JP2010214564A - Screw fastening device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw fastening device which inexpensively, properly and surely detects a screw fastening failure such as screw galling or screw looseness with respect to a screw hole, easily, simply, and in a comparatively simple constitution. <P>SOLUTION: The screw fastening device is composed of: a rotating amount detection means 32 for detecting a rotating amount based on the number of rotation or a rotating time associated with a rotational drive of the rotating tool; a screw fastening start point setting means 20 that sets the screw fastening start point by starting a drive means of the rotating tool after a screw fastening reference point is set; a screw fastening completion point detection means 26 which detects the screw fastening completion point when a load torque generated in the rotating tool reaches a predetermined torque value; and a screw fastening quality determination means 42 which determines the screw fastening quality by determining whether or not the rotating amount of the rotating tool detected by the time from the screw fastening start point to the screw fastening completion point is within the allowable range compared with a predetermined reference value after the setting of the screw fastening reference point. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a screw tightening device configured to rotationally drive a driver bit by driving means such as an electric motor, and when the screw tightening operator grasps the device main body by hand and manually operates the screw bit, A screw tightening device provided with a screw tightening quality judgment means that can detect a screw tightening failure such as screw galling or screw floating with respect to a screw easily and simply and with a relatively simple configuration at a low cost appropriately and reliably. It is about.

  Conventionally, as a screw tightening device that performs screw tightening work by rotationally driving a driver bit by driving means such as an electric motor, etc., it has various functions that can achieve screw tightening work properly, smoothly and quickly. Screw fastening devices have been proposed and put into practical use.

  However, when a screw is tightened with a screw tightening device into a screw hole provided in a required object to be screwed, the screw is not completely screwed in and the predetermined screw tightening torque is reached. The screw tightening device may complete the screw tightening. If a screw that does not fit into the screw hole is used, the screw will idle in the opening of the screw hole or inside the screw hole, and the screw tightening device will complete the screw tightening without reaching the predetermined screw tightening torque indefinitely. It may become a state that does not.

  The cause of such screw tightening failure is, for example, a case where it is caused by a poor fitting between a screw and a screw hole (a galling phenomenon) or a case where it is caused by a molding failure of a screw or a screw groove in a screw hole (screw floating phenomenon) ) Etc. are known.

  Therefore, in the conventional screw tightening device, as a means for detecting or determining the screw tightening failure as described above, the relative movement between the screw and the work is stopped after the screw is brought into contact with the work and the screwing is started. Until the tightening of the screw is completed, the means for detecting the position of the spindle that rotates the screw, the data obtained by this detecting means, and the permissible normal value stored in advance are compared, There has been proposed a screw tightening failure detection device provided with means for determining screw tightening failure (see Patent Document 1).

  However, in such a screw tightening failure detection device, it is possible to detect the above-described screw floating phenomenon by simply detecting the position of the main shaft that rotates the screw, but the screw is appropriate for the screw hole. Even if the screw is screwed into the correct position, if the spindle that rotates the screw rotates the screw more than necessary, the screw or screw hole may be damaged, and it is necessary to tighten the screw. If it is less than the number of rotations, there is a possibility that the screw does not screw properly into the screw hole, and there is a difficulty that these disadvantages cannot be solved.

  Conventionally, the rotational speed of the drive source of the nut runner, the current value supplied to the drive source, and the torque value generated on the output shaft of the nut runner are detected, and the detection data of the rotational speed, current value, and torque value are respectively detected. Output to the output device as time-dependent fluctuation patterns and display them at the same time, and compare these fluctuation patterns with fluctuation patterns of rotation speed, current value, and torque value when screw parts are tightened normally. Therefore, a nut runner tightening quality determination method has been proposed in which the nutrunner drive state, torque detection unit state, or screw part tightening state is determined (see Patent Document 2).

  However, in such a nutrunner tightening pass / fail judgment method, it is necessary to accumulate a large amount of detection data, and the means for tightening pass / fail judgment becomes complicated, which not only significantly increases the equipment cost, but also, for example, In order to cope with various types of screw tightening operations, further enormous detection data for tightening quality determination is required, and there is a difficulty in further increasing the equipment cost for the screw tightening operation.

  From such a point of view, for example, in a screw tightening device having a bit tightening mechanism that includes a bit shaft for tightening a male screw into a female screw hole portion of a workpiece and capable of controlling the torque of the bit shaft, (1) (2) Based on the rotation amount detected by this rotation amount detection means, a predetermined torque generated when the head of the male screw tightened by the bit shaft is seated in the female screw hole during the screw tightening operation. A rotation change amount calculating means for calculating a rotation change amount from when the first set torque set as described above is generated to when a predetermined second set torque corresponding to completion of tightening of the male screw is generated; ) If the rotation change amount calculated by this rotation change amount calculation means is within a predetermined range corresponding to the rotation change amount when the screw is tightened well, Tightening is determined to be good, also the screw tightening quality determining means for determining to be defective if outside the predetermined range, the screwing device provided with has been proposed (see Patent Document 3).

  In the screw tightening device described in Patent Document 3, (4) the first set rotation amount required until the time when the first set torque corresponding to the case of good screw tightening is generated and the first (2) a second set torque that stores the second set rotation amount required until the time when the set torque is generated; and (5) the second set torque despite the completion of the rotation operation for the first set rotation amount. It has been proposed to include a screw tightening failure determination unit that determines that the screw tightening is defective without performing the calculation process by the rotation change amount calculation unit when the rotation has not occurred.

  Further, as an alternative, a driver bit that engages with a screw to give a rotational force, an electric motor that rotationally drives the driver bit, a rotational torque detecting means that detects the rotational torque of the electric motor, and a rotational torque detecting means Rotation amount for detecting the rotation amount of the screw (or measuring the rotation time of the electric motor) from when the detected rotation torque reaches the predetermined first rotation torque until reaching the second rotation torque higher than the first rotation torque. Detection means (or time measurement means) and first determination means (or third) for determining a screw tightening failure based on the rotation amount (or rotation time) detected by the rotation amount detection means (or time measurement means). And a screw tightening device having a determination means) (see Patent Document 4).

  In each of the screw tightening devices described in Patent Document 3 and Patent Document 4 described above, the detected rotation amount is used for screw tightening by detecting the screw rotation amount during the screw tightening operation by the required driving means. It is determined whether or not it is within a required predetermined range. In this case, when detecting the amount of rotation of the screw, how to properly and simply set the time from the reference point where the detection is started until the detection is completed depends on whether the screw is tightened or not. It is extremely important to determine

  However, in the screw tightening device described in Patent Document 3, the time point at which the first set torque set to a predetermined torque or more generated when the head of the male screw is seated in the female screw hole is set as the reference point. The rotation change amount until the predetermined second set torque corresponding to the completion of tightening of the male screw is generated is set. Further, in the screw tightening device described in Patent Document 4, the time point when the screw head of the screw reaches the rotational torque (first rotational torque) when contacting the periphery of the opening of the screw hole is set as the reference time point. The amount of rotation until the screw reaches the rotation torque (second rotation torque) that is tightened in the screw hole in a predetermined tightening state is set.

  As described above, in the conventional screw tightening device, when detecting the rotation amount of the screw, the reference point for starting the detection is set as a preset torque value. Therefore, in the screw tightening operation, the screw tightening operation is always performed. Since it is necessary to detect the torque, there is a problem that the configuration of the control device of the screw tightening device becomes complicated. As for the setting of the torque value as the reference point, the torque generated when the head of the male screw is seated in the female screw hole and the rotational torque when the screw head of the screw is in contact with the periphery of the opening of the screw hole are: Since the torque value varies slightly depending on the dimensions and type of the screw and the material of the object to which the screw is attached, it is difficult to detect an appropriate and simple amount of rotation. Therefore, the reliability of the pass / fail judgment when tightening the screw is difficult. There is also a problem.

  Therefore, as a result of intensive studies and studies to solve the problems in the conventional screw tightening device, the present inventor rotationally drives a rotary tool such as a driver bit by a driving means such as an electric motor to perform screw tightening work. And detecting a load torque generated in the rotary tool upon completion of tightening of the screw with respect to a required screw attachment object, and when the load torque reaches a preset torque value, the rotary drive of the rotary tool is driven. In the screw tightening device configured to stop and control, when the screw tightening operator grasps the device main body by hand and manually operates the device main body, the screw tightening device is based on the rotation speed and the rotation time associated with the rotational drive of the rotary tool. A rotation amount detection means comprising an encoder for detecting the rotation amount is provided in the rotary tool or drive means, and the screw is tightened at the tip of the rotary tool during the screw tightening operation. When the screw shaft tip of the screw fitted with the head is positioned and brought into contact with the screw hole of the object to be screwed, the screw tightening operator presses and displaces the rotary tool in the axial direction. A screw tightening reference time setting means comprising various displacement detection sensors for setting a screw tightening reference time for starting the drive means is provided, and after the reference time is set, the drive means of the rotary tool is started. A screw tightening start time setting means including a drive switch for setting a screw tightening start time for performing screw tightening is provided, and the load torque generated in the rotary tool as the screw tightening progresses reaches a preset torque value. A screw tightening completion time point detecting means comprising a clutch mechanism or the like for detecting the screw tightening completion time point at the time, and a reference time point (t1) by the screw tightening reference time point setting means After the setting, the rotation from the screw tightening start time (t2) of the rotary tool driving means by the screw tightening start time setting means to the screw tightening completion time (t3) detected by the screw tightening completion time detecting means. By determining whether or not the rotation amount of the rotary tool detected by the amount detection means is within the allowable range compared with a reference value as a rotation amount required for proper tightening of a screw set in advance, It has been found that it is possible to easily and easily determine whether or not a screw is tightened and to achieve a proper and reliable operation at a low cost with a relatively simple configuration.

  Accordingly, an object of the present invention is to provide a screw tightening device configured to rotationally drive a driver bit by a driving means such as an electric motor. It is an object of the present invention to provide a screw tightening device that can detect the quality of screw tightening such as screw galling or screw floating with respect to a screw hole easily and simply with a relatively simple configuration at a low cost in an appropriate and reliable manner. .

In order to achieve the above object, a screw tightening apparatus according to claim 1 of the present invention performs a screw tightening operation by rotating a rotary tool such as a driver bit by driving means such as an electric motor, and a required screw. A load torque generated in the rotary tool upon completion of tightening of the screw with respect to the attachment target is detected, and when the load torque reaches a preset torque value, the rotational drive of the rotary tool is controlled to stop. In the screw fastening device,
A rotation amount detection means provided in the rotary tool or drive means for detecting a rotation amount based on the rotation speed and rotation time associated with the rotation drive of the rotary tool;
When the tip of the screw shaft with the screw head fitted to the tip of the rotary tool is positioned and abutted against the screw hole of the screw mounting target, the screw tightening reference point is determined by pressing the rotary tool in the axial direction. Screw tightening reference time setting means for setting (t1);
A screw tightening start time setting means for setting the screw tightening start time (t2) by starting the drive means of the rotary tool after the screw tightening reference time setting means is set by the screw tightening reference time setting means;
A screw for detecting a screw tightening completion time (t3) when a load torque generated in the rotary tool reaches a preset torque value by rotating a screw positioned and abutting on the screw hole by rotation of the rotary tool. A fastening completion point detection means;
After the screw tightening reference time point (t1) is set by the screw tightening reference time point setting means, from the screw tightening start time point (t2) when the screw tightening start time setting means starts the driving means of the rotary tool, the screw tightening completion time point is reached. Whether or not the rotation amount of the rotary tool detected by the rotation amount detection means is within an allowable range compared to a preset reference value until the screw tightening completion time point (t3) detected by the detection means. Screw tightening quality judgment means for judging and judging screwing quality is provided.

  The screw tightening device according to claim 2 of the present invention is configured such that the rotation amount detection means calculates the rotation speed or the rotation time based on the rotation drive of the rotary tool by the encoder provided in the rotary tool or the drive means. It is characterized by being.

  According to a third aspect of the present invention, there is provided the screw tightening apparatus according to the present invention, wherein the screw tightening reference time setting means supports the rotary tool or a support member that supports the support shaft so as to displace the support shaft in a returnable manner in the axial direction. Alternatively, a displacement detection sensor or a switch mechanism for detecting a pressing displacement in the axial direction of the support shaft is provided, and configured to detect a pressing displacement in the axial direction of the rotary tool and output a screw tightening reference time setting signal. It is characterized by.

  According to a fourth aspect of the present invention, there is provided the screw tightening device according to the present invention, wherein the screw tightening start time setting means is rotated by a drive switch or sensor provided so as to be operated by a switch operating member on the outer surface of the gripping part casing of the screw tightening device. The driving means for rotationally driving the tool is started to output a screw tightening start time setting signal.

  The screw tightening device according to claim 5 of the present invention is the displacement provided by the screw tightening start time setting means with respect to the support member that supports the rotary tool or its support shaft so as to be displaced in the axial direction. A detection displacement of the rotary tool in the axial direction is detected by a detection sensor or a switch mechanism, and a screw tightening reference time setting signal is output, and a driving means for rotationally driving the rotary tool is started to start a screw tightening start time setting signal. It is characterized by being comprised so that it may output.

  The screw tightening device according to claim 6 of the present invention is such that the screw tightening completion time detection means is provided by a torque setting clutch mechanism provided at a shaft coupling portion between the drive shaft of the drive means for rotating the rotary tool and the rotary tool. In the screw tightening operation by the rotary tool, when the load torque reaches a torque set value preset in the clutch mechanism, the clutch is operated to output a screw tightening completion time detection signal. .

In the screw tightening device according to claim 7 of the present invention, the screw tightening completion time detection means detects the load current of the electric motor that rotationally drives the rotary tool, and the screw current is tightened by the rotary tool. When the detected load current of the electric motor reaches a load current value preset in the load current detecting means, a screw tightening completion time detection signal is output.

  According to the screw tightening device of the first aspect of the present invention, the screw tightening operation is performed by rotating the rotary tool such as the driver bit by the driving means such as an electric motor, and the screw for the required screw mounting object is fixed. A screw tightening device configured to detect a load torque generated in the rotary tool upon completion of tightening and stop the rotation drive of the rotary tool when the load torque reaches a preset torque value. When the tip of the screw shaft with the screw head fitted to the tip of the rotary tool is positioned and brought into contact with the screw hole of the screw mounting target, the screw is tightened by pressing the rotary tool in the axial direction. By providing the screw tightening reference time setting means for setting the reference time, after the screw tightening reference time (t1) is set by the screw tightening reference time setting means, The rotation of the rotary tool detected by the rotation amount detection means from the screw tightening start time (t2) for starting the rotary tool drive means to the screw tightening completion time point (t3) detected by the screw tightening completion time detection means. By determining whether the amount is within the allowable range compared with the preset reference value, it is easy and simple to determine whether the screw is tightened or not, and a relatively simple configuration makes it appropriate at low cost. And the screwing apparatus which can be achieved reliably can be provided.

  According to the screw tightening device of the second aspect of the present invention, the rotation amount detection means calculates the rotation speed or the rotation time based on the rotation drive of the rotary tool by the encoder provided in the rotary tool or the drive means. By configuring, it is possible to achieve the above-described determination of whether or not the screw is tightened properly and reliably at a low cost with a relatively simple configuration that is easy and simple.

  According to the screw tightening device of the third aspect of the present invention, the screw tightening reference time setting means is provided for the support member that supports the rotary tool or its support shaft so as to be displaced in the axial direction. By determining a pressing displacement in the axial direction of the rotary tool by a displacement detection sensor or a switch mechanism and outputting a screw tightening reference time setting signal, the above-described determination of screw tightening can be easily and easily performed. It is simple and has a relatively simple configuration, and can be achieved appropriately and reliably at low cost.

  According to the screw tightening device of the fourth aspect of the present invention, the screw tightening start time setting means is provided by a drive switch or a sensor provided so as to be operated by the switch operating member on the outer surface of the gripping part casing of the screw tightening device. By configuring the driving means for rotating the rotary tool to output the screw tightening start time setting signal, the above-described determination of the screw tightening quality can be made easy, simple and relatively simple. Therefore, it can be achieved appropriately and reliably at low cost.

  According to the screw tightening device of the fifth aspect of the present invention, the screw tightening start time setting means is provided for the support member that supports the rotary tool or its support shaft so as to be displaced in the axial direction. The displacement detection sensor or switch mechanism detects a pressing displacement in the axial direction of the rotary tool and outputs a screw tightening reference time setting signal, and also starts a driving means for rotationally driving the rotary tool to start screw tightening. By configuring so as to output the setting signal, the above-described determination of whether or not the screw is tightened can be achieved easily and simply and with a relatively simple configuration, and can be achieved appropriately and reliably at low cost.

  According to the screw tightening device of the sixth aspect of the present invention, the torque setting clutch mechanism in which the screw tightening completion time detection means is provided at the shaft coupling portion between the drive shaft of the drive means for rotating the rotary tool and the rotary tool. Thus, in the screw tightening operation by the rotary tool, when the load torque reaches a torque set value preset in the clutch mechanism, the clutch is operated to output a screw tightening completion time detection signal as described above. The determination of whether or not the screw is tightened can be achieved easily and simply and with a relatively simple configuration, and can be achieved appropriately and reliably at a low cost.

  According to the screw tightening apparatus of the seventh aspect of the present invention, the screw tightening operation by the rotating tool is performed by the load current detecting means for detecting the load current of the electric motor that rotationally drives the rotating tool. The screw tightening completion time detection signal is output when the load current of the electric motor detected in step reaches the load current value set in advance in the load current detecting means. Judgment can be achieved easily and simply and with a relatively simple configuration, and can be achieved appropriately and reliably at low cost.

It is explanatory drawing which shows schematic structure of the electric screwdriver as one Example of the screw fastening apparatus which concerns on this invention, and its control system. It is a wave form diagram which shows the load torque characteristic of the screw fastening process in the electric screwdriver shown in FIG. 1 when performing screw fastening quality determination in the screw fastening apparatus according to the present invention. It is a flowchart figure which shows the screw tightening control program for performing the screw tightening quality determination by the electric screwdriver shown in FIG. It is explanatory drawing which shows schematic structure of the electric screwdriver as another Example of the screw fastening apparatus which concerns on this invention, and its control system.

  Next, embodiments of the screw tightening device according to the present invention will be described in detail below with reference to the accompanying drawings.

  FIG. 1 is an explanatory diagram of a schematic configuration of an electric screwdriver and its control system showing an embodiment of a screw tightening device according to the present invention. That is, in FIG. 1, reference numeral 10 indicates an electric driver configured to be driven by a built-in electric motor 12 such as a brushless motor. In the electric driver 10, a driven shaft that couples and holds a driver bit 14 as a rotary tool is coupled to the output shaft of the electric motor 12 through a speed reduction mechanism as appropriate, and is equal to or greater than a predetermined value set in advance with respect to the driven shaft. There is provided a torque setting clutch mechanism 16 having a cam engaging portion that operates so as to cut off the coupling between the output shaft and the driven shaft when the load torque is applied. The driver bit 14 is held by a support member 18 so that the driver bit 14 is displaced so as to be able to return when a pressing operation is performed in the axial direction at a coupling portion between the output shaft and the driven shaft of the electric motor 12. Further, a switch operating member 22 for operating a drive switch 20 for starting the electric motor 12 or a sensor such as a magnetic sensor is provided on the outer side surface of the grip casing of the electric driver 10 incorporating the electric motor 12. It has been.

  In the electric screwdriver 10 of the present embodiment, the displacement due to the pressing operation of the driver bit 14 in the axial direction is detected with respect to the support member 18 of the driver bit 14, and the operation time point is set as the screw tightening reference time point. As the screw tightening reference time setting means, for example, a displacement detection sensor 24 such as a magnetic sensor composed of a Hall element used in combination with a detection magnet or a switch mechanism such as a limit switch is provided. For the torque setting clutch mechanism 16, as a screw tightening completion time point detecting means for detecting a clutch operation as a screw tightening completion time point, a switch mechanism 26 including a displacement detection sensor or a limit switch or the like, as described above, or magnetic A sensor such as a sensor is provided.

  In the electric motor 12, a drive control circuit 30 for controlling the driving and stopping of the electric motor 12 is connected and arranged, and as a rotation amount detection means for detecting the rotation amount of the driver bit 14 as a rotary tool. Encoder 32 is provided. The drive control circuit 30 and the encoder 32 are provided with a CPU 40 for performing these controls. Reference numeral P indicates a power source for driving the electric motor 12 via the drive control circuit 30.

  That is, the CPU 40 sends the electric motor 12 to the drive control circuit 30 based on the drive switch 20 as a screw tightening start time setting means or a drive switch operation signal S21 as a screw tightening start time setting signal by a sensor. The screw tightening completion time detection signal output from the switch mechanism 26 serving as the screw tightening completion time detecting means provided in the torque setting clutch mechanism 16 is input. The electric motor stop control signal S31b for performing the stop control of the electric motor 12 based on the clutch operation signal S27 is input.

  The CPU 40 receives an encoder output signal S33 as a rotation amount detection signal from the encoder 32 as the rotation amount detection means, and detects displacement as screw tightening reference time setting means provided in the support member 18. Based on the input of the displacement detection signal S25 of the driver bit 14 as the screw tightening reference time setting signal output from the sensor 24 or the switch mechanism, the drive is stopped from the screw tightening start time at which the driving of the electric motor 12 is started. Up to the time of completion of screw tightening, the rotation amount of the driver bit 14 as the rotary tool is calculated. Based on the rotation amount detection value calculated in this way, the screw tightening quality determination means 42 and the alarm display means 44 are used to determine whether the screw tightening state is good and to indicate screw tightening failure. The

  Next, a screw tightening process for determining screw tightening quality by the electric screwdriver 10 according to the present embodiment having the above-described configuration and the contents of the process will be described with reference to FIGS.

  FIG. 2 is a waveform diagram showing the load torque characteristics of the screw tightening process in the electric screwdriver 10 shown in FIG. As shown in FIG. 2, in the electric screwdriver 10 of the present invention, at the time of screw tightening operation, a screw head of a screw to be used is first fitted to the tip of the driver bit 14, and the screw shaft tip of the screw is screwed into the screw. At the time of positioning contact with the screw hole of the attachment object, the driver bit 14 is pressed in the axial direction. By this pressing operation, as described above, the displacement detection sensor 24 or the switch mechanism as the screw tightening reference time setting means provided on the support member 18 of the driver bit 14 is activated, and the displacement detection signal as the screw tightening reference time setting signal. S25 is output, and this screw tightening reference time setting signal S25 is input to the CPU 40 to set the screw tightening reference time (t1).

  After the screw tightening reference time (t1) is set, the drive switch 20 or the sensor switch operating member 22 as the screw tightening start time setting means provided on the outer surface of the grip casing of the electric screwdriver 10 is operated. As described above, the drive switch operation signal S21 as the screw tightening start time setting signal is output by the operation of the drive switch 20 or the sensor, and the drive switch operation signal S21 is input to the CPU 40, so that the electric motor 12 The drive is started to set the screw tightening start time (t2), and the electric motor drive control signal S31a is output to the drive control circuit 30 of the electric motor 12 to control the drive of the electric motor 12.

  As the electric motor 12 is driven, the encoder 32 serving as a rotation amount detecting unit is operated to output a rotation amount detection signal S33 relating to the rotation speed and rotation time of the driver bit 14 for performing screw tightening work. The amount detection signal S33 is input to the CPU 40, and the rotation amount is calculated. After that, when the required screw tightening is performed and the screw tightening torque reaches a preset torque value in the torque setting clutch mechanism 16 provided in the electric screwdriver 10, the screw provided in the torque setting clutch mechanism 16 is used. The switch mechanism 26 or sensor as the tightening completion time detection means is operated to output a clutch operation signal S27 as a screw tightening completion time detection signal. This clutch operation signal S27 is input to the CPU 40 and the screw tightening completion time (t3). ) And an electric motor stop control signal S31b is output to the drive control circuit 30 of the electric motor 12 to stop the electric motor 12.

  Thus, in the present invention, when the electric motor 12 is driven, the rotation amount detection signal S33 of the encoder 32 is set from the set screw tightening start time (t2) to the screw tightening complete time (t3). By calculating the rotation amount based on the above, it is possible to detect an appropriate screw tightening rotation amount. Therefore, in the present invention, the screw tightening reference time (t1) set by the screw tightening reference time setting signal S25 obtained by the displacement detection sensor 24 or the switch mechanism as the screw tightening reference time setting means is the amount of rotation in the CPU 40. In the calculation of the rotation amount based on the rotation amount detection signal S33 obtained by the encoder 32 as the detection means, it can be set as the timing for resetting.

  FIG. 3 is a flowchart showing a screw tightening control program for performing screw tightening quality determination by the electric screwdriver shown in FIG. As described above, in the present invention, the screw head of the screw used at the tip of the driver bit 14 is first fitted, and the tip of the screw shaft is positioned and brought into contact with the screw hole of the screw mounting object. At the time point, by pressing the driver bit 14 in the axial direction (STEP-1), the CPU 40 sets the screw tightening reference time point (t1) (STEP-2). The screw tightening reference point setting signal S25 for setting the screw tightening reference point (t1) functions as a reset signal when calculating the rotation amount based on the rotation amount detection signal S33 obtained by the encoder 32 in the CPU 40 (STEP- 3).

  Next, as described above, the driving of the electric motor 12 is started in the CPU 40 by operating the drive switch 20 or the sensor as the screw tightening start time setting means for starting the driving of the electric screwdriver 10 (STEP-4). Is set, that is, a screw tightening start time t2 is set (STEP-5). Then, the CPU 40 controls the drive of the electric motor 12 by outputting the electric motor drive control signal S31a to the drive control circuit 30 of the electric motor 12 (STEP-6). Along with the drive control of the electric motor 12, the encoder 32 is operated to output the rotation amount detection signal S33 relating to the rotation speed and rotation time of the driver bit 14 that performs the screw tightening operation. An operation is performed (STEP-7).

  Thereafter, as described above, the required screw tightening is performed, and the switch mechanism 26 or sensor serving as the screw tightening completion time detection means provided in the torque setting clutch mechanism 16 provided in the electric driver 10 operates (STEP- 8) The screw tightening completion time t3 is set in the CPU 40 by the clutch operation signal S27 as the screw tightening completion time detection signal (STEP-9). Then, the CPU 40 outputs an electric motor stop control signal S31b to the drive control circuit 30 of the electric motor 12 to perform stop control of the electric motor 12 (STEP-10). With the stop control of the electric motor 12, the operation of the encoder 32 is stopped, and the calculation of the rotation amount in the CPU 40 ends (STEP-11).

  Upon completion of the above-described screw tightening, the CPU 40 rotates the encoder 32 from the set screw tightening start time (t2) to the screw tightening complete time (t3) when driving the electric motor 12, as described above. A rotation amount based on the detection signal S33 is calculated (STEP-12). The rotation amount detection value calculated in this way is compared with a reference value set in advance in the screw tightening quality determination means 42. If the detected value exceeds the allowable range of the reference value, it is determined that the screw tightening is defective. It sets so that it may determine (STEP-13). Then, when it is determined that the screw tightening is defective, the alarm display unit 44 is configured to perform a required alarm display (STEP-14).

  FIG. 4 is an explanatory diagram of a schematic configuration of an electric screwdriver and its control system showing a modified embodiment of the screw tightening device according to the present invention. In the present embodiment, instead of the torque setting clutch mechanism 16 and the switch mechanism 26 or the sensor as the screw tightening completion time detection means provided in the above-described embodiment shown in FIG. Load current detection means for detecting the load current of the electric motor is provided, and compared with a set load current value that is a screw tightening completion torque preset in the CPU 40 based on a load current detection signal S29 detected by the load current detection means. Thus, the screw tightening completion time (t3) is set. Other configurations are the same as those of the embodiment shown in FIG. Therefore, in FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the screw tightening device of the present embodiment configured as described above, only the configuration of the detecting means is different for the setting of the screw tightening completion time (t3). The processing contents are exactly the same as those shown in FIGS. 2 and 3 described above, so refer to the above description.

  As still another embodiment of the screw tightening device according to the present invention, although not shown, in the structure of the screw tightening device of the embodiment shown in FIG. The switch operating member 22 for operating the drive switch 20 as the screw tightening start time setting means provided on the side surface is omitted, and the function as the drive switch 20 is performed when the driver bit 14 is pressed in the axial direction. It is provided in a displacement detection sensor 24 or a switch mechanism as screw tightening reference time setting means provided on the support member 18 of the operating driver bit 14. That is, in this case, the displacement detection sensor 24 or the switch mechanism is configured to have a function as a screw tightening reference time setting means and a function as a drive switch 20 (push operation switch) that is a screw tightening start time setting means. Is done.

  In the screw tightening device of the present embodiment configured as described above, in the screw tightening operation, as described above, the screw head of the screw used at the tip of the driver bit 14 is first fitted, and this screw When the tip end of the screw shaft is positioned and brought into contact with the screw hole of the object to be screwed, the driver bit 14 is pressed in the axial direction. By this pressing operation, first, the displacement detection sensor 24 or the switch mechanism provided on the support member 18 of the driver bit 14 is operated to output a displacement detection signal S25 as a screw tightening reference time setting signal, and this screw tightening reference time setting signal. S25 is input to the CPU 40, and the screw tightening reference time point (t1) is set. At substantially the same time, the displacement detection signal S25 is input to the CPU 40 as a drive switch signal as a drive switch (push operation switch), and the time point when the drive of the electric motor 12 is started, that is, the screw tightening start time point (t2). In addition, the electric motor drive control signal S31a can be output to the drive control circuit 30 of the electric motor 12 to control the drive of the electric motor 12.

  Therefore, according to the screw tightening apparatus of the present embodiment, the screw tightening reference time (t1) and the screw tightening start time (t2) are set almost simultaneously. In this case, regarding the screw tightening process for determining whether or not the screw tightening is performed by the electric screwdriver 10 and the processing content thereof, in the screw tightening control program shown in FIG. The tightening start time (t2) is set (STEP-5), and only the operation of the drive switch (STEP-4) is omitted, and the subsequent control program can be applied as it is.

  Although the preferred embodiments of the present invention have been described above, the screw tightening device of the present invention is not limited to the electric screwdriver of the above-described embodiments, and is also suitable as a screw tightening device including, for example, an air driver or an impact driver. In addition, the present invention can be applied to various other design changes without departing from the spirit of the present invention.

10 Electric Screwdriver 12 Electric Motor 14 Driver Bit (Rotary Tool)
16 Torque setting clutch mechanism 18 Support member 20 Drive switch (screw tightening start time setting means)
22 Switch operation member 24 Displacement detection sensor (screw tightening reference time setting means)
26 Switch mechanism (screw tightening completion time detection means)
30 Drive control circuit 32 Encoder (rotation amount detecting means)
40 CPU
42 Screw tightening quality determination means 44 Alarm display means S21 Drive switch operation signal (screw tightening start time setting signal)
S25 Displacement detection signal (screw tightening reference point setting signal)
S27 Clutch operation signal (screw tightening completion point detection signal)
S29 Load current detection signal (screw tightening completion point detection signal)
S31a Electric motor drive control signal S31b Electric motor stop control signal S33 Encoder output signal (rotation amount detection signal)
P Electric motor drive power source t1 Screw tightening reference time t2 Screw tightening start time t3 Screw tightening completion time

Japanese Patent Laid-Open No. 4-1515837 Japanese Patent No. 2585750 JP-A-7-223132 JP-A-9-183027

Claims (7)

Rotating a rotary tool such as a driver bit by a driving means such as an electric motor to perform screw tightening work, and detecting load torque generated in the rotary tool upon completion of screw tightening on a required screw mounting object, When the load torque reaches a preset torque value, the screw tightening device configured to stop and control the rotation drive of the rotary tool,
A rotation amount detection means provided in the rotary tool or drive means for detecting a rotation amount based on the rotation speed and rotation time associated with the rotation drive of the rotary tool;
When the tip of the screw shaft with the screw head fitted to the tip of the rotary tool is positioned and abutted against the screw hole of the screw mounting target, the screw tightening reference point is determined by pressing the rotary tool in the axial direction. Screw tightening reference time setting means for setting (t1);
A screw tightening start time setting means for setting the screw tightening start time (t2) by starting the drive means of the rotary tool after the screw tightening reference time setting means is set by the screw tightening reference time setting means;
A screw for detecting a screw tightening completion time (t3) when a load torque generated in the rotary tool reaches a preset torque value by rotating a screw positioned and abutting on the screw hole by rotation of the rotary tool. A fastening completion point detection means;
After the screw tightening reference time point (t1) is set by the screw tightening reference time point setting means, from the screw tightening start time point (t2) when the screw tightening start time setting means starts the rotary tool driving means, the screw tightening completion time point is reached. Whether or not the rotation amount of the rotary tool detected by the rotation amount detection means is within an allowable range compared to a preset reference value until the screw tightening completion time (t3) detected by the detection means. A screw tightening device comprising: a screw tightening quality determination unit that determines and determines screw tightening quality.   2. The screw tightening device according to claim 1, wherein the rotation amount detection means is configured to calculate a rotation speed or a rotation time based on the rotation drive of the rotary tool by an encoder provided in the rotary tool or the drive means. .   The screw tightening reference time setting means is arranged in the axial direction of the rotary tool by a displacement detection sensor or a switch mechanism provided on a support member that supports the rotary tool or its support shaft so as to be displaced in the axial direction. The screw tightening device according to claim 1 or 2, wherein a screw displacement reference time setting signal is output by detecting a pressing displacement of the screw tightening device.   The screw tightening start time setting means starts screw tightening by starting drive means for rotationally driving the rotary tool by a drive switch or sensor provided to be operated by a switch operating member on the outer surface of the gripping casing of the screw tightening device. The screw tightening device according to any one of claims 1 to 3, wherein a time setting signal is output.   The screw tightening start time setting means is arranged in the axial direction of the rotary tool by a displacement detection sensor or a switch mechanism provided on a support member for supporting the rotary tool or its support shaft so as to be displaced in the axial direction. A screw tightening reference time setting signal is detected and a screw tightening reference time setting signal is output, and a driving means for rotationally driving the rotary tool is started to output a screw tightening start time setting signal. The screw fastening apparatus in any one of 1 thru | or 3.   The screw tightening completion time point detection means uses a torque setting clutch mechanism provided at the shaft coupling portion between the drive shaft of the drive means for rotating the rotary tool and the rotary tool, so that the load torque in the screw tightening operation by the rotary tool is the clutch. The screw tightening device according to any one of claims 1 to 5, wherein a clutch operation is performed and a screw tightening completion time point detection signal is output when a torque set value preset in the mechanism is reached.   The screw tightening completion time point detection means detects the load current of the electric motor detected in the screw tightening operation with the rotary tool by the load current detection means for detecting the load current of the electric motor that rotationally drives the rotary tool. The screw tightening device according to any one of claims 1 to 5, wherein a screw tightening completion time point detection signal is output when a preset load current value is reached.

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