening can be realized.

Example An embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a perspective view of a screw tightening robot in a first embodiment of the present invention. In FIG. 1, 11 is an air cylinder, 21 is a vertical motion detection sensor, 22 is an assembly robot, 23 is a taping screw supply unit, and 13 is a vacuum suction pipe. FIG. 2 is a circuit block diagram of the screw tightening control device in the first embodiment. In FIG. 2, 24 is a control CPU, 25 is a ROM containing control software and screw tightening patterns, and 2θ is a RAM that stores screw tightening conditions. 2nd place is chopper type power supply section,
28 is an analog-to-digital converter (hereinafter referred to as an A/D converter), 29 is a current detection conversion circuit, and 3o is a speed detection/seating detection circuit.

31 is a part of the motor driver, and there is a power Tr 32 inside.
It includes a power transistor control circuit 33, a current detection 34, and the like. 3
is an electric driver motor, and 36 is a rotation detector. 3
e is a display section for screw tightening torque values and tightening conditions, etc., 3 is a switch for data and manual operation, and 38 is an interface circuit for connection with external equipment (hereinafter referred to as I/F), which displays start and screw tightening conditions 39, etc. and outputs signal 4Q indicating completion, failure, torque data, etc. 41 is a command signal to the chopper type power source, 42 is an output voltage to the electric driver motor, and 43 is a control signal and a brake signal for the power Tr that drives the electric driver motor 3.

Regarding the screw tightening control device configured as above,
The operation will be explained using FIG. 1, FIG. 2, FIG. 3, and FIG. 4. FIG. 3 shows a current curve flowing through the electric driver motor 3, and its value is read by the current detector 34, current detection conversion circuit 29, and A/D converter 28, and the current curve shown in FIG. Changes in speed caused by the rotation detector 36 are also read through the speed detection seating detection circuit 30 and the A/D converter 28, and the chipper type power supply unit 27 and the power T
rs2 is controlled by PWM. When the motor 3 was started, a starting current 44 in FIG. 3 flowed. The tip of the bit 16 moves onto the taping screw supply unit 23, descends, and takes out the screw 16 by vacuum suction as shown in FIG. At the same time, the bit 16, which had been rotating at a low speed until then, rotates at a high speed when the vertical movement detection sensor 21, which detects the relative positional relationship between the bit 16 and the vacuum suction vibrator 13 in the vertical direction, turns ON in the state shown in Fig. 4, and rotates at a high speed. to move to.

Next, after the screw 15 is screwed into the workpiece 46, when the screw head is seated on the workpiece, the current changes as shown at the inflection point 46 in FIG. By reading this displacement by the rotation detected by the rotation detector 35 and speed detection/seating detection circuit 30 shown in FIG. 33 for 11 hours and the current is limited from 1 to 3, the brake current 47 in Figure 3 flows for the set time, and then a low primary tightening torque current depending on the type of workpiece and screw 15. With a value of 48, output is performed for 2 hours to prevent the bit 16 from impacting the screw head groove. Finally, the torque of the electric screwdriver motor 3 is used as a current, and it is gradually increased as shown in the curve 49, and the set torque current value is 6o.
The electric driver motor is driven for t3 hours and stopped so that there is no inertia in the motor and gear. In this way, screw tightening is completed.

Effects of the Invention As described above, the present invention provides a low-cost screw tightening device with an expanded torque control range that greatly improves the reliability of separating and extracting screws and simultaneously realizes a significant improvement in torque accuracy. can.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a robot incorporating a screw tightening device according to the first embodiment of the present invention, FIG. 2 is a tightening control circuit diagram of the screw tightening device according to the first embodiment, and FIG. Current curve diagram of the current driver motor according to the circuit, Figures 4a and b are diagrams showing the state of screw extraction in the screw supply unit, Figure 6 is a side sectional view of the conventional screw tightening device, Figure 6 is the conventional electric FIG. 7 is a current curve diagram of the same, FIG. 8 is a sectional view of the bit showing the conventional mechanical configuration, and FIG. 9 is an electric circuit diagram of the same. 3...Driver motor, 11...Air cylinder, 12...Electric screwdriver, 1
3...Vacuum suction pipe, 15...Screw, 16...Bit, 21...Vertical movement detection sensor, 23...Taping screw Supply unit, 24... Control CPU. Name of agent: Patent attorney Shigetaka Awano and one other person working in Figure 1f-L7-Cylinder 1 + 2-4.

Claims (7)

[Claims] (1) In a method in which a threaded part is sucked by a suction part from a threaded parts supply part and the threaded part is screwed at a predetermined position with a rotatable bit, the suction part synchronized with the lowering of the bit, the bit rotates at a low speed in the first step, the bit holds the threaded part, and then the bit rotates at high speed in the second step, and the bit moves to a predetermined position and rotates at a preset speed. A screw tightening method characterized by having a third step of tightening the screws using a torque value. (2) A threaded parts supply part of the taping structure that stores threaded parts, a vertically slidable suction part capable of vacuum suction, a rotatable bit provided inside this suction part, and this bit. In the screw tightening device, the detection part detects that the screw component from the screw component supply section is held by the bit, and the bit is configured to be able to rotate at high speed. screw tightening device. (3) The screw tightening device according to claim 2, wherein the bit starts rotating at high speed in response to a signal transmitted from a sensor indicating that the suction part is pressed against the screw component supply part. (4) A rotary drive unit, a screwdriver capable of tightening a screw by receiving the rotation thereof, a support plate to which the rotary drive unit and the driver are attached, and a screw of a taping structure on the travel path of the bit attached to the tip of the driver. A conveying section capable of pitch-feeding a component assembly and a supply unit equipped with this conveying section are arranged, the support plate is configured to move independently by the operation of an air cylinder attached to a frame, and a screw component assembly is arranged. In a screw tightening device that tightens the screw parts housed in the body to a workpiece by pressing a vacuum suction pipe formed in the circumferential direction of the bit from above against the workpiece, the vacuum suction pipe that can be slid in the vertical direction and the vertical direction of the bit are used. While a sensor is provided to detect the relative position, the control unit drives the air cylinder at a low speed when the air cylinder starts to operate, that is, to start lowering, based on a detection signal that detects the rotation of the drive unit and a current signal that detects the current flowing through the drive unit. Starting with
the vacuum suction pipe is pressed against the threaded parts assembly, and after detecting a signal from the sensor, increasing the current of the drive unit;
A screw tightening device that performs pulse-wide modulation control of power applied to a motor and drive pulses applied to a power transistor that drives the motor so as to move to a predetermined position and tighten the screw with a preset torque value. . (5) The screw tightening device according to claim 4, wherein the means for moving the support plate comprises a servo motor for vertical movement mounted on the tip of the robot to speed up the movement. (6) A fixed type screw tightening device according to claim 4, wherein the means for moving the support plate in the vertical direction is a servo motor. (7) The means for moving the support plate consists of a robot and a servo motor for vertical movement mounted on the tip of the robot in order to speed up the movement, and the sensor signal is based on a positioning signal from the robot controller. A screw tightening device according to claim 4.