JPS6114865A - 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 Field of the Invention The present invention relates to a method for properly tightening bolts.

``Prior art'' Every time a bolt is tightened to a predetermined angle, the torque gradient is detected, and when this torque gradient decreases by more than one foot from its maximum value, the bolt is tightened to the yield point.
A method has been proposed in the past to stop the bolt from collapsing.

[Invention solves the problem 1. If a bolt is loose, and there is dirt, scratches, rust, etc. on the surface that the bolt's seating surface contacts, the friction coefficient of the bolt's contact surface will change. Tightening is the increase in torque,
In other words, the torque gradient described above is greatly reduced. In other words, when tightening a bolt, a phenomenon (called slippage) occurs in which the rotation angle increases but the torque does not increase.

Further, if a gap exists between the members fastened by the POL K, the above-mentioned slipping phenomenon will similarly occur while this gap disappears.

In the conventional method described above, when such a slipping phenomenon occurs, it is mistakenly determined that the bolt has been tightened to the yield point, so the tightening of the bolt is stopped even though the bolt has not been completely tightened, which is an inconvenience. was occurring.

``Means for Solving the Problems'' The present invention addresses the problems of the conventional method, and the bolt is further rotated by a predetermined angle when the torque gradient decreases by a certain amount from its maximum value. The authenticity of the bolt's yield point is determined based on the torque value and torque gradient value before and after, and the changes in the torque value and torque gradient value during this rotation, etc., and only when the true yield point is detected, the test is performed. I try to stop tightening the bolts.

"Operation" In the present invention, when the torque gradient decreases by more than a certain value from its maximum value, a judgment is made as to whether or not it indicates a true yield point. .

[Implementation 1ull J Hereinafter, the present invention will be described in detail with reference to the drawings.

1 and 2 are flowcharts showing an embodiment of the bolt tightening method according to the present invention. Further, FIG. 3 shows an example of a bolt tightening device for carrying out this method, and the processing steps shown in the above flowchart are executed by the microcomputer 1 provided in this tightening device.

The bolt tightening device shown in FIG. 3 includes a bolt tightening machine 3 for tightening the bolt 2. This bolt fastening machine includes a reversible motor 4, a reducer 6 and a clutch 7 that transmit the power of the motor to a socket wrench 5, and a torque that detects the torque of the bolt 2 by the socket wrench 5 as an electric signal. A detector 8 and a pulse generator 9, such as an incremental encoder, which outputs a pulse signal every time the socket wrench 5 is rotated by a minute angle θ.
It is composed of.

The bolt tightening method according to this embodiment is the device i7! It can be implemented as follows using i-.

That is, as shown in FIG. 6 times), the determination reference value δ of the torque difference ΔT, and the coefficient α (for example, 0
7 to 0.3), a coefficient β for setting a threshold value for determining the authenticity of the yield point (MGXβ), and other conditions are set (step 100).

After setting these conditions, the central processing of the microcomputer 1 shown in FIG. 4110 (hereinafter abbreviated as CPU)
Then, a tightening start signal is applied to l10de-)11. As a result, the motor 4 and clutch 7 are activated via the drive circuit 12, and tightening of the bolt 2 is started (step 101).

FIG. 2 shows details of the difference value calculation process shown in step 102 of FIG. As shown in FIG. 2, in this Stella F102, the count value of the difference counter built in the CPU]O and the count value a of the number counter are initialized to =o and a=OK, respectively. (Steps 102A, 102B).

Next, the value of the difference counter is incremented by one (step 102C), and the Oki port IIK rotation angle input signal is output. As a result, the pulse signal outputted from the pulse generator 9 is taken in, and the number of pulse signals is increased to a preset number or more to a number corresponding to the rotation angle θ□ for sand ringing shown in FIG. A determination is made whether it has been reached (step 102D). When this determination becomes Is, the value a of the sampling number counter is incremented by one (step 102E), and at the same time, the output of the torque detector 8 indicating the torque value Tai at that time is sampled (step 102F).

The sampled Dorkui direct Ta is added to the stored value of this register (initially zero) in the average value register in the CPU 10, and the addition result is the average value 5A(k) for S(k) = □ is drawn in S (step 102G).

Stella 7' 102E to 102GK perform the processing shown in step 102H until the judgment shown in the next step 102H becomes YES. 5 indicates the average value of a=M torque values sampled during the angle step θs in FIG.

If the determination in step 102H is YES, it is determined whether the value k of the difference counter is k)1 (step 1021). Since the value of this difference counter is 1 at the present time, the determination in step 102I is NO (89), and therefore the contents shown in step 102El-1021 are executed again. Then, when k) becomes 1, that is, when two average values 5A(k) are found, the difference between the average value 5A(k) at the current angle step θs and the average value 5A(k-1) at the previous angle step θs G(k) is calculated as the torque gradient (Stella f102J).

Once the difference value G(k) is calculated, step 10 in FIG.
The maximum difference value advancement process shown in 3 is executed, but since only one difference value c(k) has been obtained at this point, this difference value is stored in the maximum difference value register as the maximum difference value MG. be remembered.

In step 104, it is determined whether the bolt 2 has been tightened to the yield point. That is, the difference value G(k) which is the torque gradient obtained in step 102J in FIG.
is the maximum difference value MG K coefficient α (in this implementation, 0.
5) It is determined whether or not the value multiplied by t is equal to or less than the value MGXα. Since G(k)=MQ at this moment, this determination is No, and therefore the contents of Stella 7°102B~]02J shown in FIG. 2 are executed again.

In this way, each time the t, V seat 9 is rotated by 08 degrees, the difference value G(k), which is the torque gradient, is calculated, and the maximum value MG of this difference value G(k) is updated. This difference value G
(k) shows a tendency to decrease as the bolt 9 begins to yield as shown in FIG. 5, and its peak value is left in the register as the final maximum difference value MG.

By the way, even if the determination in step 104 is YES, this does not necessarily indicate a yield point. In other words, if there is dirt, scratches, rust, etc. on the surface that the bolt seating surface contacts, or if there are gaps between the parts fastened by the bolt, then section B in Figure 5, As shown in C, the above-mentioned slippage occurs, and therefore, even though the bolt is not tightened to the yield point K, the degree of increase in torque, that is, the torque gradient, may decrease from the above value MGXα. be.

Therefore, in the present invention, as shown in step 105, when the judgment in step 104 is Y]18S, the bolt is further rotated by an angle θo, and then the next step 1 is performed.
In step 06, it is determined whether the above judgment indicates the true yield point.

4, FIG. 6, FIG. 8, FIG. 10, FIG. 11, and FIG. 13 each show an embodiment of the judgment process in step 106, and in the embodiment shown in FIG.
The tightening angle at which the judgment in step 4 was YES (C, , C in Figure 5)
, point), the above angle θ is determined from the torque value and this angle.
Tightening angle at which the bolt is rotated by o (Fig. 5)
, D2 point) to calculate the difference ΔT in torque values.
106-IA), it is fully determined whether this difference ΔT is ΔT minus δ with respect to the preset value δ (step) 06-
IB).

As shown in FIG. 5, if the Stellar f104 makes a YES decision at point 01, which is not the true yield point, the tightening during rotation at the angle θo has a large torque increase ΔTl, but the true yield point Step 1 at point C2 showing
If the determination in step 04 is YES, the tightening during the rotation of the angle θo will be extremely small by the degree of torque increase ΔT2.

The above preset value δ is set to a value slightly larger than the above increase rate ΔT2 for the true yield point. Therefore, if the judgment of Stella f106-I B is NO, this is the true yield point. In this case, the content shown in steps 102 to 105 is repeated again. When the true yield point is detected in step 104, the determination in step 106B becomes YES, and in this case, a stop signal is output to the I10 port 11 and the tightening of the bolt 2 is stopped (Stella 7"l O7 ).

Note that the tightening angle θo is set to a size that can clear the slip shown in the section BICI, and is set to about 2 to 6 times the sampling angle θs as described above.

Next, the implementation sequence shown in FIG. 6 will be explained. In FIG. 7, if Stella f104's decision is YES at point 61 due to the pseudo-yield point as described above, then straight lines B and D indicated by dotted lines in the same figure, that is, angle θs backward from point 01, A straight line B, DI (for determining the authenticity of the yield point (torque characteristic) is located above the curve BIC+D+ (actually measured torque characteristic) indicating the actually measured torque value variation.

On the other hand, when the true yield point is detected at point 02, the actual torque curve 8 corresponds to the 1st white line 4,
It will be located below 2C2D2.

Therefore, in the embodiment shown in FIG. 6, the above eight points (B1) are selected.

Torque value T8 at point Bx) and point D (D+, D*
) and perform the calculation (step 106-2A).
, ΣTx(θs+θo) based on each torque value sampled between BI Dl r BI Dl
) is calculated (step 106-2B), and it is further determined whether the calculation results Ta and Tb at steps 106-2A and 106-2B have the relationship Ta (Tb) (step 106-2B). -2C).

The value Ta obtained in step 106-2A above, the seventh
In step 10, calculate the area below the straight line Y1'' in the figure.
The value Tb obtained in 6-2A each indicates an area smaller than the curve BCD (B, own DBllhCIB2). Therefore, the judgment of Ste and Zo 106-2C is NO.
If this is the case, [11BCD is below the straight line 100, and a pseudo yield point was detected in step 104 of FIG. 1.On the other hand, the above judgment is YE
In the case of S, the true yield point is detected in the same step fl04.

In addition, in this example, the authenticity of the yield point is determined based on the above-mentioned area size relationship, but the function form under the straight line W is determined, and the value of the rotation angle corresponding to the 0 point is substituted into this function. Alternatively, the torque value on the straight line may be determined, and this torque value may be compared with the torque value at the zero point.

In the embodiment shown in FIG. 8, the 0 point (CI) shown in FIG. 9 corresponds to YES in step 104 shown in FIG.

Torque difference value G(k) at point Cz) and point D (D+
+B2) immediately before the same difference value G(k10.) or G(k10.).

<G(k) (Stella 7'106-3A).

As is clear from FIG. 9, if the decision in step 104 is YES based on the pseudo yield point (point C1), G(
k10. ) > G(k), but the true yield point (Cz point)
If the judgment in the same step is YES, then G(
k10. )<G(k), the relationship S holds true.

Therefore, the judgment in Ste.zo 106-3A above is YES.
.

Based on No., it is determined whether the yield point is true or false.

In the embodiment shown in FIG. 0, the torque difference value G (k100) shown in FIG. 9 is the threshold M G for detecting the yield point.
It is determined whether the relationship G(k+θo)<MGxα exists for Xα (step 106-4A).

When a pseudo yield point is detected at point C1, (c(k 〇〇) > MGXα as shown in Fig. 9, but when a true yield point is detected at point 02, G ) (MGXα. Therefore, the true yield point can be determined based on the determination result of step 106-4A above.

In the embodiment of FIG. 11, a threshold value MGXβ(β〈]) different from the force threshold value MG
is set, and it is determined whether the torque difference value G(k+00) has a relationship of G(k + θo)(MG×β) with respect to this threshold value MGXβ (Stella 7'105-A)
. As is clear from the figure, if the bolt is tightened to the true yield point, the determination is YES.

FIG. 13 shows another implementation ρat of yield point authenticity determination. As is clear from FIG. 14, when a pseudo yield point is detected at point 01, the difference value always tends to increase by at least one degree between point C and the above eight points. When the true yield point is detected at point 02, the light minute value tends to decrease by the order of llji between point C2 and point B2.

In this embodiment, all determinations of whether the yield point is true or false are made by focusing on this point. That is, after setting the value nkn=o of a counter (provided in the CPU 10) that counts the number of difference values between the 0 point and the D point, (step!/7''
106-6A) and increase this value n by 1 (step 1
06-613), then G(k+nXθs)≦G(
k+(n-1)XθS) (Stella: 7'106-6C).

In this step 106-6C, when n=1, G
(k+θs) or G(k), that is, G(k)≦M
For the difference value c(k) at the time of GXα, C,
A determination is made as to whether or not the first detected difference value G(k+θB) between D is decreasing. If a pseudo yield point C, appears then, in the example of FIG. 14, the first detected difference value G(k+θS) becomes larger than G(k). As a result, if the determination in step 106-6C is No, the contents shown in steps 102 to 105 shown in FIG. 6 are executed again.

Note that the first detected difference value G(k108) is G(k
), that is, if the determination in step 106-6C is YES, a determination is made as to whether the counter value n is negative (step 106-6D), and if this determination is NO, step I06-6 B.

The contents of 106-6C are executed again. and interval CI
In DI, if there is always an increasing trend in the difference value, the answer is No.

If the true yield point is detected at point C2, sections C and D
The difference values detected at , , , and the like sequentially decrease as described above. Therefore, it is determined that the counter value G(k)2 indicates the true yield point.

There are further methods for detecting the true yield point as follows. That is, as shown in FIG.
, D, the degree of increase in torque during section C2D2 is gentler than that between section C2D2. The torque increase/turn at the angle θo after the pseudo-yield point appears and the torque increase/turn at the same angle θo after the true yield point appears are different from each other. Therefore, one or both of the torque increase patterns during the angle θo for the pseudo yield point and the true yield point are stored in advance in the RAM 13K shown in FIG. If YES, the above angle θ
The increase pattern of the measured torque during o and the above RAM1
If we use the correlation method to find the degree of similarity with the No.4 turn stored in No.3, the above steps can be achieved.

It can be determined whether the YES determination in step 104 indicates a pseudo yield point or a true yield point.

FIG. 15 shows the shaft extension diagram of the M12ytr bolt, the conventional bolt tightening method and the bolt tightening method according to the present invention, and the stopping accuracy (1) and (2) of each tightening method. The data of (2) are shown in Figures 4, 6, 8, 10, and 1 when θo = 20° and α = 0, 6.
This is based on the embodiments shown in FIGS. 1 and 13.

In Fig. 15, the tightening and stopping accuracy according to the conventional method is shown when the pseudo yield point described above does not appear, and the variation in the axial force is ±20%.

By using the method according to the present invention, the variation in axial force is within ±1.2% regardless of whether the above-mentioned pseudo-yield point appears, which suggests that tightening has excellent stopping accuracy. are doing. In addition, in the method of the present invention, after the bolt is tightened until it reaches its yield point, it is further tightened by the above-mentioned angle θo, so the bolt will extend by 80 μm toward the plastic region, but this degree of elongation is not There are no problems.

In the above embodiment, the torque difference value, which is the torque gradient, is detected in the manner shown in FIG. 2, but the torque gradient may be determined by other methods. That is, for example, as shown in Fig. 16, for each tightening sampled in the section of angle θs, the average value 5 (J) of the torque (6 in the figure) is calculated every time the number of samples increases by 1, and the average value is calculated. 5(J) and the average value S'(J-m) before m sampling steps may be determined as the torque gradient.

Further, the number of differential samplings of torque between the start and end of the section of angle θ6 in the figure is set to one.

In the above embodiment, the threshold shown in step 104 is set to MG
For example, the maximum difference value MG and the second
, take the average value of the third largest difference value, and calculate this '11
- A value obtained by multiplying the average value by α may be used as the threshold value in this step f104.

Similarly, the threshold value MGXβ shown in FIG. 11 can also be replaced with a value obtained by multiplying the above average value by one.

"Effect" According to the present invention, a pseudo yield point is caused by dirt, scratches, rust, etc. existing on the surface where the bolt seating surface contacts, or by gaps between members fastened by the bolt. Even if the above-mentioned pseudo-yield point appears, bolt tightening continues until the true yield point appears.Therefore, this method solves the problem of the conventional method in which bolt tightening is stopped due to the above-mentioned pseudo yield point. Can be tightened properly and reliably.

[Brief explanation of drawings]

1 and 2 are flowcharts showing an embodiment of the bolt tightening method according to the present invention, FIG. 3 is a block diagram showing a line of equipment for carrying out the method of the present invention, and FIG. 4
The figure is a flowchart showing an example of the processing procedure of the yield point authenticity determination step in the flowchart shown in Figure 1. Figures 6, 8, 10, 11, and 13 are FC flowcharts showing other sequences of processing procedures in the point truth judgment steno, Fig. 5, Fig. 7, Fig. 9
The figures and FIGS. 12 and 14 are respectively shown in FIGS.
8, 10, 11, and 13 are graphs explaining the contents of the processing procedure, and FIG. 15 shows a conventional bolt tightening method and a bolt tightening method according to the present invention. Attached are graphs showing each stopping accuracy, and FIG. 16 is a diagram illustrating another method for determining the torque gradient. 1...Microcongeator, 2...Volt, 3.
...Bolt fastening machine, 4...Motor, 8...Torque detector, 9...Pulse generator, 10...CPU. Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 10 Fig. 9 Fig. 11 Fig. 12 Fig. 13

Claims (7)

[Claims] (1) Every time the bolt is tightened by a predetermined angle θ_s, the gradient of the tightening torque is detected, and when this torque gradient becomes less than the maximum value or a value close to it multiplied by α (<1), the tightening torque The above bolt is further tightened by a predetermined angle θ_o set to a size that can clear the slippage, and the value of the tightening torque at the end of tightening at this angle θ_o and the value of the tightening torque at the start of tightening at this angle θ_o is A bolt tightening method characterized in that a difference is determined and tightening of the bolt is stopped when the difference is larger than a predetermined value. (2) Every time the bolt is tightened by a predetermined angle θ_s, the gradient of the tightening torque is detected, and when this torque gradient becomes less than the maximum value or a value close to it multiplied by α (<1), the tightening torque The bolt is further tightened by a predetermined angle θ_o that is set to a size that can clear the slippage, and the above angle is calculated from the tightening torque value at the end of tightening at this angle θ_o and the angle at the start of tightening at this angle θ_o. The torque characteristic for yield point authenticity determination is determined by a straight line connecting the tightening torque value at the tightening angle θ_s before, and the actually measured torque characteristic between both ends of the straight line is located above the above torque characteristic for authenticity determination. A method for tightening a bolt, characterized in that tightening of the bolt is stopped when the above-mentioned case occurs. (3) Every time the bolt is tightened by a predetermined angle θ_s, the gradient of the tightening torque is detected, and if this torque gradient becomes less than the maximum value or a value close to it multiplied by α (<1), the tightening torque Further tighten the bolt by a predetermined angle θ_o set to a size that can clear the slippage, and make sure that the value of the torque gradient at the end of tightening at this angle θ_o is greater than the value of the torque gradient at the start of tightening at this angle θ_o. A bolt tightening method characterized in that tightening of the bolt is stopped when the bolt is small. (4) Every time the bolt is tightened by a predetermined angle θ_s, the gradient of the tightening torque is detected, and when this torque gradient becomes less than the maximum value or a value close to it multiplied by α (<1), the tightening torque The bolt is further tightened by a predetermined angle θ_o set to a size that can clear the slippage, and the value of the torque gradient at the end of tightening at this angle θ_o is smaller than the maximum value or a value close to it multiplied by α. A method for tightening a bolt, characterized in that tightening of the bolt is stopped when the above-mentioned case occurs. (5) Every time the bolt is tightened by a predetermined angle θ_s, the gradient of the tightening torque is detected, and when this torque gradient becomes less than the maximum value or a value close to it multiplied by α (<1), the tightening torque The bolt is further tightened by a predetermined angle θ_o that is set to a size that can clear the slippage, and the value of the torque gradient at the end of tightening at this angle θ_o is the maximum value or a value close to it β (<1)
A bolt tightening method characterized by stopping bolt tightening when the value is smaller than the multiplied value. (6) The gradient of the tightening torque is detected every time the bolt is tightened by a predetermined angle θ_s, and if this torque gradient becomes less than the maximum value multiplied by α (<1), the slippage of the tightening torque is cleared. Tighten the bolt further by a predetermined angle θ_o that is set to a size that allows the angle θ_o to be
A bolt tightening method characterized in that tightening of the bolt is stopped when the torque gradient in the angular range from the start of tightening to the end of tightening tends to decrease sequentially from the value of the torque gradient at the start of tightening. . (7) Every time the bolt is tightened by a predetermined angle θ_s, the gradient of the tightening torque is detected, and if this torque gradient becomes less than the maximum value multiplied by α (<1), the slippage of the tightening torque is cleared. Tighten the bolt further by a predetermined angle θ_o that is set to a size that allows the angle θ_o to be
The above angle θ_
A bolt characterized in that it is determined whether or not the torque gradient at the start of tightening of o indicates the true yield point of the bolt, and if the torque gradient indicates the true yield point, the tightening of the bolt is stopped. Tightening method.