JP5562153B2 - Screw tightening failure prevention system and screw tightening failure prevention program - Google Patents

Description

  The present invention relates to a screw fastening failure prevention system and a screw fastening failure prevention program for preventing a screw fastening failure.

  In product assembly work, screw tightening work is performed by an operator. The screw tightening work depended largely on the skill and sense of the worker. For this reason, there has been a problem that insufficient strength due to looseness due to screw fastening failure or torque shortage occurs. Therefore, conventionally, the behavior data (tightening torque, tightening angle, etc.) of the electric screwdriver during screw fastening is measured and compared with the behavior data in the normal state to automatically check whether the fastening operation has been completed normally. There is a screw fastening device configured as described above (for example, see Patent Document 1).

JP 2001-162548 A (FIGS. 1 and 2)

  A conventional screw tightening device checks the presence or absence of a fastening failure based on behavior data of an electric driver at the time of screw fastening. However, there are various factors that cause a screw fastening failure, such as a screw selection error and a displacement of a member to be fastened with respect to a workpiece, and it is insufficient to simply check the behavior data of the electric screwdriver. In addition, after detecting the fastening failure, the worker will tighten the screw again, but the conventional screw fastening device does not particularly mention the device operation after the fastening failure is detected, and the screw is tightened again. It seems that it is possible to move to the next screw tightening operation without performing the above. For this reason, from the viewpoint of preventing leakage of defective fasteners to the market, the certainty is lacking.

  The present invention has been made in view of the above points, and comprehensively checks the occurrence of screw tightening failure, and prevents a screw tightening failure prevention system and screw tightening failure prevention that can prevent a poorly tightened product from flowing into the market. The purpose is to provide a program.

A screw tightening failure prevention system according to the present invention includes an electric screwdriver for tightening a screw for fixing a member to be fastened to a workpiece, and torque detection for detecting screw tightening torque and screw tightening axial force by the electric screwdriver. , A rotation angle detector that detects the screw tightening angle of the electric screwdriver, and a screw tightening location as a detection area, and each normal abnormality of a plurality of preset management items that can cause screw tightening failure A plurality of screw tightening point detecting means for detecting data for determination, a plurality of management items based on detection data from the plurality of screw tightening point detecting means , presence / absence of a washer, position of a member to be fastened with respect to a workpiece determining at least one or more of the normal abnormality of rotation of the fastening member against displacement and workpiece, also detection of the torque detector and a rotation angle detector Control means for restricting the operation of the electric screwdriver so that it is not possible to move to the next process until it is determined that the abnormality is resolved based on the data to determine whether the screw fastening state is normal or abnormal .

  The screw tightening failure prevention program according to the present invention is a program for causing a computer to function as control means of the screw tightening failure prevention system.

  According to the present invention, the situation where a screw fastening failure occurs is comprehensively checked, and when an abnormality is detected, the operation of the electric screwdriver is limited so that the next process cannot be performed until the abnormality is resolved. did. For this reason, it is possible to obtain a system and a program that can prevent inconvenience that a defective fastening product flows out to the market.

It is a figure showing the schematic structure which applied the screw tightening failure prevention system concerning one embodiment of this invention to a production line. It is a block diagram which shows the structure of the screwing defect prevention system which concerns on one embodiment of this invention. It is explanatory drawing of the screw length detection by the screw fastening location detection sensor of FIG. It is explanatory drawing of the screw washer presence detection by the screw fastening location detection sensor of FIG. It is a figure which shows an example of a countermeasure table. It is a flowchart which shows the flow of a process in the screw fastening defect prevention system which concerns on one embodiment of this invention.

FIG. 1 is a diagram showing a schematic configuration in which a screw tightening failure prevention system according to an embodiment of the present invention is applied to a production line. FIG. 2 is a block diagram showing a configuration of the screw tightening failure prevention system according to the embodiment of the present invention.
The production line shown in FIG. 1 is a production line in which the work W flowing on the production line is subjected to various operations including a screw tightening operation to produce a product. In this screw tightening operation, the sheet metal 1 (fastened member) is aligned with the workpiece W (fastening member) so that the screw hole of the workpiece W and the through hole of the sheet metal communicate with each other, and the screw is inserted into the communication hole. This is an operation for screwing and fixing the sheet metal 1 to the workpiece W. In this example, it is assumed that an operation is performed in which screw tightening locations 2 provided at four locations per sheet metal are tightened in a predetermined order.

  The screw tightening failure prevention system 10 applied to this production line includes a plurality of screw tightening point detection sensors 11 whose detection regions are screw tightening points. In the example of FIG. 1, an arch through which products on the production line can pass. The gate 12 is installed. The plurality of screw tightening point detection sensors 11 are sensors that detect data for determining normality of each of a plurality of management items in which factors causing screw tightening failure are set in advance. The screw tightening failure prevention system 10 further includes an electric screwdriver 20 for screw tightening, a personal computer 30, and a relay controller 40. The electric driver 20 and the relay controller 40 are connected by a cable 50, and the relay controller 40 and the personal computer 30 are connected by a communication line 51. The plurality of screw tightening point detection sensors 11 are connected to the personal computer 30 by cables 52.

  The electric screwdriver 20 measures the rotation angle of the electric screwdriver 20, the motor 21 for rotationally driving the tip of the screwdriver, the torque detector 22 for detecting the torque and axial force of the screw in a minute unit (1/1000 second level). And a rotation angle detector 23. Since the torque is affected by the screw diameter, the friction coefficient of the screw surface, and the friction coefficient of the seat surface, the axial force is also detected here and used for judgment of abnormality of the management item. The electric screwdriver 20 periodically transmits the behavior data regarding the screw tightening detected by each of these detectors to the personal computer 30 via the relay controller 40 during the screw tightening period.

  The plurality of screw tightening position detection sensors 11 are a screw length detection sensor for detecting the length of a screw set (unfastened state) at the screw tightening position, and a washer presence / absence detection sensor for detecting the presence / absence of a screw washer. A sheet metal displacement detection sensor for detecting displacement of the sheet metal with respect to the product body, an order detection sensor for detecting the tightening order, and a sheet metal slip detection sensor for detecting slippage of the sheet metal with respect to the product body. Detection data detected by each screw tightening location detection sensor 11 is transmitted to the personal computer 30 via the cable 52. Each of these sensors may be a separate sensor, or may be a sensor that detects several collectively. Further, the specific configuration of each sensor is not particularly limited, and any sensor that can detect the detection target may be used. The sensor for detecting the length of the screw is specifically constituted by an imaging means such as a CCD camera, for example, and as shown in FIG. 3, the image is taken from a direction orthogonal to the shaft portion of the screw 3 and the image is taken by the personal computer 30. It is possible to detect the screw length by processing on the side. Similarly, as shown in FIG. 4, the washer presence / absence detection sensor is constituted by photographing means such as a CCD camera, and is photographed from a direction orthogonal to the shaft portion of the screw 3, and the image is processed on the personal computer 30 side to provide a washer. The presence or absence of 4 can be detected.

  The personal computer 30 controls the entire screw tightening prevention system 10 and also functions as a data processing device that processes detection data from the screw tightening point detection sensor 11 and behavior data from the electric driver 20. As shown in FIG. 2, the personal computer 30 includes an input unit 31 such as a keyboard and a mouse, a display unit 32 such as a display, a storage unit 33 that stores various programs and data, and a plurality of screw tightening point detection sensors 11. And a communication interface unit 34 for performing data communication with the electric screwdriver 20 and a control unit 35 for controlling the entire screw tightening prevention system 10.

  The storage unit 33 stores a screw tightening failure prevention program, a work instruction, a countermeasure table, and the like. The screw tightening failure prevention program is a program that performs a fastening part abnormality detection process, a fastening state abnormality detection process, and an abnormality handling process. The fastening part abnormality detection process is a process of determining the normal abnormality of each of the plurality of management items set in advance based on the detection data of the plurality of screw fastening part detection sensors 11. The abnormality detection process is a process of calculating later-described profile data based on behavior data of the electric screwdriver 20 during the screw tightening period, and determining whether the screw tightening is normally completed based on the profile data. A conventionally existing algorithm can be adopted for the abnormality detection process.

  The profile data includes tightening time, final fastening time, tightening torque inclination, screw tightening angle, and axial force at the time of screw tightening. The fastening time is the time from the start of fastening to the completion of fastening. The completion of tightening is determined to be complete when the target torque set in advance is reached. The final fastening time is the time from when the seat is reached (the seat surface of the screw head is in contact with the surface of the sheet metal 1) until the target torque is reached. The tightening torque inclination is (torque at completion of tightening−torque at seating) / final fastening time. The screw tightening angle is a tightening rotation angle from when the user is seated until the target torque is reached.

  The abnormality handling process is a process of executing a countermeasure according to the countermeasure table 36 stored in the storage unit 33 when it is determined that there is an abnormality by the fastening part abnormality detection process and the fastening state abnormality detection process. This countermeasure performs, for example, limiting the operation of the electric screwdriver 20 so that the process cannot proceed to the next process until the abnormality is resolved. This countermeasure is preset for each abnormality detection item including the plurality of management items, and the setting contents are stored in a countermeasure table shown in FIG. The work instruction sheet describes the type of screw used for the product to be produced, the tightening order of the screw, and the like. In the countermeasure table, countermeasures are registered when an abnormality is detected by the fastening part abnormality detection process and the fastening state abnormality detection process.

FIG. 5 is a diagram illustrating an example of a countermeasure table. In this example, the first table 36a in which a plurality of abnormality detection items are registered and the second table 36b in which the details of a plurality of specific countermeasures are registered are associated by countermeasure names A to D, and the countermeasure table. 36 is configured.
Anomaly detection items include: 1. Screw type (screw length) 2. Screw type (with or without screw seat) 3. Non-tightening (sheet metal misalignment); 4. Non-tightening (tightening order) There are five management items for rotation (sheet metal sliding) of the fastened member (sheet metal). In addition, as a countermeasure at the time of abnormality detection based on behavior data from the electric driver 20, 6. The item of screw tightening failure is also registered in the countermeasure table 36 as an abnormality detection item.

  Countermeasure A does not proceed to the next step until the abnormality is resolved. Specifically, operation restriction is applied to the electric screwdriver 20. For the ○ part of the countermeasure A, the electric screwdriver 20 is interlocked so that the electric driver 20 does not move, and for the triangle of the countermeasure A, the electric driver 20 can be operated with respect to re-tightening of the abnormal part. For other operations, the electric screwdriver 20 is interlocked so as not to move. Countermeasure B displays a work instruction on the display unit 32 and warns the operator that there is a screw tightening failure. Countermeasure C performs a warning display on the display unit 32 for prompting confirmation of the current state (for example, confirmation of used screws). In addition, when the production line is provided with a red, yellow, and green three-color lamp called a patrol light, the patrol light is lit in yellow. Countermeasure D performs a warning display on the display unit 32 to notify that a screw tightening failure has occurred. In addition, when the production line is provided with a red, yellow, and green three-color lamp called a patrol light, the patrol light is lit in red.

  The control unit 35 acquires detection data from the plurality of screw tightening point detection sensors 11 via the communication interface unit 34 and periodically receives behavior data from the electric driver 20. And the control part 35 performs a fastening location abnormality detection process and a fastening state abnormality detection process according to the screw tightening failure prevention program memorize | stored in the memory | storage part 33. A countermeasure according to the stored countermeasure table 36 is executed.

FIG. 6 is a flowchart showing a flow of processing in the screw tightening failure prevention system according to the embodiment of the present invention. Hereinafter, the control operation in the screw tightening failure prevention system will be described with reference to FIG.
First, the operator operates the personal computer 30 to read a work instruction sheet and display it on the display unit 32 before the screw tightening operation is started. Further, initial setting is performed by operating the personal computer 30 (S1). Initially set data includes the type of screw (screw length, presence / absence of screw washer) instructed in the work instruction, the number of screw tightening locations, the screw tightening order, and the like. When the operation of the production line is started, each of the plurality of screw tightening point detection sensors 11 starts sensing and sequentially outputs detection data to the personal computer 30. In addition, when screw tightening by the electric screwdriver 20 is started, behavior data is periodically transmitted from the electric screwdriver 20 to the personal computer 30.

  When the control unit 35 of the personal computer 30 receives the detection data from the plurality of screw tightening point detection sensors 11 and the behavior data from the electric screwdriver 20 (S2), the control unit 35 determines whether there is an abnormality based on the received data (S3). And when it determines with it being abnormal, in addition to restricting operation to the electric screwdriver 20, countermeasures for each item are taken (S4). When the abnormality is resolved (S5), the operation restriction of the electric screwdriver 20 is released (S6), and the process returns to step S2. Hereinafter, each abnormality detection item will be specifically described in order.

1. Thread type (screw length)
The control unit 35 compares the screw length from the screw length detection sensor with the screw length set in the initial setting. When an error in the screw length is detected, it is determined that there is an abnormality, and countermeasures A to D are performed. If the screw length detected by the screw length detection sensor is longer than the initial setting, there is a possibility that the wiring or piping arranged on the back side of the screw hole of the workpiece W may be damaged by being struck. For this reason, by detecting the length of the screw as a management item, it is possible to prevent a product with damaged wiring or piping from leaking to the market.

2. Screw type (with or without screw seat)
The control unit 35 compares the detection data from the washer presence / absence detection sensor with the set content of the washer presence / absence set in the initial setting, and if the detection data from the washer presence / absence detection sensor is different from the initial setting, an abnormality is detected. And measures A, B, and D are implemented. Usually, the presence / absence of a screw seat is selected according to the product specifications and the application of the screw. Therefore, by detecting the presence / absence of a screw seat, it is possible to prevent a product that has been misused from a washer from leaking into the market.

3. Non-tightening (displacement of sheet metal)
The control unit 35 detects whether or not there is a deviation between the screw hole of the workpiece W and the through hole of the sheet metal 1 by a sheet metal deviation detection sensor before fastening the screw. A, B, and D are performed. If an attempt is made to fasten a screw while the sheet metal 1 is displaced, there is a possibility that the fastening will be oblique and insufficient fastening will occur. Therefore, by detecting the displacement of the sheet metal 1, it is possible to prevent a product having a screw tightening portion that is insufficiently tightened from flowing out to the market.

4). Non-tightening (tightening order)
The control unit 35 detects the screw tightening order for the four screw tightening points of the sheet metal 1 by the order detection sensor, and if it detects that the tightening order is different from the initial setting, it determines that it is abnormal and responds. Measures A to C are performed. If the fastening order is wrong, the through hole of the sheet metal 1 and the screw hole of the workpiece W may be misaligned, and there is a possibility that screw tightening cannot be performed. Therefore, this inconvenience can be prevented by detecting the tightening order.

5. When the sheet metal slip detection sensor detects the slip of the sheet metal 1 with respect to the workpiece W, the rotation control unit 35 of the fastened member determines that it is abnormal and performs countermeasures A and D. As a result, it is possible to prevent the screw metal from being broken due to the slid metal plate 1 so that the screw thread is broken and the fastening is impossible.

6). The screw tightening failure control unit 35 appropriately calculates profile data for determining the presence or absence of screw tightening failure based on the behavior data from the electric screwdriver 20, compares the profile with the profile in the normal state, and determines screw tightening failure. To detect. When a screw tightening failure is detected, it is determined that there is an abnormality and countermeasures A and D are performed. Thereby, it can prevent beforehand that the product in which a fastening defect location exists flows out to a market. The countermeasure A in this case is slightly different from the above, and the electric screwdriver 20 can be operated with respect to re-screwing of the abnormal portion, and the electric screwdriver 20 is interlocked with the electric screwdriver 20 for other operations. Shall not work.

  Here, the operation restriction release of the electric screwdriver 20 will be described. For example, if there is an incorrect screw length, the operator selects the correct screw and tries to tighten it again. At this time, the screw length detection sensor among the screw tightening location detection sensors 11 outputs detection data in a state where a correct screw is selected to the control unit 35, and the control unit 35 detects from the screw length detection sensor. Based on the data, the screw length is determined to be normal here. Then, the control unit 35 determines that the screw length abnormality has been eliminated and releases the interlock of the electric screwdriver 20. In addition, for example, when it is determined that there is a screw tightening abnormality based on behavior data from the electric screwdriver 20, the control unit 35 interlocks the electric screwdriver 20 so as not to move. However, when it is determined that re-screw tightening to the abnormal location based on the detection data from the screw tightening location detection sensor (for example, the order detection sensor) 11, the interlock is released and the electric screwdriver 20 is operated with limitations. Make it possible. The torque detector 22 and the rotation angle detector 23 output detection data to the control unit 35 while the electric screwdriver 20 re-screws the abnormal part, and the control unit 35 receives the received detection data. If it is determined that the re-screw tightening is normally completed based on the above, the interlock of the electric screwdriver 20 is completely released, and the next work can be performed.

  As described above, in this embodiment, the situation where a screw fastening failure occurs is comprehensively checked, and when an abnormality is detected, the electric screwdriver is set so that the next process cannot be performed until the abnormality is resolved. 20 operations were restricted. For this reason, it is possible to obtain a system and a program that can prevent inconvenience that a defective fastening product flows out to the market.

  Further, as an operation restriction of the electric driver 20 when an abnormality is detected, specifically, in the case of detecting an abnormality based on each detection data from the screw tightening point detection sensor 11, the electric driver 20 is interlocked and the electric driver 20 20 was completely stopped. In addition, in the case of detecting an abnormality based on the behavior data of the electric screwdriver 20, the electric screwdriver 20 can be operated with respect to re-tightening of the abnormal portion, and otherwise the electric screwdriver 20 is prevented from moving. As described above, the operator can be surely aware of the occurrence of an abnormality by stopping the electric screwdriver 20 from the viewpoint of the operator, and as a result, normal screw tightening can be completed.

  Further, in this example, screw length difference, presence / absence of a screw washer, displacement of the sheet metal 1 with respect to the workpiece W, fastening sequence, and rotation of the sheet metal 1 with respect to the workpiece W are set as factors that cause screw fastening failure. Therefore, the screw tightening failure prevention system 10 can determine whether each of these management items is normal or abnormal. However, the screw tightening failure prevention system 10 is not limited to determining whether each of the management items is normal or abnormal, and may be configured to be able to determine at least one or more of the management items. Management items are not limited to the above five items.

  DESCRIPTION OF SYMBOLS 1 Sheet metal, 10 Screw fastening defect prevention system, 11 Screw fastening location detection sensor, 12 Gate, 20 Electric screwdriver, 21 Motor, 22 Torque detector, 23 Rotation angle detector, 30 PC, 31 Input part, 32 Display part, 33 Storage unit, 34 communication interface unit, 35 control unit, 40 relay controller, 50 cable, 51 communication line, 52 cable, W work.

Claims (5)

An electric screwdriver that tightens the screw to fix the member to be fastened to the workpiece;
A torque detector for detecting a screw tightening torque and a screw tightening axial force by the electric screwdriver;
A rotation angle detector for detecting a screwing angle of the electric screwdriver;
A plurality of screw tightening point detecting means for detecting data for determining normality of each of a plurality of preset management items, which are arranged as a detection region, and may cause a screw tightening failure,
Normality of at least one or more of the plurality of management items , the presence / absence of a washer, the displacement of the member to be fastened with respect to the work, and the rotation of the member to be fastened with respect to the work , based on the detection data from the plurality of screw tightening point detecting means Judgment of abnormality, and determination of normal abnormality of the screw fastening state based on the detection data of the torque detector and the rotation angle detector, and if it is judged abnormal, proceed to the next process until the abnormality is resolved A screw tightening prevention system comprising control means for restricting the operation of the electric screwdriver so that the operation cannot be performed.   The control means determines normality / abnormality of each of the plurality of management items based on the detection data from the plurality of screw tightening point detection means. Applying an interlock to control the electric screwdriver so that it does not move, and determining whether the screw fastening state is normal or abnormal based on the detection data of the torque detector and the rotation angle detector. 2. The screw tightening failure prevention system according to claim 1, wherein control is performed to interlock the electric screwdriver so that the electric screwdriver operation other than re-screwing of the abnormal portion cannot be performed until the abnormality is resolved. An electric screwdriver that tightens the screw to fix the member to be fastened to the workpiece;
A torque detector for detecting a screw tightening torque and a screw tightening axial force by the electric screwdriver;
A rotation angle detector for detecting a screwing angle of the electric screwdriver;
A plurality of screw tightening point detecting means for detecting data for determining normality of each of a plurality of preset management items, which are arranged as a detection region, and may cause a screw tightening failure,
Normality / abnormality of each of the plurality of management items is determined based on the detection data from the plurality of screw tightening point detection means, and the screw tightening state is determined based on the detection data of the torque detector and the rotation angle detector. determine normal or abnormal, and when it is determined that abnormality, Bei example and control means for restricting the operation of the abnormality is the electric screwdriver to so as not to shift to the next step is eliminated,
The control means determines normality / abnormality of each of the plurality of management items based on the detection data from the plurality of screw tightening point detection means. Applying an interlock to control the electric screwdriver so that it does not move, and determining whether the screw fastening state is normal or abnormal based on the detection data of the torque detector and the rotation angle detector. A screw tightening failure prevention system that performs control to interlock the electric screwdriver so that the electric screwdriver operation other than re-screwing of the abnormal portion cannot be performed until the abnormality is resolved . The screw tightening position detecting means detects data capable of determining at least one of a screw length, presence / absence of a screw washer, positional displacement of a member to be fastened with respect to a work, fastening order, and rotation of a member to be fastened with respect to the work. The screw tightening failure prevention system according to claim 3 . A screw tightening failure prevention program for causing a computer to function as the control means of the screw tightening failure prevention system according to any one of claims 1 to 4 .

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