JPS618285A - Method of tightening 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] "Industrial Application Field" What does the present invention cover? Relates to methods for properly tightening bolts.

“Conventional technology”? Every time the bolt is tightened to a predetermined angle, the torque gradient is detected, and what happens when this torque gradient decreases beyond a certain level beyond its maximum value? Conventionally, a method has been proposed in which the tightening of the I-rut is stopped by assuming that the I-rut has been tightened to the yield point.

[Problem to be solved by the invention] When tightening a bolt, if there are dents, scratches, rust, etc. on the surface that the seat of the bolt contacts, the friction of the contact surface of the bolt will increase. The coefficient changes and tightening is the degree of increase in torque,
tbThe above torque gradient is greatly reduced.

Further, if a gap exists between each member fastened by a bolt, the torque gradient similarly decreases significantly while the gap disappears.

What if the above conventional method does not work? Since it is determined that the bolt has been tightened to the yield point, this causes an inconvenience in that the tightening of the bolt is stopped even though the bolt has not been completely tightened.

"Means for Solving the Problems" In the present invention, the relationship between the torque range and torque gradient is determined in advance for tightening at which the yield point should appear. Then, when a decreasing change in the value of the torque gradient is detected at the time of actual tightening, the torque value of the tightening at the time of detection is the above-mentioned tightening which is determined in advance with respect to the torque gradient at the time of actual tightening. It is determined whether or not the torque is within the range, and if it is within the range, tightening is completed as the decreasing change in the torque gradient value indicates the yield point, and if it is not within the range. I am trying to continue tightening.

"Function" 4 According to the present invention, when the torque gradient decreases, 1
When tightening at the time of change, a judgment is made as to whether the torque value is within the range of torque at which the yield point should appear. Tsutb
A determination is made whether the port has been tightened until the true yield point appears.

Embodiment FIG. 1 is a flowchart showing an embodiment of the bolt tightening method according to the present invention. FIG. 2 shows an example of a device for carrying out this method, in which the procedure shown in FIG. 1 is carried out by a microcomputer l of this device.

The device shown in FIG. 2 includes a motor 2, a reducer 4 and a clutch 5 that transmit the power of the motors to a socket wrench 3, a torque detector 6 that detects the tightening torque of the socket wrench 3, and a torque detector 6 that detects the tightening torque of the socket wrench 3. NoJ every time 3 rotates by a small angle?
The bolt fastening machine 8 is provided with a pulse generator 7 such as an incremental encoder that outputs a pulse signal, and the port 9 is tightened by this fastening machine 8.

Figure 3 shows that the friction coefficient μ is large when the bolt 9 is tightened.
For medium and small tightening, the tightening torque change characteristics A, B, and C with respect to the rotation angle θ are shown as examples, respectively.

As these characteristics A, B, and C show, when the cult is tightened within its elastic range, the gradient of torque -Ti- (hereinafter referred to as torque gradient) is almost constant; In the plastic region where the torque is tightened above the elastic limit (yield point), the torque gradient decreases rapidly. Therefore, based on the torque gradient, it is possible to detect the yield point indicating the boundary between the elastic region and the plastic region, and steps 100 to 111 in FIG. It shows.

First, in Stella 7'100, the sampling interval M'',
,) The maximum value of the gradient (dθ Wa
Conditions such as the number of X are set. The central processing unit lO (hereinafter referred to as CPU) of the microcomputer 1 shown in FIG.
), a tightening start signal is output to the capo) 11, which starts the motor 2 and clamp 5 via the drive circuit 12, and starts tightening the bolt 9 (Stella 7). °101).

Simultaneous random access memory 13 (hereinafter referred to as RAM)
The maximum torque slope stored in (Stella fl 02 ) is initialized (abbreviated as Stella fl 02 ), and the CPU 10 is also initialized. A torque acquisition signal is output to the torque detector 11, and the current torque T, which is outputted by the torque detector 6, is inputted via the power converter 14 (step 103) @further to the CPU 10. , 9 The output/base pulse of the pulse generator 7 is read by the rotation angle capture signal output to the I10 port, and the number of pulses is set to the preset number J? Lus number increase: When the Lus number reaches the 4 Lus number that indicates the sampling interval θ8, the angle counter value a in the RAM 13 is increased by one, and at the same time the tightening torque value T at that time is increased.
is loaded.

is applied. Then, after changing from T1 to T3 (No because the step is the initial value 0, and then step 1
At step 10, the calculation result T of step 106 is stored in RAM 13 as (69)mlLX. Thereafter, the contents of steps 104 to 110 are repeatedly executed nine times until the determination in step 7'109 becomes YES.

If the judgment in Step 109 becomes YES, then the torque gradient decreases, and the torque gradient at the time when the judgment becomes YES becomes the value obtained by multiplying the maximum torque gradient (d#) by the multiplier K. It is determined whether or not the size is also small (step 111). (11) × means a threshold value for detecting the yield point based on the d9 maX torque gradient, and the multiplier is usually set to 0.6 to 0.4.

By the way, even if the above judgment result is YES, it cannot necessarily be said that it suggests a yield point. In other words, for example, there may be dirt, scratches, or
If there is rust, etc., or if there are gaps between the parts that are tightened together, the torque gradient will suddenly decrease during the bolt tightening process, as shown in Figure 4. As shown in , the pseudo yield point P′ appears before the true yield point P appears.
appears. In the yield point detection algorithm described above, even if such a pseudo yield point P' appears, the determination in step 111 is YES. Therefore, even if Ste.zo111's decision is YES, it does not necessarily indicate the true point of surrender.

Therefore, in the present invention, the true yield point is detected in the following manner.

In other words, as shown in Figure 3, the torque gradient in the elastic region differs depending on the magnitude of the friction coefficient, and this difference is due to the tightening torque range δ (hereinafter abbreviated as torque range) that corresponds to the yield point. The torque gradients shown in the figure and their corresponding torque ranges δ1. δb, δ. There is a correlation.

In the present invention, paying attention to this point, we experimentally measured a plurality of torque gradient values in the above-mentioned elastic region and the values of the torque range H for them using the apparatus shown in FIG. It is stored in the RAM 13 in advance and used to determine the yield point during actual tightening. In addition, the above tightening was conducted in an experiment where the tightening torque was 3rd.
When the changes shown in the figure occur, the above experimental data will be as shown in the table below.

The yield point determination based on the above experimental data is as follows. For actual tightening, sometimes the judgment in step 111 is Y.
If it becomes ES, the tightening at that point reads the torque TK (step 112), and calculates the average value of the torque gradient position F at each sampling time stored in Stella f107 (Stella 7''113). Then, the torque range δ for the calculated average torque gradient is stored in RAM 1
3 (step 114), and it is determined whether the tightening read by the step 112 includes the torque value TK within the read torque range δ (step 115).

Therefore, for example, if the average torque gradient calculated by Stella f113 is the torque gradient (7-) for characteristic A in FIG.
, the torque range δ=δ is read out from the RAM 13, and within this torque range δ1, the torque value TK shown in the figure is
A determination is made in step 115 whether & is included. The above torque TI.

The tightening in which the true yield point should appear is included in the torque range δ1, so in this case, the above step 115
The judgment becomes YES.

On the other hand, due to the pseudo yield point P' shown in FIG.
If the determination in step 11 is YES, the torque value TQ shown in the figure is read in step 112. In this case, the torque value TK& is not included within the torque range δ1, and therefore the determination at step 115 is
becomes.

In step 115, it is determined whether the yield point is the true yield point P or the pseudo yield point P', and if it is the true yield point, the tightening of the bolt 5 is stopped (stellar 7° 1
16), if the yield point is a pseudo yield point, the bolt 5 is continued to be tightened (lO) until the true yield point P' is determined.

As a result, according to this embodiment, it is possible to avoid the problem of the conventional device, that is, the inconvenience that bolt tightening is stopped when the pseudo yield point P' is detected.

Note that while the bolts are tightened, the necessary data is sent to the printer 16 and CRT via the interface 15.
recorded and displayed.

``Effects of the Invention'' According to the present invention, a pseudo yield point is caused by dirt, scratches, rust, etc. existing on the surface where the seating surface of the bolt contacts, or by gaps between members fastened by the bolt. Even if this occurs, tightening of the gel continues until the true yield point appears.

Therefore, the problem of the conventional method in which gelt tightening is stopped due to the pseudo yield point is solved, and gelt can be reliably tightened.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an embodiment of the gel tightening method according to the present invention, FIG. 2 is a block diagram conceptually showing an example of an apparatus for carrying out the method of the present invention, and FIG.
The figure is a graph illustrating the change characteristics of torque for tightening with respect to the rotation angle, and FIG. 4 is a graph illustrating the change characteristics of torque for tightening when a pseudo yield point appears.

Claims (1)

[Claims] The relationship between the tightening torque range in which the yield point should appear and the torque gradient is determined in advance, and when a decreasing change in the value of the torque gradient is detected during actual tightening, the tightening torque value at the time of detection is determined in advance. It is determined whether the torque gradient during tightening is within the range of the above-mentioned tightening torque determined in advance, and if it is within the range, the tightening is performed assuming that the decreasing change in the above-mentioned torque gradient value indicates the above-mentioned yield point. A bolt tightening method characterized in that the bolt tightening method is characterized in that the bolt tightening is continued if the