JPH04115834A - Automatic screw tightening device - Google Patents

Abstract

PURPOSE:To obtain an automatice screw tightening device with a height detection means wide in application range and of quick responsibility by detecting height of a bit by an encoder installed on a motor and controlling a rotating speed of the bit with data of a screw head below length and a screw tightening position height input to an information input part. CONSTITUTION:A screw tightening head 1 goes down rotating at a bit rotating speed PW1 from a Z0 position which is an original position toward a Z1 position to start screwing against a work 3. The screwing start position Z1 is calculated from a screw head below length and a screw tightening position height input to an information input part 17, and when it is computed that a screw tightening head 1 arrives at the Z1 position from an input pulse of an encoder 15 of a bit lift drive motor, a bit rotating speed PW2 changes and at the point when the distance of the seat surface of a screw 2 and the seat surface of the work 3 comes to be X, the bit rotating speed is changed to a low speed PW3. When the screw 2 arrives at a seat position Z2 and a tightening torque reaches a specific value, idling occurs inside the screw tightening head 1 and screw tightening is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic screw tightening machine that performs optimum tightening for each point in accordance with conditions.

Conventional technology In recent years, automatic screw tightening machines that detect the height of the bit and change the rotation speed of the bit have become mainstream so that tightening can be performed point by point and optimal tightening can be achieved that meets the conditions. ing. The configuration will be described below with reference to the drawings.

FIG. 4 shows a schematic diagram of the drive section of a conventional automatic screw tightening machine. In the figure, 1 is a screw tightening head, 7 is a guide member for vertically moving the screw tightening head 1, 8 is a feed screw for vertically moving the screw tightening head l, and 9 is a motor for vertically moving the screw tightening head 1. , 11 is a screw tightening bit (hereinafter simply referred to as a bit), 12 is a motor for rotating the bit 11, 15 is an encoder for detecting the rotation angle of the motor 9, and 18 is information about the encoder 15 and the screw tightening height position, which will be described later. 19 is a drive circuit that drives the motors 9 and 12 for vertical movement and rotation of the bit 11.

In the device configured in this way, a screw is held at the tip of the bit 11, and a signal from the drive circuit 19 rotates the head vertical movement motor 9 to lower the bit J1, and further the bit rotation drive motor 12 is rotated. It rotates and screws are tightened.

Hereinafter, the configuration and operation of the above conventional example will be explained in more detail with reference to FIGS. 5 and 6.

FIG. 5 is a longitudinal sectional view of a screw tightening head used in a conventional automatic screw tightening machine. In the figure, reference numeral 11 denotes a bit, which applies rotational force to the screw 2 and fastens the screw 2 to the workpiece 3. 4 is a suction vibrator that suctions screw 2 and removes bit 1.
1 holds screw 2. 5 is a magnet fixed to the attraction vibrator 4. 6 is a proximity switch fixed to bit 11.

The operation will be explained below.

First, bit 11. Screw 2. Adsorption vibe 4. The magnet 5 and the proximity switch 6 start moving in the A direction to fasten the screw 2 to the workpiece 3. When the tip of the suction vibrator 4 reaches the seating surface of the workpiece 3, the suction vibrator 4 stops, but
Bit 11 continues to move without stopping. The magnet 5 is fixed to the attraction vibrator 4, so it stops, while the proximity switch 6 is fixed to the bit 11, so it continues to move. When the proximity switch 6 approaches the magnet 5, the proximity switch 6 operates and the distance i1B between the seating surface of the workpiece 3 and the tip of the human 11 is detected.

FIG. 6 is a diagram showing the relationship between each process chart and the rotational speed of the bit drive shaft. In the figure, a catcher 10 holds the screw 2 until the screw 2 is engaged with the bit 11.

4 is a suction vibrator and 3 is a warp. a is the movement start step of the human 11. b is a step of engaging the screw 2 with the bit 11. C is a process in which screwing is started after the tip of the screw 2 reaches the workpiece 3. d is a step in which the moving speed of the bit 11 is slowed down to prevent excessive torque from being applied to the screw 2 due to the inertia of the bit 11 at the end of screwing, and the distance between the seating surface of the screw 2 and the seating surface of the workpiece 3 is
When this happens, deceleration is performed. e is the process of seating the screw 2, and f is the process of completing the tightening of the screw 2.

The fact that the tip of the screw 2 reaches the surface of the workpiece 3 in step C is detected by the height detection device shown in FIG. Further, the distance X required in step d is obtained by the control circuit 18 counting and calculating the pulse output from the encoder 15 shown in FIG. 4 after the proximity switch 6 is operated in FIG.

Problems to be Solved by the Invention However, in the conventional height detection device shown in FIG. 5, when the length under the neck of the screw 2 and the screw tightening position height change, the magnet 5. The position of the proximity switch 6 had to be changed, resulting in a narrow application range and lack of coordination.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an automatic screw tightening machine that has a height detection method that has a wide range of application and is coordinated.

Means for Solving the Problems In order to achieve the above object, the present invention includes a screw tightening bit that is moved up and down by a motor, and an encoder and a calculation section for detecting the position of the bit from the rotation speed of the motor. an information input section for inputting the length under the head of the screw and the height of the screw tightening position; An automatic screw tightening machine is constructed from a control circuit that controls the rotational speed of the bit to be varied to a preprogrammed speed.

Function: By the means described above, the height of the bit is detected by the encoder attached to the motor, and the rotational speed of the bit is controlled by the data of the length under the screw head and the height of the screw tightening position input into the information input section. Therefore, even if the length under the head of the screw and the height of the screw tightening position change, it can be handled simply by changing the input data to the information input section. A tightening machine can be realized.

Embodiment FIG. 1 shows an embodiment of an automatic screw tightening machine according to the present invention. In the figure, the same parts as in FIG. 4 of the conventional example are given the same numbers, detailed explanations are omitted, and the differences will be briefly explained.

In FIG. 1, 16 is a height calculation unit that calculates the height of the bit 11 from the output pulse of the encoder 15, 17 is an information input unit for manually inputting the length under the neck of the screw and the length of the screw tightening position, and 18a is a control circuit that controls the rotational speed of the bit 11 for each screw tightening process to be varied to a preprogrammed speed based on signals from the height calculation section 16 and the information input section 17.

Next, the operation will be explained with reference to FIG.

As shown in FIG. 2, the screw tightening head 1 starts screwing into the workpiece 3 from the origin position Zo.
It descends toward the + position while rotating at the bit rotation speed PWI. The screwing start position z1 is the information input part 17
The bit rotation speed is calculated from the screw neck length and the screw tightening position height input in changes to PW2 and rotates while moving toward position 22 where screw 2 is seated.
At the point where the distance between the seating surface of screw 2 and the seating surface of workpiece 3 becomes After that, when the tightening torque reaches a certain value, idle rotation occurs in the screw tightening head 1, the screw tightening is completed, and the screw tightening head 1 returns to the original position Zo.

As described above, according to this embodiment, as shown in FIG.
Even for workpiece 3 where the screw tightening position height h and the screw head length e change continuously, the data of the screw tightening position height h and the screw head length e are continuously input to the control device. This can be addressed by making a specific change.

Effects of the Invention As is clear from the above explanation, according to the present invention, continuous screw threading can be performed by inputting the underhead length of the screw and the height of the screw tightening position, without adjusting the height detection proximity switch. This enables automatic screw tightening with a wide range of applications, which can quickly respond to changes in the under-neck length and the height of the screw tightening position.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an embodiment of an automatic screw tightening machine of the present invention, Fig. 2 is a diagram showing the relationship between the position of the screw tightening head and the rotation speed of the bit drive shaft in the same embodiment, and Fig. 3 is a diagram of the same embodiment. Fig. 4 is a schematic configuration diagram showing a conventional example of an automatic screw tightening machine, and Fig. 5 shows the tip of the screw tightening head of the conventional example. 6 is a diagram showing the rotational speed of the bit drive shaft in each step of screw tightening in the conventional example. 9...Motor for vertical movement, 11...Screw tightening bit, 12...Motor for rotational drive, 1
5. Old... Encoder, 16... Height calculation section,
17... Information input section, 18a... Control circuit. Name of agent: Patent attorney Haruaki Koebi No. 2: Figure 9--kT%IhNAt Da(fri)I+ --hl
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Claims (1)

[Claims] A screw tightening bit that moves up and down by a motor, a height detection means for detecting the height of the screw tightening bit from the rotation speed of the motor, and a means for inputting the length under the neck of the screw and the height of the screw tightening position. and a control circuit that controls the rotational speed of the bit for each step in screw tightening to a preprogrammed speed based on signals from the height detection means and the information input section. Machine.