JPH04115836A - Inspection of tightening - Google Patents

Abstract

PURPOSE:To check missing of a washer at the time of tightening a screw by detecting existence of the washer by means of comparing a detected value with a set value by way of an actual time required after screw tightening is started until a screw member on the tightening side is seated or an angle of rotation is detected. CONSTITUTION:A torque sensor 11 is installed on a fixing part to hold a bolt holder 8 free to rotate and a tightening torque detected by the torque sensor 11 is input to a controller 12 in a bolt tightening device 9. Thereafter, a biting point of time (a) and a seated point of time (c) of a bolt 6 are detected by using the tightening torque. Additionally, a rotational angle sensor 13 is installed on the bolt tightening device 9, and an angle of rotation of a bolt 5 and the bolt holder 8 detected by the sensor 13 is input to the controller 12. A set angle of rotation in the case when there is a washer and a set angle of rotation in the case when there is missed a washer are memorized in the controller 12, and an actual angle of rotation of the bolt 5 is integrated by a signal from the rotational angle sensor 13 and it is compared with the set angle of rotation to judge existence of the washer 6.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a tightening inspection method, and more specifically, the present invention relates to a method for inspecting tightening, and more specifically, by automatically inspecting a tightening side screw member such as a bolt against a tightened side screw member together with a washer. Concerning inspection methods when tightening.

(Prior Art) As is well known, the manufacture of vehicles such as automobiles is done through assembly line operations, but in recent years robots have been used to save labor and to perform these operations efficiently and accurately. Automation is being widely adopted in various types of work, as typified by equipment.

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, by welding bolts or nuts in advance to the vehicle body being transported through the assembly line, the suspension 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) In the above automation, for example, when tightening a bolt (or nut) to a nut (or bolt) attached to the vehicle body side, a washer is attached to the bolt side. Therefore, the washer must be fitted into the shaft of the bolt prior to tightening, but for some reason there is a risk that the bolt may be tightened without the washer missing.

This can be dealt with by visually checking for missing washers at a later inspection stage, but if missing washers can be detected at the tightening stage, the subsequent response will be quicker and workability will be improved.

Therefore, it is an object of the present invention to provide an inspection method that can check for missing washers when tightening screws.

(Means for Solving the Problems) That is, the tightening inspection method of the present invention is a method for determining the presence or absence of a washer when tightening a tightening side screw member together with a washer to a tightened side screw member side.
detecting that the thread of the tightening side screw member is bitten by the tightening side screw member, and detecting the time or rotation angle from that point until the tightening side screw member is seated;
The present invention is characterized in that it is determined that the washer is missing when the tightening side screw member cannot be seated within a preset time width or rotation angle width.

(Function) According to the above method, the actual time or rotation angle from the start of tightening until the screw member on the tightening side seats on the screw member to be tightened is detected, and this detected value is compared with the set value. By doing this, the presence or absence of the washer is detected, so that automatic detection of the missing washer can be performed at the screw tightening stage.

Furthermore, since this method detects the time or rotation angle from the time when the thread of the tightening side screw member is bitten into the tightened side screw member until the tightening side screw member is seated, the screw is securely tightened. The above detection is performed based on the point in time when the bolt is screwed in, and the detected value becomes accurate in accordance with the tightening. Therefore, the preset time width or rotation angle width can also be precisely determined, and the presence or absence of the washer can be accurately determined by comparing these preset time widths or rotation angle widths with the detected time or rotation angle. can.

Furthermore, since the above method determines whether or not seating can be achieved within the set time width or rotation angle width, it is possible to In this case, it is easy to determine that the tightening is defective, and it is therefore possible to deal with the above-mentioned trouble.

(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 warp 21 from below and fastened.

For this fastening, 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. Further, the washer 6 is attached to the bolt 5 as described above. The bolt 5 is loaded into the bolt holder 8 by an automatic loading means (not shown) while the bolt tightening device 9 is lowered relative to the work 1.

Further, the bolt tightening device 9 is attached to a robot device so as to be able to perform predetermined movements such as ascending and descending and turning. However, since this robot device, along with the automatic loading device described above, is not directly related to the gist of the present invention, 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 the torque T when tightening the bolt.
The tightening torque T detected by the torque sensor 11 is configured to be input to the controller 12.

In this controller 12, the torque detected by the torque sensor 11 is used to control the rotational speed of the motor 7 as shown in the second section.

With the bolt 5 and washer 6 loaded in the bolt holder 8 as described above, the bolt tightening device 9 is raised,
As shown in Fig. 1, when the tip of the bolt is put against the nut 3 through the bolt through hole 4, this contact is made from the state of the motor 7.
Rotate at low speed and screw bolt 5 into nut 3. As a result of this screwing, the first thread of the bolt 5 becomes 1
When the mountain is bitten by nut 3, this one mountain is tightened at the moment (
Point a in Figure 2. The period from when the rotation speed is increased (hereinafter referred to as the biting point) until the washer 6 or the workpiece 1 is seated (
(from point b to point C in Figure 2), the motor 7 is rotated at a constant speed, and then at the point C when the washer 6 is seated, the motor 7 is rotated once.
After stopping, final tightening (increasing tightening) is performed again by rotating at 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 this 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 6, 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, a rotation angle sensor 13 is attached to the bolt tightening device 9, and the bolt 5 is detected by the sensor 13.
The rotation angle θ of the bolt holder 8 is also input to the controller 12 described above.

On the other hand, the controller 12 integrates the rotation angle θ from the biting detection time a to the seating time C based on the rotation angle signal inputted from the rotation angle sensor 13, and also uses this integrated value and the seating time From the relationship with C, washer 6
It is determined whether the tightening was performed with the washer 6 missing or whether the washer 6 was normally used.

In other words, the length of the shaft portion 5a of the bolt 5 is L (single thread), and the thread pitch is P (hoho) (however, this thread pitch P and one thread of the tip of the bolt 5 biting into the nut 3 are To distinguish, the thread pitch for one thread at the tip of the bolt is Pl.
), and when the thickness of the washer 6 is W (-■) and the thickness of the work 1 is A (am), the washer 6 is attached to the work 1 from the state where one thread of the screw is bitten. The rotation angle of the bolt 5 required until it is seated is expressed by the following formula.

θs = 360 (L-W A Pt )/P-θ
0 However, when the washer 6 is missing from the bolt 5, the following equation is obtained.

θt = 360 (L-A Pt )/P-θ0 Note that θ is common to both formulas. is the detection adjustment angle (Deg>), which will be described later.

Therefore, when the washer 6 is present and when it is missing, the rotation angle until seating (at the time of seating) is different, and when seating cannot be achieved even if the rotation angle θE is exceeded, it is obvious that the washer 6 Since it can be determined that the washer 6 is missing, the presence or absence of the washer 6 can be determined by checking the relationship between the rotation angles θS and θE and the seating time C.

Therefore, in the controller 12, the set rotation angle θS when the washer is present and the set rotation angle θE when the washer is missing are stored in memory, and the actual rotation angle θ of the bolt 5 is integrated based on the signal from the rotation angle sensor 13. and set the integrated value to the above set rotation angle θ5. The presence or absence of the washer 6 is determined based on the comparison with θE to check whether seating can be achieved between the set rotation angles θS and θE. As mentioned above, the seating detection is performed using the fact that the torque T becomes the seating torque T5 shown in FIG. There is some variation in the timing at which the seating torque is generated, such as the timing at which the seating torque is generated, not the point at which it is completely crimped to the workpiece 1, but the point at which it starts contacting the workpiece 1. Therefore, in the above two equations, the detection adjustment angle θ0 is subtracted, and the set rotation angles θS and θE are slightly shifted. .

Next, a method for inspecting tightening in the above configuration will be explained with reference to a flowchart shown in FIG.

When the bolt 5 is coaxially aligned with the nut 3 by the bolt tightening device 9 after various numerical values of the control system shown in FIG. The motor 7 is subjected to the rotational speed control shown in FIG. 2, and the bolt 5 is first rotated at a low speed to start tightening. Further, in step S2, the torque T for tightening detected by the torque sensor 11 and the torque T1 for single thread tightening are compared according to the tightening operation.

Then, when one thread of the first screw of the bolt 5 is bitten into the nut 3, and the torque T detected by the torque sensor 11 exceeds T1, the controller 12 detects the biting or biting in step S3. as the starting point (θ1 shown in Figure 3)
At the point in time), the integration of the rotation angle θ of the bolt 5 is started based on the rotation angle signal input from the rotation angle sensor 13.

At the same time, the controller 12 controls the motor 7 to
is rotated at a constant speed from point b to point 0 in Fig. 2 at high speed.

The above-mentioned integrated rotation angle θ is compared with the set rotation angles θ3 and θ2 stored in the controller 12, and if the integrated rotation angle θ exceeds the rotation angle θ5 with the washer in step S4, the controller 12 uses the torque sensor 1
1, detection tightening determines whether the torque T has reached the seating torque Ts. Then, as in step S5, the seating torque Ts is detected before the rotation angle θ integrated from the rotation angle sensor 13 exceeds the set rotation angle θE in the case of missing washer (in the case of the solid line curve in FIG. 3), As shown in FIG. 2, the motor 7 is once stopped at the seating point C, and then the final tightening is performed in step S6.

On the other hand, if the seating torque TS is not detected even though the cumulative rotation angle θ exceeds the set rotation angle θ8 in the case of a missing washer in step S (in the case of the broken line curve in Fig. 3), this time Assuming that the tightening is performed with the washer 6 missing, the controller 12 displays the washer missing signal in step S8, for example, on the display means 14.
In addition to outputting another output or recording the washer missing state, the motor 7 is stopped in step S9 to prevent final tightening.

In this way, it is automatically determined during the bolt tightening process whether or not the bolt 5 is tightened with the washer 6.
Alternatively, the integration of the rotation angle θ until the bolt 5 is seated is started from the point in time when one screw at the tip of the bolt is bitten into the nut 3. In other words, the calculation is performed from the point a when the bolt 5 is securely engaged with the nut 3. Therefore, the integrated value of the rotation angle θ becomes accurate in accordance with the tightening of the bolt 5,
The set rotation angle θ5 stored in the controller 12.
The comparison of θ8 can be performed precisely, and the determination of whether a washer is present or whether a washer is missing based on this comparison is accurate.

Furthermore, since it is determined whether or not seating can be achieved between the set rotation angles θ5 and θ8, the seating torque Ts
It is also possible to deal with cases where this occurs. In other words, bolt 5
When the shaft length of the controller is short, or when tightening involves biting of foreign matter, the tightening torque T will exceed the seating torque T9 before reaching the set rotation angle θS as described above, so the controller In such a case, in No. 12, it is possible to determine that the tightening is defective.

Further, since accurate determination of the presence or absence of a washer can be made at times when bolts are tightened, the labor and other costs required for subsequent inspection steps can be significantly reduced.

By the way, in the above-mentioned embodiment, the presence or absence of the washer 6 is determined by integrating the rotation angle θ of the bolt 5 from the biting point a of the bolt 5, but this is calculated based on the time required from biting point a to seating. It can also be judged by the length of .

That is, the time t required from the biting state to the seating position is expressed by the following equation in the case of normal tightening with the washer 6.

ts = I (LA Pl)/PK)/
N However, N is the rotation speed for tightening at a constant speed, K is the detection time setting coefficient (a coefficient for adding correction with the same purpose as the detection adjustment angle θ0 in the rotation angle detection formula described above), and other The sign is the same as for the rotation angle type.

In addition, in the case of tightening in which the washer 6 is missing, the following equation is obtained.

tε= ((L-p+)/P-KL'/N Therefore, in the controller 12 shown in FIG. 1, the first timer 15 sets the time t5 when the washer is present, and the time tE when the washer is missing. The presence or absence of the washer 6 can be determined by providing a second timer 16 to be set and determining whether or not the seating torque Ts is obtained during the time difference set by both timers 15 and 16.The presence or absence of the washer 6 can be determined by detecting this time. In this case, the rotation angle sensor 13 shown in FIG. 1 becomes unnecessary.

Next, the operation based on this time detection will be explained with reference to the flowchart of FIG.

At step sit, while various numerical values of the control system shown in FIG. 1 are cleared, the controller 12 controls the rotational speed of the motor 7 to start tightening the bolt 5 at a low speed. Further, the tightening torque T detected by the torque sensor 11 is compared with the torque T1 for single tightening in step S12.

Then, when the torque T for detection tightening exceeds the torque T1 for one peak tightening, each timer 15.1 is set in steps S13 and S14.
6. In other words, the starting point is the biting detection time (tl
) to run timers 15 and 16. Moreover, it goes without saying that the bolt 5 is fastened at high speed from the time when the jamming is detected.

Next, the first timer 15, which sets the seating time t when the washer is present, is activated at step S+5 as the time ts elapses.
When the time has elapsed, the controller 12 determines whether the tightening torque T detected by the torque sensor 11 has reached the seating torque Ts. Then, as in step S16, if the seating torque Ts is detected before the second timer 16, which sets the seating time of 1g in the case of missing washer, times out, the process moves to final tightening in step S17.

On the other hand, if the seating torque T5 is not detected even though the second timer 16, which sets the seating time tE in the case of missing washer 6, has timed up in step StS, the current tightening is performed when the washer 6 is missing. If the process is executed in a state where the process is performed, the controller 12 outputs a washer missing signal or the like in step S19, and prevents final tightening in step S20.

In this embodiment as well, the presence or absence of the washer 6 is determined during the bolt tightening process, which greatly reduces the labor and other work required for the subsequent inspection process, and it is possible to accurately determine whether a washer is missing. It turns out. Further, as in the case of rotation angle detection, it is also possible to detect defects in tightening due to troubles such as the aforementioned foreign matter getting caught.

Note that in both the rotation angle detection method shown in FIG. 4 and the time detection method shown in FIG.
The tightening method is based on the premise that the speed is accurately controlled as shown in FIG. This is because the friction coefficient of the threaded engagement portion of the nut 3 and bolt 5 varies individually, but if the speed control described above is not applied, the seating point will be shifted and it will not be possible to accurately determine the presence or absence of a washer.

In the above embodiment, the bolt 5 is fastened to the nut 3 fixed to the workpiece 1 side, but it goes without saying that the present invention is also applicable to the opposite case. Furthermore, bolt 5
Detection of biting is not limited to biting of a single screw thread,
There may be two peaks, and the point is that it is sufficient as long as it detects the point in time when the biting becomes stable.

(Effects of the Invention) As is clear from the above description, according to the present invention, the actual time or rotation angle from the start of screw tightening until the tightening side screw member is seated is detected, and this detected value is used as the set value. Since the presence or absence of a washer is detected by comparing it with , the presence or absence of a washer can be automatically detected at the screw tightening stage if a washer is missing. Therefore, the subsequent inspection process can be simplified and labor can be reduced, and the missing portion of the washer can be quickly dealt with, improving work efficiency.

Moreover, the method of the present invention detects the time or rotation angle from the time when the thread of the tightening side screw member is bitten into the tightened side screw member until it is seated, so that the screw is reliably screwed. Since the above-mentioned detection is performed based on the time point, the detected value becomes accurate in accordance with the tightening.

Therefore, the preset time width or rotation angle width can also be precisely determined, and the presence or absence of the washer can be accurately determined by comparing these preset time widths or rotation angle widths with the detected time or rotation angle. can improve reliability.

Furthermore, since the method of the present invention determines whether or not normal seating can be achieved within a set time range or rotation angle range, this method will not be able to handle seating that occurs before entering the above range due to some trouble. It is also possible to determine that the tightening is defective. Therefore, it is possible to easily deal with defects in tightening other than missing washers.

[Brief explanation of the drawing]

The drawings show an embodiment of the tightening inspection method according to the present invention. Fig. 1 is a block diagram embodying the above method, Fig. 2 is a graph explaining motor rotation speed control, and Fig. 3 is a graph showing the above method. Graphs for explaining the method, FIG. 4 is a flowchart of the inspection method using rotation angle detection, and FIG. 5 is a flowchart of the inspection method using time detection. 3... Screw member on the tightened side (nut), 5... Screw member on the tightening side (bolt), 6... Washer, 11... Torque sensor, 12... Controller, 13... Rotation angle sensor.

Claims (1)

[Claims] (1) A method for determining the presence or absence of a washer when tightening a tightening-side screw member together with a washer to the tightened-side screw member, in which the thread on the tightening-side screw member is bitten by the screw member on the to-be-tightened side. from that point on,
The time or rotation angle until the tightening side screw member is seated is detected, and when the tightening side screw member cannot be seated within a preset time range or rotation angle width, the washer is missing. A method for inspecting tightening characterized by determining that the tightening has been performed.