JPS5871079A - Automatic screwdriver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention temporarily tightens the screw against the workpiece, starts the final tightening after the temporary tightening is completed, and issues a final tightening completion signal when the shaft torque of the dofiba bit reaches a predetermined final tightening torque. This invention relates to an automatic screw tightening machine that completes screw tightening.

When tightening a screw onto a workpiece with this type of screw tightening machine, there is a certain probability that the screw will bite diagonally, the screw will come loose, and one neck will be skipped. However, such a screw tightening failure cannot be detected as a tightening failure as long as the tightening torque reaches a predetermined final tightening performance.

One possible way to detect such defects as poor tightening is to observe the change in the tightening torque over time and compare that change with the change over time when tightening is performed normally. It will be done. In other words, in general, the tightening torque for screws measures the change over time as shown by the solid line in Figure 1g1 in the case of normal tightening. In the same figure, there is a dashed line (as shown by J), which rises with a sudden change in time, and if an abnormality in the screw causes the neck to jump, etc., the dashed line (as shown by J) is drawn. Therefore, by detecting the temporal change in the tightening torque of the screw, it is possible to determine whether the screw is properly tightened or not.

However, on the other hand, this method is easily affected by instantaneously applied noise, etc., and in order to prevent this, the detection method becomes extremely complex and adjustment becomes difficult. the result,
The disadvantage is that the cost of the control device and the like increases.

Therefore, the present invention provides a new means for determining whether there is a tightening failure with a low cost and simple configuration, in place of the method of looking at hourly changes.

That is, the present invention provides two timers that count the time at the same time as the start of the final tightening or screw tightening operation, and calculates the minimum required time for final tightening when one timer does not cause any tightening defects to the other timer. The maximum required time for final tightening without causing any tightening defects is set for each timer, and the final tightening is determined depending on when the final tightening completion signal f is issued before or after the two timers time up. The gist is that it is configured to determine pass/fail.

Next, one embodiment of the present invention will be described based on the drawings. Figure 2 shows a stationary single-shaft type automatic screw tightening machine as an example of an automatic screw tightening machine. Part (3) (3
One rod +41 is inserted into 1 so as to be vertically slidable. A mounting member (6) for mounting the screw tightening machine main body 15) is inserted into the rod (4) so as to be vertically slidable, and a tension spring connects the two. Further, this rod (4) is provided with a retaining ring (not shown), and the upper end of the rod (4) and the attachment member (6) are held at a constant distance. Furthermore, the rod (4) has a support plate (
8) is slidably inserted through the rod and is received by a nut (91) screwed into the lower end of the rod.
G, driver hit αB, and a transmission shaft QB that transmits rotational power from the rotational drive source to driver hit α1).
A torque sensor α3 for detecting torque is provided. Further, this screw tightening machine main body (5) is configured to be able to move up and down by a lifting cylinder a center provided on the support plate F (2).

The vertical movement of the lifting cylinder O@ is also transmitted to the catcher (7) via the rod (4), so the catcher (7) also moves up and down together with the screw tightening machine body 15), but the amount of descent is determined by the rod rod (4). 4) The catcher (7) is controlled by the upper end and the upper arm part (31. Also, the catcher (7) is controlled by a nut (I6) provided at the tip of the rod of the cylinder (σ) as a driving means ll51.
a), and can be moved upwardly by the weak operation of the drive means, independently of the driver pitch Fα11. Although not shown, a switch for confirming return to the original position, such as a limit switch, which is turned on when the screw tightening machine main body (5) has been raised and returned to the original position, is provided.

The puffless motor 01, the lifting cylinder 110, and the driving means α are controlled by a circuit shown in FIG. 3, so as to perform an automatic screw tightening operation. In FIG. 3, gradient indicates the screw tightening starter ti, and CI2 indicates a buffer amplifier that amplifies the detection signal of the torque sensor II3.

■ indicates the caliper that performs zero correction and gain correction of the detection signal; The setting device, ■ is the minimum required amount μ when the wood tightening is completed.
(lower limit set to a value)/0 which is a reflex setting device.For each of these setting devices α to ■, for example, a 10-turn type potentiometer is used. ■ is a comparator that compares the detected torque value of sensor 03 and the temporary tightening torque value set on the setting device α, and ■ is the comparison between the detected torque value and the final tightening torque set on the setting device ωt. The reason for this is a comparator that compares the I torque value with the detected torque value and the lower limit torque value set in the setter (2). (Reset due to poor tightening) l! , Gll is a limit switch for confirming the return of the screw tightening machine to its original position.
°ω is a cycle time over reset section. Here, cycle time refers to the time required for one screw tightening when screw tightening is performed normally. Therefore, if it takes more than this cycle time to tighten a screw, it means that there is an abnormality on the screw tightening machine side.

σa) to σi) are timers, and timer σa) is set to the cycle time. The timer σb) is set to the charging completion time. The charging completion time here refers to the power supply section (which supplies power to the pulse motor + IG).
This timer (Crb) is necessary because a pulse motor is used as the rotational drive source for the driver bit. , and is unnecessary when using other motors. Timer qC) is set to machine time. Machine time is the time required to complete the final tightening when screws are tightened normally. While the cycle time was used as a guide to check whether the screw tightening machine is normal or abnormal, the 77 cycle time is used to determine whether the screw tightening operation is being performed without a screw or whether the screw is loose by 4 tons.
This is the time that serves as a guideline for checking whether the screw or workpiece is normal or abnormal. The timer (TI is set to the break-in time after the temporary tightening is completed.The break-in time is the time for the workpiece or screw that was included in the shaft torsion detected by the torque sensor αJ up to the time of completion. This is the time taken into account the initial detection error due to material and abnormalities, transmission efficiency, transmission delay until the transmission reaches the screw, etc.

It is necessary to adjust the length of this break-in time depending on the material of the workpiece or screw.As a result, the tightening torque of the screw after break-in becomes equal to the measured radius detected at that time.For example, the workpiece may be urethane rubber, etc. When using a screw, the transmission efficiency is poor, and it takes time for the screw to become familiar with the workpiece. The tightening torque of the screw gradually changes due to the effect of kudder, etc., and it takes time until it stabilizes. Therefore, in such cases, it is necessary to increase the break-in time! There is.

However, the minimum time of the break-in time setting timer CI'd) is
Due to the characteristics of the pulse motor, there are cases where the pulse motor rotates an extra amount of time corresponding to 1 pass, so consideration should be given to the time equivalent to 1 pass or more.

σe) σ0 are two timers that are essential components of the present invention, and each counts the time at the same time as the main tightening starts. However, the setting time of one timer (Te) is the minimum required time for final tightening when no tightening defects occur, and the setting time of the other timer (Tf') is the minimum time required for final tightening when no tightening defects occur. If you have not done so, adjust the time as much as possible for final tightening.

The minimum and maximum required time for final tightening when no such tightening defects occur can be determined empirically. Normally, a large number of screws are tightened under the same conditions to find the standard final tightening time To (average value) and standard deviation J, and T8-3/ is the minimum required time, and Tg+3
7 should be the maximum necessary time. This is because if the final tightening is done statistically normally, most of the tightening will be within the range of T8±3/. Of course, the minimum time and maximum time may be set to Tsj4/, s/, etc.
Ru.

Further, although not shown, the timer (To) and σ may be configured to count the time at the same time as the start of the screw tightening operation. In this case, the set time of each timer may be the set time plus the time from the start of the screw tightening operation to the start of the final tightening. The timer Crg) is set to the break-in time after the final tightening is completed. This break-in time has the same sound emission as the break-in time after completion of temporary tightening described above.

However, due to the characteristics of the pulse motor, even after the final tightening is completed, the
The timer σg)
The minimum setting time is considered to be a time equivalent to this 12M1 minute. The timer ('rh) is -'
The conversion amount starts when the timer Crρ times up.
- Time counting starts with the conversion completion signal from the D converter (described later), and the time-up is considerably delayed from the time when the main tightening is completed. This timer (Th) determines whether the final tightening i/rek is higher or lower than the setting Fv value of the lower limit torque setting device (2).

14 ff (ri) C. After the power supply to the bus motor drive circuit is cut off, the charge is transferred to the O smoothing capacitor, which is set to the time required for the charge accumulated in the smoothing capacitor of the power supply section to be discharged. As long as the
This is because the pulse motor is in an excited state and is restrained by a stall meter.

If the screw tightening machine main body (5) is moved upward in this state, the driver pin will separate from the screw while torque is applied to the screw, resulting in damage to the workpiece. Therefore, by providing this timer σ1), the excitation of the pulse motor is released and the rotating shaft becomes free, and then the screw tightening machine holder 15) can be raised. In the detection section, timer cr
When a) times up, it displays a cycle time over and issues a signal to the outside. 0 (Incorporated) is a machine time over detector 1tl [and timer (Ta) l): When the time goes up, it issues a machine time over signal. As described later, if this machine time over signal No. 6 is issued before the final tightening is completed, regardless of the stage of the screw tightening work,
At the same time as the screw tightening operation is completed, a tightening failure signal is issued.

At the same time, the supply of the puff train to the pulse motor 0[I is stopped, and an operation command for the drive means a9 is issued. Completion of screw tightening work means stopping power supply to the buffless motor and returning the screw tightening machine to its original position.
Machine time overs are caused by an abnormality on the screw or workpiece side, such as the absence of a screw or a loose screw.
After temporary tightening is completed, even if the machine time-over signal is not issued, the two timers σe) and σf) will eventually determine that the tightening is defective, but the pulse motor will continue to run until this determination is made. This was pointless and would be a waste of electricity, so in order to end this pointless situation as soon as possible, we decided to issue a machine time over credit and finish the screw tightening work. .

However, if the two timers (cre) and crt) are configured to count the time at the same time as the screw tightening movement starts, the timer ('re) crO
Poor tightening is determined by the determination. (To) is the final tightening that determines whether there is a gap between the time required for the final tightening and the time set in the timer (To) and the time set in the timer ('I'f'). Time judgment section.

■ is the detection point μ when the timer (Th) times up.
A lower limit determination unit that determines whether the torque value is larger or smaller than the torque value set in the lower limit torque setting device; This is a judgment display section that displays whether the tightening is good or bad based on the signal from ). This display section does not perform a display operation unless the timer CI'i) times up. ■ is a power supply unit for supplying power to the pulse motor αα, and when the screw tightening start unit operates, it starts supplying power, and when the timer (Th) times up, or the overtime detecting unit detects an idiot detection signal. or when the final tightening time determining section (to) r, , issues a judgment 1 signal, the power supply is stopped. (to) is a double integral type A-D converter which is resistant to noise, and converts the detected threshold value when the timer σ times up into a digital quantity and inputs it to the display driving section. Here, the A/value is detected without going through the peak hold circuit.
- In the case of a pulse motor, the rotating shaft that is directly input to the D converter (to) is 1 when it is under excitation and when the supply pulse is stopped.
This is because the rotation is stopped and the rotation is stopped and the rotation is stopped. Therefore, in the case of motors other than pulse motors, the rotating shaft becomes free after one rotation is stopped, so it is necessary to hold the detected M value in the peak hold circuit and then input it to the A-D converter. . The display drive section is synchronized so that the display timing is the same as that of the judgment display section -, so the digital quantity input from the A-D converter ■ is displayed at the same timing as the judgment display section ■. It is output and digitally displayed on the display I411. (0 is the comparison output of the pre-tightening comparator section and the one-tightening comparator As a result, the solenoid valves that operate the lifting cylinder I and the drive means α are controlled to be energized or de-energized, and the pulses supplied to the pulse motor drive circuit are switched between high and low speeds and supplied.

This switching is performed at the stage when temporary tightening is completed.

A high-speed pulse is a pulse that is higher than the self-starting frequency of the pulse motor+IG, and a low-speed pulse is a pulse that is lower than the self-starting frequency.

When a high-speed pulse is applied, the pulse motor (l) rotates at a high speed, and when a low-speed bar I is applied, it rotates at a low speed. The reason for this is to shorten the screw tightening time, and the reason for making it rotate at a low speed at the stage of starting tightening is to enable highly accurate FTV control.

Next, FIG. 3 shows the automatic screw tightening operation with the above configuration.
'Explain according to the flowchart. When the screw tightening start section operates, the power supply section operates and starts supplying power to the pulse motor drive circuit, and at the same time the meter display and judgment display section are reset.
Also, the timers σa) and σb) start counting time. When the smoothing capacitor in the power supply section (to) has completed charging and the timer σb) has timed up, the logic circuit issues a command to supply pulses and lower the high-speed bus train, causing the pulse motor 0 (I to rotate at high speed). At the same time as starting the screw tightening machine (
5) descends and starts the temporary tightening work. Also, at the same time, the timer σC) starts counting time. If there is no abnormality in the temporary tightening work, the timer σC) will not time up during the work, but if there is an abnormality, such as a screw being twisted in the catcher, and the temporary tightening has not been completed, this will happen. , timer σC) times up during temporary tightening. Then, the machine time over signal is sent to the logic circuit (42
, is added to the power supply [L timer (Ti) % judgment display section, the supply of column 31177 is stopped, and at the same time, an operation command for the drive means (19), completion of screw tightening work, and indication of poor tightening are given. However, the timer σ1) indicates poor tightening.
This will not be done until after the time has expired. The reason why we decided to issue the operation command for the drive means αb in response to the machine time over signal from the catcher (
By raising the catcher (7) and ejecting the screws inside the catcher (7), you can remove the catcher (7) for the next screw tightening operation.
7) In order to eliminate the situation where there are two screws inside the 0 flowchart)
■ indicates the start of returning the screw tightening machine main body (5) to its original position, and ■ indicates the display command by the timer crO's time-up. *
, ■ When the return to home position operation is started, the power supply to the pulse motor (Il) is stopped at the same time as shown in Figure 5. On the other hand, there is no abnormality in the temporary tightening work, and the timer (Tc) is Until the time-up occurs, when the detected torque value of the torque sensor reaches the pre-tightening torque value of the electrical design device and a pre-tightening completion signal is issued from the comparator, the timer /σd)
At the same time that the timer starts, the supply of the high speed bass train is stopped from the logic circuit, and at the same time, a driving means activation command is issued. The pulse motor stops rotating due to the supply stop of the bus train, and the drive means O9 is driven by the drive means operation command.
The catcher (7
) rises independently, so even if the head of the temporarily tightened screw is held or caught in the catcher when the temporary tightening is completed, that state will not change after the catcher (7) rises. This has been resolved, and the torque sensor 03 can now detect only the axial torque related to the tightening/reflex.

After the temporary tightening is completed, the screw becomes stiff in the workpiece, and when the timer σ time is up, the logic circuit (42-) generates a low 11 < pulse train supply pulse I-res. Final tightening is performed while rotating at the following low speed.At the same time as the first tightening starts, two timers Crc) and (Tf) start counting time.

In this case, if the timer ('I'c) times up even though the final tightening has not yet been completed due to an abnormality such as loose screws, the pulse motor α
The supply of the bassis row to G is stopped, and at the same time, the screw tightening work is completed and a tightening failure is indicated.

On the other hand, when there is no abnormality in the screw and the detected torque value of the torque sensor (%) 7 reaches the final tightening torque value of the setting device υ, a final tightening completion signal is issued from the comparator. Based on this, the supply of the low-speed bias train from the logic circuit (42) is stopped, and the pulse motor 1G stops rotating. At the same time, the timer (Tc) σ0 is reset, and the timer σρ starts counting time.

In this case, the quality of the tightening is determined depending on whether the final tightening completion signal is issued before or after the timers σe) and (Tf) time up. If the final tightening completion signal is issued before the timer (Te) has timed up or after the timer CrO has timed up, the screw may have some kind of abnormality such as diagonal biting or skipping one neck. Since this has occurred, the screw tightening work is completed and a tightening failure display (■) is displayed. On the other hand, if the time when the single tightening completion signal is issued is after the timer σe) has timed up and before the timer crO has timed up, the final tightening has been completed normally and the timer (Tg) does not time up. Waiting for this, the A-D conversion Masuda is activated, and the detected torque value of the torque sensor a3 at the time when the timer σg) times out is converted into a digital value and inputted to the display drive section (411I.Display drive section (411I). &1 temporarily holds this input signal and returns 1
The A-D converter (0), which operates to display at the same timing as the judgment display section, operates and at the same time as outputting the conversion completion output, the timer σh) starts counting time. In response to the time-up signal of the timer σh), the lower limit determining section (2) performs a determining operation. By this judgment operation, the detected torque value of [M
) is higher or lower than the lower limit of torque μ.
The reason why we chose this value as the target of judgment is that it is equivalent to an extension of the break-in time after the final tightening is completed, and is the final means of determining whether or not the tightening has been completed. It has the same meaning as the break-in time after completion of final tightening, and creep phenomenon is promoted by increasing stress relaxation, increasing tightening torque/rec, or increasing temperature by increasing the time a little longer by one hour. This also takes into account the fact that tightening torque tends to decrease due to If the detected torque value is lower than the lower limit torque value of the setting device (1), the torque is insufficient, so wait for the timer σ1) to time up, and then the determination display section 201 will display an indication of poor tightening in response to the display command 0. On the other hand, if the Z reflex value (detected) is higher than the lower limit value of the setting device ■, wait for the timer (Ti) to time up and use the display command ■ to display the judgment display cylinder during tightening. In addition, a display device (41) displays a digital M value of the detected value held in the display driving section 1a. Furthermore, when the lower limit determination section (to) makes the above determination, the screw tightening work is completed regardless of whether the determination result is good or bad.

Next, the operation of returning the screw tightening machine main body 15) to its original position will be explained based on the flowchart shown in FIG. Screw tightening machine body (
As mentioned above, the condition for starting the return to the original position in 5) is when the timer ('rh) times up or when the timer (T
When o) times up and exceeds the machine time,
Alternatively, an abnormal signal is generated from the final tightening time determination section (to). Due to this start condition, the power supply from the power supply section (to) to the pulse motor drive circuit (6) is stopped, and the simultaneous timer (Ti) starts counting time. Eventually, the timer CI'i) times up, and the buffless motor When the rotary shaft of the cylinder becomes free, a rising command is issued from the logic circuit, and the lifting cylinder aO begins to move upward. Further, due to the time-up of the timer σ1), a command 0 for displaying a tightening pass/fail judgment is issued to the judgment display cylinder, and at this point, the judgment display cylinder displays the above-mentioned insufficient tightening/tightening interval. At this time, the display drive unit (a)
The detected threshold value held in is displayed on the display i4I+.

When the screw tightening machine main body 15) returns to its original position due to the upward movement of the elevating cylinder a41, the timer (ra)
is reset and the logic circuit - issues a deactivation command to lower the drive means +151. The catcher (7) is lowered by the lowering of the drive means α5, and returns to a state in which it can receive a new screw. In this case, even if the logic circuit issues a raise command, the screw tightening machine body (5) does not return to its original position, and therefore, when the timer (Ta) times out,
The cycle time over display section ■ will display the cycle time over.The cycle time over display will occur when the screw tightening start section operates and the screw tightening machine body (5) descends from its original position. This cycle time vl14 is displayed even if the timer σa) times out, indicating that there is an abnormality in the screw tightening machine, and appropriate repair work can be carried out.

Although the present embodiment has been described with respect to a foot-mounted single-shaft type automatic screw-driving machine, similar effects can be obtained with a stationary-type multi-shaft type automatic screw-driving machine.

Since the automatic screw tightening machine according to the present invention is configured as explained above, it has the following effects. 0. In the current automatic screw tightening machine, the actual tightening torque is not reached due to diagonal biting of the screw, screw floating, etc. Even in cases where the final tightening has been reached but the tightening is defective, it is possible to reliably determine whether the final tightening is good or not.

■Since the quality of final tightening is determined simply by the time set in two timers, adjustment is easy, the circuit is simple, and the number of components can be reduced. Therefore, the cost of the device does not increase as much.

[Brief explanation of drawings]

Figure 1g1 is a diagram showing the temporal change in the tightening torque of a screw.
Fig. 2 is a side view of an automatic screw tightening machine showing an embodiment of the present invention, and Fig. 3 is an electric circuit diagram of the screw tightening machine. Fig. 4 (inno(port Jl"J) is a flowchart explaining the screw tightening operation of the screw tightening machine, and Fig. 95 is a flow chart explaining the original position return operation of the screw tightening machine. 11)...Driver bit. (Te) σ...Two timers, Patent applicant Nitto Seiko Co., Ltd. Figure 1 Figure M5.2

Claims (1)

[Claims] (1) The screws are temporarily tightened to the workpiece, and after the temporary tightening is completed, the final tightening is started, and when the shaft torsion of the driver screwdriver/soft screw reaches the specified final tightening torque, a final tightening completion signal is issued. The automatic screw tightening machine is equipped with two timers that count the time at the same time as the final tightening or screw tightening operation starts.
Set the minimum time required for final tightening when no tightening defects occur on one timer, and the maximum required time for final tightening when no tightening defects occur on the other timer, respectively. An automatic screw tightening machine characterized in that it is configured to determine the quality of final tightening depending on when the final tightening completion signal is issued before and after the two timers time up. 1 (2) In addition to the above two timers, a timer is provided that starts counting time from the time when the screw tightening operation starts, and if this timer times out before the final tightening completion signal is issued, the screw tightening operation stage is stopped. An automatic screw tightening machine as set forth in claim 11, characterized in that the screw tightening machine is configured to end the screw tightening work regardless of the situation and to display an indication of poor tightening.