JPS6186142A - Screw fastening control - Google Patents

Abstract

PURPOSE:To prevent fastening torque from increasing over a preset value by decelerating a runner which revolves at a high speed to a low speed before a nut is set, thus reducing the inertia force on setting. CONSTITUTION:A DC servomotor 25 is revolution-driven at a high speed N1 by a screw-fastening starting instruction, and a nut runner 20 screws a nut 12 into a housing 13. With said starting instruction, a timer 27 is started, and when said timer times-up before the nut 12 is set onto a bearing 11, the revolu tion of the DC servomotor 25 is reduced to a low speed N2. When the nut 12 is set onto a bearing 11, and it is confirmed that the torque signal input by a torque detecting apparatus 24 reaches a previously set torque value T1, the revolution of the DC servomotor 25 is suspended. Further, the DC servomotor 25 is started further at a low speed N3, and the nut 12 is further tightened, and when the torque reaches a set value T2, the revolution of the DC servomo tor 25 is suspended.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a screw tightening control method for tightening a screw component to a set torque.

<Prior art> In general, when tightening threaded parts such as bolts and nuts using a nut runner using a DC servo motor, the nut runner is rotated at high speed until the threaded part is seated, as shown in Fig. 4. The nut runner is temporarily stopped when seating is confirmed, and then the nut runner is started at low speed and tightened to the set torque.

<Problems to be solved by the invention> However, as mentioned above, in the case where threaded parts are tightened using two-speed control, especially when tightening large-diameter nuts, etc., the inertia of high-speed rotation is used to set the screws when seated. There are cases where the torque exceeds the limit, and there is a problem that torque control becomes impossible.

〈Means for solving problems〉.

The present invention has been made to solve the above-mentioned conventional problems.
Then, after a certain period of time, the nut runner is decelerated to low speed,
The nut runner is stopped after confirming that the threaded part is seated, and then the nut runner is started at a low speed and tightened to a set torque.

<Example> Embodiments of the present invention will be described below based on the drawings. .

FIG. 1 shows an example in which a nut 12 that applies a preload to a bearing 11 that rotatably supports a rotating shaft 10 is screwed to a housing 13. A nut runner 20 is provided with a head 21 that is rotatably and axially movable. This head 21
A driving pin 22 that removably engages with the engagement hole 12a of the nut 12 and a grip claw 23 that grips the nut 12 on the inner diameter are provided at the tip of the nut 12. The head 21 is connected to a DC servomorph 25 via a torque detection device 24, and the DC servo motor 25 rotates the head 21 at high speed and low torque or at low speed and high torque.

Reference numeral 26 indicates a control circuit for controlling the DC servo motor 25, and this control circuit 26 controls the rotation of the DC servo motor 25 by Nl, N2, . It is designed to control to the third speed of N3. A torque signal detected by the torque detection device 24 is input to the control circuit 26, and this torque signal is used as the preset seating torque Tl or the set torque T2.
When the rotation of the DC servo motor 25 is reached, the rotation of the DC servo motor 25 is stopped. Reference numeral 27 indicates a timer activated by the screw tightening start command, and as described later, this timer 27 is time-amplified before the nut 12 is seated on the bearing 11, and this time-amp signal is input to the control circuit 26. This causes the control circuit 26 to control the DC servo motor 25.
It is designed to slow down the rotation of.

Next, the operational steps for controlling the tightening of the nut 12 will be explained based on FIGS. 2 and 3. In response to the screw tightening start command, the DC servo motor 25 is driven to rotate at high speed N1 in step 31, and the nut runner 20 holding the nut 12 screws the nut 12 into the housing 13 at high speed.

Along with this screw tightening start command, the timer 27 is energized,
When this timer 27 times up before the nut 12 is seated on the bearing 11, this time up occurs in step 3.
2, and the rotation of the DC servo motor 25 is decelerated to a low speed N2 in step 33. From this, the nut runner 20 screws the nut 12 at low speed, and it is confirmed in step 34 that the nut 12 is seated on the bearing 11, and that the torque signal input from the torque detection device 24 has reached the preset seating torque T1. Then, the rotation of the DC servo motor 25 is stopped by the stator 35. Next, in step 36, the DC servo motor 25 is started at a lower speed N3, and the nut 12 is further tightened. When it is confirmed in step 37 that the torque signal detected by the torque detection device 24 has reached the preset torque T2, the rotation of the DC servo motor 25 is stopped in step 38, and the screw tightening is stopped. Complete.

In this way, by first rotating the nut runner 20 at high speed N1 and then decelerating it to low speed N2 before the nut 12 is seated, the inertial force at the time of seating can be reduced, and as a result, as shown in FIG. The tightening torque does not exceed the set value, and the nut 12 is tightened during subsequent retightening.
You will be able to accurately tighten screws to the set torque value.

In the embodiment described above, an example was described in which the rotation of the nut runner 20 is controlled by the DC servo motor 25, but the rotation drive device may be one using air as the drive source.

It goes without saying that the present invention is applicable not only to nuts but also to other threaded parts such as bolts whose tightening torque must be controlled.

<Effects of the Invention> As described above, in the present invention, since the nut runner is decelerated to a low speed before the nut is seated, the inertia force at the time of seating can be reduced, and therefore, by starting the nut launcher at a low speed afterwards, It has the effect of accurately tightening the nut to the set torque value.

[Brief Description of the Drawings] Fig. 1 is a diagram showing an example of tightening a nut according to an embodiment of the present invention, Fig. 2 is a flowchart showing steps of the screw tightening control operation, and Fig. 3 is a nut runner according to the present invention. FIG. 4 is a diagram showing a rotational speed diagram and a torque diagram of a nut runner in a conventional method. 12...Natsuto, 20...Natsutranna, 24...
・Torque detection device, 25...DC servo motor, 26
...Control circuit, 27...Timer.

Claims (1)

[Claims] (1) A method of tightening threaded parts such as bolts or nuts to a set torque using a torque-detectable nut runner, in which the nut runner is first rotated at high speed, and after a certain period of time, the nut runner is decelerated to a low speed to seat the threaded part. A screw tightening control method characterized in that the nut runner is stopped upon confirmation, and then the nut runner is started at a low speed and tightened to a set torque.