JPH04129627A - Inspecting method for fastening - Google Patents

Abstract

PURPOSE:To rapidly detect the occurrence of racing of a fastening device during fastening by stopping fastening when seating of a screw member on the fastening side is not detected until an elapsing time starting from a point of time when fastening is started or rotation angle attains a given value. CONSTITUTION:When a bolt 5 is coaxially matched with a nut 3, a controller 12 rotates the bolt at a low speed with the aid of a motor 7 to start fastening, and simultaneously a set timer 13 is started. Meanwhile, torque occasioned by fastening is detected by a torque sensor 11 and compared with seating torque. When the fastening torque does not exceed the seating torque until a time set by the set timer 13 elapses, it is decided that fastening is effected in a racing state, the controller 12 outputs a racing detecting signal to, for example, a display means 14, and stops the motor 7 to stop fastening. This method prevents a racing state from continuing to completion of a fastening cycle time and removes a useless fastening time when racing occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for inspecting the state of tightening when fastening a fastening side threaded member such as a bolt to a fastened side threaded member such as a nut.

(Prior Art) As is well known, the manufacture of vehicles such as automobiles is carried out through assembly line operations.
In recent years, automation has been widely adopted in various types of work, as typified by robotic devices.

In that case, it will be required to automatically assemble these suspension parts using bolts and nuts on the line for assembling the suspension parts to the vehicle body.

To deal with this, for example, Japanese Patent Publication No. 14675/1983 discloses that the screws are tightened using the force of a motor, and it is determined whether or not the screws are completely tightened based on the magnitude of the torque at the time of tightening. The technology has been disclosed.

If such technology is used, bolts or nuts are welded in advance to the vehicle body being transported through the assembly line, and the underbody parts can be assembled to the bolts or nuts on the assembly line. By doing so, the assembly can be automated.

(Problem to be solved by the invention) By the way, in the above-mentioned automation, when considering the normal and efficient fastening of a bolt (or nut) to a nut (or bolt) attached to the vehicle body, the first step is to In order to ensure that the tip is firmly caught in the nut, it is necessary to rotate the bolt at low speed at the beginning of tightening, and once biting occurs, it is necessary to rotate the bolt at high speed to seat the bolt in a short time. Therefore, as shown in Fig. 8A, the rotational speed control for this purpose is such that the bolt is rotated at a low speed (Sl) from the start until the time a when the jamming condition occurs, and then the tightening is increased once the jamming condition has multiplied. The bolt is then rotated at a constant speed (Ss) from point b to the seating point C, and then once the bolt is seated, the bolt rotation is stopped and then rotated at a low speed from point d to point e. It is possible to perform final tightening (increasing tightening).

In addition, as a method for detecting jamming and seating in this control, torque is detected for tightening, and as shown in FIG. It is conceivable to detect that the seating torque Ts is reached.

However, if for some reason the bolt is not loaded in the device or the nut is not secured to the vehicle body, the tightening device will idle. In that case, the detected tightening torque T will not increase as shown by the broken line in FIG. On the other hand, as mentioned earlier, the speed from seating to final tightening is controlled depending on whether or not bolt seating is detected and bolt tightening is achieved within the cycle time. It cannot be checked until the time t5 has elapsed, and tightening continues in this idling state until the end of the cycle time, and unnecessary tightening wastes time and poses a problem in terms of work efficiency.

Therefore, the first object of the present invention is to provide a fastening inspection method that can promptly detect when idling occurs in fastening.
This will be the subject of this study.

Furthermore, as described above, it is desirable to tighten the bolt at a low speed until the bolt is bitten into the nut, and to shift to high-speed tightening upon detection of the squealing. Therefore, detection of the biting point a becomes important. However, as sensors for performing the speed control shown in FIG. 8, it is conceivable to separately provide a sensor for detecting the biting time point a and a sensor for detecting the seating time point C. In that case, even though the seating detection sensor is working normally, if the sensor that detects the jamming is disconnected, short-circuited, or malfunctions,
It becomes impossible to accurately detect the biting point a, and the normal rotational speed control shown in FIG. 8A cannot be performed.

For example, if the biting point a cannot be detected, it is not possible to shift the bolt to high-speed tightening, so the low-speed tightening state continues as shown in Figure 8, and the tightening continues even after the cycle time ts has elapsed. It is not completed, and in this case, the fastening is clearly defective (insufficient fastening force). Furthermore, if there is a malfunction in which a biting signal is obtained at the same time as tightening starts even though stable biting has not yet occurred,
As shown in Figure C, since the fastening immediately starts, there is a risk that seizure or other abnormalities may occur in the biting portion.

Therefore, the second object of the present invention is to provide a fastening inspection method that can control the speed of fastening from the time when a stable biting state is obtained toward seating.

(Means for Solving the Problems) The present invention is characterized by being configured as follows in order to address the above problems.

That is, the invention according to claim 1 of the present invention (hereinafter, the first
The invention) is a method for inspecting the state of tightening when fastening a fastening side screw member to a fastened side screw member,
Tightening of the fastening side screw member is performed by measuring the elapsed time or rotation angle from the start point, and when the seating of the fastening side screw member is not detected before the time or rotation angle reaches a preset time or rotation angle. It is characterized by stopping the tightening.

Further, the invention according to claim 2 of the present invention (hereinafter referred to as the second invention) is such that the screw thread of the fastening side screw member is bitten into the fastened side screw member from the start of tightening of the fastening side screw member. While the time for tightening is set in advance with a predetermined time width, the elapsed time from the start of the tightening is measured, and the biting is detected while this elapsed time is within the set time range. If the jam is detected before the elapsed time reaches the set time width, the shift to high-speed tightening is started when the set time is reached, and the elapsed time If no jamming is detected even after the set time range has elapsed, the fastening is shifted to high-speed tightening when the set time range has elapsed.

Furthermore, the invention according to claim 3 of the present invention (hereinafter referred to as the third invention) is such that the thread of the fastening side screw member is bitten into the fastened side screw member from the start of the tightening of the fastening side screw member. While the time for tightening is set in advance with a predetermined time width, the elapsed time from the start of the tightening is measured, and the biting is detected while this elapsed time is within the set time range. If the jam is detected before the elapsed time reaches the set time width, the shift to high-speed tightening is started when the set time is reached, and the elapsed time If jamming is not detected even after the set time range has passed, the fast tightening is started when the set time range has elapsed, and the fastening side screw member is tightened according to the elapsed time or The present invention is characterized in that the rotation angle is measured, and when seating of the fastening side screw member is not detected before the rotation angle reaches a preset time or rotation angle, the tightening is stopped.

(Function) According to the above-described first aspect of the present invention, if the tightening is performed normally, the fastening side screw member sets the time or rotation angle required from the start of tightening to the seating. Since tightening is a method of stopping further tightening when the elapsed time from the start or the rotation angle exceeds the set time or rotation angle, if idle rotation occurs, it is assumed to be normal. Tightening can be stopped immediately after the seating point, and the idle state can be prevented from continuing until the end of the cycle time.

Further, according to the second aspect of the present invention, in the device for detecting the biting of the fastening side screw member with respect to the fastened side screw member, even if biting is detected, the high speed is maintained until a preset time is reached. It does not shift to tightening, and if the above-mentioned biting is not obtained even after this set time range, it shifts to high-speed tightening, so the timing at which biting is detected varies greatly back and forth due to malfunction of the biting detection sensor, etc. However, it is possible to shift to high-speed tightening at a more or less constant time.

(Example) Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a nut 3 fixed to a workpiece 1 (for example, a floor panel in an automobile) by welding 2.
An embodiment will be shown in which a bolt 5 with a washer 6 fitted to the shaft portion 5a is passed through a bolt through hole 4 formed in a workpiece 1 from below and fastened.

For this purpose, a bolt tightening device 9 having a bolt holder 8 rotated by the rotational force of the motor 7 is provided. In this device 9, a hexagonal hole bolt fitting part 8a is formed at the top of the bolt holder 8, and the bolt head 5b of the bolt 5 is fitted into the bolt fitting part 8a before the above-mentioned fastening. Loaded in an inverted position. The bolt 5 is loaded into the bolt holder 8 by an automatic loading means (not shown) while the device 9 is lowered relative to the work 1.

Further, the bolt tightening device 9 is attached to a robot device so that predetermined movements such as lifting and lowering and turning can be performed. However, since this robot device is not directly related to the gist of the present invention along with the automatic loading means described above, a detailed explanation thereof will be omitted.

Further, in the bolt tightening device 9, a torque sensor 11 is attached to a fixing member 10 that rotatably holds the bolt holder 8, and detects a torque T during bolt tightening. The output is refined so that the torque T is input to the controller 12.

In this controller 12, the torque T detected by the torque sensor 11 is used to control the rotational speed of the motor 7 as shown in FIG. This rotational speed control is the same as that described in the explanation of FIG. As shown in Fig. 1, the tip of the bolt is passed through the bolt through hole 4 so as to correspond to the nut 3, and from this state of correspondence, the motor 7 is rotated at a low speed to screw the bolt 5 into the nut 3. Then, when the first thread of bolt 5 is bitten into nut 3 by screwing,
This single thread tightening is done at point a in Figure 2. (hereinafter referred to as the biting point), the rotation speed is increased, and the washer 6 is moved to the washer 21.
(Between point b and point C in Figure 2)
, the motor 7 is rotated at a constant speed at a high speed, and then the motor 7 is temporarily stopped at a point C when the washer 6 is seated, and then the final tightening (increasing tightening) is performed by rotating at a low speed for a short time from point d to point e. .

Due to this rotational speed control, the bolt 5 rotates relatively slowly until it is bitten into the nut 3, so that the biting is ensured, and once it is bitten, it is tightened at a high speed, and the tightening takes time. In addition, after seating, final tightening is performed again at low speed to prevent excessive tightening.

Furthermore, as is clear from the above description, the controller 1
2, the tightening is performed by using torque T to detect the biting point a and the seating point C of the bolt 5, and in the biting detection, the torque T is preset for the tightening detected by the torque sensor 11. The torque T+ (third
Seating detection is similarly performed when the torque T reaches the seating torque Ts (shown in FIG. 3).

Furthermore, the controller 12 is provided with a setting timer 13 that is activated when tightening is started. This setting timer 13
Tightening is to set the time from start to seating. That is, if rotational speed control is applied to the motor 7 as described above, it is possible to calculate an approximate value of the time from the start of tightening to seating when normal fastening is performed. Therefore, if we add to this approximate value the variation in time X at the time of sitting (in order to clearly represent the variation in seating time, the range of variation is exaggerated in Figure 3), it will take more time than this. It is possible to set a seating time tD, which becomes a reference for determining that the idle state is clearly idle after the elapse of time. Setting timer 1 above
3 sets this seating time tD. Note that it is clear from the above-mentioned viewpoint of rotational speed control that this set seating time to is significantly shorter than the tightening cycle time ts.

Then, based on the relationship between the seating time tD set by the setting timer 13 and the seating time point C, the controller 12 calculates the following:
Tightening has been refined to determine idle rotation during operation.

Next, the idle rotation detection operation will be explained using the flowchart shown in FIG.

For bolt tightening, when the bolt 5 is coaxially aligned with the nut 3 by the device 9, in step S1 the controller 12 controls the rotational speed of the motor 7 as shown in FIG. Start tightening. Further, at the same time as the tightening is started, the setting timer 13 is started in step S2.

On the other hand, the torque T accompanying the tightening is detected by the torque sensor 11, and the detected tightening torque T is compared with the seating torque Ts in step S3, and before the setting timer 13 times up (that is, the tightening is started from the start). When the tightening torque T reaches the seating torque Ts before the set seating time t [, shown in FIG. On the other hand,
If the tightening torque T does not exceed the seating torque T5 before the setting timer 13 times up, that is, if the tightening torque T does not increase as shown by the broken line in FIG. Along with the time-up in S5, the controller 12 assumes that the current tightening is being performed in a idling state for some reason, and outputs an idling detection signal to the display means 14 or the like in step S5, or records the occurrence of idling, and in step S7 The motor 7 is stopped and further tightening is stopped.

In this way, it is automatically determined whether or not the tightening was performed in an idle state, but the timing of this determination is such that under normal tightening, the bolt 5 is seated in the nut 3. The brazing seating time TD is set, and if the seating torque T5 is not obtained by the set seating time TD, it is determined that the slip has occurred, so the above determination is made without having to wait until the end of the cycle time ts for tightening as in the past. This means that the wasted time for this determination can be significantly reduced.

Incidentally, in the above embodiment, the time tD from the start of tightening to seating is determined by the setting timer 13, and the idling is determined. Attached is the integration of the rotation angle θ of the bolt 5 from the start to the seating, and this rotation angle θ is set as the seating rotation angle θD.
You may also adopt a method of comparing.

In order to achieve this, the bolt tightening shown in FIG. At the same time, the set rotation angle θD is stored in the controller 12 instead of the set timer 13. Then, when the tightening is started, the controller 12 integrates the rotation angle θ based on the rotation angle signal input from the rotation angle sensor 15, and performs an operation of comparing the integrated value with the set rotation angle θD stored in the memory.

To explain the operation by rotation angle control in this way using the flowchart of FIG. 5, as soon as the tightening in step S11 is started, the controller 12 uses the rotation angle sensor 15 to control the rotation angle θ in steps from the start. Accumulate in S12,
In step S1B, the torque sensor 1 starts tightening.
The tightening detected by No. 1 determines whether the torque T has reached the seating torque T5.

If the seating torque Ts is reached before the cumulative rotation angle θ exceeds the set rotation angle θD, the process moves to step SI4.
Perform final tightening. On the other hand, when the seating torque Ts cannot be detected even though the cumulative rotation angle θ exceeds the set rotation angle θD in step SI5, in other words, the tightening is performed without increasing the torque T as shown by the broken line in FIG. has passed, the current tightening is performed in an idle state for some reason, and the controller 12 displays the idle rotation detection signal in step 16, for example, on the display means 14.
In addition to outputting other information or recording the occurrence of idle rotation, the motor 7 is stopped in step S17, and further tightening is stopped.

With this method as well, the idle state can be determined without unnecessary tightening.

By the way, in the bolt tightening shown in FIG. 1, the device 9 uses one torque sensor 11 to detect the biting point a and the seating point C in the rotation control shown in FIG. It is conceivable that times a and C may be detected by separate torque sensors (or other detection sensors in place of the torque sensor). In that case, as mentioned at the beginning, if the sensor for detecting jamming (hereinafter referred to as the torque sensor 16, not indicated by the chain line in Fig. 1) malfunctions, it may cause poor fastening, seizure, etc. .

This can be countered by providing two delay timers 17.1 and 172 (both indicated by chain lines in FIG. 1) in the controller]2.

In other words, if the rotational speed control shown in Fig. 2A is applied and the bolt is tightened normally, the point a when one thread of the bolt 5 is bitten into the nut 3 is the point at which the tightening is started. When the time ta is reached, the first delay timer 171 is activated at the same time as the tightening starts, and times up Δ at a time tal earlier than the above-mentioned ta,
The second delay timer 172 is also started at the same time as the tightening is started, and is set to time up at a time point ta2, which is a time delay of Δ from the above-mentioned ta.

! Note that even if the torque sensor 16 detects torque T for single tightening, the controller 12 will control the speed of the motor 7 (seating torque T) before the first delay timer 17□ times up. (transition control to high-speed tightening for Furthermore, if the jammed state is not detected until the second delay timer 172 times up, the fastening is forcibly shifted to high-speed tightening from the time ta2 when the timer 172 times up.

Such a control operation will be explained using the flowchart shown in FIG.

After various numerical values of the control system have been cleared in step S2□, in step S22, the controller 12 applies rotational speed control to the motor 7 as shown in FIG. Along with this, step 32B+
In 324, the tightening is performed from the start to the first and second delay.
Timers 171 and 172 are started.

Then, in step S25, first the first delay
Timer 17. When the time is up for a time taI, the tightening torque T is engaged.

It is determined in step S26 whether or not this has been reached, and if a jammed state is detected, the process moves to high-speed tightening in step S27 and ends the operation.

However, the controller 12 uses the first delay timer 17.
Since the system is configured to shift to high-speed tightening only after a time-up of 1 or more, due to malfunction of the torque sensor 16, the biting torque T1 is detected at the same time as the tightening starts even though biting has not occurred. However, without immediately shifting to high-speed tightening, the time t is shown in Figure 2 C.
When a1 has elapsed and the first delay timer 171 has timed up, the process is shifted to high-speed tightening. Therefore, even if there is a slight time lag Δt, the rotational speed control in this case is almost the same as that shown in Figure 2 A.
High-speed tightening from an early point in time when the biting torque T1 is detected is eliminated, and biting defects such as seizure do not occur.

Further, when the second delay timer 172 times up in step 328 without any jamming being detected in step S26, the controller 12 outputs the jamming detection signal at the time ta2 when the time has elapsed, and the tightening torque T is set to the biting torque. Even though T1 has not yet been reached, it is output in step S29 and the process is shifted to high-speed tightening in step S27.

In this way, at time ta2, the tightening is shifted to high-speed tightening even though the torque T has not detected any biting, so the tightening is not performed even though biting has actually occurred due to malfunction of the torque sensor 16. Even when the torque T does not increase to the biting torque T1, it is possible to shift to high-speed tightening, and in that case, the rotation control is as shown in Figure 2, even if there is a slight time lag Δt. The control is almost the same as A, and even after the biting point a, a fastening failure (insufficient fastening force) due to low-speed fastening will not occur.

In this way, two delay lines with different time-up times can be used.
By using the timers 171 and 172, it is possible to prevent a fastening failure due to malfunction of the torque sensor 16 for detecting jamming.

Note that the control method for dealing with malfunction of the jamming detection torque sensor 16 can also be configured in combination with the above-mentioned idling detection control. A flowchart in that case is shown in FIG.

In this flowchart, the first timer corresponds to the setting timer 13 shown in FIG.
Set the time until. The second timer corresponds to the first delay timer 171 in FIG. 1, and the third timer similarly corresponds to the second delay timer 172.

In FIG. 7, the tightening is started at steps SSI to S35, and the above-mentioned timers 13, 171, 172 are started, and the second timer 17 is started at steps S36 to S39.
The presence or absence of clogging is determined from the time ta1 when □ times up, and when clogging is detected, or if clogging is not detected even after the third timer 172 times out, the process shifts to high-speed tightening at time ta2. do.

Then, from step SaO to step 344, the idling state is detected from the relationship between the time to set by the first timer 13 and the seating detection time point, as in the case of the flowchart of FIG.

Further, although the flowchart in FIG. 7 uses the time detection control shown in FIG. 4 for idle rotation determination, it can be easily replaced with the rotation angle detection control shown in FIG.

In the above embodiment, the bolt 5 is screwed into the nut 3 fixed to the workpiece 1, but it goes without saying that the present invention can also be applied to the case where a nut is fastened to the bolt fixed to the workpiece 1. be. Further, in the embodiment, the biting of the bolt 5 is detected when one thread of the screw is bitten, but the present invention is not particularly limited to this. For example, this can be done using a sensor that detects the amount of movement of the bolt holder 8 in FIG. 1 as it is bitten.

(Effects of the Invention) As is clear from the above description, according to the first aspect of the present invention, if the fastening side screw member is tightened normally, it is determined that the tightening side screw member is required to be seated from the start. When the time or rotation angle accumulated from the start of tightening exceeds the set time or rotation angle, further tightening will stop the operation. If this occurs, the tightening can be stopped immediately after the normal seating point, and the idling state can be prevented from continuing until the end of the cycle time. Therefore, it is possible to eliminate wasted time in tightening when idle rotation occurs, and the tightening work becomes more efficient.

Further, according to the second aspect of the present invention, in the device that detects the biting of the tightening side screw member with respect to the fastened side screw member, even if biting is detected, high-speed tightening is not performed until a preset time. If the above-mentioned bite is not obtained even after the set time has passed,
Since the shift to high-speed tightening is forcibly performed, even if the time point at which jamming is detected varies greatly back and forth due to a malfunction of the jamming detection sensor, etc., the shift to high-speed tightening can be made almost always at the same time. Therefore, defects in tightening due to insufficient fastening force or abnormal biting can be prevented.

[Brief explanation of the drawing]

The drawings show an embodiment of the fastening inspection method according to the present invention, and FIG. 1 is a block diagram embodying the above method, and FIG.
Figures 1 and 2 show the normal rotational speed control state when tightening (a), the rotational speed control state with correction applied for non-detection of jamming (b), and the corrected state for early detection of jamming. FIG. 3 is a graph for explaining the idle rotation detection operation, FIG. 4 is a flowchart for explaining the idle rotation detection operation by time setting, and FIG. 5 is a graph for explaining the idle rotation detection operation by setting the rotation angle. FIG. 6 is a flowchart explaining the transition operation for high-speed tightening due to defective jamming detection, and FIG. 7 is a flowchart when the two control functions of FIGS. 4 and 6 are provided. Figure 8 A, C, and C are graphs of the prior art, showing the normal rotational speed control state for tightening (A), the rotational speed control state when no jamming is detected (B), and the rotation when jamming is detected early. Graphs each representing the speed control state (c) and FIG. 9 are graphs explaining the idling detection operation in the prior art. 3... Screw member on the fastened side (nut), 5... Thread member on the fastening side (bolt), 11.16... Torque sensor,
12...Controller, 13.17+172...Timer, 15...Rotation angle sensor. hi ε Graph Graph Graph □ Poem Graph Graph Graph □ Time Graph □ Time

Claims (3)

[Claims] (1) A method for inspecting the tightening state when fastening a fastening side screw member to a fastened side screw member, which measures the elapsed time or rotation angle from the time when tightening of the fastening side screw member starts, and measures the elapsed time or rotation angle of the fastening side screw member. A fastening inspection method characterized in that tightening is stopped when seating of a fastening-side screw member is not detected before the angle reaches a preset time or rotation angle. (2) A method for inspecting the tightening state when fastening a fastening-side threaded member to a fastened-side threaded member, the thread of the fastening-side threaded member starting from the time of starting tightening of the fastening-side threaded member to the fastened-side threaded member. The time required for the tightening to occur is set in advance with a predetermined time width, and the elapsed time from the start of tightening is measured, and the jamming is detected while this elapsed time is within the set time range. If the jam is detected, the system will shift to high-speed tightening from the time of the jam, and if the jam is detected before the elapsed time reaches the set time width,
The present invention is characterized in that when a set time is reached, the fastening is performed, and if no jamming is detected even after the elapsed time exceeds the set time range, the fastening is performed when the set time range has elapsed. Fastening inspection method. (3) A method for inspecting the tightening state when fastening a fastening-side threaded member to a fastened-side threaded member, the thread of the fastening-side threaded member starting from the time of starting tightening of the fastening-side threaded member to the fastened-side threaded member. The time required for the tightening to occur is set in advance with a predetermined time width, and the elapsed time from the start of tightening is measured, and the jamming is detected while this elapsed time is within the set time range. If the jam is detected, the system will shift to high-speed tightening from the time of the jam, and if the jam is detected before the elapsed time reaches the set time width,
When the set time is reached, the fastening is performed, and if no jamming is detected even after the elapsed time exceeds the set time range, the fastening is performed when the set time range has elapsed, and the fastening side Measures the elapsed time or rotation angle from the start of tightening of the screw member until it seats, and when the seating of the tightening side screw member is not detected before the time or rotation angle reaches a preset time or rotation angle. , a fastening inspection method characterized by stopping tightening.