JPS5856772A - Bolt clamping method using load control washer - 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 The present invention relates to a bolt tightening method that uses a load control washer that plastically deforms under a predetermined tightening load and controls the amount of tightening by a digital calculation device.

Conventionally, the dυ bolt is tightened with a predetermined tightening load using a load control washer that plastically deforms with a predetermined tightening amount 1 within the elastic deformation range of the bolt. As this load control washer, for example, LC washer (trade name) manufactured by Nippon Steel Corporation and Nippon Steel Rutin Corporation is known.

FIG. 1 is a diagram showing the state in which such a load control washer is used, with the figure shown before tightening and the figure shown after tightening completed. In these figures, reference numerals 51 and 52 are bodies to be tightened, 53 is a bolt passing through these bodies 51 and 52, 54 is a load control washer, and 55 is a nut. As the nut 55 is tightened from the state shown in (6) in the same figure, the plastic deformation of the washer 54 progresses and becomes flat, resulting in the state shown in (B). In the process of plastic deformation of the washer 54, the gel 53 Since the axial force is approximately constant, the tightening torque during that period is also approximately constant. Therefore, if the tightening is stopped at the end of the plastic deformation range of the washer 54, the tightening torque can be set to a predetermined value determined by the type of the washer 54.

The second head shows the relationship between the tightening torque T and the tightening time t, and point A in the figure indicates the starting point of plastic deformation of the load control washer 54, and point B indicates the ending point of plastic deformation.

In this way, the tightening torque T is approximately constant in the plastic deformation range between points A and B.

Various methods have been proposed in the past to detect the plastic deformation range A-Bt of It is difficult to maintain the calculation result t with high precision, and since the drive type #t and ft are smoothed when detecting the tightening torque based on the drive current of the motor, the phase difference in signal processing is This invention was made in view of the above circumstances, and it detects the end point of plastic deformation with high precision and tightens the bolt or nut with high precision. H using a load control washer that can control force tightening with high precision.
- We are committed to providing bolt tightening methods.

In order to achieve such an object, the present invention uses a load control washer that plastically deforms under a predetermined applied load, and a method in which the amount of tightening by an electric motor is controlled by a digital calculation device, the tightening torque of the load control washer is a threshold value determination step for determining that the deformation start torque has exceeded a set threshold value smaller than the deformation start torque; a point detection step for detecting when the rate of increase in the tightening torque has become less than a predetermined value; The present invention includes a stop determination step for outputting a tightening stop signal when the tightening amount is tightened, and is configured to cause the electric machine to stop when the dispensing stop signal is applied.

Also, if the screw threads of a bolt or nut are deformed and the threads cannot be screwed in smoothly, or when the bolt is screwed in.

The bolts may rotate together and tightening may not progress.

A second object of the present invention is to provide a bolt dispensing method using a load control washer that promptly detects an abnormality in the tightening process and generates an alarm.

In order to achieve this second object, the present invention is provided in at least one of the steps, and detects an abnormality when the time required to satisfy the determination condition of that step is outside the set time range. ; an abnormality detection step is added that generates a reward and outputs a benefit stop signal. The present invention will be described in detail below based on examples.
Various methods are possible for the operation (hereinafter referred to as the first half operation) and the operation for detecting the predetermined tightening amount after the deformation start point A (hereinafter referred to as the second half operation). Embodiment t--can be constructed by various combinations. For this reason, an example of the first half operation up to detecting the deformation start point A and an example of the second half operation after the deformation start point A will be explained separately below.

FIG. 3 is a block diagram showing a first embodiment of a bolt tightening device according to the present invention, and FIGS. 4 and 5 are flowcharts showing an example of the first half operation of this embodiment device, respectively.

In FIG. 3, the symbol l is an AC power supply, and this power supply l
The power is supplied to a closed circuit consisting of a switch 2, a semiconductor switch 3, and a DC series motor 4.

5 is a rotation angle detector which outputs an angle/base pulse P(Δθ)t- for each tightening rotation angle Δθ of bolts and nuts as the electric motor 4 rotates; 6 is a torque detector; this torque detector Reference numeral 6 includes a strain gauge attached to a portion that receives the tightening reaction force of the electric motor 4, and detects the tightening torque by converting the strain caused by the tightening reaction force into an electric signal. 7 is an A6 converter that converts this electrical signal indicating the tightening torque into a digital signal T. 8 is a digital arithmetic unit f, and this arithmetic unit 8 sequentially performs predetermined arithmetic operations according to the flowcharts shown in FIGS. 9 is a memory (ROM) that stores an arithmetic program for this arithmetic unit 8 to perform predetermined arithmetic operations; lO is an input/output for setting various setting values such as a threshold value Tth and a gauge related to < 11 is a phase control circuit, and 12 is a gut pulse generation circuit. The phase control circuit 11 operates based on the tightening stop signal S generated by the arithmetic unit 8,
The generation of the dirt pulse Gi is stopped, and the semiconductor switch 3 is opened to cut off the power to the electric motor 4. Reference numeral 13 denotes a power supply voltage detector t' which detects whether the switch 2 is fully closed and outputs a computation start signal to the computation device 8.

Next, an embodiment of the first half operation shown in FIG. 4 will be described.

First, the input/output device lO sets the torque TO threshold value TthX within the elastic range of the bolt, and the maximum value ΔTrrlax of the increase rate ΔT of the tightening torque T within this elastic range.
A sufficiently small predetermined value ΔTo and other company values for detecting lined abnormalities are set.

1) The threshold value Tth is sufficiently smaller than the final target fine f-1 torque Ts corresponding to the yield point A.

When the switch 2 is closed, the power supply voltage detector 13 detects the closing of the switch 2 and sends a computation start signal to the computation device 8 . The arithmetic device 8 sequentially reads programs from the memory 9 based on this arithmetic start signal and starts executing the series of arithmetic operations shown in FIG. First, the arithmetic unit 8 starts the tightening operation (sends the if signal to the phase control circuit 11, and generates a phase-controlled dart pulse G from the Kate Yars generation circuit 12. Therefore, the semiconductor switch 3 is triggered - The ignition occurs in phase synchronized with the bolt G, and the drive current begins to flow to the motor 4, which begins to rotate.However, as the bolt is tightened, the rotation angle detector 5 rotates at a predetermined rotation angle. Angle pulse P (Δθ) is output for each angle Δθ.
The D converter 7 continues to output the tightening torque Ti as a digital signal that changes every moment.

The arithmetic device 8 reads the threshold value T'th set by the input/output device 10, while reading the digitalized tightening torque Tt.
-Read each angle pulse P (Δθ) and compare the two (Stella f100), read new tightening torque T one by one until the delivered torque T exceeds the threshold 'rth, and repeat this comparison operation. . On the other hand, the arithmetic unit 8 has a built-in pulse generator and integrates the required time t after the start of tightening. When this required time t until the condition in step 100 is satisfied is equal to or greater than the set time t1, this means that the condition is satisfied in step 100.
It is determined that the bolt is rotating together with the nut, an alarm is issued, and the tightening is stopped in step 104). Furthermore, if the time t required for the condition to be satisfied in step 100 is less than the set time t2, this is determined in step 106, and an alarm is issued if the bolt or nut is locked due to deformation of the screw thread, etc. Stella F10
4), Stop tightening. That is, step 102,1
04゜106 may indicate that the time t required for the tightening torque T to reach the threshold value Tth is outside the range of t2<t<tt, and an abnormality is detected and a side alarm is generated, while a stop signal with h1f is generated. S is sent to the phase control circuit 11 and the semiconductor switch 3'
f: This is an abnormality detection step in which the circuit is opened and the power supply to the electric motor 4 is completely disconnected.

The arithmetic unit 8 calculates the respective tightening torques Tn at the rotation angle on-1 and the rotation angle θ after a predetermined rotation angle Δθ,
Tnffi, stored in built-in memory (RAM), and these tightening torques T, Tf: n-I of rotation
n It is rewritten sequentially as it progresses. The calculation device 8 calculates the difference ΔT between the tightening torques Tn-1 and Tn at each predetermined rotation angle Δθ.
is calculated (step f108), and this operation is repeated until this difference ΔT becomes equal to or less than the predetermined value ΔTo stored in advance (deformation start point detection step 110). The time t required until the condition of step 110 is satisfied is the same as that of steps 112 and 114 as in the above-mentioned Stella 7'102°106.
It is compared with the set value tl'+L2' to determine whether there is a tightening abnormality. Note that the difference ΔTn is also the rate of increase of the tightening torque T with respect to the rotation angle θ, and this difference ΔTn is the rate of increase of the tightening torque T with respect to the rotation angle θ.
ll, 0 conditions are satisfied, and step 112゜114
If no tightening abnormality is detected, then the tightening torque Tn at this time is set to a previously stored set value T 1 + T
I can't tell if it's within the range of 2 or not, 11
6) If it is within this range T1 to T2, it is assumed that the tightening is proceeding normally and the latter half operation to be described later is performed.

Next, another embodiment of the first half operation will be explained with reference to FIG. In this embodiment, the maximum rate of increase in tightening torque within the elastic range is stored, and the deformation starting point A is detected when the rate of increase becomes less than a predetermined percentage of this maximum rate of increase. Calculate the tightening torque difference ΔTn1, that is, the rate of increase between the predetermined rotation angles 40 (Stella f200), and if this difference ΔT is increasing or constant (step 202), the difference ΔTnei is stored as the large increase rate ΔTmax.

204), this maximum increase rate ΔTmax is sequentially replaced by the newly determined difference ΔT.
is a different school detection step that is the same as steps 102 and 106 above. As a result, the memory (
The maximum increase rate ΔTmax corresponding to the slope of the maximum slope line M in FIG. When the condition of step f202 is satisfied and the difference ΔTn starts to decrease, a new difference ΔTm is found again (-step 21O), and this difference ΔTm is the product of the maximum value ΔTmax and the constant C (however, 0 (C(1)). Each of these steps 210, 2
Repeat step 12.

Note that in FIG. 5, steps that are the same as those in FIG. 4 are given the same reference numerals, so their description will not be repeated.

In the embodiment shown in Fig. 4.5 above, the tightening torque T was obtained by converting the output of the strain gauge for obtaining the tightening reaction force into a digital signal using the AD converter 7, but in this invention, various It is possible to determine the tightening torque T using the following method.

FIG. 6 and FIG. 7 are a block diagram showing another embodiment and a flowchart of the first half of the operation. In this embodiment, the tightening torque T is calculated from a torque characteristic equation of the motor based on the motor current IM and the angular velocity. Note that in FIG. 7, each step for abnormality detection is omitted.

In FIG. 6, 20 is a current detection resistor connected in series to the motor 4, and 22 is an AD that detects the motor current from the voltage across this resistor 20 and converts it into a digital signal.
The converter, 24, is this digital signal engineer. Rotation angle θ of Yoshi-inkura. A second digital arithmetic device 26 calculates the tightening torque Tn and the angular velocity ω, and 26 is a memory that stores the arithmetic program of this second arithmetic device. In this figure, the same parts as in FIG. 3 are given the same reference numerals, so their description will not be repeated.

Next, the operation of this embodiment will be explained based on FIG. When the switch 2 is closed, the arithmetic unit 8 is connected to the phase control circuit 11,
The semiconductor switch 3 is ignited via the gate pulse circuit 12, and the electric motor 4 is started. The AD converter 22 quantizes the voltage across the resistor 20, which indicates the motor current, under an extremely short period compared to the AC power supply 1, and converts it into a digital signal. shall be. The second arithmetic unit 24 integrates this dezotal signal ID over a half-peak period or one period of the AC power source 1 to calculate the effective value of the stain current. =ΣID is calculated, and the angular velocity ω is calculated from the reciprocal of the number of pulses N, which is integrated within the time interval of the angular pulse P(Δθ).
). This second arithmetic unit 24 also outputs two successive angles P(Δθ) and the rotation angle θ. -4,
Angular acceleration dc$dt is calculated from the difference in angular velocity at On (step 3o2).

On the other hand, in a DC motor, its output torque T is T=Φ■h
+. Here, Φ is magnetic flux and k is a constant. However, the torque T that actually contributes to tightening as an electric tightening machine is expressed by the following equation, taking into consideration the influence of inertia (J-) during one speed fluctuation, t, and friction torque (T, )'f:

T=niΦI−J−−T ・・・・Song・(1)M
dtf The second calculation device 24 calculates the actual tightening torque T by calculating the equation (1) (step 304).

The arithmetic unit 8 reads the tightening torque Ti angle/gurus P (Δθ) output from the second arithmetic unit 24, and performs the same calculation as in the embodiment shown in FIG. As described above, since the operation in the latter half of FIG. 7 is completely the same as that in FIG. 5, the same steps are given the same reference numerals and the explanation thereof will not be repeated.

In this embodiment, the rotation angle θ is determined by a rotation angle detector 5 as shown in FIG. The angular velocity ω is calculated using the formula shown in FIG. You may.

FIG. 8 is a block diagram of this embodiment, and FIG. 9 is a flowchart showing the first half of the operation. In FIG. 8, 30 represents the motor voltage as a digital signal ■. An AD converter that converts into
32 is the second digital arithmetic device, 34 is this arithmetic device 3
This memory stores the calculation program No. 2. In this figure, the same parts as in FIGS. 3 and 6 are designated by the same reference numerals, so their description will not be repeated.

In this embodiment, when a current flows through the lightning motor 4 due to the closing of the switch 2, the motor current and voltage are each converted into a digital signal by the AD converter 22, 30, which is quantized with a cycle extremely short as the AC power supply cycle. . + Converted to VD. The second arithmetic unit 32 uses these digital signals ID+V
, are read in sequence and integrated over a half cycle or one cycle of the AC power supply to obtain the effective value■. = Σ Engineering. and vM=ΣvD
is calculated (step 400 in FIG. 9).

Generally, the respeed ω of a series-wound commutator motor is determined by the following speed characteristic equation.

Vh, -RIM ω＝に□・・・・・・・・・(2)Φ Here, R is the electric single armature resistance, Φ is the magnetic field, and K is a constant.

Although the magnetic field Φ is generally a function of the current IM, it is assumed that its changing characteristics are stored in the memory 34 in advance.

The second arithmetic unit 32 receives the current (2) output from the AD converter 22.30. and read the voltage vM j@ next (2)
While calculating the angular velocity ω by calculating the equation (step 4
02) Perform the operation X of the above equation (1) to obtain the tightening torque T'tR that actually contributes to tightening (step 404).

The second arithmetic unit 32 outputs this tightening torque T every half cycle or every cycle of the power supply.

The arithmetic unit 8 sequentially reads the torque T output from the second arithmetic unit 32 at predetermined time intervals, and performs the same operation as in each of the embodiments described above.

In the embodiments shown in FIGS. 1 to 9 above, the angular velocity ω changes as the tightening progresses, but the present invention can also be applied to a system in which the angular velocity ω is controlled to be constant. For example, a device that uses the fact that the pendulum back electromotive force is proportional to the angular velocity ω and controls the conduction angle of the semiconductor switch 3 according to changes in this back electromotive force to keep the angular velocity ω constant. be.

FIG. 10 is a flowchart of an embodiment of the first half operation in which the angular velocity ω is kept constant as described above. In this embodiment, after converting the electric-like voltage t-AD converter into a digital signal VD, the effective value of the stain pressure is determined by integrating this signal over a half cycle or one cycle of the AC power source (step 500). ), calculate the motor current IM using the speed characteristic equation (2) above (Stella f 502), and use this current M to calculate the tightening torque T according to the above equation (1) (step 504). Hereafter, tightening is performed using the same calculation as in the embodiment shown in FIG. 9.

In the embodiment shown in FIGS. 3 to 5, an abnormality detection step 1 for detecting an abnormality in tightening is included in both the threshold value determination step 100 and the deformation start point determination step 110 and 212.
02, 106, and 112°114i, the abnormality detection becomes more reliable, but in this invention, Stella 7
This abnormality detection step may be provided at either 6100t or 110°212. In these embodiments, it is determined in step 116 whether the tightening torque at the deformation start point A is within a predetermined range, and in the embodiment of FIG.
．． Since abnormality detection steps 206 and 208 are also provided in 204), tightening abnormalities can be detected more reliably and reliability is further improved. Next, an example of the operation after the deformation start point A (second half operation) will be explained. °Illustrate. . In the embodiment of FIG. 11, the time at the deformation start point AK is stored as tt-t, step 600).
, time 1 calculated from this time ta = 1-
1 (step 602), the time when the pre-stored time t8 or more is reached is regarded as the deformation end point B, and the tightening is stopped (stop determination step 604).

The embodiment shown in Fig. 11 has a very simple configuration because it can use the timer built into the calculation device 8, but it can be combined with the embodiments of the first half of the force shown in Figs. In this case, the detection of the deformation end point B is likely to be inaccurate. However, when combined with the embodiment of FIG. 10 in which the tightening speed is controlled to be constant, the delivery can be stopped precisely at the deformation end point B, which is preferable.

In the second half operation example of FIG. 12, the rotation angle θ of the deformation start point A is θ, and the rotation angle θ8 is calculated from the starting point (Step 650), and the rotation angle is 0°=θ−08 and then angular velocity ω. (Embodiment of FIG. 7) is first stored as an initial value (step.

Pro 52). Then, inertia compensation described below is performed (step 654).

That is, if we omit friction now, the equation of motion during tightening becomes as follows.

Here, J is the inertia factor as seen from the output shaft of the motor, θ is the tightening angle after the bolt starts tightening, E is the spring constant of the bolt, T is the torque of the motor, and t is time.

Since T becomes zero after the power is cut off, the following holds true at this time. In this equation ft=0, θ=θ. , dθ/df=
ω. If we solve under the initial conditions, we get Here, β2=VJ, ψ=i1 (θ.Me.). According to this formula (3), the maximum value θ of the tightening angle θ after blocking the stain source
max becomes.

On the other hand, the maximum tightening torque Tmax of the bolt is 1i1 angle θ
Since it is at the maximum value θmax of θmax, it is as follows.

Here, if the speed fluctuation rate of the motor immediately before the power is shut off is small, the tightening torque T immediately before the power is shut off. Since T0=Eθ0, it ends up being like a law.

TmaX=T,'+JE*,' ,,,,,
,,,・(5) Therefore, the rotation angle θ immediately before the power is cut off. and angular velocity ω. If is known, the final rotation angle θe including the amount of additional tightening due to inertia can be calculated using equation (4), and the tightening torque T can be determined in the same way.

and angular velocity ω. is known, the final tightening torque Te is (5
) can be predicted using the following equations.

The embodiment shown in FIG. 12 uses the above equation (4) to obtain the rotation angle θ
. In step 654), predict the final rotation angle Oe when the power supply t- is cut off, and use this predicted final rotation angle θ. Tightening is stopped when the rotation angle reaches a pre-stored rotation angle of 08 or more (stop determination step 656).

Note that in FIGS. 11 and 12, steps 606, 608.
610 is for abnormality detection similar to the embodiment shown in FIG. 4.5.
This is the next step.

In the embodiment shown in FIG. 13, the deformation end point B is determined because the tightening torque TO increase rate ΔT (step 700) exceeds the pre-stored setting value 417 by a procedure similar to that shown in FIG.
f: is what is sought (stop determination Stella 7'702).

In the embodiment shown in FIG. 14, a procedure similar to that of FIG.
The increase rate ΔTm (step 756) after the start of increasing after the deformation end point B is the predetermined value C·ΔTml.

(However, C>1) (stop determination step 758
) This is a device that outputs a tightening stop signal to stop tightening.

In the embodiment shown in FIG. 15, first, the angular velocity ω is calculated from the reciprocal of the black and white recesses eN within a predetermined rotation angle Δθ (step 800). If the tightening speed is not controlled constant, the angular velocity ω will be approximately constant between the plastic deformation range A and B.
Since the angular velocity ω decreases as the tightening torque increases after the deformation ends A and B, the deformation end point Be is detected (stop determination step 802).

The embodiments of the latter half of the operations shown in FIGS. 11 to 15 above are as follows.
By appropriately combining this with the embodiment of the first half of the IO diagram, it is possible to configure an optimal tightening method for different types of bolts and different tightening conditions.

In the present invention, as described above, all calculations are performed by digital signal processing, so compared to analog signal processing, there is no phase delay during signal processing or errors caused by the signal holding means, and tightening accuracy is significantly improved.

In addition, if an abnormality detection Stella f is provided in the threshold value determination step, deformation start determination step, or stop determination step to detect tightening abnormalities based on the time required to satisfy these determination conditions, the co-rotation of bolts and thread It can reliably detect abnormalities in the mountains.

Furthermore, since the present invention uses a digital arithmetic unit, an abnormality detection step can be provided by simply changing the program. In addition, it is possible to flexibly deal with changes in bolt types and striping conditions by changing various setting values and programs, and has the effect of being highly versatile.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the usage state of the load control washer, Fig. 2 is its tightening characteristic diagram, Fig. 3.6.8 is a block diagram of various embodiments of the present invention, Fig. 4.5, 7, Figures 9 and 10 are flowcharts showing various embodiments of the cup-and-half operation, and figures 11-15.
The figure is a flowchart showing an example of insertion of the latter half operation. 4'--Electric motor, 8-Digital arithmetic unit, 54-
...Load control washer, 100...Threshold value determination step, 102, 106, 112, l14, 60
6, 608... Abnormality detection step, 1.10, 21
2...Deformation start point detection Stella 7'% 604, 65
6, 702, 758. 802...Stop determination step. Patent applicant Shibaura Seisakusho Co., Ltd. Figure 1 Figure 2 Figure 6 Figure q Figure 11

Claims (1)

[Claims] (1) A method in which a load control washer that plastically deforms under a predetermined tightening load is used and the amount of tightening by an electric motor is controlled by a digital calculation device a, wherein the tightening torque of the load control washer is a threshold value determination step for determining whether a set threshold smaller than the deformation start torque has been exceeded; a deformation start point detection step for detecting a deformation start point of the washer based on the increase rate of the tightening torque; and a stop determination step for outputting a supply stop signal when a predetermined tightening amount is tightened from the deformation start point, and the load control washer is characterized in that the electric motor is stopped in response to the tightening stop signal. Bolt tightening method. (2) The tightening torque is the torque L that measures the tightening reaction force of the electric motor.
A bolt tightening method using a load control washer according to claim 1, which can be claimed by converting the output of the /i/gauge into a digital signal using an IkAD converter. (3) The bolt tightening method using a load control washer according to claim 1, wherein the tightening torque is calculated from an electric torque characteristic equation based on the motor current and the angular velocity. (4) The angular velocity is determined by the number of clock pulses accumulated between the angular normals output by the rotation angle detector for each predetermined rotation angle. (5) A bolt tightening method using a load control washer according to claim 3, in which the angular velocity is calculated from the speed characteristic equation of the motor based on the motor current and the motor-like voltage. (6) The angular velocity of the motor is Load control according to claim 1, in which the phase is controlled to be constant, and the tightening torque is calculated from a torque characteristic formula using a motor voltage and a motor current calculated from this motor voltage and a speed characteristic formula. Bolt tightening method using a washer. (7) In the deformation start point detection step, the deformation start point of the washer is detected when the increase rate of the tightening torque becomes less than a pre-stored set value. The bolt tightening method described in Paragraph 1 is the bolt tightening method. (8) In the deformation start point detection step, the maximum increase rate of the tightening torque is memorized, and the tightening torque is increased by a predetermined percentage from this maximum increase rate. The bolt tightening method according to claim 1, in which the deformation start point of the washer is detected from the decrease in the deformation rate. (9) In the stop determination step, a predetermined tightening amount is determined from the elapsed time from the deformation start point. A bolt tightening method using a load control washer according to claim 1. In the stop determination step, a predetermined tightening amount is determined from the tightening rotation angle from the deformation start point. Bolt tightening method using the described load control washer. In the stop determination step, the rate of increase in tightening torque from the deformation start point is determined, and if this rate of increase exceeds a predetermined value, the specified tightening is performed. A bolt tightening method using the load control washer according to claim 1, which detects the amount of attachment. (6) In the stop determination step, the minimum increase rate of the tightening torque from the deformation start point is memorized, The bolt tightening method according to claim 1, characterized in that the predetermined tightening amount is determined because the increase rate of the tightening torque increases by a preset predetermined percentage from the minimum increase rate. α field stop determination step Now, a bolt tightening method using a load control washer according to claim 1, which calculates the angular velocity from the deformation start point and detects the predetermined delivery amount from the fact that this angular velocity starts to decrease. α◆ Predetermined amount In a method in which a load control washer that plastically deforms under a tightening load of a deformation start point detection step of detecting a deformation start point of the washer since the increase rate of the tightening torque has become less than a predetermined value; When setting the stop determination step that outputs a tightening stop signal when the amount of application is tightened, and the time required to satisfy the determination condition for that step, which is provided in at least one step of each of the above-mentioned steps, it is outside the range. and an abnormality detection step of detecting an abnormality and generating a notification as well as outputting a tightening stop signal, and is characterized in that the power supply to the electric motor is cut off in response to any of the tightening stop signals. Bolt tightening method using load control washers.