JPS63156626A - Thread fastening device - Google Patents

Abstract

PURPOSE:To perform the fastening conformed to seating torque, by detecting the generating torque of an electric driver with a torque sensor, and making the detected value feedback to a controller which gives the specified voltage to the driver and starts or stops it. CONSTITUTION:An electric driver 13 is made to go down by a cylinder, and when a screw 28 comes nearer to a seating point, a proximity switch operates, the signal comes in a sequencer 27, and it is fed to a driver controller 25, thus the driver 13 is suddenly stopped. Simultaneously, this signal is fed to a torque sensor controller 26 whereby torque value of the seating point is detected, fed back to the driver controller 25, and hereat voltage for restarting the electric driver 13 is determined. This restarting torque is patternized in advance, selected and thereby hard wood can be fastened with strong torque and soft wood with weak torque, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a screw tightening device suitable for tightening screws into materials such as wood, particularly plywood made by heat-compressing wood chips, plywood veneer, etc., which have different hardness and softness depending on the location. It is related to.

BACKGROUND OF THE INVENTION In recent years, various torque control methods have been invented for tightening screws, with the aim of equalizing the tightening torque and reducing variations, as the torque is one of the factors for improving the quality of products.

An example of the conventional screw tightening device mentioned above will be described below with reference to the drawings.

FIG. 6 shows the configuration of a conventional screw tightening device.

In FIG. 6, 1 is an electric screwdriver fixed to a block 2 that moves in the direction of the arrow with a cylinder (not shown) or the like.
Its output shaft is connected to a bit 4 via a universal joint 3.

A pipe holder that holds the suction pipe 5 together with a spring 6 between the blocks 2 is attached to the pro 2, and a proximity switch 9 fixed to the sensor holder 8 is attached to this, and the proximity switch 9 is attached to the suction pipe 5. A sensor block 1o is fixed.

Driver controller 11 for controlling the electric screwdriver 1
．． The sequencer 12 of the screw tightening device exchanges signals as shown in the figure.

FIG. 7 is an example of a torque curve when tightening a screw to plywood. As shown in this figure, even if the material is the same, the torque curve will be 1 to 6 depending on the location where it is tightened, and the screw breakage torque (breaking torque) will also vary. If we were to temporarily tighten the screws by applying a constant torque using the electric screwdriver 1 to this plywood, then with a torque of 10 to 9faO1l, the position 2 would be too loose, and the position 6 would not be tightened enough.

It can be seen that if you tighten 6 to 1tsKpf, cm to compensate for the deficiency, 1 to 6 will become loose screws.

In the conventional screw tightening device shown in Fig. 6, when the bit 4 reaches a certain height, the proximity switch 9 is activated and the rotation of the electric screwdriver 1 is temporarily stopped, or the output torque of the electric screwdriver 1 is changed to adjust the final tightening torque. I decided on it and tightened it. Therefore, even if the screw seating torque t fluctuates, the electric screwdriver 1 is driven until the signal from the proximity switch 9 is input, and the torque up to that point is the highest seating torque (7th
In the figure, 1. ) requires a larger torque.

Problems to be Solved by the Invention However, as mentioned above, with plywood where the screw looseness torque varies greatly depending on the tightening point, tightening with a constant torque after stopping at the seating point will result in loose screws and insufficient tightening. The problem with this method is that the defect rate is high and the yield is very low.

In view of the above-mentioned problems, the present invention provides a screw tightening device that tightens a screw with a high torque with a high torque, and a screw with a low torque with a low torque.

Means for Solving the Problems In order to solve the above problems, the screw tightening device of the present invention has the following features:
Torque sensor that detects the output torque of an electric screwdriver
This is a screw tightening system that includes a controller that applies a predetermined voltage to an electric screwdriver to start or stop it, and feeds back the detected value of the torque sensor to the driver controller.

Operation The present invention has the above-described configuration, and utilizes the relationship between the seating torque t and screw loose torque T shown in FIG. 7 of the conventional example,
First, a constant torque is applied until the seating point is reached, and the torque at this time (seating torque) is picked up by a torque sensor. At this time, a judgment is made as to whether the tightening point is hard or soft. When restarting, the starting torque, that is, the final tightening torque value is determined and the electric screwdriver is controlled by the driver controller.

For this reason, screws with a low screw torque (low seating torque) are tightened with a weak torque, and screws with a high screw torque are tightened with a strong torque.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. Fig. 1 is a device diagram of an embodiment of the present invention, Fig. 2 is a system diagram, and Fig. 3 is a flow chart showing the flow of the system. 15, it is fixed to a vertically movable block 1θ, and its output shaft is connected to a bit 18 via a universal joint 17. The bit 18 is biased by the spring 19 and the block 16
A suction pipe 21 held in an aligned state is fitted into a pipe holder 20 fixed to the pipe holder 20 . pipe holder 2
0 is connected to the proximity switch 23 by the sensor block 22.
is fixed, and on the other hand, a position block 24 is fixed to the suction pipe 2.

The electric screwdriver 13 is connected to the driver controller 25,
The torque sensor 14 is a torque sensor controller 26
, the proximity switch 23 is connected to the sequencer 2 of the screw tightening device.
7, and mutual signal exchange is as shown in Figure 2.

Further, the screw 28 slides through the shoe 30 from the hopper 29, is delivered directly below the suction pipe of the catcher 31, and is tightened to fix the hinge 32 to the wood 33. 34 is a column that supports the entire screw tightening head, and 35 and 36 are optional equipment such as a printer and an electromagnetic oscilloscope.

The operation of the screw tightening device configured as described above will be described below.

The electric screwdriver 13 is lowered by the cylinder 16, attracts the screw 28, and carries it to the tightening position, but the suction pipe 2
The bit 1 comes into contact with the top surface of the hinge 32 and compresses the spring 19, and the bit 1 further descends and screws the screw 28 into the wood 33, but the screw 28 is seated as shown in Figure 4. When the point is near, the distance between the proximity switch 23 and the position block 24 approaches the distance Sa and Sb, and the proximity switch 23 is activated. The signal of the proximity switch 23 is sent to the sequencer 2
7, the signal is immediately sent to the driver controller 25 and the electric screwdriver 13 stops suddenly.At the same time, this signal is also sent to the torque sensor controller 26 and at that point (
The torque value at the seating point) is detected by the torque sensor 14. The seating torque is determined by the torque sensor controller 26.
The voltage is fed back to the dry nozzle controller 26, where the voltage for restarting the electric screwdriver 13 is determined. The voltage is, for example, as shown in FIG. 6, and the seating torque range of 2 to 6 Kyf-α is set in small increments.

The relationship between restart voltage and restart torque is electric screwdriver 13
Determined by the output characteristics of Further, as shown in the flowchart of FIG. 4, if the torque of the torque sensor 14 is less than 1 Kyf-α, it is assumed that the screw is completely loose or there is no screw, and the tightening is finished without restarting.

Further, if the voltage is greater than 10Kgf-α, restarting is performed at the maximum voltage. An example of the automatic torque setting (variable pattern) shown in FIG. 3 is shown in FIG.

As described above, according to this embodiment, the torque sensor 14 is provided to detect the output torque of the electric screwdriver 13, and the torque at the seating point of the screw 28 with respect to the hinge 32 is detected. Select the restart torque to tighten hard wood with a strong torque, and soft wood with a weak torque.

Effects of the Invention As described above, the present invention uses a torque sensor and a driver controller in which the restart torque (final tightening torque) is stored in advance for the seating torque. It is possible to tighten objects with a strong torque, while soft wood can be tightened with a weak torque.This means that no matter what type of wood you are tightening, once the relationship between the seating torque and the screw loose torque is clear, you can always tighten the appropriate value for the screw loose torque. can be tightened. Therefore, it is a very advantageous tightening method for workpieces where conventional tightening with a constant torque would easily cause loose screws, and it is an indispensable system 11 for assembly processes centered on woodworking.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of a screw tightening head in an embodiment of the present invention, FIG. 2 is a block diagram showing the system of the present invention, and FIG. 3 is a flow chart showing the overall flow. Figure 4a, b. C is a partial cross-sectional view of the suction/sheep showing the height positional relationship between the workpiece and the screw bit, FIG. 6 is a diagram showing the relationship between the seating torque of the screw and the final tightening torque, and FIG.
The figure is a block diagram showing a conventional screw tightening method, and FIG. 7 is a torque curve diagram when tightening a screw on a workpiece. 13...Electric screwdriver, 14...Torque sensor, 16...Cylinder, 18...
・・・Bisoto, 田・・・・・・Proximity switch, 24
...position block, 25 ...driver -
Controller, 26...Torque sensor controller. Name of agent: Patent attorney Toshio Nakao and 1 other person:
t---4 Tsukasa: 41 Kairaiha" 23--Ichireshi Bansui, ysu 24--4tr1t Deraga 1.To 5th figure) da torque (qfC hat g---ni4)\゛()゛9-Ichimochi Switch

Claims (3)

[Claims] (1) An electric screwdriver, a torque sensor that detects the torque generated by the electric screwdriver, a means of moving the electric screwdriver to the tightening position, a bit directly connected to the output shaft of the electric screwdriver, and a bit that detects the position of the bit relative to the tightening position. A screw tightening device comprising: a sensor for detecting the electric screwdriver; and a controller for applying a predetermined voltage to the electric screwdriver to start or stop the electric screwdriver. (2) The screw tightening device according to claim 1, wherein the means for moving the electric screwdriver to the tightening position comprises a robot and a vertically moving cylinder mounted on the tip of the robot. (3) The screw tightening device according to claim 1, further comprising a display or a printer for displaying the torque value detected by the sensor.