JPH11138459A - Impact screw fastening method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of seizure of a screw part and suppress dispersion of fastening force by sensing torque which is generated when screwing impact energy (fastening force) is added, and adding, the fastening force by the specified number of times at the start point when the generated torque is a threshold value or more to carry out screw fastening. SOLUTION: A torque threshold T1 smaller than the target fastening torque is set. The number of impact times from the time sensing the torque threshold value T1 to obtain the target fastening torque is set as In. It is determined whether or not the read value (output value) of the generated torque sensed by a torque sensor 30 reaches or exceeds the torque threshold value T1, when an output shaft 104 of a main body 101 of a screw fastening device is turned for fastening. When the answer is YES, the number of effective impact times for screwing, to be added hereinafter, is counted. When the value of a counter Cn reaches or exceeds the present impact number In, turning of the output shaft 104 is stopped. Screwing is thus completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact-type screw tightening method and apparatus, such as an impact wrench or impact-type nut runner, for tightening a screw using impact energy.

[0002]

2. Description of the Related Art Conventionally, bolts or nuts (hereinafter, also collectively referred to as threaded portions) utilizing impact energy.
An impact-type screw tightening device is known as a screw tightening device for tightening a screw in which a tightening torque of a screw portion is controlled to obtain a predetermined axial force.

In this type of impact-type screw tightening device, a torque detector is provided on an output shaft of a main body of the screw tightening device. In this device, screw tightening is performed while applying impact energy for screw tightening to the screw portion and detecting a generated torque generated at this time and transmitted to the screw portion by a torque detector.

FIG. 9A is a diagram showing a temporal change in the output of the torque detector, and FIG. 9B is a diagram showing a temporal change in the axial force of the bolt. As shown in FIG. 9A, the output of the torque detector has a comb-like waveform, and each one of them indicates the occurrence of an impact. Further, as shown in FIG. 9 (B), the application of impact energy to the threaded portion causes the axial force of the bolt to exhibit a waveform that rises stepwise.

[0005] The peak value of the output waveform of the torque detector for each impact at the time of, for example, bolt tightening, which is generated from the torque detector, reaches a predetermined tightening completion set value indicating a predetermined tightening completion. Where we did
By stopping the driving of the output shaft of the main body of the screw tightening device, the tightening torque of the screw portion is controlled.

[0006]

By the way, in the conventional impact-type screw tightening device in which the tightening torque of the screw portion is controlled to obtain a predetermined axial force, a constant impact energy is applied to the screw portion. Is common.
At this time, as shown in FIG. 9A, almost no change is observed in the output waveform of the torque detector after the point indicated by a in the figure despite the increase in the axial force.

That is, the output of the torque detector and the axial force of the bolt have a linear relationship in a region before the position indicated by a in FIG. This means that observing the output of the torque detector and controlling the tightening torque of the screw portion to obtain the predetermined axial force of the bolt is limited to the above-mentioned region lower than the tightening ability of the screw tightening device itself. It is shown that it is possible.

In such a situation, in order to obtain the linearity between the output of the torque detector and the fastening (axial) force in order to detect a predetermined fastening torque while ensuring accuracy, the target fastening torque ( Eventually, a large impact energy is required with a margin for the corresponding target axial force). That is, it is necessary to apply impact energy enough to rotate the bolt or nut sufficiently at the time of impact. For this reason, there has been a problem that the tightening rotation speed of the bolt or the nut is increased, and for example, a large amount of heat is generated between the bolt and the mating member, which tends to cause seizure. Therefore, the friction coefficient of the screw surface, the bolt seat surface, and the like changes, and a phenomenon occurs in which the fastening force is low for the fastening torque value.

On the other hand, if the impact energy applied to the screw portion is reduced without changing the target tightening torque, the output of the torque detector is shown in FIG. 9A in which the waveform hardly changes. Since the region is a horizontal portion, there is a problem that the resulting variation in the tightening torque (and, consequently, the corresponding axial force) of the screw portion is large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to reduce the variation in fastening force while preventing seizure of a screw portion due to impact. It is an object of the present invention to provide an impact-type screw fastening method and apparatus that can be used.

[0011]

According to a first aspect of the present invention, there is provided an impact-type screw tightening method in which an impact energy is applied to a screw portion by using a driving source to fasten the screw portion to an object to be fastened. In the impact-type screw tightening method, a target tightening torque corresponding to the target tightening force is determined based on a relationship between the tightening torque and the tightening force of the screw portion obtained in advance, and a predetermined torque smaller than the target tightening torque is determined. A threshold is set, a torque generated when impact energy for screw tightening is applied to the screw portion is detected, and a predetermined number of impact energy starting from the impact energy when the generated torque is equal to or larger than the torque threshold is detected. It is characterized by adding screws and tightening.

According to a second aspect of the present invention, there is provided an impact-type screw tightening device having a torque generating portion to which power from a drive source is transmitted and which applies impact energy to a screw portion attached to a member to be fastened. In an impact-type screw tightening device in which the screw portion is fastened to an object to be fastened by a torque generating portion, a generated torque generated when impact energy for screw tightening is applied to the screw portion and transmitted to the screw portion And the generated torque detected by the torque detector is set to be smaller than a target tightening torque determined from a target tightening force based on a relationship between the tightening torque and the tightening force of the screw portion. After the predetermined torque threshold is reached, a predetermined number of impact energies are applied to the screw portion starting from the impact energy at this time. And having a control unit for performing obtaining control.

According to a third aspect of the present invention, in the impact type screw tightening apparatus according to the second aspect, when the target tightening torque is Ta, the torque threshold T1 and the impact energy are applied to the screw portion. The predetermined number of times In is set so as to satisfy the following equation.

(1/4) · Ta ≦ T1 ≦ (3/4) · Ta 10 ≦ In ≦ 40 According to a fourth aspect of the present invention, in the impact type screw tightening device according to the second aspect, the control section Is characterized in that it is determined whether or not a predetermined management value obtained from the waveform of the generated torque at the end of screw tightening is within a predetermined range.

According to a fifth aspect of the present invention, in the impact-type screw tightening device according to the second aspect, the control unit obtains a rising angle from a rising amount of a rising portion of the waveform of the generated torque with respect to a predetermined time width. In addition, when the rise angle is equal to or greater than a predetermined value, the occurrence of an effective impact for screw tightening is detected, and the value of the generated torque is corrected based on the value at the starting point of the predetermined time width at this time. Features.

[0016]

According to the first or second aspect of the present invention, it is only necessary to add the minimum impact energy required to obtain the target tightening torque, so that the rotational speed of the screw portion due to the impact is reduced. Thus, seizure can be prevented, and the variation in the fastening force can be reduced.

According to the third aspect of the present invention, in addition to the functions and effects according to the second aspect, it is possible to obtain a target tightening torque and a target fastening force with high accuracy while improving workability and reducing costs. It has the function and effect that it can be done.

According to the fourth aspect of the present invention, in addition to the operation and effect according to the second aspect, it is possible to determine whether or not the impact energy applied to the screw portion is appropriate. Can be warned to the operator.
Accordingly, it is possible to prevent a problem that the impact energy is too high or too low due to some obstacle, so that the seat surface of the screw portion is seized or a desired fastening force cannot be obtained.・ Effective.

According to the fifth aspect of the present invention, in addition to the operation and effect according to the second aspect, a zero point at which an unbalanced load is input to the torque detector for some reason and the screw tightening torque becomes zero is determined. Even if the output value of the torque detector shown
It is possible to reliably prevent a predetermined number of times of applying impact energy effective for screw tightening from being mistaken. In addition, it is possible to detect an unacceptable eccentric load input with a deviation of the output value of the torque detector indicating a zero point at which the screw tightening torque becomes 0. In such a case, for example, a warning may be issued to an operator. It has the function and effect of being able to do it.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram of an impact-type screw tightening device according to Embodiment 1 of the present invention, and FIG. 2 shows a specific example of the impact-type screw tightening device (impact wrench 19 for handheld). It is a partially broken side view.

The illustrated impact-type screw tightening device is an impact-type screw tightening device that generates and uses impact energy by compressed air or electricity, and manages both the tightening torque of a screw portion and the number of impacts to be added. Thus, a predetermined axial force is obtained. The impact energy can be adjusted based on the amount of compressed air, the current value, the voltage value, and the like.

As shown in FIG. 1, a fastening portion 10 for fastening a nut n to a bolt v to a workpiece W with a predetermined fastening torque.
0, a main body 101 of a hand-held screw tightening device is arranged, a socket 106 is provided at a tip of an output shaft 104 at a lower portion of the main body 101, and a torque generator 103 and a torque detector 30 are provided in the middle. A pulse-like torque is transmitted to the socket 106 by the rotation force of M. Thereby, the nut n fitted in the socket 106 can be rotated, and the nut n can be screwed to the bolt v.

The torque detector 30 detects a torque generated when the nut n is tightened, and a signal generated from the torque is processed by the control unit 109. This control unit 109
Has a torque signal processing unit 1 that generates a torque signal by inputting a signal from the torque detector 30 and an impact generation control unit 2 that outputs a signal for generating an impact to the motor M based on the torque signal. I have.

In this embodiment, a linear relationship between the tightening torque of the threaded portion and the fastening force (axial force) is determined in advance, and based on this, a target fastening torque corresponding to the target fastening force is determined. Next, an appropriate impact energy is obtained by an experiment in advance. Here, the appropriate impact energy is a minimum value necessary for obtaining the target tightening torque, that is, a magnitude that can be tightened by, for example, about 10% higher than the target tightening torque even if the number of impacts is increased from the initial stage of tightening. Set to. Accordingly, it is possible to prevent a situation in which when the impact energy is applied to the screw portion, the rotation speed of the screw portion is too high, and the screw surface, the bolt or the nut seat surface generates heat and seizure occurs.

Then, a predetermined torque threshold smaller than the target tightening torque is set, and from when the torque detector 30 detects the torque threshold until when the target tightening torque (and the corresponding target tightening force) is obtained. The appropriate number of impacts is determined by experiment and set.

When the screw portion is tightened by applying the impact energy set as described above, the output of the torque detector and the tightening torque (and the corresponding tightening force, ie, bolt axial force) up to a predetermined torque threshold. Are in a linear relationship, it is possible to accurately grasp the tightening torque by the torque detector 30, and it is possible to minimize the variation in the finally obtained fastening force of the screw portion.

Next, the tightening operation of the screw portion by the device according to the first embodiment will be specifically described with reference to a control flowchart shown in FIG. 4A and 4B are diagrams for explaining the tightening operation of the screw portion by the present device, wherein FIG. 4A is a diagram showing a temporal change in the output of the torque detector, and FIG. It is a figure which shows the time change of force.

The torque threshold is set in advance to T1,
After setting the number of impacts from the detection of the torque threshold value T1 until the target tightening torque is obtained as In, the tightening operation of the screw portion by the impact type screw tightening device is started.

First, an impact number counter Cn, which is provided in the control unit 109 and counts the number of times impact energy is applied to a screw portion, is set to 0 (step S1). And the output shaft 1 of the main body 101 of the screw tightening device
04 starts (step S2).

When the occurrence of an impact effective for screw tightening is detected based on a signal from the torque detector 30 (step S3), the reading (output value) of the generated torque detected by the torque detector 30 is used as the torque threshold. It is determined whether or not T1 or more has been reached (step S4).

Here, the detection of the occurrence of an impact effective for screw tightening is performed in the present embodiment by determining whether or not the output value of the torque detector 30 is equal to or larger than a predetermined value set to be smaller than the torque threshold T1. It is determined by whether This predetermined value is a value higher than usual, which is detected only when an impact can be determined to determine that effective impact energy for screw tightening has been applied, and is set in advance by an experiment.

If it is determined in step S4 that the output value of the torque detector 30 is equal to or larger than the torque threshold value T1 (YES in step S4), in steps S5 to S7, the impact effective for the screw tightening applied thereafter is determined. Count the number of times.

That is, in step S5, step S5
As in the case of 3, the occurrence of an impact effective for screw tightening is detected, and in step S6, the impact number counter Cn
Is a value obtained by adding 1 to the value. In step S7, it is determined whether or not the value of the impact number counter Cn is equal to or greater than a predetermined impact number In.

When it is determined that the value of the impact number counter Cn has become equal to or greater than the impact number In (step S7).
YES), the output shaft 104 of the main body 101 of the screw tightening device.
Is stopped, and the tightening of one screw portion is completed (step S8).

In step S9, when there are a plurality of screw portions to be tightened, it is determined whether or not the tightening of all the screw portions has been completed. (NO in step S9), the process returns to step S1, and the tightening operation is repeated.

Here, assuming that the target tightening torque is Ta, the torque threshold T1 and the number of impacts In are as follows: (1/4) · Ta ≦ T1 ≦ (3/4) · Ta (1) 10 ≦ In ≦ 40 (2)

In the case of the screw tightening by the impact type screw tightening device, if the impact energy is set so as to be able to be tightened at least up to the target tightening torque, one to two times after the seating surface of the screw portion is seated on the member to be fastened. A torque of 1/4 of the target tightening torque Ta can be obtained by impact (see FIG. 4A). Therefore, the lower limit of the torque threshold value T1 is determined from the viewpoint of reliably detecting that the seat is seated.

On the other hand, if the impact energy is set to a magnitude that can only be tightened by about 10% higher than the target tightening torque even if the number of impacts is increased from the initial stage of the tightening, it is larger than 3/4 of the target tightening torque Ta. The shape and size of the output waveform of the torque detector 30 with respect to the torque generated in the fastening state by the fastening torque hardly change. If an attempt is made to control the driving of the output shaft 104 by the motor M based on the output value of the torque detector 30 in a region where the output waveform of the torque detector 30 hardly changes, the variation in the fastening force increases. I will. Therefore, the upper limit of the torque threshold T1 is determined from the viewpoint that a desired fastening force can be obtained by performing drive control based on the output value of the torque detector 30. If the detection accuracy of the torque detector 30 increases, the torque threshold value T1 can be made closer to the target tightening torque Ta, and the variation in the fastening force can be reduced, but it is technically difficult. , Leading to higher costs.

Further, the lower limit of the number of impacts In is such that when the impact energy is set to about 10% higher than the target tightening torque, even if the torque detector 30 detects 3/4 of the target tightening torque Ta, It is determined from the viewpoint of the minimum number of times required to reach the tightening torque.

On the other hand, the upper limit of the number of impacts In is such that when the impact energy is set to about 10% higher than the target tightening torque, the tightening hardly progresses after the seating surface of the threaded portion is seated on the workpiece. It is determined from the viewpoint of the number of times. The time required to apply one impact energy is about 50 msec.
Since it takes about 2 seconds per time, this upper limit value matches the required value from the workability in the assembly line. The impact energy added to the threaded portion is set to the minimum value required to obtain the target tightening torque.
Can be increased to, for example, 50 to 60 times.

For example, in the case shown in FIGS. 4A and 4B, when the torque threshold T1 is set to (1/4) · Ta, the number of impacts In is set to 19, and When the torque threshold value T1 is set to (3/4) · Ta, by setting the number of impacts In = 15, the target tightening torque Ta and thus the target fastening force can be accurately obtained.

As described above, according to the first embodiment, it is only necessary to add the minimum impact energy required to obtain the target tightening torque. Therefore, the rotational speed of the threaded portion due to the impact is reduced to prevent image sticking. In addition, the variation in the fastening force can be reduced.

(Embodiment 2) FIG. 5 is a control flowchart showing a tightening operation of a screw portion by an apparatus according to Embodiment 2.

The impact-type screw tightening device according to this embodiment differs from the first embodiment in that the impact energy added to the threaded portion is added to the control to determine whether or not the impact energy is appropriate. Although this device is different from the above device, the other points are the same, and the description thereof is omitted.

In this embodiment, when an appropriate impact energy determined in advance by an experiment is applied, a predetermined control value of a torque waveform generated at the time of impact upon completion of tightening of the screw portion is defined as an area of the torque waveform. (Integral value) is checked, and an appropriate range of impact energy is set. Then, when the value does not fall within the appropriate range, the abnormality of the impact type screw tightening device is notified to the operator.

Before the tightening operation of the screw portion by the impact-type screw tightening device is started, the torque threshold value is set to T1, and the target tightening torque is detected after detecting the torque threshold value T1 as in the first embodiment. Is set as In, and in addition to this, the maximum value Smax and the minimum value Smin of the appropriate torque waveform area are determined by experiments.

Next, the tightening operation of the screw portion by the device according to the second embodiment will be specifically described with reference to a control flowchart shown in FIG.

First, an impact number counter Cn, which is provided in the control unit 109 and counts the number of times impact energy is applied to the threaded portion, is set to 0, and when the impact energy is actually added to the threaded portion, The accumulated value S1 of the torque waveform area obtained from the torque is set to 0.
(Step S11). Then, the driving of the output shaft 104 of the main body 101 of the screw tightening device is started (step S12).

When the occurrence of an impact effective for screw tightening is detected based on the signal from the torque detector 30 (step S13), the reading (output value) of the generated torque detected by the torque detector 30 is used as the torque threshold. It is determined whether or not T1 or more has been reached (step S14).

If it is determined in step S14 that the output value of the torque detector 30 is equal to or larger than the torque threshold value T1 (YES in step S14), in steps S15 to S17, an effective impact on the screw tightening added thereafter is obtained. Count the number of times.

That is, in step S15, as in step S13, the occurrence of an impact effective for screw tightening is detected, and in step S16, the value of the impact number counter Cn is set to a value obtained by adding one. Step S17
Then, it is determined whether or not a value obtained by subtracting n from the impact number counter Cn (= Cn−n) is equal to or greater than a predetermined impact number In. The reason why n is set is that an average value of the torque waveform areas obtained a plurality of times immediately before the end of the tightening of the screw portion is obtained, and it is more preferable to set n to 2 to 6.

When it is determined that the value of Cn-n has become equal to or greater than the number of impacts In (YES in step S17), the torque waveform area S at the time of the impact is calculated (step S18), and the torque waveform area is calculated. S to cumulative value S1
Is added (step S19). Such calculations are repeated, and when the impact counter Cn reaches the preset impact count In (YE in step S20).
S), the driving of the output shaft 104 of the main body 101 of the screw tightening device is stopped, and the tightening of one screw portion is completed (step S21).

When the tightening of one screw portion is completed, in step S22, the average value S1 / n of the torque waveform areas obtained a plurality of times immediately before the completion of the tightening of the screw portion is determined by calculating the maximum torque Smax and the proper torque waveform area. It is determined whether it is between the minimum values Smin (step S22). And S1 / n
Is within the range of the appropriate torque waveform area (step S
22 (YES), a predetermined indication of tightening OK is made (step S23). Next, in step S24, it is determined whether or not the tightening of all the screw portions has been completed, for example, when there are a plurality of screw portions to be tightened, and if the screw portions to be tightened still remain (step S24). N of S24
O), returning to step S11, the above-described tightening operation is repeated. On the other hand, if it is determined in step S22 that S1 / n is not within the range of the appropriate torque waveform area (NO in step S22), a predetermined display of the fastening NG is performed (step S25).

As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained, and it can be determined whether or not the impact energy applied to the screw portion is appropriate. In addition, it is possible to warn an operator of an abnormality of the device. Therefore, it is possible to prevent a problem that the impact energy is too high or too low due to some obstacle, such that the seating surface of the screw portion is seized or a desired fastening force cannot be obtained.

In the second embodiment, the area of the torque waveform is used as the predetermined control value of the torque waveform generated at the time of impact when the tightening of the screw portion is completed.
The present invention is not limited to this. For example, the peak value of the torque waveform can be used.

(Embodiment 3) In the impact-type screw tightening device according to Embodiment 3, the rise angle (inclination) of the torque waveform generated when impact energy is added to the screw portion is effective for screw tightening. It is configured to detect the occurrence of an impact that is effective for screw tightening based on a predetermined value that is larger than normal and is detected only when an impact can be determined that an impact energy has been applied. ing. The base of the rising of the waveform of the generated torque is defined as the zero point (reference) of the output of the torque detector 30. In such a point, the impact-type screw tightening device according to the third embodiment is different from the device according to the first or second embodiment, but the other points are the same. Omitted.

FIG. 6 is a diagram for explaining a method of detecting the occurrence of an impact effective for screw tightening. FIG.
The impact is shown in a partially enlarged manner. In the case of the impact-type tightening as in the present device, the rotation of the nut n stops every time each impact is completed, so the first torque waveform affected by the coefficient of static friction And the second peak of the torque waveform affected by the dynamic friction coefficient are detected.

In this embodiment, as shown in FIG.
The output (voltage) value of the torque detector 30 at the time t0 at the rising portion of the waveform of the generated torque is V (t0), and the output (voltage) of the torque detector 30 before the time t0 is t1.
Assuming that the value is V (t0−t1) and the threshold voltage value for detecting the occurrence of an impact effective for screw tightening is ΔV, the condition for detecting the occurrence of an impact effective for screw fastening is V (t0) −V ( t0-t1) .gtoreq..DELTA.V. Here, the time t1 is hereinafter also referred to as an impact detection time.

In this case, the voltage value V (t0−t1) at the foot of the rising edge of the generated torque waveform is expressed as
An output voltage value when the torque detector 30 outputs zero point (reference), that is, when the screw tightening torque is zero.

FIG. 7 is a diagram for explaining a more specific method of the above method for detecting the occurrence of an impact effective for screw tightening.

In this method, the output V (t (i)) at the i-th time ti, which is an analog output signal of the torque detector 30 and is sampled at a fixed time interval (sampling cycle), is converted into an A / D signal. The data is converted and stored in a memory (not shown). Then, the output value of the torque detector 30 that has just been A / D converted is compared with the value before the time t1 stored in the memory. Here, the time t1 is the above-described impact detection time, and corresponds to, for example, n sampling periods (time corresponding to the sampling number n). That is, comparison with the n-th data before sampling is performed. Here, if the difference between the two is a difference that appears only when the impact energy effective for screw tightening is applied, it is considered that the impact effective for screw tightening has occurred.

Therefore, the output (voltage) value of the torque detector 30 at the time ti is V (ti), and the digitized value of the output (voltage) is d (V (ti)), which is an impact detection time longer than the time ti. Torque detector 3 before time t1
The output (voltage) value of 0 is V (ti-n), the digitized version is d (V (t (i-n))), and the threshold digital value for detecting the occurrence of an impact effective for screw tightening is When D is set, the condition for detecting the occurrence of an impact effective for screw tightening is d (V (ti))-d (V (t (i-n))) ≥D.

As described above, according to the third embodiment, an eccentric load is input to the torque detector 30 for some reason.
Torque detector 3 indicating a zero point where the screw tightening torque becomes 0
Even if the output value of 0 is shifted, it is possible to reliably prevent the predetermined number of times of applying the impact energy effective for screw tightening from being incorrect. Also, with a shift in the output value of the torque detector 30 indicating a zero point at which the screw tightening torque becomes 0,
Unacceptable unbalanced load input can be detected,
In such a case, for example, a warning can be issued to the worker.

FIG. 8 is a view for explaining a specific method for detecting an eccentric load input to the torque detector.
(A) is a diagram showing an output waveform of the torque detector when there is no offset load, and (B) is a diagram showing an output waveform of the torque detector when there is an offset load.

That is, the zero point voltage which is the output of the torque detector at the foot of the rise of the waveform of the torque generated at the first impact is V01, and the zero point voltage at the i-th impact is
The point voltage is V0i, and the threshold voltage value for detecting the input of the unbalanced load is Vd.
In this case, the eccentric load input detection condition is | V01−V0i | ≧ Vd.

As described above, the difference between the zero-point voltage at the time of the first impact, that is, the output voltage value of the torque detector detected before screw tightening and the zero-point voltage detected at each subsequent impact is determined by the predetermined threshold value. When the above is detected, it is possible to issue a warning to the operator that screw tightening is NG, assuming that an unacceptable unbalanced load is input.

The embodiments described above are not described to limit the present invention, and various changes can be made within the scope of the claims.

[Brief description of the drawings]

FIG. 1 is a block diagram of an impact-type screw fastening device according to Embodiment 1 of the present invention.

FIG. 2 is a partially broken side view showing a specific example of the impact type screw tightening device.

FIG. 3 is a control flowchart showing a tightening operation of a screw portion by the device according to the first embodiment.

4A and 4B are diagrams for explaining a tightening operation of a screw portion by the present device, wherein FIG. 4A is a diagram showing a temporal change of an output of a torque detector, and FIG. It is a figure showing a temporal change.

FIG. 5 is a control flowchart showing a tightening operation of a screw portion by the device according to the second embodiment.

FIG. 6 is a diagram for explaining a method of detecting occurrence of an impact effective for screw tightening in the device according to the third embodiment.

FIG. 7 is a diagram for explaining a more specific method for detecting occurrence of an impact effective for screw tightening.

8A and 8B are diagrams for explaining a specific method of detecting an unbalanced load input to the torque detector, and FIG. 8A is a diagram illustrating an output waveform of the torque detector when there is no unbalanced load;
(B) is a diagram showing an output waveform of the torque detector when there is an eccentric load.

9A and 9B are views for explaining a tightening operation of a screw portion in a conventional device, wherein FIG. 9A is a diagram showing a temporal change in the output of a torque detector, and FIG. FIG. 6 is a diagram showing a temporal change of the data.

[Explanation of symbols]

 Reference numeral 30: torque detector, 100: fastening part, 103: torque generating part, 106: socket, 109: control part, M: drive source, W: workpiece, n: nut, v: bolt, Ta: target tightening torque , T1: torque threshold, In: predetermined number of times of applying impact energy to the thread portion.

Claims (5)

[Claims] 1. An impact-type screw tightening method in which impact energy is applied to a screw portion by using a drive source (M) to fasten the screw portion to a workpiece (W). The target tightening torque corresponding to the target tightening force is determined based on the relationship between the tightening torque and the tightening force of the portion, and a predetermined torque threshold smaller than the target tightening torque is set, and the impact for screw tightening on the screw portion is set. An impact-type screw, wherein a torque generated when energy is applied is detected, and a predetermined number of impact energies are added to tighten the screw starting from the impact energy when the generated torque is equal to or greater than the torque threshold. Tightening method. 2. A torque generator (103) to which power from a drive source (M) is transmitted and that applies impact energy to a screw portion (n, v) attached to an object to be fastened (W). An impact-type screw tightening device in which the screw portion is fastened to an object (W) by a torque generating portion (103), wherein the screw portion is generated when impact energy for screw tightening is applied to the screw portion. A torque detector (30) for detecting a generated torque transmitted to the screw member, and the generated torque detected by the torque detector (30) is set to a target engagement based on a relationship between a tightening torque and a fastening force of the screw portion. After a predetermined torque threshold that is set to be smaller than the target tightening torque determined from the force becomes equal to or greater than a predetermined torque threshold, the impact energy at this time is used as a starting point, and a predetermined number of impact energy is applied. Impact screw clamping device characterized by having a control unit for controlling the addition to the serial threaded portion. 3. When the target tightening torque is Ta, the torque threshold T1 and the predetermined number of times In for applying impact energy to the screw portion are set so as to satisfy the following expression. The impact type screw tightening device according to claim 2. (1/4) · Ta ≦ T1 ≦ (3/4) · Ta 10 ≦ In ≦ 40 4. The control unit according to claim 2, wherein the control unit determines whether a predetermined management value obtained from the waveform of the generated torque at the end of the screw tightening is within a predetermined range.
The impact type screw tightening device as described. 5. The control section calculates a rise angle from a rise amount for a predetermined time width in a rise section of the waveform of the generated torque, and when the rise angle becomes a predetermined value or more, an impact effective for screw tightening is obtained. 3. The impact-type screw tightening device according to claim 2, wherein the occurrence of the torque is detected and the value of the generated torque is corrected based on the value at the starting point of the predetermined time width at this time.