JPH0310728A - Thread fastening method and machine - Google Patents

Abstract

PURPOSE:To enable a stabilized thread fastening by engaging the tip of a rotating bit with the screw of a work, moving it at 1st high speed and fastening the screw forcibly at 2nd low speed after stopping it instantaneously. CONSTITUTION:A thread fastening bit 16 is fitted to the tip of the shaft of a motor 15 for fastening a fastening head 1. The tip of the bit 16 is engage with the groove of the screw of a work. A control circuit 20 outputs according to the pitch of the screw, the fastening height, the kind and the diameter, rotating a motor 11 for moving via a driving circuit 21 and lifting the thread fastening head 1 by a guide member 7. At first a motor 15 is rotated at a 1st high speed and stopped once after rapidly moving the bit 16 to a specific position. The bit 16 is then rotated forcibly at a 2nd low speed to fasten the screw. A sure thread fastening is performed efficiently accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a screw tightening method and a screw tightening machine, and more particularly to a screw tightening machine equipped with a means for moving a screw tightening head and capable of automatically tightening screws. be.

Conventional technology In conventional automatic screw tightening machines, an air cylinder device is generally used as a means of moving the screw tightening head in the distance direction relative to the workpiece because it can easily apply a constant pressure force. It is used.

Problem to be Solved by the Invention However, when using an air cylinder device, it is extremely difficult to change the speed during movement, so if you try to increase the movement speed by increasing the speed, the pressing force when screwing in will be excessive. Become. As a result, due to the frictional force generated by this pressurizing force, the tightening torque will be affected, making the tightening torque unstable, and in some cases, the tightening operation may end with the screw floating, resulting in a screw-in failure. There is a problem that there is.

In view of the above conventional problems, the present invention provides a highly reliable screw tightening method in which a screw tightening bit or a screw tightening head is moved at high speed to the vicinity of the screwing start position, and an appropriate pressing force is obtained during subsequent screwing. The purpose is to provide screw tightening machines.

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for tightening a screw to a workpiece set at a predetermined position using a rotatable bit, the tip of the bit being connected to the head of the screw. a first step in which the tip of the screw is moved at a first speed to a position where it approaches the workpiece at a predetermined interval to complete positioning; The present invention is characterized by comprising a second step of starting the movement of the bit, tightening the screw when the tip of the screw reaches the workpiece, and forcibly advancing the bit until completion of positioning.

In addition, as a screw tightening machine, a screw tightening head equipped with a screw tightening bit and a tightening motor that rotationally drives the screw tightening machine, and a moving device configured with a linear sliding bearing that allows the screw tightening head to be moved in the distance direction relative to the workpiece. A block A, a moving block B comprising the linear sliding bearing that transmits power from the moving motor to the moving block A via a spring, and a control means for controlling drive of the moving motor in response to a screw tightening process. It is characterized by having the following.

According to the present invention, the predetermined interval (
5m or less), high-speed movement is possible by moving at a high first speed up to this side, and at the same time, when starting screw tightening, the screw is moved at a slow speed with a gradual start-up after an instantaneous stop. Even if the type or pitch changes, the screw bite will be stable, and the impact with the workpiece will be cushioned and absorbed by the spring. The second screw is forced until the screw tightening is completed.
Since the movement is performed at a speed of It can be carried out.

Further, according to the configuration of the screw tightening machine of the present invention, the screw tightening head can be moved at any speed by the moving motor;
By controlling the movement speed according to the screw tightening process using the control means, it is possible to move the screw at high speed to the vicinity of the screwing start position, and prevent the pressurizing force from becoming excessive during screwing. The screw tightening torque can be stabilized without being affected by inappropriate pressing force.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 to 4.

First, the overall structure of the screw tightening machine will be explained with reference to FIG.

In FIG. 2, reference numeral 1 denotes a screw tightening head, which is supported so as to be movable in the horizontal direction by X-Y axis moving means 2 and movable in the vertical direction by Z-axis moving means 3. X-Y
The axis moving means 2 is a Y-axis tape movable in the Y direction by a moving body 6 movable in the X direction on the X-axis tape/L/4)v
6, this Y-axis tape/L/6
A guide member 7 of the two-axis moving means 3 and a screw supply means 8 are attached to one end of the shaft. The screw tightening head 1 is
A moving block A1 mounted on a guide tray A/9 that constitutes a linear sliding bearing provided on the guide member 7.
0, and is supported by a moving motor 1.
The moving block B13 is connected via a spring 14 to a moving block B13 that can be raised and lowered by a feed screw 12 that is rotationally driven by a feed screw 12. Reference numeral 16 denotes a drive motor that rotationally drives the screw tightening bit 16 of the screw tightening head 1.

17 is a main controller, which controls the X-Y axis moving means 2;
It is configured to control a moving motor (not shown) and a moving motor 11 of the Z-axis moving means 3, and output command signals regarding screw tightening conditions such as a screw tightening pattern and screw tightening torque to the screw tightening controller 18. , the screw tightening controller 18 is configured to control the tightening motor 16 of the screw tightening head 1.

Next, the configuration of the lifting/lowering driving section of the screw tightening head 1 will be explained in detail based on FIG. 1. Movement motor 11
consists of a servo motor, and is equipped with an encoder 19 for detecting its rotational position. Reference numeral 2o denotes a control circuit for the moving motor 11, and the moving motor 11 is controlled via a drive circuit 21 based on a control signal output from the control circuit 20.

The control circuit 20 receives an output signal from the encoder 19 and an output signal from a rotation detecting means (encoder ho 1vIC, etc.) 22 attached to the tightening motor 15 of the screw tightening head 1. Furthermore, as shown in FIG. 3, the screws Sl, S2 . S3
Since the screw pitch, screw length l, type of screw such as machine screw or self-tapping screw, screw diameter d, screw tightening height position, etc. vary, these screw tightening data are input to the control circuit 20. be done.

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

In advance, the horizontal screw tightening position of the workpiece, the screw tightening conditions by the screw tightening head 1 such as the screw tightening pattern and tightening torque at that screw tightening position, and the above screw tightening data are programmed and sent to the main controller 17.
is entered and stored.

When the start switch is pressed, the main controller 18 rotates the tightening motor 15 of the screw tightening head 1 according to predetermined screw tightening conditions.

Next, the moving motor 11 is started in the control circuit 2o via the drive circuit 21, and the screw tightening head 1 is moved so that the tip of the screw is at a predetermined interval from the Z0 position, which is the origin position, as shown in FIG. 4a. Approach the workpiece by placing H (within about 5ff)
As shown in Fig. 4 toward the 1st position, the high velocity v1
descend with The tightening motor 16 picks up the screw during this downward movement, and when the screw engages with the screw tightening bit 16 rotating at low speed, the screw can be screwed in at high speed.
The drive voltage is increased as shown in FIG. 4C, and the drive is driven to rotate at high speed.

The Z1 position is calculated from the screw tightening position data h, screw length l, and predetermined interval H input in the control circuit 20,
When the screw tightening head 1 reaches the 21st position, after completing the positioning, it stops instantaneously, and then the drive to the moving motor 11 is switched so that the descending speed becomes v2, and thereafter screw tightening is completed at this speed v2. move towards a position. This speed v2 is determined by the rotation detection means 2 of the screw tightening head 1.
The speed is determined from the rotational speed of the screw tightening bit 16 detected by the output signal from 2, that is, the rotational speed of the screw, and the pressing force of the screw tightening bit 16 against the workpiece by the spring 14, and the correlation between the two is experimentally determined. The moving motor 11 is driven such that the lowering speed is such that reliable screw tightening is achieved. In addition, the spring 14 is designed and installed so that an appropriate pressing force can be obtained when tightening the screw, and the moving motor 11 is designed and installed so that such a pressing force can be obtained.
The driving torque of is controlled.

The screw tightening head 1 descends, and as the speed v2 rises, the screw tip stably bites into the workpiece, and an impactful collision with the workpiece is cushioned and absorbed by the spring 14. When it is detected that the distance to the seat has reached a height of 1 fl, for example, the screw tightening controller 18 is activated as shown in FIG.
At , the driving voltage of the tightening motor 16 is lowered and the rotational speed is lowered. This rotational speed is also determined by the descending speed v2 and the pressure applied to the workpiece by the spring 14, and the correlation thereof has been experimentally evaluated, and the tightening motor 15 is driven so as to enable highly reliable screw tightening. .

After that, the output signal of the rotation detecting means 22 is determined by the control circuit 20.
confirms that the person is seated. When the screw is properly seated, reverse braking is applied to temporarily stop the screw, and after eliminating the influence of mechanical inertia on the screw tightening bit 16, the current value flowing through the tightening motor 15 is gradually increased to gradually increase the screw tightening torque. When the current value reaches a predetermined value, the screw tightening is completed by tightening the current for a predetermined time. Next, the moving motor 11 is driven in the reverse direction to return or move to the origin position Z0 or the vicinity of the next screw tightening position (not shown) at a high speed of V2, thereby completing one screw tightening operation.

As described above, according to this embodiment, after the screw tightening bit is stably engaged with the screw head, it is lowered at high speed to near the screwing position, and after that, the screw bit stably bites into the workpiece and the screw tightens at high speed. It is possible to tighten screws with a large and stable tightening torque, and automatic screw tightening can be performed reliably and stably for all types of screws.

Effects of the Invention According to the screw tightening method of the present invention, as is clear from the above explanation, it is possible to move the bit at high speed up to the vicinity of the position where screw tightening is started, and at the same time, when starting screw tightening, Since the machine moves at a slow speed with a gradual start-up after an instantaneous stop, even if the type or pitch of the thread changes, the screw bite will be stable, and the impact with the workpiece will be cushioned and absorbed by the spring. . Since the screw is forcibly moved at the second speed until the screw is tightened, the appropriate pressure force is not applied to the spring. Screw tightening can be performed efficiently and reliably.

Further, according to the screw tightening machine of the present invention, the screw tightening head is moved at high speed near the screwing start position, and
It is possible to prevent the pressurizing force from becoming excessive during screwing, and as a result, the screw tightening torque can be stabilized without being affected by inappropriate pressurizing force. .

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of a driving section of a moving block, which is the main part of the present invention,
Fig. 2 is a perspective view showing the overall configuration, Fig. 3 is an explanatory diagram of various screws and screw tightening height positions, and Fig. 4 a, b, and c are elevational movements of the screw tightening head in the screw tightening process and their speeds. FIG. 2 is an explanatory diagram of screw tightening drive voltage and screw tightening torque. FIG. 6 is a perspective view of a conventional screw tightening robot. 1... Screw tightening head, 7... Guide member, 9... Guide rail, 10...
Moving block A, 11...Moving motor, 12
...Feed screw, 13...Moving block B114, old...Spring, 16...Tightening motor, 16...Screw tightening bit, 2°.
...Control circuit.

Claims (2)

[Claims] (1) A method of tightening a screw to a workpiece set at a predetermined position using a rotatable bit, in which the tip of the bit is engaged with the head of the screw, and then the tip of the screw is tightened at a predetermined interval. The first step is to place the screw and move it at the first speed to the position where it approaches the workpiece to complete the positioning. After the first step, it stops instantaneously and then starts moving at the second speed until the tip of the screw reaches the workpiece. A screw tightening method comprising a second step of forcibly advancing the bit until completion of positioning. (2) a screw tightening head equipped with a screw tightening bit and a tightening motor that rotationally drives the screw tightening bit; and a moving block A configured with a linear sliding bearing that allows the screw tightening head to move in the distance direction relative to the workpiece; A moving block B comprising the linear sliding bearing that transmits power from the moving motor to the moving block A via a spring, and a control means for driving and controlling the moving motor in response to a screw tightening process. A screw tightening machine featuring