JP2004283948A - Thread fastening device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thread fastening device capable of quickly performing thread fastening requiring high fastening torque. <P>SOLUTION: The thread fastening device has a socket 2 capable of being engaged with a bolt to transmit a driving force to the bolt, a driving shaft 4 connected to the socket 2 so as to transmit the driving force, a first electric screwdriver 5 capable of rotating and driving the driving shaft 4 at a high speed, a one-way clutch 6 disposed in the driving shaft 4, and a second electric screwdriver 8 capable of transmitting the driving force to the one-way clutch 6 and drivable at torque higher than that of the first electric screwdriver 5. Thus, the first electric screwdriver 5 is driven to perform high-speed fastening in a low fastening torque region, and after that in a high fastening torque region, the second electric screwdriver 8 is driven to perform high-torque fastening. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a screw fastening device used for fastening a screw component such as a screw or a bolt to a work.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an example of a screw fastening device, a screw fastening device disclosed in Patent Document is known. This screw tightening device has a structure in which a screw tightening bit that can be engaged with a driving hole formed in the head of the screw is connected to an electric screwdriver via a bit driving shaft. When a screw is tightened to a work with this screw tightening device, the electric driver is driven in a state where the screw tightening bit is engaged with the drive hole of the screw. As a result, the torque is transmitted from the screw tightening bit to the screw, and the screw is tightened into a predetermined screw hole of the work.
[0003]
[Patent Document] JP-A-6-39653
[Problems to be solved by the invention]
However, in the conventional screw tightening device described above, in order to obtain a high final tightening torque, an electric driver having a large output torque is naturally used. In such an electric screwdriver, the maximum rotation speed of a screw tightening tool such as a screw tightening bit is reduced due to the reduction ratio of the speed reducer set to obtain a high torque. Therefore, even at the screwing stage until the seat does not require much tightening torque, screwing at a high torque and at a low speed is performed, so that the time required for tightening the screw parts becomes extremely long. Had occurred. Further, an electric driver having a large output torque has a very large inertia at the time of driving due to the influence of a speed reducer and the like. Therefore, if the electric screwdriver is driven at a high rotational speed during the screwing stage until seating, the inertia torque by the drive of the electric screwdriver acts on the screw component when the head seat surface of the screw component is seated on the work, and the screw component is required. Problems such as tightening with the above tightening torque have occurred.
[0005]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and has a screw tightening tool capable of engaging with a screw component and transmitting a rotational force to the screw component, and a drive coupled to the screw tightening tool so as to be capable of transmitting rotation. A shaft, a first rotation driving means capable of driving the driving shaft to rotate at a high speed, a one-way clutch provided on the driving shaft, and a torque capable of rotating the one-way clutch and having a higher torque than the first rotation driving means. In the screw tightening device having a drivable second rotary drive unit, the first rotary drive unit is configured not to tighten the screw component to a predetermined torque when the screw component is seated due to inertia at the time of driving. The second rotation driving means is configured to be drivable with an output torque sufficiently larger than the maximum output torque of the first rotation driving means.
[0006]
It is preferable that the first rotation drive means is driven at a rotation speed at which the screw component is not tightened to a predetermined torque due to inertia when the screw component is seated. In the one-way clutch, when the first rotation driving means is driven to rotate the screw tightening tool in a direction for tightening the screw component, an idling action occurs on the drive shaft, and the second rotation driving means tightens the screw component. When the screw tightening tool is driven to rotate in the direction, it is preferable that the screw tightening tool is configured to rotate integrally with the drive shaft. In addition, it is preferable that the first rotation driving means and the second rotation driving means are driven to rotate the screw tightening tool in a direction opposite to a direction in which the screw parts are tightened after the tightening of the screw parts is completed. Further, it is preferable that each of the first rotation driving means and the second rotation driving means is provided with a rotation detecting means. In this case, it is desirable to have a control unit for comparing the rotation angles obtained from the signals of the respective rotation detecting means.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a screw fastening device. The screw tightening device 1 is used when a hexagonal bolt (not shown; hereinafter, simply referred to as a bolt), which is an example of a screw component, is tightened to a work. It has a socket 2 which is an example of a screw tightening tool capable of transmitting a rotational force. The socket 2 is connected to a drive shaft 4 rotatably disposed on a housing 3. The drive shaft 4 is connected to an output shaft 5 a of a first electric driver 5, which is an example of a first rotation driving unit, and is configured to rotate by receiving the drive of the first electric driver 5. A one-way clutch 6 is mounted on the drive shaft 4, and a driven gear 7 is mounted on the one-way clutch 6 so as to rotate integrally therewith. The driven gear 7 is meshed with a drive gear 9 that rotates when driven by a second electric driver 8 which is an example of a second rotation drive unit. With such a structure, it is also possible to change the reduction ratio in various ways with the combination of the driven gear 7 and the driving gear 9 while keeping the first electric driver 5 and the second electric driver 8 as they are.
[0008]
The first electric driver 5 includes an AC servomotor and a speed reducer that reduces the output of the AC servomotor at a predetermined gear ratio. Due to the gear ratio of the speed reducer, the first electric driver 5 is configured so that the bolt head seat surface is seated on the work surface and the tightening torque is slightly increased, so that the first electric driver 5 is easily stalled. The actual maximum output torque of the first electric driver 5 is about several N · m. For this reason, the first electric driver 5 can perform rotational driving at an extremely high speed, and has very small inertia when rotationally driven in a high rotational speed range. The “stall” described above refers to a phenomenon in which the output shaft 5a of the first electric driver 5 cannot rotate due to a rotational load.
[0009]
On the other hand, the second electric driver 8 is composed of an AC servomotor having a sufficiently larger capacity than that of the first electric driver 5, and a speed reducer for reducing the output of the AC servomotor at a predetermined gear ratio. The gear ratio of the speed reducer is configured to obtain an output torque (several hundred N · m) sufficiently larger than that of the first electric driver 5.
[0010]
The one-way clutch 6 has an inner wheel 6a fixed integrally with the drive shaft 4, and an outer wheel 6b located on the outer periphery of the inner wheel 6a is fixed to the driven gear 7. The outer ring 6b is configured to be fixed to the inner ring 6a and rotate integrally with the inner ring 6a when rotation in the bolt tightening direction is given, and to idle with respect to the inner ring 6a when rotation in the opposite direction is given. Have been. In other words, the inner ring 6a idles with respect to the outer ring 6b when the rotation in the bolt tightening direction is given. Therefore, when the first electric screwdriver 5 is driven to rotate the socket 2 in the direction of tightening the bolt, the inner ring 6a and the outer ring 6b slip, and only the driving force of the first electric screwdriver 5 is transmitted to the socket 2. Is done. When the second electric driver 8 is driven to rotate the socket 2 in the direction of tightening the bolts, the inner ring 6a and the outer ring 6b are fixed and can be integrally rotated. Is transmitted.
[0011]
A cylindrical strain tube 10 through which the drive shaft 4 is inserted is attached to a lower portion of the housing 3. The mounting flange 11 to which the lower part of the strain tube 10 is fixed is fixed to a table 12 which is operated to reciprocate in the axial direction of the drive shaft 4 by a reciprocating unit (not shown). Thereby, the reaction force of the tightening torque when the socket 2 tightens the bolt is transmitted to the strain tube 10, and the strain tube 10 is twisted according to the reaction force. A strain gauge 13 is attached to the strain tube 10 so as to output an electric signal corresponding to the strain of the strain tube 10. A torque sensor is constituted by the strain tube 10 and the strain gauge 13, and the control unit 14 determines a tightening torque from a signal of the strain gauge 13.
[0012]
Further, the first and second electric drivers 5 and 8 have built-in encoders 5b and 8b that emit pulse signals corresponding to the rotation of the output shafts 5a and 8a as an example of rotation detection means. The control unit 14 is configured to detect the bolt tightening angle by processing each output of the encoders 5b and 8b.
[0013]
Next, the operation of the main screw tightening device 1 will be described.
As an example of the tightening of a screw component by the present screw tightening device 1, a so-called plastic region tightening in which a bolt is tightened to a plastic region based on a snag torque generated after a head seat surface of a bolt is seated on a work surface will be described. Note that the plastic region tightening introduced in the present embodiment shows the tightening torque characteristics of FIG. 2 with the snug torque being Ts and the tightening torque at the time of completion of the tightening being Te. As shown in FIG. 2, the snug torque is a torque value indicating an inflection point of the tightening torque curve, and takes a sufficiently small value with respect to the final tightening torque Te.
[0014]
When the table 12 is lowered while the socket 2 is rotated in the bolt tightening direction by the driving of the first electric screwdriver 5, and the socket 2 is engaged with the head of the bolt fitted in the prepared hole of the work, the bolt becomes Rotation is transmitted from the socket 2 and screwed into the screw hole. At this time, the drive shaft 4 idles with respect to the driven gear 7 by the action of the one-way clutch 6. Therefore, only the driving force of the first electric driver 5 is transmitted to the socket 2.
[0015]
At the moment when the bolt head seat surface is seated on the work, an impact torque acts on the bolt due to the inertia of the first electric driver 5. Due to this impact torque, the bolt is tightened with a torque higher than the capability of the first electric screwdriver 5. On the other hand, the first electric driver 5 is driven and controlled at the maximum rotational speed at which the bolt is not tightened to the snag torque Ts by the impact torque. In this regard, since the first electric screwdriver 5 is configured to stall with a slight increase in the tightening torque at the initial stage when the bolt is seated, the inertia is very small. Therefore, even when the first electric driver 5 is driven in a high rotation speed range, it is possible to prevent the bolt from being tightened to the snag torque Ts by the impact torque at the time of sitting. For this reason, in the main screw tightening device 1, the bolt can be screwed up to the seating at a high speed.
[0016]
Further, since the first electric screwdriver 5 is of such a degree that it easily stalls when the bolt is seated, for example, when the bolt cannot be screwed in normally due to the influence of poor forming of the female screw, oblique biting of the bolt or the like. Also stall. Therefore, in such a case, the bolt can be forcibly screwed in to prevent a problem such as damage to the bolt and the female screw.
[0017]
The control unit 14 detects that the AC servomotor of the first electric driver 5 has been stalled from the pulse signal of the encoder 5b, and detects a volt from a signal from a sensor (not shown) for detecting the height of the socket 2 or the like. When it is detected that the bolt has been screwed to the seating height, the control unit 14 determines that the bolt is seated normally. Thus, the driving of the first electric driver 5 is stopped and the second electric driver 8 is driven. As a result, the driving force is transmitted to the one-way clutch 6 via the driving gear 9 and the driven gear 7. At this time, the inner wheel 6a and the outer wheel 6b of the one-way clutch 6 are locked, so that the driving force of the second electric driver 8 is transmitted to the drive shaft 4 or the socket 2.
[0018]
Thereafter, when it is determined from the signal of the strain gauge 13 that the tightening torque has reached the snag torque Ts, the control unit 14 monitors the pulse angle of the encoder 8b and monitors the rotation angle of the bolt from the snag torque generation point. When the rotation angle reaches the predetermined value θ, the driving of the second electric driver 8 is stopped, and it is checked whether or not the final tightening torque Te is within a predetermined range, and it is determined whether or not the bolt is tightened. . The rotation angle θ of the bolt from the snag torque generation point described above corresponds to an angle at which the bolt is tightened to a plastic region beyond the yield point.
[0019]
Subsequently, the controller 14 drives the second electric driver 8 in a direction opposite to the direction in which the bolts are tightened (hereinafter, this driving is referred to as reverse driving; the same applies to the first electric driver 5), and the first electric driver 5 Is reversely driven by a predetermined angle (about 5 °). As a result, the socket 2 is slightly rotated in the bolt loosening direction in response to the reverse drive of the first electric driver 5, so that the crimping between the socket 2 and the bolt head can be reliably released. Thereafter, the driving of the first and second electric drivers 5, 8 is stopped, and the table 12 is returned to the original position by the operation of the reciprocating unit to prepare for the next operation. When the first electric driver 5 and the second electric driver 8 are driven in reverse, it is preferable that the second electric driver 8 is driven at a higher rotation speed than the first electric driver 5.
[0020]
When the second electric driver 8 is driven during the above-mentioned bolt tightening operation, the output shaft 5a of the first electric driver 5 that is not driven also receives the rotation of the drive shaft 4 and rotates accordingly. Therefore, the control unit 14 can also obtain the signal of the encoder 5b. Therefore, the control unit 14 can know the rotation angle from each signal of the encoders 5b and 8b, and can compare these to determine the rotation angle with high accuracy. Further, for example, when the one-way clutch 6 and the drive shaft 4 are slipped under the driving of the second electric driver 8 due to the deterioration of the one-way clutch 6, for example, the rotation angle obtained from the signals of the encoders 5b and 8b is reduced. There is a difference. From this, it is possible to detect an abnormality in the component part at an early stage and replace it, and it is possible to maintain the tightening quality of the bolt.
[0021]
In tightening bolts in the above-mentioned plastic region, a very high tightening torque (several hundred N · m) is finally required. Correspondingly, the second electric driver 8 can rotationally drive the socket 2 with high torque. Under the driving of the second electric screwdriver 8 that can obtain such a high tightening torque, the rotation speed of the socket 2 necessarily decreases, but as described above, the first electric screwdriver 5 does not rotate until the bolt is seated. Since screwing is performed at a high speed by driving, the time required for bolt tightening is greatly reduced as a whole. As described above, in the main screw tightening device 1, the work can be quickly and efficiently performed even in the tightening of the bolt in the plastic region where a high tightening torque is required.
[0022]
In the above description, a bolt is used as an example of a screw component. However, similar effects can be obtained with other screw components such as small screws. Further, although the first electric driver and the second electric driver employ an AC servo motor, other motors or means can be applied thereto. Furthermore, an example of tightening the bolt by a predetermined angle θ based on the snag torque generation point was introduced.
-A method of obtaining snag torque etc. in the tightening process by the so-called torque method, which tightens the bolts until a preset final tightening torque is reached.-The so-called torque gradient method in which the gradient of the tightening torque is checked from the point at which snag torque is generated. The technical idea of the present invention is extremely effective in a tightening method for acquiring a relatively low torque value generated after seating of a screw component as data, such as a tightening method based on a screw. In addition, examples of detecting the seating of the bolt other than the above include various methods such as a method of detecting the seating from the stall of the AC servomotor of the first electric driver 5 and the time from the start of tightening.
[0023]
【The invention's effect】
According to the screw tightening device of the present invention, the first rotary drive unit is driven in the tightening region with a low tightening torque, and the screw tightening driven by the second rotary drive unit is performed in the tightening region where a high tightening torque is required. It can be carried out. Therefore, there is an advantage that the tightening operation of the screw component requiring a high tightening torque can be performed quickly. When it is necessary to detect a relatively low level of predetermined torque generated after the threaded component is seated, the drive is switched from the first rotation driving means to the second rotation driving means before reaching the predetermined torque. However, the tightening torque does not exceed the predetermined torque due to the inertia of the first rotation drive means. Therefore, there is an advantage that a high-precision screw component can be tightened by reliably detecting the predetermined torque.
[Brief description of the drawings]
FIG. 1 is an enlarged partial cutaway sectional view of a main part of a screw fastening device according to the present invention.
FIG. 2 is an explanatory diagram showing characteristics of a tightening torque with respect to a rotation angle in a plastic region angle method tightening operation.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 screw tightening device 2 socket 3 housing 4 drive shaft 5 first electric screwdriver 6 one-way clutch 7 driven gear 8 second electric screwdriver 9 drive gear 10 strain tube 11 mounting flange 12 table 13 strain gauge 14 control unit

Claims (6)

A screw tightening tool capable of transmitting a rotational force to the screw component by engaging with the screw component, a drive shaft connected to the screw tightening tool so as to transmit the rotation, and a first shaft capable of rotating the drive shaft at high speed. A screw tightening device comprising: a rotary drive unit; a one-way clutch provided on the drive shaft; and a second rotary drive unit capable of rotating the one-way clutch and driving with a higher torque than the first rotary drive unit. ,
The first rotary drive unit is configured not to tighten the screw component to a predetermined torque when the screw component is seated due to inertia at the time of driving, and the second rotary drive unit is configured to have a maximum output torque of the first rotary drive unit. A screw tightening device characterized in that the screw driving device is configured to be drivable with a sufficiently large output torque. 2. The screw tightening device according to claim 1, wherein the first rotation driving unit drives the screw at a rotation speed that does not tighten the screw to a predetermined torque due to inertia when the screw is seated. 3. The one-way clutch generates an idling action on the drive shaft when the first rotary drive means drives the screw tightening tool in a direction to tighten the screw component, and the second rotary drive means sets the screw in the direction in which the screw component is tightened. The screw tightening device according to claim 1, wherein the screw tightening device is configured to rotate integrally with the drive shaft when the tightening tool is driven to rotate. The first rotation driving means and the second rotation driving means are configured to drive the screw tightening tool to rotate in a direction opposite to a direction in which the screw is tightened after the tightening of the screw is completed. The screw tightening device according to claim 1. The screw tightening device according to any one of claims 1 to 4, wherein the first rotation drive unit and the second rotation drive unit each include a rotation detection unit. The screw tightening device according to claim 5, further comprising a control unit configured to compare rotation angles obtained from signals of the rotation detection units.

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