JPH1058341A - Screw tightening control method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Even if foreign matter is present on a screw surface or the like, an estimated seating point is accurately determined, and the screw is rotated based on the estimated seating point to ensure that the target fastening force is reached. The present invention provides a screw tightening control method. The A threaded portion obtains a torque rate Te tightening et at a predetermined torque value T, calculates the estimated seating point theta ₁ from the torque rate, in tightening control method for a screw to perform using tightening screws so , the position of the estimated seating point theta _1, corrected in consideration of the torque value varies by contaminants present in the threaded surface, perform tightening of the screw the corrected estimated seating point as a reference so It is characterized by the following.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw tightening control method capable of improving the tightening accuracy when a screw is tightened on a member to be fastened.

[0002]

2. Description of the Related Art As a general method for controlling a fastening force when a screw such as a bolt or a nut is fastened to an object to be fastened, there are a torque fastening method and a rotation angle fastening method.

According to the torque tightening method, when a screw such as a bolt or a nut is tightened to an object to be fastened, the tightening torque is controlled by the torque at the time of tightening by utilizing the property that the magnitude of the tightening torque is proportional to the axial force. Is the way. put it here,
The relationship between the screw fastening force and the torque is represented by the following equation (1).

[0004] Fastening force by screw = Torque coefficient × Torque (1) Since “Torque coefficient” is a constant determined by the material, it does not affect the variation in fastening force.
Is affected by the coefficient of friction between the bearing surface and the threaded surface, so if this torque fluctuates, the fastening force of the screw will vary greatly, resulting in poor reliability.

The rotation angle tightening method utilizes a property that when a screw such as a bolt or a nut is tightened to an object to be fastened, the angle at which the screw such as a bolt or a nut rotates by a tightening torque is proportional to a tightening axial force. In this method, the axial force is controlled by the rotation angle at the time of tightening. Here, the relationship between the fastening force of the screw and the rotation angle is represented by the following equation (2).

[0006] In this rotation angle tightening method, if the seating point of the screw can be accurately estimated, the only cause of the variation is the variation in the spring constant of the screw. Generally, the variation in the spring constant of the screw is small, so that it is possible to control the fastening force with high accuracy.

Therefore, recently, a screw tightening control method for estimating the seating point with high accuracy has been proposed (for example, see Japanese Patent Application Laid-Open No. 62-102,978).

According to this method, a torque at the time of tightening a screw is actually measured, an estimated seating point at which the torque becomes zero is obtained from the actually measured torque curve, and the screw is rotated by a predetermined rotation angle with reference to the estimated seating point. And tightening is performed.

That is, after the screw is tightened to a predetermined first torque value, the screw is tightened by a predetermined rotation angle, and a torque rate is determined from the second torque value at the time when the tightening by the rotation angle is completed and the first torque value. An estimated seating point is calculated from the torque rate, and the screw is tightened by rotating the seat by a predetermined rotation angle from the estimated seating point.

Generally, when the screw is tightened normally, as shown in FIG. 10, the torque does not change much until the snag torque is reached even when the tightening angle is increased, and when the screw reaches the snag torque, it is almost linearly sharp. And the torque curve increases. Further, the fastening force for fastening to the body to be fastened also has substantially the same curve.

Therefore, when the slope line of the torque curve is extended and the estimated seating point which intersects the horizontal axis where the torque is zero is obtained, the estimated seating point is connected to the torque curve as shown in FIG. Since the origins of the force curves substantially coincide with each other, the seating point of the screw can be accurately estimated, and even if the screw is tightened by the above-described screw tightening control method, accurate tightening is possible.

In the present specification, the amount of rotation of the screw when the screw is tightened with reference to the estimated seating point is referred to as the "rotation angle of the screw" or "rotation angle". The amount of rotation from the time when the rotation is performed is referred to as “screw tightening angle” or “tightening angle”.

[0013]

However, if foreign matter such as cutting powder is present on the screw surface or the like, it will bite during tightening, and the torque curve will be reduced as shown in FIG. As shown, a relatively large abnormal torque is generated from the beginning, and further increases after sitting. On the other hand, the fastening force is generated after the generation of the torque.

In this case, when the estimated seating point at which the torque becomes zero is obtained from the actually measured torque curve as in the above-described screw tightening control method, as shown in FIG. The point where the force becomes zero, that is, the point at which the screw tightening is started, deviates from the estimated seating point, and when the shaft is rotated by a predetermined rotation angle, the tightening is completed before reaching the target fastening force, and the fastening is completed. There is a problem that power shortage occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and even if foreign matter is present on a screw surface or the like, an estimated seating point is accurately obtained, and based on this, It is an object of the present invention to provide a screw tightening control method which ensures that a target fastening force is reached by rotating a screw.

[0016]

According to a first aspect of the present invention, there is provided a screw tightening control method according to the first aspect of the present invention, wherein the screw portion configured to have a predetermined target rotation angle upon completion of the tightening has a predetermined first torque value. And a second torque value at a time when the first torque value is further tightened by a fraction of the target rotation angle from the first torque value, and the first torque value and the second torque value are measured. In the screw tightening control method, a torque rate of an actually measured torque curve is obtained from the second torque value and the rotation angle, an estimated seating point is calculated from the torque rate, and the screw is tightened based on the estimated seating point. The torque value for the tightening rotation angle applied to the screw portion is stored, and if there is an abnormal portion of the torque value in the actually measured torque curve, the torque value variation in this abnormal portion is determined by the first time. An angle is subtracted from the torque value at the time of tightening by the second rotation angle, and a corrected seating point obtained by correcting the estimated seating point based on the torque rate is obtained from the obtained torque value. The screw is tightened.

With this configuration, the estimated seating point is corrected in consideration of the fluctuation of the torque value caused by the presence of impurities on the screw surface or the like, and the screw is rotated based on the corrected seating point. Therefore, the target fastening force can be reliably and accurately reached.

In the screw tightening control method according to the second aspect of the present invention, if the corrected seating point has an abnormality in the torque value before reaching the snag torque, the corrected seating point is determined from the stored torque value by the estimated seating point. The third torque value is extracted, the third torque value is subtracted from the fourth torque value at the time of further tightening from the first rotation angle to a predetermined second rotation angle, and the third torque value is obtained from the obtained fifth torque value. It is characterized in that it is determined based on the rate.

In this way, even if foreign matter gets into the screw surface or the like at the time of tightening and the torque value increases due to an increase in the initial friction, the second torque is considered in consideration of the increased torque value.
Since the estimated seating point is obtained, the seating point can be accurately estimated, and if the screw is tightened based on the accurate second estimated seating point, the seating point may be affected by foreign substances, etc. Further, the screw can be fastened to the fastened object with high accuracy.

According to a third aspect of the present invention, in the screw tightening control method, the tightening of the screw portion based on the corrected seating point is performed based on the corrected seating point based on the tightening angle at the time when the screw is tightened by the second rotation angle. , And a screw is tightened by a difference between the difference and the target rotation angle.

In this way, the screw may be tightened at a slight rotation angle from the time of completion of the tightening, and the desired target rotation angle can be easily reached.

According to a fourth aspect of the present invention, the first torque value is a snug torque value.

The value of the snag torque differs depending on the type of the screw to be tightened, but has a property of always being constant if the same type. Using such an accurate point as one criterion not only simplifies the operation for obtaining the torque rate, but also improves the accuracy.

According to a fifth aspect of the present invention, in the screw tightening control method, the correction seating point is obtained by calculating a sum of torque value fluctuations at a discontinuous point of a torque curve, and further determining a predetermined value from the first rotation angle. Is calculated by subtracting the sum of the fluctuations from the fourth torque value at the time when the tightening is completed by the second rotation angle, and the torque rate is obtained from the obtained fifth torque value. It is characterized by the following.

In this way, even when foreign substances such as cutting chips bite in the initial stage of tightening and then come off, the point where the torque curve becomes discontinuous is utilized, and the torque head at this discontinuous point is utilized. The corrected seating point can be determined in consideration of
The corrected seating point can be accurately estimated, and the tightening force of the screw tightening becomes high.

The invention according to claim 6 is characterized in that the final fastening force at the time of completion of the tightening is calculated, and when it is smaller than the target fastening force, it is transmitted to an operator.

In this way, the impact energy of the screw tightening device changes, and the operator can know that the screw tightening has been completed in an incomplete state, and can detect deterioration of the screw tightening device. Incomplete screw tightening can be prevented.

[0028]

According to the first aspect of the present invention, since the screw is rotated based on the corrected seating point, the target fastening force can be reliably and accurately reached.

According to the second aspect of the present invention, even if the torque value increases abnormally at the beginning of screw tightening, the corrected seating point is determined in consideration of the increased torque value. Screws can be tightened, and screw tightening accuracy is improved. When the screw is tightened on the basis of the corrected seating point, the screw is tightened only by an insufficient rotation angle from the current tightening angle, so that the screw tightening is completed very quickly and the screw tightening accuracy is improved.

In the method according to the third aspect of the present invention, the screw may be tightened at a small rotation angle from the end of the tightening, and the desired target rotation angle can be easily reached.

In the method according to the fourth aspect of the present invention, since the first torque value is the torque value of the snug torque, the torque rate can be easily obtained, and the accuracy is improved.

In the method according to the fifth aspect of the present invention, the estimated seating point can be accurately obtained even when the foreign matter which has been caught at the beginning of the screw tightening comes off, and the tightening and tightening force of the screw tightening is accurate. Will be good.

According to a sixth aspect of the present invention, when the final fastening force of the screw does not reach the target fastening force due to a change in the impact energy of the screw fastening device, the screw fastening is terminated in an incomplete state. Therefore, if the worker notifies this, the deterioration of the screw tightening device can be detected,
Incomplete screw tightening can be prevented beforehand, and deterioration of the device can be known.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing a first embodiment of a screw tightening control method according to the present invention.
Is an explanatory view showing a method for obtaining an estimated seating point when a foreign matter bites into a screw surface or the like at the time of tightening in the first embodiment; FIGS. 3 and 4 are flowcharts of the first embodiment; 9 is a table showing a comparison between the first embodiment and the conventional technology. In addition,
In the following description and drawings, members common to those shown in FIGS. 10 to 13 are denoted by the same reference numerals.

(Embodiment 1) Generally, screw tightening within the elastic limit of a screw portion is performed by applying impact energy to a bolt v or a nut n (screw portion) by a screw tightening device as shown in FIG. Will be The screw fastening device includes a fastening portion 10 for fastening a nut n to a bolt v attached to an object W such as an iron plate with a predetermined fastening torque.
And a main body 11 of the screw tightening device provided on the upper part of the fastening part 10, and disposed between the main body 11 and the fastening part 10, after the screw part comes into contact with the fastening part 10, that is, after seating. And a rotation angle detector 12 for measuring the rotation angle of the screw portion.

The main body 11 has a motor M powered by electricity or compressed air, and a torque generator 13 for converting the torque of the motor M into a pulsed torque. The torque is transmitted to the output shaft 14.

The output shaft 14 is connected to a socket 16 rotatably supported by a housing 15 of the rotation angle detector 12. The output shaft 14 rotates the socket 16 to rotate, and a nut fitted to the socket 16. n is screwed into the bolt v.

The rotation angle of the nut n is measured by detecting the rotation of the socket 16. That is, the rotation of the socket 16 is transmitted to the code wheel 17 of the rotary encoder, and the rotation of the code wheel 17 is measured by detecting the rotation of the detection head 18 of the rotary encoder.

The signal emitted from the rotation angle detector 12 is processed by the control unit 19. The control unit 19 includes a rotation angle detection unit 20 that generates a rotation angle signal by inputting a signal from the rotation angle detector 12, and a torque detection unit 22 that detects torque by inputting a signal from the torque detector 21.
And a storage means 23 to which signals from the torque detection means 22 and the rotation angle detection means 20 are respectively inputted. Based on the signals from the storage means 23, the estimated seating point is corrected and the remaining tightening angle is corrected from the current tightening angle. Find the tightening angle of
And a correction calculating means 24 for outputting a signal for generating an impact to the motor M.

When the screw is tightened by using such a screw tightening device, if foreign matter such as cutting chips is present on the screw surface or the like, as shown in FIG. From the actual torque curve at which abnormal torque occurs from the beginning of tightening, the point at which the torque becomes zero, that is, the estimated seating point is obtained from the actual measured torque curve, and the estimated seating point and the screw tightening start point at which the fastening force becomes zero are obtained. Will shift.

However, in the present embodiment, after the estimated seating point θ ₁ is obtained from the actually measured torque curve, the corrected seating point θ ₂ is obtained from the estimated seating point θ ₁ in consideration of the abnormal torque, and the corrected seating point θ ₂ is obtained. and to perform the tightening of the screw point theta ₂ as a reference.

Further description will be made with reference to FIGS. 2, 3 and 4. When the screw is tightened by the screw tightening device, such as setting the target rotation angle θ, the target rotation angle θ and the like are set in advance. Usually, the target fastening force is determined based on the shape and material of the screw portion and the material and shape of the fastening portion, and the target rotation angle θ is determined based on the target fastening force. Is the angle from the start of rotation from the seating point until the target fastening force is obtained.

Therefore, in tightening the screw, first, in step S1 in FIG. 3, the target rotation angle θ is set.

Next, in step S2, about one third of the target rotation angle θ, which is an angle at which the gradient of the torque curve becomes constant.
The rotation angle is set to a degree, and a range for obtaining a torque rate described later is determined.

In the presence of the contaminants, the torque fluctuation is clearly different from the case where the normal screw is tightened as shown in FIG. 10, and as shown by the broken line in FIG. However, it does not increase linearly, but increases abruptly and then slightly increases until the snag torque is reached. Therefore, it is checked whether or not foreign substances are present due to this torque fluctuation. For this purpose, and in order to extract various torque values to be described later, in step S3, the socket M is rotated by the motor M, and tightening of the screw, that is, rotation of the screw is started.

In step S4, during the tightening operation, the torque value and the rotation angle are stored or recorded at fixed time intervals (for example, every 2 msec). That is, a rotation angle signal is generated by the rotation angle detection means 20 to which a signal from the rotation angle detector 12 for measuring the rotation angle of the threaded portion after the seating is input, and the torque detection to which the signal from the torque detector 21 is input. Means 2
2, a torque signal is generated, and these two signals are stored or recorded by the storage means 23 during the tightening operation.

In step S5, a predetermined first torque value T ₁
It is determined whether or not has been reached. This first torque value T ₁ is
If the torque value as a reference, what may be a value, but is preferably, for example, it is to use a Sunagutoruku T _s. The Sunagutoruku T _s, since it becomes a constant value by means of a screw as described above, the value 1
It is preferable to use the two criteria because not only the operation for obtaining the torque rate described later is simplified, but also the accuracy is improved.

Although not shown, if means for judging whether or not the first torque value T ₁ is larger than a predetermined threshold value is provided after step S4, it is possible to determine whether or not the foreign matter is caught. This makes it possible to prevent incomplete screwing beforehand.

Determining the Estimated Seating Point θ ₁ After reaching the first torque value T ₁ , the estimated seating point θ ₁ is determined. In obtaining the estimation seating point theta _1, first obtaining a torque rate. Since the torque rate is a gradient of a substantially linear portion of the torque curve, it can be obtained by determining two points on the torque curve. However, as shown in the figure, the torque value increases while fluctuating within a predetermined range. Therefore, a regression line is obtained by the least square method, and the gradient of the regression line is used as the torque rate. In the present embodiment, the rotation angle and at least three torque values corresponding to the rotation angle are extracted within a predetermined rotation angle range, and the torque rate is obtained by the least square method.

Here, in the present embodiment, θ / 3 is set as the predetermined rotation angle range. However, since this angle range is for obtaining data for obtaining a regression line, Any value may be used, and the value is not limited to θ / 3.

Therefore, in step S6, the first
It is determined whether the rotation angle θ _s at the time of the torque value T ₁ has advanced to the first rotation angle θ / 3, and if “Yes”, in step S7, the torque value T at this time is determined.
₂ and, on the basis of the torque value or the like of the Sunagutoruku first torque value is T _s T ₁ or these intermediate points, considering the rotation angle data, calculated by the least square method regression line A,
Determine the torque rate.

In step S8, the rotation angle of the point at which the regression line thus obtained intersects the horizontal axis, that is, the point where the torque value becomes zero on the regression line is obtained by calculation.
The rotation angle is estimated seating point theta _1.

[0053] Then obtain the correction seating point theta _2, in the present embodiment obtains the corrected seating point theta _2, performing screwing the basis of this. First, when the obtaining this correction seating point theta _2, first, at step S9, extracts the torque value applied to the threaded portion at the estimated seating point theta _1. The torque value is the third torque value T _3.

Next, at step S10, the first torque value T
It determines proceeding or I from the rotational angle theta _{s 1} time point to the second rotation angle 2 [Theta] / 3. In other words, the first rotation angle θ / 3 is further tightened by a predetermined rotation angle, for example, θ / 3. In other words, the rotation angle from the time of sitting is 2
θ / 3. The torque values obtained by the clamping and fourth torque value T _4.

[0055] In step S11, the obtained fourth performs the torque value T ₄ operation subtracting the third torque value T ₃ has, to the obtained torque value and the fifth torque value T _5.

In step S12, the fifth torque value T ₅
Then, the corrected seating point θ ₂ is obtained from the torque rate obtained in step S7. That is, the fifth torque value T ₅
From this point, a straight line B (shown by a broken line in the figure) parallel to the regression line A is obtained, and the rotation angle of the point where the straight line B intersects the horizontal axis, that is, the point on the straight line B where the torque value becomes zero, When obtained by calculation, this rotation angle is corrected seated point theta _2.

The corrected seating point θ ₂ is a seating point obtained by subtracting an increase in the torque value due to an increase in the initial friction due to the entry of foreign matter into the screw surface or the like at the time of tightening. Therefore, when the correction seating point theta ₂ relative performs clamping of a predetermined rotation angle by screws, so that the desired fastening force can be obtained.

Therefore, in the present embodiment, step S1
3, extracts the current fastening angle K _1, the tightening difference K ₃ angles K ₂ fastening the angle K ₁ correction seating point theta ₂ determined, the with the difference K ₃ target rotational angle (theta) and the Find the difference X.

[0059] In step S14, obtains the final fastening angle theta _e considering this difference X, in step S15, the clamping determines whether reached this final fastening angle theta _e.

When it is determined that the final tightening angle θ _e has been reached, the tightening is completed. Preferably, in step S16, the final tightening force at the time of completion of the tightening is measured, and the final tightening force is measured. Is larger than the target fastening force C. If it is equal or greater, it is determined that the desired fastening force has been obtained, and the tightening is completed in step S17. If it is smaller, NG is output to the operator in step S18 indicating that the screw member is not properly tightened. This allows the operator to determine whether or not the screw portion has been tightened with a predetermined fastening force, and it is possible to reliably reduce the occurrence of a screw portion that has been improperly tightened.

When the thus obtained screw portion is compared with the fastening force of the screw portion performed by the above-described conventional screw tightening control method, the results shown in the table of FIG. 5 are obtained. In this table, the target rotation angle θ is 100 degrees, and the target fastening force is 5 KN. As is clear from this table, the method according to the above embodiment is
It can be seen that a value very close to the target fastening force was obtained, and the standard deviation was also reduced to about half.

(Embodiment 2) Next, Embodiment 2 of the method of the present invention will be described. FIG. 6 is an explanatory view showing the state of the torque and the fastening force when the foreign matter is disengaged, FIG. 7 is an explanatory view showing the outline of Embodiment 2 of the present invention, FIG.
9 is a flowchart of the second embodiment. Steps 31 to 40 are the same as those in the first embodiment described above, and a description thereof will not be repeated.

According to the second embodiment, even when foreign substances such as cutting chips bite in the initial stage of the tightening and then come off, the corrected seating point is accurately estimated, and the tightening and tightening force of the screw tightening is improved. It was done.

When foreign substances such as cutting chips bite in the initial stage of the tightening and then come off, the torque curve becomes discontinuous as shown in FIG. In this case, the normal torque value increases when biting, and decreases when it deviates. However, when determining the corrected seating point θ ₂ , if the torque variation ΔT at this discontinuous point is taken into consideration, the corrected seating can be obtained. The point θ ₂ can be accurately estimated.

As shown in FIG. 6, when the torque value is measured from the start of the screw tightening, there are a plurality of discontinuous points in the torque value. It is assumed that ΔT ₁ and ΔT ₂ . It should be noted that these torque fluctuations are assumed to be “+” for an increase and “−” for a decrease, and it is assumed that the torque fluctuation ΔT is obtained when their sum is obtained.

In FIGS. 8 and 9, there is no need to extract the torque value applied to the threaded portion at the estimated seating point θ ₁ , so there is no equivalent to step 9, but there are no other steps 31 to 40. Is the same as in the first embodiment.

After the estimated seating point θ ₁ has been obtained in steps 31 to 40, when the rotation angle becomes 2θ / 3 from the time of seating, in step 41, it is determined whether or not there is a discontinuity in the torque value. Do. If there is a discontinuity in the torque value, it is determined in step 42 whether there is a plurality of torque values.

If there is a single discontinuous point, in step 43, the torque value after the discontinuous point is subtracted from the torque value before the discontinuous point, and the difference is obtained, and the difference is determined as the torque value variation ΔT.
If there are a plurality of discontinuous points, the torque value difference ΔT is added in step 44 by adding the torque value differences to each other.
Ask for.

Then, in step 46, an operation of subtracting the variation ΔT of the torque value from the fourth torque value T ₄ is performed, and in step 47, the obtained fifth torque value T
₅ to obtain a correction seating point theta ₂ by the torque rate from. Thereafter, step 48 to 53 is an operation such as performing screw tightening on the basis of the correction seating point theta ₂ is the embodiment 1
The description is omitted because it is the same as.

On the other hand, if there is no discontinuity in the torque value, the variation ΔT is set to zero in step 45 and the
53 to 53 may be performed.

It should be noted that the present invention is not limited to only the above-described embodiment, but can be variously modified within the scope of the claims. For example, the second embodiment
In this method, the torque is measured and stored or recorded while the screw is being tightened.However, the torque is preliminarily applied to the screw portion, and the torque value is measured from the start to the completion of the tightening. If a discontinuous point exists, the corrected seating point θ ₂ may be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating Embodiment 1 of the present invention.

FIG. 2 is an explanatory diagram showing a method for obtaining an estimated seating point when a foreign matter bites into a screw surface or the like at the time of tightening in the first embodiment.

FIG. 3 is a flowchart of the first embodiment.

FIG. 4 is a flowchart of the first embodiment.

FIG. 5 is a table showing a comparison between the first embodiment and a conventional technique.

FIG. 6 is an explanatory diagram showing a state of a torque and a fastening force when a foreign matter is released after being bitten.

FIG. 7 is an explanatory view schematically showing a second embodiment of the present invention.

FIG. 8 is a flowchart of the second embodiment.

FIG. 9 is a flowchart of the second embodiment.

FIG. 10 is an explanatory diagram showing a torque and a fastening force at the time of screw tightening in a normal state.

FIG. 11 is an explanatory view when a screw is tightened by a conventional method in a conventional normal state.

FIG. 12 is an explanatory diagram showing a torque and a fastening force when a foreign matter is caught.

FIG. 13 is an explanatory diagram when screwing is performed by a conventional method when a foreign substance is caught.

[Explanation of symbols]

C: target fastening force, T _{1 to} T ₅ : first to fifth torque values, T _s : snag torque, ΔT: variation in torque value at discontinuous points, θ: target rotation angle, θ ₁ : estimated seating point , Θ ₂ : Corrected seating point, θ / 3: First rotation angle, 2θ / 3: Second rotation angle, n, v: Screw part.

Claims (6)

[Claims] 1. A predetermined target rotation angle (θ) when tightening is completed.
The threaded portion (n, v) configured to be
A torque value when tightened up to the torque value (T ₁ );
A second torque value (T ₂ ) at the time when the first torque value (T ₁ ) is further tightened by a first rotation angle (θ / 3) that is a fraction of the target rotation angle (θ) is measured, A torque rate of an actually measured torque curve is obtained from the first torque value (T ₁ ) and the second torque value (T ₂ ) and the rotation angle, an estimated seating point (θ ₁ ) is calculated from the torque rate, and the estimated seating is calculated. In a screw tightening control method for tightening a screw based on a point (θ ₁ ), a torque value for a tightening rotation angle applied to the screw portion (n, v) is stored,
If there is an abnormal portion of the torque value in the measured torque curve, the torque value variation (ΔT) at the abnormal portion is further calculated from the first rotation angle (θ / 3) to the second rotation angle (2).
θ / 3) is subtracted from the torque value (T ₄ ) at the time of tightening, and the corrected seating point (θ ₁ ) is corrected from the obtained torque value (T ₅ ) based on the torque rate. (Θ ₂ ), and the tightening of the screw is performed based on the corrected seating point (θ ₂ ). 2. If the corrected seating point (θ ₂ ) is abnormal in the torque value before reaching the snag torque (T _s ), the corrected seating point (θ ₂ ) at the estimated seating point (θ ₁ ) is determined from the stored torque value. 3) extracting the torque value (T ₃ ) and calculating the first rotation angle (θ /
The third torque value (T ₃ ) is subtracted from the fourth torque value (T ₄ ) at the time of further tightening to the second rotation angle (2θ / 3) from ₃ ) to obtain a fifth torque value (T ₅ )
2. The screw tightening control method according to claim 1, wherein the torque is obtained based on the torque rate. 3. The tightening of the screw portion (n, v) based on the corrected seating point (θ ₂ ) is performed by the second rotation angle (2θ /
3) The difference between the tightening angle of the corrected seating point (θ ₂ ) is obtained from the tightening angle at the time of tightening only, and the screw is tightened by the difference between the difference and the target rotation angle (θ). The method for controlling screw tightening according to claim 1. 4. The screw tightening control method according to claim 1, wherein the first torque value (T ₁ ) is a torque value of a snag torque (T _s ). 5. The corrected seating point (θ ₂ ) is obtained by calculating the sum of torque value fluctuations (ΔT) at discontinuous points of a torque curve.
From the first rotation angle (θ ₁ ), further tightening to a predetermined second rotation angle (θ ₂ ), and from the fourth torque value (T ₄ ) at the time when the tightening is completed by the second rotation angle (θ ₂ ), A calculation for subtracting the sum of the variation (ΔT) is performed, and the obtained fifth
Screw tightening control method according to claim 1, characterized in that the torque value from (T ₅₎ was as determined by the torque rate. 6. The screw according to claim 1, wherein a final fastening force at the time of completion of the fastening is measured, and when the fastening force is smaller than a target fastening force (C), the screw is transmitted to an operator. Tightening control method.