JPH0556327U - Automatic screw tightener - Google Patents

Abstract

(57) [Summary] [Purpose] The bolts are automatically installed in the screw holes of the work,
The screw tightened state can be detected if there is a small space near the screw hole. A driver bit is driven by a motor, and an elongated rod-shaped contact member is provided in the vicinity of the driver bit along the axis of the driver bit. The contact member adjusts the axial length of the moving body. It is mounted so that it can optically detect the relative displacement between the moving body and the driver bit.
This makes it possible to detect the quality of the screw tightened state.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to an automatic screw tightener that automatically attaches screws such as screws and bolts to electronic devices.

[0002]

[Prior Art]

 BACKGROUND ART Conventionally, automatic screw tighteners that automatically attach screws to electronic devices have been known. The operator visually confirms whether or not the screw is securely tightened using this automatic screw tightener. Alternatively, the position of the screw head is detected by a microswitch or an optical detection element, and it is confirmed that the screw does not float.

[0003]

[Problems to be solved by the device]

 In this way, in the past, the operator has confirmed whether or not the screw is attached, and whether the screw is in a floating state due to insufficient tightening, but the operator can surely find it visually. It is difficult to detect, but even if the screw lift can be detected, it is impossible to find an abnormal state without a screw and the defective semi-finished product undergoes a post process. There is.

In order to solve this problem, the applicant of the present application has already proposed an automatic screw fastening machine as Japanese Patent Application No. 2-103119. In this technology, a driver bit, which is rotationally driven by a rotational driving means such as a motor, is displaceable in the guide tube in the axial direction relative to the guide tube, and a bolt is attached to the end of the guide tube. It is configured to contact the surface of the workpiece to be mounted, detect the relative displacement between the driver bit and the guide tube, and detect the screw tightening state.The outer peripheral surface of the driver bit and the inner peripheral surface of the guide tube. A vacuum pump is connected between and to vacuum-adhere the bolt head to the tip of the driver bit.

A new problem with such a configuration is that the guide tube through which the driver bit is inserted is relatively large, and therefore, in the vicinity of the screw hole where the bolt is to be mounted, the end of the guide tube is on the surface of the workpiece. This means that the work requires a large space in the vicinity of the screw hole in order to make sure that the work can be abutted against, and therefore the work that can be automatically screwed is limited.

[0006] An object of the present invention is to provide an automatic screw tightener capable of surely detecting an abnormal state of screw tightening and not requiring a large space around the bolt.

[0007]

[Means for Solving the Problems]

 The present invention includes a driver bit that engages with an engaging groove formed in a bolt head, a rotation driving means that drives the driver bit to rotate about its axis, and a rod-shaped member that is formed in the vicinity of the driver bit so that the driver bit is aligned with the axis of the driver bit. Along the axis of the abutment member, which is slenderly extended along the abutment member, is displaceable relative to the driver bit, and abuts the surface of the workpiece on which the bolt is mounted, and the end of the abutment member opposite to the workpiece. An automatic screw tightening machine comprising: a moving body whose length is adjustable and a detecting means for detecting a relative displacement between the moving body and a driver bit to detect a screw tightening state. ..

The present invention is also characterized in that the driver bit is magnetized so that the bolt can be magnetically attracted.

[0009]

[Action]

 According to the present invention, a rod-shaped contact member is provided in the vicinity of the driver bit that is rotationally driven around the axis by the rotational driving means so as to be displaceable relative to the driver bit along the axis of the driver bit. The abutting member and the moving body are mounted so that their axial lengths can be adjusted and set, and the screw tightening state corresponding to the relative displacement amount of the moving body and the driver bit is detected by the detection means. To detect. As a result, when the bolt is properly tightened on the work surface, the back surface of the bolt head is in contact with the work surface, and therefore the driver bit is set at the height of the bolt head and the engaging groove. It is located away from the surface of the work by the difference from the depth. When the back surface of the head of the bolt is separated from the surface of the work and the so-called bolt is in a floating state, the driver bit is located a relatively large distance from the surface of the work, and When there is no, the driver bit abuts the surface of the work. Therefore, by detecting the relative displacement between the abutment member and the moving body and the driver bit, the screw tightening condition is normal, the bolt is floating, or the bolt is not present. It is possible to detect if there is.

Further, according to the present invention, since the abutting member and the moving body can adjust and set the axial length, the axial length can be adjusted and set according to the size of the bolt head. It is possible to prevent false detection.

Furthermore, in adsorbing the bolt to the driver bit, the driver bit is magnetized to form a permanent magnet. Note that vacuum suction may be used to suck the bolt to the driver bit.

[0012]

【Example】

 FIG. 1 is a partial sectional view of an embodiment of the present invention. A bolt 40 is screwed to the work 1 with a driver bit 33. The bolt 40 is screwed in such a state that the free end portion 134a of the contact member 134 is in contact with the surface of the work 1. This corresponds to the relative amount of displacement of the member 134 and the driver bit 33 in the upper and lower axial directions in FIG. The contact member 134 is rod-shaped, and extends in the vicinity of the driver bit 33 along the axis of the driver bit 33. The driver bit 33 is made of a ferromagnetic material such as iron and is magnetized into a permanent magnet. The bolt 40 is made of a ferromagnetic material such as iron, is magnetically attracted to the driver bit 33, and the end of the driver bit 33 is engaged with the engaging groove formed on the head of the bolt 40.

The base end portion 135 of the contact member 134 has a right cylindrical shape, and the base end portion 135 is loosely fitted into the mounting recess 137 of the mounting member 136. A mounting bolt 138 is screwed onto the mounting member 136, and the outer peripheral surface of the base end portion 135 of the contact member 134 is pressed inward in the radial direction, whereby the contact member 134 and the mounting member 136 are fixed. It In this way, the contact member 134 can be adjusted by angular displacement about the axis 33b of the driver bit 33. Therefore, the free end portion 134a of the contact member 134 can be brought into contact with the surface of the work 1 at a desired position around the axis 33b in the vicinity of the bolt 40.

An external thread 139 is formed on the mounting member 136, and the external thread 139 is screwed onto the internal thread 140 of the guide tube 34, whereby the end of the abutting member 134 on the side opposite to the work 1 has an axial length. Can be adjusted and set. The lock nut 141 is screwed onto the outer screw 139 of the mounting member 136 and abuts on the end of the guide cylinder 34. The mounting member 136 and the guide tube 34 form a moving body 142 that is displaced relative to the driver bit 33.

FIG. 2 is a perspective view of an embodiment of the present invention. The work 1 to be screwed is positioned and mounted on the mounting table 2 and can be reciprocally displaced in the Y direction on the base 3. A pair of columns 4 are erected on the base 3, and the upper portions of the columns 4 are connected by a beam 5 to form a portal structure as a whole, along which the screw tightening means 6 is provided. It can be reciprocally displaced in the X direction, and the screw tightening means 6 can be displaced up and down in the vertical Z direction.

A screw feeder 7 is provided on the base 3 to sequentially feed screws such as screws and bolts mounted on the work 1 one by one. The screw tightening means 6 moves in the X direction and the Z direction to take out one screw from the screw feeder 7, attach the screw to the work 1 on the mounting table 2 moving in the Y direction, and tighten the screw. To do. By repeating such a screw tightening operation, the screw tightening operation is performed at each of a plurality of screw tightening positions on the work 1. The base 3 is provided with operation input means 8 to control the operation.

FIG. 3 is a simplified plan view of the base 3, and FIG. 4 is a sectional view taken along the section line IV-IV of FIG. The mounting table 2 is movable in the Y direction along a rail 9 provided on the base 3. The mounting table 2 is fixed to one stretched portion 10 a of an endless belt 10. The belt 10 is wound around a pair of pulleys 11 and 12, and one of the pulleys 11 is driven to rotate forward and backward by a motor 13 such as a pulse motor. As a result, the mounting table 2 can be reciprocally displaced in the Y direction as described above. Legs 14 are attached to the bottom 15 of the base 3.

An endless belt 17 is wound around pulleys 18 and 19 so that the screw tightening means 6 can be reciprocally displaced in the X direction, and one pulley 18 is driven by a motor 20 to rotate in the forward and reverse directions. .. Such a configuration is similar to the configuration for reciprocally displacing the mounting table 2 in the Y direction. In this way, the screw tightening means 6 is displaced in the X direction, the mounting table 2 is displaced in the Y direction, and the above-mentioned screw tightening means 6 is displaced in the Z direction. The screw tightening operation can be selectively performed at a plurality of positions on the work 1.

FIG. 5 is a front view of the screw tightening means 6, FIG. 6 is a left side view of the screw tightening means 6, and FIG. 7 is a sectional view of the screw tightening means 6 as viewed from the right side. With reference to these drawings, the first attachment member 22 is fixed to the endless belt 17 for moving the screw tightening means 6 in the X direction via the first fixing member 101. The first mounting member 22 has a flat plate shape having a rectangular surface perpendicular to the Y direction, and has long sides parallel to the Z direction and short sides parallel to the X direction. A double-acting pneumatic cylinder 25 is fixed by a mounting bolt 102 via a mounting piece 26 to the surface of the first mounting member 22, which is the rear surface facing the belt 17. Linear bearings 103 are fixed to the surface of the first mounting member 22 at the four corners of the first mounting member 22 by fixing bolts 104 so that the axes thereof are vertically aligned with each other in the Z direction.

The piston rod 27 of the double-acting pneumatic cylinder 25 extends upward in the Z direction, and its tip is fixed to the connecting member 105 by a fixing nut 106. A pair of guide rods 107 having female threads formed on both ends are fixed by fixing bolts 108 near both ends in the X direction of the connecting member 105 so as to extend downward in the Z direction. The guide rod 107 inserts two linear bearings 103 so as to be displaceable in the Z direction. The lower end of the guide rod 107 is fixed to the second mounting member 23 by a fixing bolt 109. Therefore, when the piston rod 27 of the double-acting pneumatic cylinder 25 is vertically expanded and contracted, the second mounting member 23 is vertically displaced in the Z direction.

The bush 110 is attached to the second attachment member 23 from the lower surface side in the Z direction. The bush 110 has a flange portion 110a and an upright portion 110b. A cylindrical support member 111 is attached to the upper surface of the second attachment member 23 so as to sandwich the second attachment member 23 between the flange 110a of the bush 110 and the lower end thereof. At the upper end of the support member 111, a forward / reverse rotatable stepping motor 30 for tightening a screw, which is a driving means, is attached. The rotational output of the motor 30 is transmitted to the output shaft 32 via the clutch 112. A driver bit 33 is attached to the output shaft 32 via an adapter 113. A guide tube 34 is provided on the outer peripheral side of the driver bit 33 and the adapter 113. A gap is provided between the inner peripheral surface of the guide cylinder 34 and the outer peripheral surfaces of the driver bit 33 and the adapter 113 so as to be mutually displaceable in the Z 2 direction. The guide cylinder 34 is inserted through the inner peripheral surface of the upright portion 110b of the bush 110 so as to be displaceable in the Z direction. A coil-shaped compression spring 36 is interposed between the upper surface of the guide cylinder 34 and the lower surface of the clutch 112, whereby the guide cylinder 34 is constantly urged downward.

FIG. 8 is a cross-sectional view for explaining a configuration related to the guide cylinder 34. The guide cylinder 34 is connected to the large diameter portion 34b formed at the upper end portion of the guide cylinder 34, and is inscribed in the inner peripheral surface of the upright portion 110b of the bush 110 and has the adapter 113 inside. It has the 2nd right cylindrical part 34c accommodated so that displacement is possible in the Z direction. The lower end of the large-diameter portion 34b is in contact with the upper end of the upright portion 110b by the downward bias of the spring 36 described above. The detection piece 87 is fixed to the large diameter portion 34b by a set screw 114. The relative position between the detection piece 87 and the optical path 88a is detected by detecting whether or not the detection piece 87 cuts across the optical path 88a described later with reference to FIG.

A space 115 is provided inside the large diameter portion 34b. The space 115 communicates with the vacuum pump 43 via the pipe joint 41 and the flexible pipe 42. When the vacuum pump 43 sucks air, the air inside the guide cylinder 34 is exhausted, and the tip 33a of the driver bit 33 inside the guide cylinder 34 holds the bolt in a state of engaging with the engaging groove of the head of the bolt 40. be able to. As another embodiment of the present invention, the vacuum pump 43 and the structure related thereto may be omitted, and the bolt 40 may only be attracted by the magnetic attraction force of the driver bit 33. When the vacuum suction is performed as described above, the right cylindrical base end portion 135 of the contact member 134 is configured to extend downward in FIG. 8 to a position in the vicinity of the bolt 40, and thus, the bolt 40. Improve the vacuum suction power of.

Referring again to FIG. 7, a slender insertion hole 116 extending vertically in the Z direction is provided on the surface side of the support member 111 in the X direction, and the detection piece 87 fixed to the guide tube 34 is inserted therethrough. .. On the front surface of the insertion hole 116, a mounting plate 117 shown in FIGS. 5 and 6 is fixed to the second mounting member 23 with a fixing screw 118. The mounting plate 117 has a vertically extending elongated insertion hole 119 at a position corresponding to the insertion hole 116 of the support member 111. The detection piece 87 can be inserted through the insertion holes 116 and 119 and protrude onto the surface of the attachment plate 117 even when the guide tube 34 is displaced relative to the second attachment member 23 in the vertical direction. .. The detection element 88 is attached to the surface of the attachment plate 117 with attachment screws 91. In this way, the base body composed of the second mounting member 23, the bush 110, the support member 111, and the like is vertically displaced in the Z direction, which is the axial direction thereof, integrally with the driver bit 33 by the double-acting pneumatic cylinder 25. The relative position of the detection piece 87 and the detection element 88 corresponds to the relative position of the driver bit 33 and the guide tube 34 in the Z direction. Therefore, the detection piece 87 and the detection element 88 constitute displacement detection means.

FIG. 9 is a bottom view of the vicinity of the contact member 134 as seen from below in FIG. It is clearly shown that the abutment member 134 extends in the shape of a rod in the vicinity of the driver bit 33.

FIG. 10 is a cross-sectional view showing a simplified view of the state when the bolt 40 is screwed onto the work 1 as viewed from the front side, and FIG. 11 is the positional relationship between the detection element 88 and the detection piece 87. It is a figure for explaining. FIG. 10 (1) shows a normal state in which the screwing of the bolt 40 to the work 1 is completed and the back surface of the head of the bolt 40 is in contact with the front surface of the work 1. At this time, as shown in FIG. 11A, the detection element 88 is attached to the mounting plate 117 so that the light path 88a from the light emitting element 89 of the detection element 88 to the light receiving element 90 is shielded by the detection piece 87. ing.

FIG. 10 (2) shows that the head of the bolt 40 is not tightened even if it is determined that the screw tightening is completed due to the change in the torque of the motor 30 that rotationally drives the driver bit 33 due to the bending of the bolt 40. Indicates the state where the screw floats above the surface of work 1. At this time, as shown in FIG. 11B, the detection piece 87 does not block the optical path 88a.

In FIG. 10 (3), the screw 40 is tightened even though the bolt 40 does not exist, and the torque is generated by the frictional force between the tip 33 a of the driver bit 33 and the screw hole 120 provided in the work 1. , Shows a state in which it is determined that the screw tightening has been performed. Also at this time, as shown in FIG. 11C, the detection piece 87 is located above the optical path 88a, so that the optical path 88a is not shielded.

As described above, the optical path 88 a is shielded by the detection piece 87 in a normally screwed state, that is, the first state, and the screw float and the bolt 40 are not present. It is possible to determine an abnormal state in which the light is not shielded by the detection piece 87, that is, the second state. The accuracy of this determination can be changed by changing the projected area of the detection piece 87 with respect to the optical path 88a. That is, if the projected area is reduced by using the thin detection piece 87, the range determined as the first state can be narrowed.

FIG. 12 is a block diagram showing the electrical configuration of the embodiment shown in FIGS. Outputs from a screw tightening position setting switch 79 provided in the operation input device 8 and a switch 69 operated for an emergency stop are given to a processing circuit 66 realized by a microcomputer or the like. The mounting table 2 is provided with work detecting means 70 for detecting whether or not the work 1 exists. A lamp 71 is provided to visually display the alarm. As will be described later, the lamp 71 has become a so-called screw idiot, in which a screw floating state is detected or the bolt 40 cannot be tightened on the work 1 with a torque exceeding a predetermined torque. Lights up when detected. This unfastened state is detected by the detection means 73.

Compressed air is supplied by a solenoid valve 74 to the double-acting pneumatic cylinder 25 for driving the screw tightening means 6 in the Z direction. A timer 78 is provided to define the screw tightening operation time. The timer 78 is started by the processing circuit 66 and notifies the processing circuit 66 of the passage of time.

With reference to FIG. 13, the operation of the processing circuit 66 for determining whether the screw tightening is normal or abnormal will be described. In step n1, the screw tightening operation is started. The screw tightening means 6 moves to the screw feeder 7, and the bolt 40 is attached to the driver bit 33 in the guide tube 34. The screw tightening means 6 is moved until the driver bit 33 reaches the screw tightening position of the work 1. By the action of the double-acting pneumatic cylinder 25, the driver bit 33 is lowered, and the guide cylinder 34 comes into contact with the surface of the work 1. The bolt 40, which is magnetically attracted or vacuum attracted, is pressed into the screw hole 120 of the work 1 by the air pressure of the double-acting pneumatic cylinder 25 and fits therein. In this state, the driver bit 33 is rotationally driven by the motor 30. At this time, if the screw cannot be tightened, it is detected by the detecting means 73. The load current detecting means 77 detects the load current of the motor 30 that drives the bolt 40.

When the screw tightening failure is not detected, the processing circuit 66 starts the operation of the timer 78 in step n2. In step n3, it is determined whether or not a predetermined time sufficient to perform the screwing operation of the bolt 40 to the work 1 has elapsed. When this specified time has not elapsed, the process returns to step n3. When the specified time has elapsed, the process moves to step n4. At step n4, it is judged whether the torque of the motor 30 is large. When the bolt 40 is normally screwed to the work 1 and fully tightened while the driver bit 33 is rotationally driven by the motor 30, the torque for rotating the bolt 40 increases. At this time, the load current of the motor 30 increases and the load torque of the motor 30 increases. By detecting the load current of the motor 30 by the detection means 77 and discriminating the level, it is possible to determine whether or not the load torque has increased. When the bolt 40 is sufficiently screwed to complete the mounting, the torque-up signal is derived from the load current detecting means 77, which is a torque detecting means, and given to the processing circuit 66.

A means for idling the motor 30 when the load torque exceeds a predetermined value, and a protection means such as a means for interrupting the current when the load current of the motor 30 exceeds a predetermined value. It may be used and the operation may be detected. Further, the above-mentioned detection means 73 may be realized by the load current detection means 77 detecting that the load current of the motor 30 does not increase even if the specified time of the timer 78 has elapsed.

When the processing circuit 66 detects that such a torque-up signal has been input, the process proceeds to step n5, and it is determined whether or not the optical path 88a is shielded by the detection piece 87, and the work is completed. To do. When the light is shielded, the process proceeds to step n6, and it is determined that the first state in which the screw tightening is normally performed is performed.

When the torque-up signal is not input in step n4, or when the light is not shielded in step n5, the process proceeds to step n7, and the screw tightening is not normally performed, that is, the second state. Is determined. In such an abnormal state, the lamp 71 is turned on to generate an alarm, the motor 30 is stopped to stop the screw tightening operation, and the work is interrupted in step n8. As a result, the operator is informed that an abnormality has occurred in the screw tightening at the screw tightening position.

In the above-described embodiment, the detection element 88 corresponds to the position of the driver bit 33 and the detection piece 87 corresponds to the position of the guide tube 34, but the detection piece 87 corresponds to the position of the driver bit 33. However, it goes without saying that the detection element 88 may correspond to the position of the guide cylinder 34. When the detection piece 87 is attached to the guide tube 34 as in the present embodiment, the detection piece 87 can be lightened, so that the guide tube 34 can be easily displaced.

Further, in this embodiment, the detection element 88 is provided with the light emitting element 89 and the light receiving element 90, but the light emitting element 89 and the light receiving element 90 are separated and their relative positions. Needless to say, it may be possible to detect. Further, in the present embodiment, the presence or absence of light shielding by the detection piece 87 with respect to the optical path 88a is detected, but it is needless to say that the presence or absence of light reflection may be detected.

[0039]

[Effect of the device]

 As described above, according to the present invention, the abnormal state of screw tightening can be automatically and reliably detected without the operator's visual inspection. In particular, according to the present invention, the abutting member is formed in the shape of a rod, so that it does not require a large space in the vicinity of the bolt to be mounted by the driver bit, thus facilitating the design of the work and the structure. Can be miniaturized. Further, according to the present invention, since the abutting member and the moving body are mounted so that the length in the axial direction can be adjusted, the length in the axial direction can be adjusted and set according to the type of bolt and the like. It is possible to reliably detect the screw tightening state without error.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the vicinity of a driver bit 33 and a contact member 134 according to an embodiment of the present invention.

FIG. 2 is an overall perspective view of an embodiment of the present invention.

FIG. 3 is a simplified plan view of a base 3.

FIG. 4 is a sectional view taken along the section line IV-IV in FIG.

FIG. 5 is a front view of a screw tightening means 6.

FIG. 6 is a left side view of the screw tightening means 6.

FIG. 7 is a partial cross-sectional view seen from the right side of the screw tightening means 6.

FIG. 8 is a cross-sectional view showing a configuration related to a guide cylinder.

9 is a bottom view of the vicinity of a driver bit 33 and a contact member 134. FIG.

FIG. 10 is a partial cross-sectional view showing a state in which a bolt 40 is tightened on the work 1.

FIG. 11 is a cross-sectional view for explaining the positional relationship between the detection piece 87 and the optical path 88a in each state of FIG.

FIG. 12 is a block diagram showing an electrical configuration of the embodiment shown in FIGS.

FIG. 13 is a flowchart for explaining the operation of the processing circuit 66.

[Explanation of symbols]

 1 Work 2 Mounting Table 3 Base 4 Support 5 Beam 6 Screw Tightening Means 7 Screw Feeder 8 Operation Input Means 13, 20, 30 Motor 22 First Mounting Member 23 Second Mounting Member 25 Double Acting Pneumatic Cylinder 33 Driver Bit 34 Guide Cylinder 36 Compression spring 40 Bolt 66 Processing circuit 73 Screw unfastening detection means 74 Electromagnetic valve 77 Load current detection means 78 Timer 87 Detection piece 88 Detection element 88a Optical path 89 Light emitting element 90 Light receiving element 110 Bush 111 Support member 134 Contact member 142 Mobile

Claims (2)

[Scope of utility model registration request] 1. A driver bit that engages with an engaging groove formed in a bolt head, a rotation driving means that rotates and drives the driver bit around its axis, and a rod-shaped axial line of the driver bit near the driver bit. Along the axis of the abutment member, which is slenderly elongated along with and is displaceable relative to the driver bit, and abuts against the surface of the work to which the bolt is mounted, and the end of the abutment member on the side opposite to the work An automatic screw tightening machine, comprising: a moving body whose length is adjustable; and a detection unit that detects a screw tightening state by detecting a relative displacement between the moving body and a driver bit. 2. The automatic screw tightener according to claim 1, wherein the driver bit is magnetized so as to magnetically attract the bolt.