JP2959946B2 - Automatic part fastening machine and fastening method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic component fastening machine such as an automatic screw fastening machine and an automatic cap fastening machine, and a fastening method.

[0002]

2. Description of the Related Art In a component fastening device such as an automatic screw tightening machine or an automatic cap tightening machine, a tool such as a driver bit or a cap driver is rotated by a motor to fasten a component such as a screw or a cap to a work. Here, when controlling the tightening torque, the load current of the motor that fluctuates according to the load applied to the tool is detected, and the detected value reaches a predetermined current value corresponding to the desired tightening torque value. Occasionally, a device configured to stop driving of a motor or a shaft torque applied to a tool is detected by a torque detector such as a magnetostrictive sensor or a strain gauge, and when this reaches a certain value, the driving of the motor is stopped. A common device is generally used.

[0003]

When a component is fastened to a workpiece in a component fastening device having a torque control mechanism of this type, the tightening torque of the component after the completion of the fastening matches a predetermined desired tightening torque value. Is desirable, but in practice,
After tightening is completed, the tightening torque for the workpiece
It tends to be smaller than a predetermined desired tightening torque value. This tendency is remarkable especially when an elastic body such as urethane rubber is interposed in the work.

[0004] This is because a part of the axial torque of the tool for rotating and driving the part is used for deformation of the elastic body. As a result, the tightening torque of the part with respect to the workpiece is reduced.
Even if it is tightened with the desired tightening torque, when the elastic body is restored, it becomes smaller by the amount used for its deformation. In addition, when an elastic body such as urethane rubber is interposed in the work, a creep phenomenon that the tightening torque of the part is reduced due to the inherent set of the elastic body even when the tool rotates the part is driven. Occur. After tightening is completed due to this creep phenomenon, the tightening torque of the parts is
The value greatly deviates from the desired tightening torque.

In view of the above problems, the present invention provides an automatic component fastening machine and a component fastening method capable of accurately fastening a component with a desired fastening torque even when an elastic member or the like is interposed in a work. It is intended to do so.

[0006]

According to the present invention, there is provided an automatic component fastening machine according to the present invention.
A motor for rotationally driving, a tool for transmitting the rotational driving force of the motor to a part for fastening the work, a shaft torque detecting unit for detecting a shaft torque of the tool, and a torque value detected by the shaft torque detecting unit being a desired value. When the first control means stops driving the motor, and after the first control means stops driving the motor, until the motor stops.
And when a predetermined time elapses after stopping the driving of the motor,
It is characterized by comprising second control means for re-driving the motor and setting means for setting the number of retightenings.

Further, the automatic part fastening machine according to claim 2 is
In the automatic component fastening machine according to the first aspect, the second control means is detected by the shaft torque detecting means after the first control means stops driving the motor and before the motor stops. When the shaft torque value decreases to a value smaller than a desired value, the motor is driven again.

[0008] The automatic component fastening machine according to claim 3 is
In the automatic component fastening machine according to claim 2, after the first control means stops driving the motor, until the motor stops, and within a predetermined time after stopping the motor driving. If the shaft torque value detected by the shaft torque detecting means does not reach a value smaller than a desired value, a third control means for completing the tightening without re-driving the motor by the second control means is provided. It is characterized by:

According to a fourth aspect of the present invention, there is provided a fastening method for an automatic part fastening machine, comprising: a motor for rotating and driving; a tool for transmitting a rotational driving force of the motor to a part for fastening a work; and a shaft for detecting a shaft torque of the tool. A first step of stopping driving of the motor when the shaft torque value detected by the shaft torque detecting means reaches a desired value after the fastening of the parts, in the automatic component fastening machine having the torque detecting means; After stopping the driving of the motor in the step, while the shaft torque value remains,
It is characterized in that it has a preset number of retightening times and a second step of re-driving the motor.

[0010]

According to the above construction, in the automatic part fastening machine according to the first aspect, when the motor is driven for the first time, the torque value detected by the shaft torque detecting means reaches a desired value after the start of the part fastening. At this time, the first control means stops driving the motor. Next, when the motor is driven again, the second
After the driving of the motor is stopped by the first controlling means, the control means restarts the motor until the motor stops and when a predetermined time elapses after stopping the driving of the motor. After the driving of the motor is stopped, the time until the motor stops is a period during which the shaft torque value remains.
The motor is driven again while the shaft torque value remains. Then, when the torque value detected by the shaft torque detecting means reaches a desired value, the first control means stops driving the motor.

[0011] By such re-driving or repetition, the tightening torque of the component approaches the desired tightening torque. The reason is considered as follows. While the shaft torque value until the motor stops remains, the elastic body is deformed, so even during the tightening, the tightening torque of the screw decreases due to the inherent set of the elastic body. Creep phenomenon occurs. Since the re-tightening is performed in a state where the creep phenomenon is occurring, the creep phenomenon is reduced each time the re-tightening is performed, and the reduction in the tightening torque is suppressed accordingly. Then, after the completion of the tightening, the tightening torque for the workpiece approaches the desired tightening torque. Furthermore, since the elastic body is re-tightened in a deformed state, the restoring force of the elastic body is reduced, and a smaller percentage of the shaft torque used by the tool to rotate the component is used to deform the elastic body. Therefore, it is often used for the tightening torque of parts to a work.

Also, while the shaft torque value until the motor stops remains, re-driving and continuous re-driving are performed, so that the net tightening torque can always be controlled in a dynamic state. When the work is loosened on the work side in positioning the work or the like, the looseness is tightened. Therefore, retightening can be performed without being affected by looseness on the work side or the like.

In the automatic part fastening machine according to the second aspect, the second control means restarts the motor when the torque value detected by the shaft torque detection means falls to a value smaller than a desired value. Therefore, by setting this desired torque value appropriately, it is possible to determine an appropriate timing for re-driving while the shaft torque value remains.

In the automatic component fastening machine according to the third aspect, the third control means controls the driving of the motor after the first control means stops driving the motor until the motor stops. If the shaft torque value detected by the shaft torque detecting means does not reach a value smaller than a desired value within a predetermined time after stopping, the tightening is completed without re-driving the motor by the second control means. I do.

Accordingly, by appropriately setting the desired torque value and the predetermined time, it is possible to determine an appropriate timing for automatically re-driving while the shaft torque value until the motor stops remains. In addition to the above, the re-driving is performed an appropriate number of times, the tightening is completed, and no extra re-driving is performed. In the fastening method of the automatic component fastening machine according to the fourth aspect, when the motor is driven for the first time, the torque value detected by the shaft torque detecting means reaches a desired value in the first step after the start of component fastening. At this time, the driving of the motor is stopped.

Next, when the motor is driven again, the first
After the driving of the motor is stopped in the step, while the shaft torque value until the motor stops remains, the motor is driven again in the second step. Then, when the torque value detected by the shaft torque detecting means reaches a desired value, the driving of the motor is stopped in the first step. Such re-driving is repeated a predetermined number of times.

By such re-driving and repetition thereof, the tightening torque value of the part with respect to the work becomes
It approaches the desired tightening torque value.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. [Example 1] An example in which a motor is driven again when a shaft torque detection value obtained by a torque sensor becomes a desired value. Fig. 1 is a block diagram showing a configuration of an automatic screw tightening machine as an example of an automatic component fastening machine according to the present invention. FIG. As shown in FIG. 1, this automatic screw tightening machine is composed of an automatic screw tightening machine main body 1 and a control device 30, and the automatic screw tightening machine main body 1 is driven up and down by a frame (not shown). Source 2
A driver base 3 which is raised and lowered by a lifting drive source 2, a driver main body 4 installed on the driver base 3, and a driver bit 10 for transmitting a rotational driving force of the driver main body 4 to a screw (not shown) fastened to a work. It is composed of

The driver main body 4 is fixed on the driver base 3 via a cylindrical gear case 5 surrounding the driver main body 4. The driver main body 4 and the driver bit 10 are moved up and down together with the driver base 3 by the elevation drive source 2. I do. The driver main body 4 includes a motor 6 that rotates and drives, a reduction unit 7 that transmits the rotation driving force of the motor 6 while reducing the speed, and a differential planetary gear mechanism that transmits the rotation driving force from the reduction unit 7 while further reducing the rotation. 20. The differential planetary gear mechanism 20 has an output shaft 24 at a lower portion thereof, and the driver bit 10 is connected to the output shaft 24 by the joint unit 9.

The motor 6 is, for example, a DC servo motor. Further, the inside of the speed reduction section 7 is filled with lubricating oil. The differential planetary gear mechanism 20 includes a sun gear 21a located at the center thereof, and three planetary gears 21b arranged so as to mesh around the sun gear 21a at equal intervals.
Ring gear portion 21c surrounding the outside of three planetary gears 21b
The ring gear 21c includes a planetary gear 21
An inner meshing portion meshing with the b is formed.

The sun gear 21a is connected to the output shaft 8 of the reduction unit 7 by a connector 22 so as to rotate together with the sun gear 21a. The ring gear 21c is a cylindrical strain tube 11 surrounding the connector 22. And is attached to the lower surface of the speed reduction unit 7 through the center. Each rotating shaft of the three planetary gears 21b is supported by a planetary gear stand 23.
The output shaft 24 is attached to the lower surface of the output shaft 3.

By the differential planetary gear mechanism 20 having such a configuration, the rotational driving force of the output shaft 8 of the speed reducer 7 is greatly reduced to a predetermined ratio and transmitted to the output shaft 24, and further transmitted to the driver bit 10. It is supposed to be. The distortion tube 11 is distorted in response to a reaction torque applied to the ring gear portion 21c, and a strain gauge 12 for converting the amount of distortion into a voltage signal is attached to the distortion tube 11. The tube 11 and the strain gauge 12 constitute an axial torque detecting means. By processing this voltage signal by the control device 30, the shaft torque value of the driver bit 10 can be detected.

The control device 30 includes a central control unit 50.
A motor drive unit 31 for driving the motor 6; a power supply unit 32 for supplying power to the motor drive unit 31; a work start unit 33 for outputting a work start command; Drive source driving unit 34 for driving the motor, an original position detecting unit 35 for detecting whether the driver bit 10 is at the original position, a good or bad judgment output unit 36 for outputting a good or bad judgment result of the screw tightening result, and a photocoupler. 37 and a display unit 38 for displaying the result of the pass / fail judgment and the like
A setting unit 39 for setting screw tightening information using a numeric keypad 40; an input circuit 41 of the setting unit 39;
, An amplifying unit 42 for amplifying the voltage signal detected by the above, a correcting unit 43 for correcting an axial torque value from the voltage signal to detect it, a filter unit 44 for removing a noise component of the signal, a fixed time S / to sample and hold each time
H circuit 45, A / D converter 46, and RA
The control unit 50 includes a control unit 50, a motor drive unit 31, a work start unit 33, an elevation drive source drive unit 34, an original position detection unit 35,
The signal is transmitted in a state of being electrically insulated from each other by interposing the photocoupler 37 between the pass / fail judgment output unit 36 and the pass / fail judgment output unit 36.

The control unit 50 includes a speed command unit 51 for giving a speed command value of the motor 6 to the motor drive unit 31, and a RAM 52.
A first control means for stopping the motor 6 when the torque value detected by the shaft torque detection means reaches a final tightening torque set value described later; After the driving is stopped, the automatic screwing machine including the second control means for re-driving the motor 6 is operated until the motor 6 stops and when a predetermined time elapses after the driving of the motor 6 is stopped. In addition to the program, a program for processing the setting data of the screw tightening information is stored (see FIGS. 2 to 6). Also, the RAM 52
Stores the setting data of the screw tightening information.

As the screw tightening information, as described later,
There are a temporary tightening torque set value, a final tightening torque set value, a re-driving start torque value, a re-tightening frequency, a restart waiting time after the completion of the temporary tightening, a lower limit torque value, an upper limit torque value, a reverse rotation time, and the like. The motor drive unit 31 employs an H circuit (see FIG. 8) using four or eight transistors so as to be suitable for the forward / reverse drive of the motor 6, so that it responds quickly to forward / reverse rotation of the motor. be able to.

Since the A / D converter 46 employs a high-speed A / D converter, the A / D converter 46 can accurately follow the fluctuation of the screw tightening torque. The pass / fail judgment output unit 36
Since a digital signal of a torque value can be output in addition to the output of determining whether or not the screw tightening result is good or a detected torque value can be output in an analog manner, it is possible to monitor the screw tightening process. In addition, the display unit 38 can display an illumination such as a determination of whether the screw tightening result is good or the like in addition to displaying the torque value of the screw tightening result, and is responsible for quality control of the screw tightening.

FIG. 7 is an example of a torque characteristic diagram of the automatic screw tightening machine, and shows the time from the work start command time to the first re-drive start time at the time of the first final tightening. As shown in the figure, at the time of temporary fastening, the motor 6 is turned off when the detected torque value reaches a preset temporary fastening torque set value 71, but the detected torque value further decreases.
Due to the overshoot 72, the torque increases to the temporarily tightened peak torque value 73, and then decreases. Subsequently, when the restart waiting time 78 after the completion of the temporary fastening has elapsed, the motor 6 is turned on.
Then, the final tightening is started, but also at the first final tightening, the motor 6 is turned off when the detected torque value reaches a preset final tightening torque set value 74. The detected torque value further increases to a final tightening peak torque value 76 to which a slight overshoot 75 is added, and then decreases.
Usually, the final tightening torque setting value 74 can be regarded as equivalent to the desired tightening torque value.

Thereafter, the redrive start torque value 77 whose detected torque value is set lower than the final tightening torque set value 74 is set.
Is reached, the motor 6 is turned on (re-driven). Hereinafter, although not shown in FIG.
4, the motor 6 is turned off. Then, the motor 6 is turned on (re-driven) and the final tightening torque set value 7 is set.
The turning off of the motor 6 at the time of reaching 4 is repeated for a preset number of retightening times (for example, 10 times).

The lower limit torque value and the upper limit torque value are used to set an allowable range of the peak torque value detected at the time of final tightening. 36 outputs an OK determination. The reverse rotation time is a time in which the motor 6 is reversely rotated for a short time after the final fastening in order to release the biting between the screw head and the driver bit 10.

Next, the operation of the automatic screw tightening machine will be described with reference to a flowchart. 2 to 6 are flowcharts showing the operation of the automatic screw tightening machine according to the present embodiment.
In the initial state, the data of the screw tightening information is written in a predetermined area of the RAM 52. When changing the setting data, the operator operates the numeric keypad 40 to set screw tightening information.

If there is a setting data change command (S1),
A setting data change subroutine described below is executed (S
2). If there is no command to change the setting data, the original position detection unit 35 confirms that the driver bit 10 is at the original position (S3), and then waits for a work start instruction from the work start unit 33 (S4). When a work start command is issued (see P0 in FIG. 7), the screw tightening information (temporary tightening torque set value, final tightening torque set value, re-driving start torque value, number of re-tightening times, lower limit, written in a predetermined area of the RAM 52). (Torque value, upper limit torque value, reverse rotation time, etc.)
5).

The elevation drive source drive section 34 drives the elevation drive source 2 to lower the driver bit 10 (S6), and in response to a motor normal rotation drive command from the motor drive section 31 (S7), Normal rotation is started (see 70 in FIG. 7). When the head seat surface of the screw reaches the work (see P1 in FIG. 7), the torque value related to the driver bit 10 increases.

The signal from the strain gauge 12 is A / D converted by the A / D converter 46 and read as a torque value (S
8) Wait until the preset temporary tightening torque set value is reached (S9), and when the detected torque value reaches the temporary tightening torque set value (see P2 in FIG. 7), a rotation stop command is sent to the motor driving unit 31 and the motor is stopped. 6 is stopped (S1).
0). At the same time, the restart waiting time timer is counted (S11). If this timer reaches the set restart waiting time after completion of the temporary fastening (see 78 in FIG. 7).
(S12), the motor 6 is driven to rotate forward to start the final tightening (S13).

Also in the final tightening, similarly, it waits until the detected torque value reaches a preset final tightening torque set value (S14, S15), and when the detected torque value reaches the final tightening torque set value (P4 in FIG. 7). Then, a rotation stop command is sent to the motor drive unit 31 to stop the supply of the drive current to the motor 6 (S16). Thereafter, when the detected torque value decreases to a re-starting torque value that is set to be smaller than the final tightening torque setting value (see P5 in FIG. 7), the motor 6 is turned on.
(Re-driving), and the motor 6 is turned off when the final fastening torque set value is reached. ON / OFF of this motor 6
Is repeated a preset number of times of retightening (S
17-S20).

At this time, the signal from the strain gauge 12 is A / D converted by the A / D converter 46 and read as a torque value. Then, the final tightening peak torque value is detected (S1).
8, S21). Wait for the motor 6 to stop (S2
2) If stopped, the final tightening peak torque value detected in step S21 is displayed on the display unit 38 (S23). Further, it is determined whether or not the final tightening peak torque value is within the allowable range of the preset torque value (between the lower limit torque value and the upper limit torque value) (S24, S26). Abnormality of the lower limit or the upper limit is displayed on the display unit 38 (S27, S25). If it is within the allowable range, OK is displayed on the display unit 38 (S28), and the pass / fail judgment output unit 36 outputs pass / fail judgment (S29).

After the final tightening is completed, a motor reverse rotation command (S30)
, The motor 6 is reversely rotated for a short time for a preset reverse rotation time, and the biting between the screw head and the driver bit 10 is released. At the same time as the motor reverse rotation command, a bit rise return command (S32) is issued to drive the elevation drive source 2 so that the driver bit
0, lift the driver bit 10 away from the screw head,
The driving of the motor 6 is stopped (S30 to S34). Thus, one cycle of operation is completed.

FIG. 6 is a flowchart showing a subroutine for changing the set data in step S2. RAM
When the setting data written in the predetermined area 52 is changed, the screw tightening information (temporary tightening torque set value, final tightening torque set value, re-driving start torque value, number of re-tightening, wait for restart after temporary tightening is completed) is required. Time, lower limit torque value, upper limit torque value and reverse rotation time)
It is possible to change to a desired value with the ten keys 40 (S41 to S56). Note that a numerical value of what percentage of the final tightening torque set value may be set as the set redrive start torque value.

According to the automatic screw tightening machine and the fastening method as described above, by setting the redrive start torque value to an appropriate value, the motor 6 can be driven while the shaft torque value until the motor stops remains. A suitable timing for re-driving can be determined. Then, while the shaft torque value until the motor 6 stops remains, the motor 6 is re-driven or the repetition thereof is performed, so that the tightening torque of the screw on the work approaches the desired tightening torque value.

It should be noted that the present invention can be similarly implemented by using an AC servomotor or the like in addition to the DC servomotor as the motor 6 of this embodiment. [Example 2] Example in which the motor is driven again after a predetermined time has elapsed after the motor is turned off.
Motor does not have a torque sensor like
The motor is configured to detect a load torque from the motor drive current. That is, the automatic screw tightening machine of the first embodiment has a mechanism in which a torque value is detected by a voltage signal sent from the strain gauge 12 to the amplifying unit 42, but in the present embodiment, instead, FIG.
Has a drive current detection unit 60 installed in the H circuit of the motor drive unit 31. The drive current detection unit 60 converts the drive current of the motor 6 into a voltage signal and amplifies the voltage signal. 42, a mechanism for detecting the load torque value. Otherwise, the configuration is the same as that of the automatic screwdriver of the first embodiment.

The drive current detector 60 is connected to the motor drive 31
After the drive current value supplied to the motor 6 is converted into a voltage value, and the voltage signal is sent to the amplification unit 42, the amplification unit 42, the correction unit 43, and the filter unit 44 are processed as in the first embodiment. , S / H circuit 45, and A / D converter 46, and a mechanism for detecting a torque value. Also,
The screw tightening information used in the present embodiment is the same as the screw tightening information of the first embodiment except that the re-driving start time is used instead of the re-driving start torque value in the screw tightening information of the first embodiment. The re-driving start time is set to a time when the motor 6 is turned on after the detected torque value reaches the final tightening torque set value and a rotation stop command is sent to the motor drive unit 31 to stop the drive current supply to the motor 6. (Re-driving) until the motor 6 stops.
Is set such that the shaft is re-driven while the shaft torque value according to the above remains.

The flowchart of the operation of the automatic screw tightening machine according to the present embodiment is the same as the flowchart of FIGS. 2 to 6 of the first embodiment except that “re-start torque value” is replaced by “re-start” in steps S5 and S45. Driving start time "is entered.
In FIG. 9, steps S61 and S62 shown in FIG. 9 are inserted in place of steps S18 and S19 surrounded by a dotted line, and the other steps are the same.

Therefore, in steps S5, S45, and S46, the redrive start time is set or registered instead of the redrive start torque value. Step S16
Subsequently, when the preset re-drive start time has been reached (see 79 in FIG. 7), the motor 6 is turned on (re-driven), and when the final tightening torque set value has been reached, the motor 6 is turned off.
F, and the ON / OFF of the motor 6 is repeated a preset number of times of retightening (S16, S17, S16).
61, S18, S62, S20). Other operations are the same as those in the first embodiment.

At this time, the drive current of the motor 6 from the drive current detector 60 is converted into a voltage signal, A / D converted by the A / D converter 46, and read as a load torque value. Then, the final tightening peak torque value is detected (S18, S2).
1). Even in the automatic screw tightening machine and the fastening method as described above, by appropriately setting the redrive start time,
While the shaft torque value until the motor 6 stops remains, an appropriate timing for re-driving the motor 6 can be determined. Then, while the shaft torque value until the motor 6 stops remains, the motor 6 is re-driven or the repetition thereof is performed, whereby the tightening torque of the screw to the work approaches the desired tightening torque value.

In this embodiment, the re-driving timing is controlled by the set time.
The control can be performed based on the voltage signal from the drive current detection unit 60 as follows. In the drive current detection unit 60, even when the motor drive unit 31 is not supplying the drive current to the motor 6, if the motor 6 is rotating due to inertia, the generated current is detected and a voltage signal is generated. Can also. Therefore, even if the automatic screw tightening machine does not have a torque sensor and detects the load torque by the drive current detecting unit 60 as in the present embodiment, the detected torque reaches the final tightening torque set value and the motor 6 After the driving of the motor 6 is stopped, the generated current of the motor 6 rotating by inertia is detected, and the timing for re-driving the motor 6 can be determined based on the detected value. [Embodiment 3] After the motor is turned off, if the shaft torque detection value by the torque sensor decreases to a value smaller than a desired value within a predetermined time during which the shaft torque remains until the motor stops, re-driving is performed. An example in which tightening is completed without re-driving if the value does not decrease to a desired value. The automatic screwdriver of the present embodiment has the same configuration as the automatic screwdriver of the first embodiment.

The screw tightening information used in this embodiment is
This is the same as the screw tightening information of the first embodiment except that the re-driving determination time is used instead of the number of re-tightenings of the first embodiment. The re-driving determination time is from the time when the detected torque value reaches the final tightening torque set value and the rotation stop command is sent to the motor driving unit 31 to stop the supply of the driving current to the motor 6 during the final tightening. It is time to check whether the tightening torque has decreased due to the creep phenomenon inherent in the elastic body, that is, while the shaft torque related to the driver bit 10 remains until the motor stops, the torque sensor is used. This is set as a value for determining a timing for determining whether or not the shaft torque detection value has decreased to a desired value smaller than the final fastening torque setting value.

The flowchart of the operation of the automatic screw tightening machine of this embodiment is the same as that of the flowchart of FIGS. 2 to 6 of the first embodiment except that "re-driving" is performed instead of "refastening number" in steps S5 and S47. 4 and the steps S17 to S20 surrounded by a dotted line in FIG.
0, S80, S18, S19, S81, S
82 is entered, and otherwise the same.

Therefore, in steps S5, S47, and S48, a redrive determination time is set or registered instead of the number of refastenings. Further, following step S16, a redrive determination timer is counted (S80). Thereafter, when the detected torque value reaches the preset redrive start torque value within the preset redrive decision time. (S1
In 9), the redrive determination timer is reset (S81),
Next, the motor 6 is turned on (re-driven), and the motor 6 is turned off when the final tightening torque set value is reached. If the redrive start torque value has not been reached within the redrive determination time, the process returns to step S18 (S82). If the redrive determination time has elapsed, the process automatically proceeds to step S21 without redrive.

As described above, the ON / OFF of the motor 6 is automatically determined based on the redrive start torque value and the redrive determination time (S16, S80, S18, S19, S81, S81).
82). At this time, the signal from the strain gauge 12 is A / D
The conversion unit 46 performs A / D conversion and reads the converted torque value.
Then, the final tightening peak torque value is detected (S18, S18).
21). Other operations are the same as in the first embodiment.

In the automatic screw tightening machine and the fastening method as described above, the re-start torque value and the re-drive judgment time are appropriately set so that the shaft torque value until the motor 6 stops remains. In between, an appropriate timing for determining whether or not the motor 6 is re-driven can be determined. Then, while the shaft torque value until the motor 6 stops remains, whether or not the motor 6 is re-driven is automatically determined and the processing is performed. Can be brought close to the desired tightening torque value.

In the first to third embodiments, an example of an automatic screw tightening machine has been described. However, the present invention can be similarly applied to an automatic cap tightening machine.

[0051]

As described above, in the automatic component fastening machine according to the present invention, after the motor driving is stopped when the shaft torque value reaches a desired value, the shaft torque value until the motor stops is maintained. During this operation, the re-driving of the motor or its repetition is performed a predetermined number of times or automatically, and the tightening torque of the component to the workpiece can be made closer to the desired tightening torque. Therefore, even when an elastic member or the like is interposed in the work, the component can be fastened with an accurate tightening torque for the work.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an automatic screwdriver according to a first embodiment.

FIG. 2 is a flowchart illustrating an operation of the automatic screw tightening machine according to the first embodiment.

FIG. 3 is a continuation of the flowchart in FIG. 2;

FIG. 4 is a continuation of the flowchart in FIG. 3;

FIG. 5 is a continuation of the flowchart in FIG. 4;

FIG. 6 is a flowchart showing a subroutine for changing setting data in step S2 shown in FIG. 2;

FIG. 7 is an example of a torque characteristic diagram in the automatic screwing machine.

FIG. 8 is a diagram illustrating a configuration of a drive current detection unit 60 according to a second embodiment.

FIG. 9 is a part of a flowchart showing the operation of the automatic screwdriver according to the second embodiment.

FIG. 10 is a part of a flowchart showing the operation of the automatic screwdriver according to the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Automatic screw-fastening machine main body 6 Motor 10 Driver bit 11 Strain tube 12 Strain gauge 30 Control device 42 Amplification part 43 Correction part 44 Filter part 45 S / H circuit 46 A / D conversion part

Claims (4)

(57) [Claims] 1. A motor for rotationally driving, a tool for transmitting a rotational driving force of the motor to a part for fastening a workpiece, a shaft torque detecting means for detecting a shaft torque of the tool, and a shaft torque detecting means for detecting a shaft torque of the tool. First control means for stopping the drive of the motor when the torque value reaches a desired value, and after the first control means stops the drive of the motor until the motor stops. An automatic component fastening machine, comprising: second control means for re-driving the motor when a predetermined time has elapsed after stopping the driving of the motor; and setting means for setting the number of refastenings. 2. In the automatic component fastening machine, the second control means is detected by the shaft torque detection means after the first control means stops driving the motor and before the motor stops. 2. The automatic component fastening machine according to claim 1, wherein when the shaft torque value decreases to a value smaller than a desired value, the motor is driven again. 3. The automatic component fastening machine according to claim 2, wherein after the first control means stops driving the motor, a period from when the motor stops to a predetermined time after the motor stops. If the shaft torque value detected by the shaft torque detecting means does not reach a value smaller than a desired value within the time, the third control means completes the tightening without re-driving the motor. 3. The automatic component fastening machine according to claim 2, further comprising control means. 4. An automatic component fastening machine comprising: a motor that is driven to rotate; a tool that transmits a rotation driving force of the motor to a part that fastens a workpiece; and a shaft torque detecting unit that detects a shaft torque of the tool. When the shaft torque value detected by the shaft torque detecting means reaches a desired value after the start of the fastening of the parts, the driving of the motor is stopped.
And stopping the driving of the motor in the first step and, while the shaft torque value remains, setting a preset number of retightening times and a second step of re-driving the motor. Characteristic method of fastening automatic parts fastening machine.