JPS60201882A - Method of clamping bolt - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of detecting the yield point of a bolt and tightening the bolt.

(Prior art) Conventionally, in the bolt yield point tightening method, both the tightening torque and the rotation angle of the bolt are electrically measured during bolt tightening, and the slope of the torque value per unit rotation angle is calculated. Then, the yield point of the bolt is detected from the change in the gradient of the obtained torque value, and the tightening of the bolt is completed.

By the way, when tightening head bolts, washers'
In the case of bolts that are tightened through a be. In addition, when conventional torque value gradient calculations are used, the electrically obtained torque signal is sensitive to the influence of noise. may drop and be detected by reaching the yield point.

(Object of the Invention) The present invention has been made in view of this point, and provides a tightening method that can accurately detect the yield point and tighten bolts even if the tightening torque decreases midway through. The purpose is to

(Structure of the Invention) The structure of the present invention that achieves this object is that when the tightening torque decreases during bolt tightening due to co-rotation of washers, etc., the torque value of the previous torque is replaced by the decreased torque amount. After correction, the yield point is determined based on the change in the gradient of the torque value per unit rotation angle of the bolt, and the bolt is tightened.

As in the present invention, if the torque amount that has decreased during tightening is corrected by adding it to the previous torque value, it is possible to accurately calculate the gradient of the torque value after the decrease.
The yield point of the bolt can be detected accurately. Therefore, even if the tightening torque decreases due to co-rotation of the washer, etc., the tightening of the bolt will not be terminated prematurely, and the bolt can be reliably tightened to its yield point.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
The figure shows a bolt tightening device used when carrying out the bolt tightening method of the present invention. A bolt tightening device 1 disposed movably in the XX direction is equipped with an air motor 3 as a rotational drive device on one side of a support plate 2, and the air motor 3 generates a rotation angle signal proportional to the rotation angle of the bolt 4. It has a rotation angle sensor 5 that generates rotation. The air motor 3 is driven by air supplied from an air source (not shown) through an air pipe 6, and a solenoid valve 7 is provided in the middle of the air pipe 6 to cut off the air supply to the air motor 3. There is.

A speed reduction mechanism 8 is connected to the air motor 3, and its output shaft 9
is equipped with a torque sensor 10 that generates a torque signal proportional to the instantaneous torque. The output shaft 9 extends to the other side of the support plate 2, and a bolt tightening socket 11 that rotates integrally with the output shaft 9 is added to the tip I11 of the output shaft 9.

Rotation angle sensor 5, torque sensor. The screws 10 are electrically connected to a measuring unit 14 of a microcomputer, which is a bolt tightening control device, via cables 12 and 13, respectively, and the rotation angle signals detected by the rotation angle sensor 5 and the torque sensor 10 are The generated torque signal is configured to be sent to the measurement unit 14. Further, the measurement unit 14 and the electromagnetic valve 7 are electrically connected via a cable 15, and a command signal is sent from the measurement unit 14 to the electromagnetic valve 7.

The measurement unit 14 includes a storage unit that stores a series of torque signals, and when a later torque value in the series of torque signals is lower than the previous torque value, the subsequent torque values are changed by the decreased torque amount. , a storage section that stores the corrected torque value in addition to the previous torque value, and a torque signal (when the torque decreases, t
a calculation unit that calculates the torque gradient per unit rotation angle from the corrected torque signal) and the rotation angle signal, and a torque gradient K when the tightening torque reaches a predetermined torque value TkK.
a storage unit that stores the set percentage value θk for the torque gradient; a determination unit that determines whether the torque gradient that changes from time to time has become equal to the value θ; It is generally composed of a valve driving section that cuts the air supply to the air motor 3 based on the determination result. Note that the comparison of the torque values before and after the series of torque signals is performed using the torque values input from the torque sensor 10. In FIG. 1, 16 is a washer, and 17 and 18 are objects to be fastened.

When tightening the bolt 4 using the device configured as described above, the rotation angle signal from the rotation angle sensor 5 and the torque signal from the torque sensor 10 are input to the measurement unit 14, and the rotation angle signal per applied rotation angle is input to the measurement unit 14. A slope calculation of the torque value is performed. Specifically, as shown in FIG. 2, the torque-rotation angle data is started to be extracted from one snug torque TQi, and when the torque exceeds the predetermined torque TkVC, the gradient calculation of the torque-rotation angle is started. The relationship between the torque gradient value calculated by the measurement unit 14 and the rotation angle is shown in FIG. 1 to the set percentage value θ of the torque gradient (reference gradient) K when the torque gradient is a predetermined torque value Tk.
In other words, when MK is reached, a valve cut command signal is sent from the measurement unit 14 to the electromagnetic valve 7, and the tightening of the bolt 4 is finished. Note that it goes without saying that the set percentage value ek is not limited to % and can be changed arbitrarily.

The torque waveform in FIG. 2 is undulating, but this is because noise is added to the electrical signal from the torque sensor 10 and the voltage varies. In order to reduce the influence of this noise, the torque gradient can be calculated using the following equation (see FIG. 4).

Torque gradient K = (TV+TI+T)/3-(T
t-1-Ts+TS)/3 In other words, out of the torque values at nine consecutive points, the average value of the first three points is subtracted from the average value of the last three points, and this is used as the torque gradient. Just calculate it. According to the calculation method B, the influence of noise is considerably smoothed, and it is possible to obtain a result t that is sufficiently satisfactory for yield point control.

By the way, in the example in which the washer 16 is sandwiched between the bolt 4 and the object to be fastened 17 as shown in FIG. 1, the bolt 4 and the washer 16 often rotate together during the tightening process. If they rotate together, a phenomenon occurs in which the tightening torque significantly decreases. FIG. 5 shows an example in which the tightening torque was significantly reduced. As is clear from Fig. 5, in the calculation method shown in Fig. 4, which calculates the torque gradient from the torque values at nine consecutive points, when the bolt 4 and washer 16 rotate together and the tightening torque decreases, According to the calculation, the torque gradient becomes % of the torque gradient (reference gradient) K when the torque value is 1"k, and the tightening of the bolt 4 ends midway.

In addition, in FIG. 5, A shows a torque curve, B shows a torque gradient curve, and C shows a pulp cut gradient value.

Co-rotation of the washer 16 can be dealt with by the gradient calculation method shown in FIG. That is, when the washer 16 rotates together and the tightening torque decreases while tightening the bolt 4, the subsequent torque value is corrected by adding the amount by which the torque decreased to the previous torque value. The black circles in Fig. 6 are the corrected torque values Ty, Ts, Ts,
Tto.

1゛ indicates the village. The torque gradient after correction is calculated using the following formula.

Torque gradient K = (TV +T9 +T11) /
3-(Tt-1-Ti+Ts)/3 In other words, take out the torque value at every other point among the 11 consecutive torque values, and calculate the torque value T7 at the latter three points. To, Tl
Torque values TI, TI of the three points earlier than the average value of l
, T5 is subtracted and the torque gradient is calculated. The bolt 4 is tightened by determining the yield point from the change in the torque gradient obtained by applying pressure in this manner. Therefore, due to the change in the torque gradient calculation method, even if the washer 16 rotates together and the torque decreases,
It is possible to accurately tighten the bolt 4 to the yield point without having to finish tightening the bolt 4 in the middle. Since the calculation method shown in FIG. 6 calculates every other torque, the influence of noise is smaller than the calculation method shown in FIG. 4. Furthermore, the method of adding only the reduced torque amount has the advantage that the calculation method is simple and the processing time by the measuring unit 14 is shorter than that of the conventional method.

Torque curve A controlled by the calculation method shown in Fig. 7 and Fig. 6
and a torque gradient curve B.

If the washer 16 does not rotate together and the bolt 4 is normally tightened, calculate the torque gradient K from the following equation using the gradient calculation method shown in FIG.

Torque gradient = (1'y-1-To-1-Ttt)
/3- (TI+T3+T!)/3 In other words, take out the torque value every other time among the 11 consecutive torque values, and calculate the torque values of the latter three points 'l'y, To, T
The one before the average value of ll.

The torque gradient is calculated by subtracting the average value of the three torque values 'I'l, Ts, and Ts.

(Effects of the Invention) As described above, according to the method of the present invention, after correcting the torque value that decreased during tightening, the bolt is tightened by determining the yield point from the change in the torque gradient. Even if the torque decreases due to the influence of noise, the bolt can be reliably tightened to its yield point.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing a bolt tightening device according to an embodiment of the present invention, FIG. 2 is a torque waveform diagram obtained by tightening bolts with the device shown in FIG. 1, and FIG. Figure 4 is a torque gradient waveform diagram obtained by tightening bolts using the device shown in Figure 1.
5 is a waveform diagram showing a torque curve and a torque gradient curve when the torque decreases. FIG. A torque waveform diagram showing a part of Figure 2 enlarged to explain a torque gradient calculation method different from the calculation method in Figure 4; Figure 7 shows the torque curve and torque curve obtained by the calculation method in Figure 6; FIG. 8, a waveform diagram showing the torque gradient curve, is a partially expanded version of FIG. It is a torque waveform diagram shown. l...Bolt tightening device 4...Bolt 5...Rotation angle sensor 10...Torque sensor 16...Washer 17.18. ...Applicant for the patent for the object to be concluded Toyota Motor Corporation

Claims (1)

[Claims] (1) If the tightening torque decreases while tightening a bolt, correct the subsequent torque value by adding the decreased amount of torque to the previous torque value, and calculate the torque per unit rotation angle after correction. A bolt tightening method characterized by tightening the bolt by determining the yield point of the bolt by changing the gradient of the value.