JPH06304826A - Automatic screw tightening machine - Google Patents

Abstract

PURPOSE:To provide an automatic screw tightening machine by which an abnormal screw tightening condition such as no screw or floating of a screw can be detected when the screw is tightened. CONSTITUTION:An automatic screw tightening machine has a driving motor 11 having a driving shaft, a screw tightening driver bit 12 which is arranged in an offset condition to the driving shaft and is driven in rotation by the driving motor 11, a slider 13 to hold the driver bit 12 by allowing the movement of the driver bit 12 in the vertical axis direction and a sensor 14 arranged in the rear of the driver bit 12 so as to detect a displacement condition of the driver bit 12 in response to the movement of the driver bit 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic screw tightener which is driven to rotate by a drive motor to automatically tighten a screw.

[0002]

2. Description of the Related Art Heretofore, there has been known an automatic screw tightening machine which is driven by a drive motor to automatically tighten screws in order to improve the efficiency of screw tightening work in the assembly process of equipment and devices. This automatic screw tightener is used by being installed in an automatic assembly machine or assembly robot, etc., but when screw tightening, it is input in advance in a series of movements according to the work program of the automatic assembly machine, assembly robot, etc. After being precisely positioned at the screw position, the screw is tightened by being lowered in the axial direction.

[0003]

However, since the operation of the automatic screw tightening machine is a predetermined uniform operation, for example, there is no screw at the tightening position, or "no screw",
Even if a screw tightening error such as "screw lift" is not complete, the specified operation is repeated only as much as possible, and the problem that screw tightening is not completed is overlooked. there were.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide an automatic screw tightening machine capable of detecting an abnormal screw tightening state such as no screw or a floating screw at the time of screw tightening. It is in.

[0005]

The above object is to provide a drive motor having a drive shaft, a screwdriver driver bit arranged in an offset state with respect to the drive shaft and rotationally driven by the drive motor, and the driver bit. Holding means for allowing the driver bit to move in the direction of the vertical axis and holding the driver bit, and detecting means arranged behind the driver bit for detecting the displacement state of the driver bit in response to the movement of the driver bit. It is achieved by an automatic screwdriver with.

[0006]

According to the present invention, the automatic assembling machine or the robot equipped with the automatic screw tightening machine is operated to move the screw to the predetermined position while the screw is adsorbed to the tip of the driver bit and insert the screw into the screw hole. Then, the driver bit is rotationally driven by the drive motor to tighten the screw. At the end of screw tightening, the driver bit moves upward with respect to the automatic screw tightener by the height of the head of the screw, but if the driver bit makes other different movements, the movement is detected by the detection means, It is possible to detect "no screw" or "screw lift" when tightening the screw.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic screw tightener according to an embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the automatic screw tightener 10 includes a drive motor 1 that is a drive source.
1, a driver bit 12 that is driven to rotate by a drive motor 11, a slider (holding means) 13 that holds the driver bit 12, and a sensor (detection means) 14 that detects the displacement state of the driver bit 12. There is.

The driver bit 12 is built in a cylindrical driver case 15, and a gear case 1 having transmission means, which will be described later, built in on the side surface of the central portion of the driver case 15.
6 is installed. A motor cover 18, which houses the drive motor 11 therein, is mounted behind the gear case 16 via a motor mount 17. Therefore, the driver case 15 and the motor cover 18 are arranged in an offset state via the gear case 16 (FIGS. 1A and 2).
reference).

The driver case 15 has a sleeve adjuster 20 threadedly connected through an adjuster nut 19 at a front end, and a pressure adjuster 22 threadedly connected through an adjuster nut 21 at a rear end. . The adjuster nuts 19, 21, the sleeve adjuster 20, and the pressure adjuster 22 form a single cylindrical body having the same flat surface on the outer surface together with the driver case 15, and from the front end opening 20a of the sleeve adjuster 20, A sleeve 23 whose front end has a reduced diameter projects.

Further, the gear case 16 and the motor mount 1
7. Adjuster nut 21 and pressure adjuster 2
A spring case 25 is attached to the inside of 2 via a drive gear 24 attached to the rear end of the driver case 15. Further, the motor cover 18 has a sensor 14
A sensor mount 26 for holding is attached.

In the drive motor 11, the mounting screw ring 27 screwed to the motor cover 18 is fixed to the motor mount 17 with the screw 28, so that the motor mount 1
It is attached to 7. Drive shaft 11 of drive motor 11
a is penetrating the motor mount 17 and is connected to the drive shaft 11
A motor pinion 29 that projects into the gear case 16 is attached to the tip of a.

Motor mount 17 and gear cap 30
In the gear case 16 whose both ends are closed by the above, several kinds of gears or the like for transmitting the power of the drive motor 11 to another rotation shaft or for optimally adjusting the rotation speed and the like are incorporated. Motor mount 17 and gear cap 30 in the gear case 16
An idle shaft 31 is stretched between the and, and the idle shaft 31 is rotatably supported by a ball bearing 32 embedded in the motor mount 17 and the gear cap 30. This idle shaft 31
, Two idle gears 33 and 34 are arranged in parallel with each other. The idle gear 33 is installed by cutting out a part of the side surface of the spring case 25.

The motor pinion 29 has an idle gear 33.
The driving force transmitted from the motor pinion 29 through the idle gear 33 is
Be transmitted to. The idle gear 34 is the drive gear 24.
The drive force from the drive motor 11 is transmitted to the drive gear 24. The driver bit 12 is composed of a bit 35 that rotates a screw, a slide shaft 36 connected to the bit 35, and an extension shaft 37 that abuts on the rear end of the slide shaft 36, and each has the same outer diameter. is doing.

The bit 35 has a reduced diameter tip portion, and the tip end 35a of the tip portion is formed in a shape that can be engaged with the head portion of a screw to be screwed. The rear end portion has a groove 35 into which a locking roller 44 described later can be engaged.
b is formed over the entire circumference, and the rear end 35c is notched on one side in a cross section passing through the vertical axis. A substantially first half portion of the bit 35 is inserted into the sleeve 23 through a sleeve guide 38 into which the bit 35 is slidably inserted, and a rear end portion of the bit 35 is inserted into a front portion of a bit holder 39. It has been stopped. The sleeve guide 38 is inserted into the rear end opening of the sleeve 23.

The rear half of the sleeve 23 is housed in the driver case 15, and is held substantially in the center of the front end opening 20a of the sleeve adjuster 20 through a center guide 40 that penetrates the sleeve 23. The outer periphery of the bit 35 is slidable in the rotational direction and the axial direction via the sleeve guide 38. The tip of the sleeve 23 is located slightly forward of the tip of the bit 35 unless an external force is applied, and an air suction hole (not shown) is formed in the substantially central portion of the sleeve 23. This hole allows the bit 3 to move from the tip of the sleeve 23 during screw tightening work.
By sucking air into the exhaust pipe 41 projecting from the side face of the driver case 15 through the gap and the hole between the sleeve 5 and the sleeve 23, the screw for screwing can be adsorbed to the tip of the sleeve 23.

The center guide 40 has a taper 40a at the front end.
Has a flat surface 40b at the rear end and has a sleeve 2
3 is formed in a thick ring shape having a through hole 40c that is slidable around the outer circumference in the circumferential direction, and the flat surface 40b has a sleeve spring 42 locked to the outer circumferential surface of the sleeve 23.
Has one end abutted. The other end of the sleeve spring 42 has a flange 4 formed on the inner surface of the driver case 15.
Since the taper 40a of the center guide 40 is locked to the center 3, the taper 40a of the center guide 40 is always in pressure contact with the inclined surface of the inner surface of the front end opening 20a by the urging force of the sleeve spring 42.

Corresponding to the center guide 40, the opening 20a of the sleeve adjuster 20 has a diameter large enough to allow the sleeve 23 to have a required degree of freedom in the radial direction. As shown in FIG. 3, the bit holder 39 is formed of a cylindrical body having an outer peripheral surface 39a having a groove 39b extending over the entire circumference.
An opening 39c that penetrates 9a is provided.

As shown in FIG. 4, a locking roller 44 having a side surface projecting is fitted into the opening 39c in the bit holder 39. Both ends of the locking roller 44 are retained by the locking spring 45 wound along the groove 39b so that the locking roller 44 is fitted in the opening 39c. Therefore, the bit 35 inserted into the bit holder 39 is prevented from coming off from the bit holder 39 by engaging the locking roller 44 with the groove 35b.

The front end portion of the slide shaft 36 is inserted into the rear portion of the bit holder 39, and the front end 36a of the slide shaft 36 is aligned with the rear end 35c of the bit 35 and fixed by a fitting screw 46 to fix the bit. 35 and the slide shaft 36 are integrally connected in the bit holder 39. Slide shaft 36 is bit 3
As shown in FIG. 3, it has four columnar keys 47a to 47d projecting at equal intervals around the center of the central portion. This slide shaft 3
A slider 13 having a slide shaft 36 inserted therein is mounted on the keys 47a to 47d forming portion of No. 6, and the slider 13 is inserted into a drive gear 24.

The front end 36a of the slide shaft 36 is notched on one side in a cross section passing through the vertical axis, and the bit 35
By combining with the rear end portion, the slide shaft 36 and the bit 35 are connected so as to be integrally rotatable around the vertical axis. The rear end portion of the slide shaft 36 is rotatably supported by being mounted in a cylindrical ball bearing 49 in a penetrating state, and the rear end 36b is exposed to the rear end surface side of the ball bearing 49.

As shown in FIG. 3, the slider 13 has an opening 13 through which the slide shaft 36 penetrates the bottom surface 13a.
The four vertical walls 1 which have b and which are left by cutting out the cylindrical peripheral wall rising from the bottom surface 13a in a cruciform shape as viewed from above.
3c to 13f, and a flange-shaped step portion that is widened outward is formed at the upper end of each vertical wall 13c to 13f.

The drive gear 24, as shown in FIG.
It is formed in a cylindrical shape having a through hole 24a that encloses each vertical wall 13c to 13f, and a notch 24c to which each step portion of each vertical wall 13c to 13f is fitted at the rear end of the peripheral wall 24b.
24f is formed. On both outer circumferences of the peripheral wall 24b,
A ring-shaped ball bearing 50 is embedded. Therefore, the slider 13 is inserted into the through hole 24a from the bottom surface 13a, and the step portions of the vertical walls 13c to 13f are cut into the notches 24c.
.. to 24f and attached to the drive gear 24, the vertical walls 13c to 13f of the slider 13 and the peripheral wall 2 are provided inside the rear end of the drive gear 24, as shown in FIG.
Four key grooves 51a to 51d are formed by 4b.

Then, after inserting the slide shaft 36 into the key grooves 51a to 51d by inserting the keys 47a to 47d into the openings 13b of the slider 13, the screws 4 are inserted.
By fixing to the bit holder 39 by 6, the slide shaft 36, the slider 13 and the drive gear 24
Slide shaft 3 together with
6, the bit holder 39 and the bit 35 are integrated.

With such a structure, the power from the drive motor 11 is transmitted to the slider 13 which rotates integrally with the drive gear 24 about the axis of ordinates as the axis of rotation, and the key grooves 51a to 51d. Is transmitted to the slide shaft 36 via the respective keys 47a to 47d engaged with. In addition, in each key groove 51a-51d, each key 47
Since a to 47d can slide along the rotation axis, the slide shaft 36 can slide along the rotation axis in the slider 13.

Therefore, the slider 13 allows the driver bit 12 to move in the vertical axis direction and allows the driver bit 12 to move.
Functions as a holding unit that holds the. Furthermore, the slider 1
Since there is a play space as play between the respective key grooves 51a to 51d of No. 3 and the respective keys 47a to 47d of the slide shaft 36, the slide shaft 36 has one point in each of the key grooves 51a to 51d. As a fulcrum, it also has freedom in the radial direction.

In addition, the tip 35a of the bit 35 is movable along the rotation axis and has a degree of freedom in the radial direction. Ball bearing 49
Has a flange 49a formed on the outer circumference of the front end. The other end of the pressure spring 52, whose one end is brought into contact with the inner surface of the rear end 22a of the pressure adjuster 22, is pressed against the flange 49a. It is energized. The ball bearing 49 may be formed integrally with the slide shaft 36 instead of being formed separately.

Since the pressure adjuster 22 is screwed to the spring case 25, it can be moved in the vertical direction of the spring case 25 by rotating the pressure adjuster 22. The position can be fixed. Therefore, by rotating the pressure adjuster 22, the vertical pressure applied to the bit 35 can be adjusted, and by removing the pressure adjuster 22 from the spring case 25 and replacing the pressure spring 52, the bit 35 can be replaced. The pressure applied to can be adjusted over a wide range.

The extension shaft 37 penetrates the pressure spring 52 and is located behind the slide shaft 36, and has a front end 37 a at the rear end 36 of the slide shaft 36.
b and a rear end 37b of the pressure adjuster 22 via a cylindrical bearing 53.
Protruding from. The bearing 53 is inserted and locked in the opening 22b of the rear end 22a by bringing the flange 53a formed on the outer periphery of the rear end into contact with the outer surface of the rear end 22a.

A retaining ring 5 is provided at the front of the extension shaft 37.
4 is attached, and by mounting the pressure spring 55 between the front end of the bearing 53 and the retaining ring 54, the extension shaft 37 is urged toward the ball bearing 49, and the front end 37a is moved to the rear of the slide shaft 36. The end 36b is always contacted. in this way,
The driver bit 12 is a drive shaft 11 a of the drive motor 11.
It is arranged in an offset state with the drive gear 2
The driving force of the drive motor 11 is transmitted through the transmission means composed of 4 and the slider 13 to be rotationally driven.

The driver bit 12 is bit 3
5, the slide shaft 36 and the extension shaft 37 may be formed by a single rod-shaped body having the respective functions. The sensor 14 includes a base 14 a fixed to the sensor mount 26 and a detector 14 b protruding from the tip of the base 14 a.
And the two shafts are arranged at positions behind and behind the extension shaft 37 (Fig. 1 (b),
(See (c)). A controller (not shown) is connected to the sensor 14 via a cable.

This sensor 14 detects the displacement state of the extension shaft 37 in response to the movement of the extension shaft 37 by blocking the light connecting between the two detectors 14b by the extension shaft 37 which has moved rearward, and the detection signal is not shown. It is a non-contact type photo sensor that is sent to the determination means and detects without directly contacting the extension shaft 37. Therefore, the sensor 14
Driver bit 1 corresponding to movement of driver bit 12
2 functions as a detection unit that detects the displacement state.

The detecting means is not limited to the sensor 14 as long as it can detect the displacement state of the extension shaft 37 in response to the movement of the extension shaft 37. For example, a transmissive sensor 14 that detects by blocking light
Instead, the light emitted from the light emitting unit is
It may be a reflection type photo sensor that is reflected by and is received by the light receiving unit to detect the reflected light. Alternatively, a proximity sensor that generates a current when a moving object approaches by using a magnetic field or an electric field may be used.

Further, instead of a non-contact type sensor such as a photo sensor or a proximity sensor, a contact type displacement sensor for directly contacting a moving object to detect a displacement state may be used. As shown in FIG. 6, the contact displacement sensor 56 has a contact 56b at the tip of the main body 56a. By directly contacting the contact 56b with the rear end 37b of the extension shaft 37,
The extension shaft 37 is displaced in accordance with the movement of the extension shaft 37, and the displacement state can be detected.

Next, the operation of the automatic screw tightener will be described.
First, an automatic screw tightener is attached to a predetermined position of an automatic assembly machine or an assembly robot to be mounted, the sleeve adjuster 20 is removed from the driver case 15, and the bit 35 and the sleeve spring 42 are removed. The bit 35 can be easily pulled out from the bit holder 39 by pulling it with a strong hand and removing the locking roller 44 from the groove 35b.

Then, the bit 35 corresponding to the screw to be tightened is selected and inserted into the bit holder 39 while paying attention to the direction of the notch at the base of the bit 35. Bit 3
When 5 is not inserted to the predetermined position, the bit 35 is rotated so that the cutout direction of the bit 35 and the cutout direction of the slide shaft 13 are aligned. When the bit 35 is inserted to a predetermined position, the locking roller 44 fixed to the bit holder 39 enters the groove 35b and the bit 35 is fixed.

Next, the sleeve 2 corresponding to the screw head diameter
3 and the sleeve spring 42 are selected so that the sleeve adjuster 20 is attached at a predetermined position when the sleeve adjuster 20 is attached to the driver case 15. When the sleeve 23 can be set at a predetermined position by adjusting the position while rotating the sleeve adjuster 20, the adjuster nut 19 is tightened to fix the sleeve adjuster 20.

The sleeve 23 is urged by the urging force of the sleeve spring 42 to push out toward the outside of the opening 20a of the sleeve adjuster 20, but one end of the sleeve spring 42 locked to the sleeve 23 is pressed. Is hit by the center guide 40 and locked, so that the sleeve 23 does not fall out of the opening 20a. Further, the center guide 40 to which the urging force of the sleeve spring 42 acts has its longitudinal axis and the opening 2 of the sleeve adjuster 20.
Since the center of the opening 20a is on the rotation axis of the bit 35 in order to maintain the state where the center of 0a coincides,
Unless an external force in the radial direction acts on the sleeve 23 and the bit 35, the axial center of the sleeve 23 and the bit 35 coincide with the rotation axis, and the centering of the bit 35 can be automatically performed.

Thus, the sleeve adjuster 20 is
Since it can be moved in the direction along the rotation axis by screwing and its position can be fixed by the adjuster nut 21, by rotating the sleeve adjuster 20 in the direction along the rotation axis,
By changing the axial force generated in the sleeve spring 42, the moving range and pressure of the sleeve 23 can be changed. Further, rotate the sleeve adjuster 20,
The bit 35 and the sleeve 23 can be easily replaced by removing them from the tip of the driver case 15.

In order to adjust the pressure applied by the tip of the bit 35 to the screw, the pressure spring 52 is replaced and the pressure adjuster 22 is rotated to obtain the required pressure in accordance with the use and type of screw. When the pressure adjuster 22 can be set to a predetermined pressure, the adjuster nut 19 is tightened and fixed.

This completes the mounting of the automatic screw tightening machine 10. Next, an automatic assembly machine or a robot equipped with the automatic screw tightening machine 10 is operated. When the automatic assembly machine or the robot operates and the automatic screw tightening machine reaches above the screw used for screw tightening, the automatic screw tightening machine 10 descends and the tip of the sleeve 23 contacts the screw head. The screw is attracted to the tip of the sleeve 23 by the vacuum action, and the bit 35 is attached to the screw head.
The tips of are engaged. At this point, bit 35 is rotating to ensure engagement.

Thereafter, the screw is moved to a predetermined position where the screw should be tightened while the screw is attracted. At the screw tightening position,
The automatic screw tightener 10 descends, and first, the screw at the tip of the sleeve 23 is inserted into the screw hole. At this time, an impact is applied to the bit 35 in the direction along the rotation axis, but the slide shaft 3
This impact can be absorbed by the slide mechanism 6 and the pressure spring 52.

Even if the mounting position of the screw is slightly displaced or the position of the hole groove of the screw head is displaced due to deformation of the screw, the tips of the sleeve 23 and the bit 35 have a degree of freedom in the radial direction. So it will properly engage with the groove in the screw head. The rotation of the drive motor 11 is transmitted to the slide shaft 36, the bit holder 39, and the bit 35 in the gear case 16, thereby tightening the screw. At this time, if the tip of the bit 35 is slightly displaced, the bit 35 will be displaced from the original rotation axis and rotate, but the slide shaft 36 in the slider 13 forms a free fulcrum with the slider 13. And can be rotated appropriately.

At the end of screw tightening when the drive torque at screw tightening reaches the set value, the drive motor 11 stops and the automatic screw tightener 10 moves up and moves toward the next screw. After that, the above operation is repeated. By the way, at the time of screw tightening, the automatic screw tightener 10 moves downward from the start of screw tightening to the end of screw tightening, and at the end of screw tightening, the driver bit 12 moves upward with respect to the automatic screw tightener 10 by the height of the screw head. If the driver bit 12 moves but otherwise makes a different movement, that movement is extended shaft 3
Since it can be detected by the sensor 14 via 7, it is possible to detect "no screw" or "screw lift" at the time of screw tightening.

This detection state will be described based on the time chart shown in FIG. When the drive motor 11 starts rotation T
1 starts to rotate with a predetermined rotational force, and the rotation speed suddenly decreases at the time of seating T2 when the screw is seated in the screw hole, then gradually decreases and stops at T3 when the screw tightening ends (( See a)). The driving torque at this time is T2 when seated.
Rapidly rises and then suddenly decreases at T3 at the end of screw tightening (see (b)). In addition, the automatic screw tightener 10
Gradually decreases from T1 at the start of rotation, passes through T2 at the time of seating, and stops at T3 at the end of screw tightening (see (c)).

At the start of rotation T1, the sensor 14 is already in the ON state in which light has passed between both detectors 14b,
At the end of screw tightening T3, the extension shaft 37 moves upward by the height of the screw head to shut off the light between the two detectors 14b to be in the OFF state (see (d)), and the predetermined screw tightening is performed. It can be detected that the normal state has been broken. On the other hand, in the case of “no screw” in which the screw is not adsorbed on the tip of the sleeve 23, the extension shaft 37 does not move upward by the height of the screw head at the time T3 at the end of screw tightening, and the two detectors 14 are not moved.
It does not turn off because it does not block the light between points b, and remains on after T3 when screwing is completed ((e)
reference).

Therefore, it is possible to detect an abnormal state in which the predetermined screw tightening is not performed by "no screw". On the other hand, when the contact type displacement sensor 56 is used, the extension shaft 37 moves upward by the height of the head of the screw as a reference, and when the extension shaft 37 is at the reference position at the end of the screw tightening, the extension shaft 37 has a predetermined position. When the extension shaft 37 is lower than the reference position in a normal state where the screw tightening is performed, it is possible to detect that the predetermined screw tightening is not performed due to "no screw". Further, when the extension shaft 37 is higher than the reference position at the end of screw tightening T3, for example, "screw lift", in which paint or the like enters the screw hole and the screw tightening is not completed and remains floating, It is possible to detect an abnormal condition where the screws are not tightened.

Thus, the automatic screw tightening machine 1 of this embodiment
According to 0, when the radial external force does not act on the sleeve 23 or the bit 35, the vertical center of the sleeve 23 and the bit 35 coincide with the rotation axis, and the centering of the bit 35 can be automatically performed. Further, when the automatic screw tightener is mounted, the pressure of the bit 35 in the rotation axis direction can be easily adjusted or the pressure spring 52 can be easily replaced, so that a wide range of pressure can be applied to the bit 35.

Furthermore, the bit 35 and the sleeve 23 can be replaced very easily and in a short time according to the size, use, type, etc. of the screw. In addition, in the case of a screw tightening abnormality such as “no screw” or “screw lift”, the state can be detected.

[0049]

As described above, according to the present invention, it is possible to detect an abnormal state of screw tightening such as no screw or screw floating during screw tightening.

[Brief description of drawings]

1 shows an automatic screw tightener according to an embodiment of the present invention, (a) is a front view, (b) a partial plan view, and (c) a partially cutaway side view.

FIG. 2 is a partial cross-sectional view of FIG.

FIG. 3 is a perspective view of a slide shaft, a slider, a drive gear, and a bit holder.

FIG. 4 is an explanatory diagram showing a state in which a rocking roller is attached to the bit holder.

FIG. 5 is an explanatory diagram showing a key groove of a slider.

FIG. 6 is a perspective view of a bit holder to which a locking roller is attached.

FIG. 7 is a time chart showing a detection state by a sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Automatic screw fastening machine 11 ... Drive motor 11a ... Drive shaft 12 ... Driver bit 13 ... Slider (holding means) 13a ... Bottom surface 13b ... Openings 13c to 13f ... Vertical wall 14 ... Sensor (detection means) 14a ... Base 14b ... Detector 15 ... Driver case 16 ... Gear case 17 ... Motor mount 18 ... Motor cover 19 ... Adjuster nut 20 ... Sleeve adjuster 20a ... Front end opening 21 ... Adjuster nut 22 ... Pressure adjuster 22a ... Rear end 22b ... Opening 23 ... Sleeve 24 ... Drive Gear 24a ... Through hole 24b ... Peripheral wall 24c-24f ... Notch 25 ... Spring case 26 ... Sensor mount 27 ... Mounting scriwl ring 28 ... Screw 29 ... Motor pinion 30 ... Gear cap 31 ... Idle shaft 32 ... Ball bearing 33 34 ... Idle gear 35 ... Bit 35a ... Tip 35b ... Groove 35c ... Rear end 36 ... Slide shaft 36a ... Front end 36b ... Rear end 37 ... Extension shaft 37a ... Front end 37b ... Rear end 38 ... Sleeve guide 39 ... Bit holder 39a ... Outer circumference Surface 39b ... Groove 39c ... Opening 40 ... Center guide 40a ... Taper 40b ... Flat surface 40c ... Through hole 41 ... Exhaust pipe 42 ... Sleeve spring 43 ... Flange 44 ... Locking roller 45 ... Rocking spring 46 ... Screw 47a-47d ... Key 49 ... Ball bearing 49a ... Flange 50 ... Ball bearing 51a to 51d ... Key groove 52 ... Pressure spring 53 ... Bearing 53a ... Flange 54 ... Retaining ring 55 ... Pressure spring 56 ... Contact displacement sensor 56a ... Main body 56b ... Contactor

Claims (1)

[Claims] 1. A drive motor having a drive shaft, a driver bit for screw tightening, which is arranged in an offset state with respect to the drive shaft and is rotationally driven by the drive motor, and a movement of the driver bit in a vertical axis direction. A holding means for allowing the driver bit to be held, and a detecting means arranged behind the driver bit and detecting a displacement state of the driver bit in response to movement of the driver bit. Automatic screw tightener.